[PATCH v10 00/16] arm64: entry: Convert to Generic Entry

[PATCH v10 00/16] arm64: entry: Convert to Generic Entry

[Jinjie Ruan]

Currently, x86, Riscv, Loongarch use the Generic Entry which makes
maintainers' work easier and codes more elegant. arm64 has already
successfully switched to the Generic IRQ Entry in commit
b3cf07851b6c ("arm64: entry: Switch to generic IRQ entry"), it is
time to completely convert arm64 to Generic Entry.

The goal is to bring arm64 in line with other architectures that already
use the generic entry infrastructure, reducing duplicated code and
making it easier to share future changes in entry/exit paths, such as
"Syscall User Dispatch".

This patch set is rebased on v6.19-rc1. And the performance was measured
on Kunpeng 920 using "perf bench basic syscall" with "arm64.nopauth
selinux=0 audit=1".

After switch to Generic Entry, the performance are below:

| Metric     | W/O Generic Framework | With Generic Framework | Change |
| ---------- | --------------------- | ---------------------- | ------ |
| Total time | 2.487 [sec]           |  2.393[sec]            | ↓3.8% |
| usecs/op   | 0.248780              |  0.239361              | ↓3.8% |
| ops/sec    | 4,019,620             |  4,177,789             | ↑3.9% |

Compared to earlier with arch specific handling, the performance improved
by approximately 3.9%.

On the basis of optimizing syscall_get_arguments()[1], el0_svc_common()
and syscall_exit_work(), the performance are below:

| Metric     | W/O Generic Entry | With Generic Entry opt| Change |
| ---------- | ----------------- | ------------------    | ------ |
| Total time | 2.487 [sec]       | 2.264 [sec]           | ↓9.0% |
| usecs/op   | 0.248780          | 0.226481              | ↓9.0% |
| ops/sec    | 4,019,620         | 4,415,383             | ↑9.8% |

Therefore, after the optimization, ARM64 System Call performance improved
by approximately 9%.

It was tested ok with following test cases on kunpeng920 and QEMU
virt platform:
 - Perf tests.
 - Different `dynamic preempt` mode switch.
 - Pseudo NMI tests.
 - Stress-ng CPU stress test.
 - Hackbench stress test.
 - MTE test case in Documentation/arch/arm64/memory-tagging-extension.rst
   and all test cases in tools/testing/selftests/arm64/mte/*.
 - "sud" selftest testcase.
 - get_set_sud, get_syscall_info, set_syscall_info, peeksiginfo
   in tools/testing/selftests/ptrace.
 - breakpoint_test_arm64 in selftests/breakpoints.
 - syscall-abi and ptrace in tools/testing/selftests/arm64/abi
 - fp-ptrace, sve-ptrace, za-ptrace in selftests/arm64/fp.
 - vdso_test_getrandom in tools/testing/selftests/vDSO
 - Strace tests.

The test QEMU configuration is as follows:

	qemu-system-aarch64 \
		-M virt,gic-version=3,virtualization=on,mte=on \
		-cpu max,pauth-impdef=on \
		-kernel Image \
		-smp 8,sockets=1,cores=4,threads=2 \
		-m 512m \
		-nographic \
		-no-reboot \
		-device virtio-rng-pci \
		-append "root=/dev/vda rw console=ttyAMA0 kgdboc=ttyAMA0,115200 \
			earlycon preempt=voluntary irqchip.gicv3_pseudo_nmi=1" \
		-drive if=none,file=images/rootfs.ext4,format=raw,id=hd0 \
		-device virtio-blk-device,drive=hd0 \

[1]: https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm/+/89bf683c9507c280e20c3e17b4ea15e19696ed63%5E%21/#F0

Changes in v10:
- Rebased on v6.19-rc1, rename syscall_exit_to_user_mode_prepare() to
  syscall_exit_to_user_mode_work_prepare() to avoid conflict.
- Also inline syscall_trace_enter().
- Support aarch64 for sud_benchmark.
- Update and correct the commit message.
- Add Reviewed-by.
- Link to v9: https://lore.kernel.org/all/20251204082123.2792067-1-ruanjinjie@huawei.com/

Changes in v9:
- Move "Return early for ptrace_report_syscall_entry() error" patch ahead
  to make it not introduce a regression.
- Not check _TIF_SECCOMP/SYSCALL_EMU for syscall_exit_work() in
  a separate patch.
- Do not report_syscall_exit() for PTRACE_SYSEMU_SINGLESTEP in a separate
  patch.
- Add two performance patch to improve the arm64 performance.
- Add Reviewed-by.
- Link to v8: https://lore.kernel.org/all/20251126071446.3234218-1-ruanjinjie@huawei.com/

Changes in v8:
- Rename "report_syscall_enter()" to "report_syscall_entry()".
- Add ptrace_save_reg() to avoid duplication.
- Remove unused _TIF_WORK_MASK in a standalone patch.
- Align syscall_trace_enter() return value with the generic version.
- Use "scno" instead of regs->syscallno in el0_svc_common().
- Move rseq_syscall() ahead in a standalone patch to clarify it clearly.
- Rename "syscall_trace_exit()" to "syscall_exit_work()".
- Keep the goto in el0_svc_common().
- No argument was passed to __secure_computing() and check -1 not -1L.
- Remove "Add has_syscall_work() helper" patch.
- Move "Add syscall_exit_to_user_mode_prepare() helper" patch later.
- Add miss header for asm/entry-common.h.
- Update the implementation of arch_syscall_is_vdso_sigreturn().
- Add "ARCH_SYSCALL_WORK_EXIT" to be defined as "SECCOMP | SYSCALL_EMU"
  to keep the behaviour unchanged.
- Add more testcases test.
- Add Reviewed-by.
- Update the commit message.
- Link to v7: https://lore.kernel.org/all/20251117133048.53182-1-ruanjinjie@huawei.com/

Chanegs in v7:
- Support "Syscall User Dispatch" by implementing
  arch_syscall_is_vdso_sigreturn() as kemal suggested.
- Add aarch64 support for "sud" selftest testcase, which tested ok with
  the patch series.
- Fix the kernel test robot warning for arch_ptrace_report_syscall_entry()
  and arch_ptrace_report_syscall_exit() in asm/entry-common.h.
- Add perf syscall performance test.
- Link to v6: https://lore.kernel.org/all/20250916082611.2972008-1-ruanjinjie@huawei.com/

Changes in v6:
- Rebased on v6.17-rc5-next as arm64 generic irq entry has merged.
- Update the commit message.
- Link to v5: https://lore.kernel.org/all/20241206101744.4161990-1-ruanjinjie@huawei.com/

Changes in v5:
- Not change arm32 and keep inerrupts_enabled() macro for gicv3 driver.
- Move irqentry_state definition into arch/arm64/kernel/entry-common.c.
- Avoid removing the __enter_from_*() and __exit_to_*() wrappers.
- Update "irqentry_state_t ret/irq_state" to "state"
  to keep it consistently.
- Use generic irq entry header for PREEMPT_DYNAMIC after split
  the generic entry.
- Also refactor the ARM64 syscall code.
- Introduce arch_ptrace_report_syscall_entry/exit(), instead of
  arch_pre/post_report_syscall_entry/exit() to simplify code.
- Make the syscall patches clear separation.
- Update the commit message.
- Link to v4: https://lore.kernel.org/all/20241025100700.3714552-1-ruanjinjie@huawei.com/

Changes in v4:
- Rework/cleanup split into a few patches as Mark suggested.
- Replace interrupts_enabled() macro with regs_irqs_disabled(), instead
  of left it here.
- Remove rcu and lockdep state in pt_regs by using temporary
  irqentry_state_t as Mark suggested.
- Remove some unnecessary intermediate functions to make it clear.
- Rework preempt irq and PREEMPT_DYNAMIC code
  to make the switch more clear.
- arch_prepare_*_entry/exit() -> arch_pre_*_entry/exit().
- Expand the arch functions comment.
- Make arch functions closer to its caller.
- Declare saved_reg in for block.
- Remove arch_exit_to_kernel_mode_prepare(), arch_enter_from_kernel_mode().
- Adjust "Add few arch functions to use generic entry" patch to be
  the penultimate.
- Update the commit message.
- Add suggested-by.
- Link to v3: https://lore.kernel.org/all/20240629085601.470241-1-ruanjinjie@huawei.com/

Changes in v3:
- Test the MTE test cases.
- Handle forget_syscall() in arch_post_report_syscall_entry()
- Make the arch funcs not use __weak as Thomas suggested, so move
  the arch funcs to entry-common.h, and make arch_forget_syscall() folded
  in arch_post_report_syscall_entry() as suggested.
- Move report_single_step() to thread_info.h for arm64
- Change __always_inline() to inline, add inline for the other arch funcs.
- Remove unused signal.h for entry-common.h.
- Add Suggested-by.
- Update the commit message.

Changes in v2:
- Add tested-by.
- Fix a bug that not call arch_post_report_syscall_entry() in
  syscall_trace_enter() if ptrace_report_syscall_entry() return not zero.
- Refactor report_syscall().
- Add comment for arch_prepare_report_syscall_exit().
- Adjust entry-common.h header file inclusion to alphabetical order.
- Update the commit message.

Jinjie Ruan (15):
  arm64: Remove unused _TIF_WORK_MASK
  arm64/ptrace: Split report_syscall()
  arm64/ptrace: Return early for ptrace_report_syscall_entry() error
  arm64/ptrace: Refactor syscall_trace_enter/exit()
  arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()
  arm64: syscall: Rework el0_svc_common()
  arm64/ptrace: Not check _TIF_SECCOMP/SYSCALL_EMU for
    syscall_exit_work()
  arm64/ptrace: Do not report_syscall_exit() for
    PTRACE_SYSEMU_SINGLESTEP
  arm64/ptrace: Expand secure_computing() in place
  arm64/ptrace: Use syscall_get_arguments() helper
  entry: Split syscall_exit_to_user_mode_work() for arch reuse
  entry: Add arch_ptrace_report_syscall_entry/exit()
  arm64: entry: Convert to generic entry
  arm64: Inline el0_svc_common()
  entry: Inline syscall_exit_work() and syscall_trace_enter()

kemal (1):
  selftests: sud_test: Support aarch64

 arch/arm64/Kconfig                            |   2 +-
 arch/arm64/include/asm/entry-common.h         |  76 ++++++++
 arch/arm64/include/asm/syscall.h              |  19 +-
 arch/arm64/include/asm/thread_info.h          |  22 +--
 arch/arm64/kernel/debug-monitors.c            |   7 +
 arch/arm64/kernel/ptrace.c                    |  94 ----------
 arch/arm64/kernel/signal.c                    |   2 +-
 arch/arm64/kernel/syscall.c                   |  29 +--
 include/linux/entry-common.h                  | 176 ++++++++++++++++--
 kernel/entry/common.h                         |   7 -
 kernel/entry/syscall-common.c                 |  96 +---------
 kernel/entry/syscall_user_dispatch.c          |   4 +-
 .../syscall_user_dispatch/sud_benchmark.c     |   2 +-
 .../syscall_user_dispatch/sud_test.c          |   4 +
 14 files changed, 282 insertions(+), 258 deletions(-)
 delete mode 100644 kernel/entry/common.h

-- 
2.34.1

[PATCH v10 01/16] arm64: Remove unused _TIF_WORK_MASK

[Jinjie Ruan]

Since commit b3cf07851b6c ("arm64: entry: Switch to generic IRQ
entry"), _TIF_WORK_MASK is never used, so remove it.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/include/asm/thread_info.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index a803b887b0b4..24fcd6adaa33 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -106,12 +106,6 @@ void arch_setup_new_exec(void);
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_TSC_SIGSEGV	(1 << TIF_TSC_SIGSEGV)
 
-#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | \
-				 _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
-				 _TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
-				 _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING | \
-				 _TIF_PATCH_PENDING)
-
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
 				 _TIF_SYSCALL_EMU)
-- 
2.34.1

[PATCH v10 02/16] arm64/ptrace: Split report_syscall()

[Jinjie Ruan]

The generic syscall entry code has the form:

| syscall_trace_enter()
| {
|	ptrace_report_syscall_entry()
| }
|
| syscall_exit_work()
| {
|	ptrace_report_syscall_exit()
| }

In preparation for moving arm64 over to the generic entry code, split
report_syscall() to two separate enter and exit functions to align
the structure of the arm64 code with syscall_trace_enter() and
syscall_exit_work() from the generic entry code.

No functional changes.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
v8:
- report_syscall_enter() -> report_syscall_entry().
- Add ptrace_save_reg() helper.
---
 arch/arm64/kernel/ptrace.c | 41 +++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index b9bdd83fbbca..03fe2f8a4d54 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2343,9 +2343,10 @@ enum ptrace_syscall_dir {
 	PTRACE_SYSCALL_EXIT,
 };
 
-static void report_syscall(struct pt_regs *regs, enum ptrace_syscall_dir dir)
+static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
+						     enum ptrace_syscall_dir dir,
+						     int *regno)
 {
-	int regno;
 	unsigned long saved_reg;
 
 	/*
@@ -2364,15 +2365,31 @@ static void report_syscall(struct pt_regs *regs, enum ptrace_syscall_dir dir)
 	 * - Syscall stops behave differently to seccomp and pseudo-step traps
 	 *   (the latter do not nobble any registers).
 	 */
-	regno = (is_compat_task() ? 12 : 7);
-	saved_reg = regs->regs[regno];
-	regs->regs[regno] = dir;
+	*regno = (is_compat_task() ? 12 : 7);
+	saved_reg = regs->regs[*regno];
+	regs->regs[*regno] = dir;
 
-	if (dir == PTRACE_SYSCALL_ENTER) {
-		if (ptrace_report_syscall_entry(regs))
-			forget_syscall(regs);
-		regs->regs[regno] = saved_reg;
-	} else if (!test_thread_flag(TIF_SINGLESTEP)) {
+	return saved_reg;
+}
+
+static void report_syscall_entry(struct pt_regs *regs)
+{
+	unsigned long saved_reg;
+	int regno;
+
+	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
+	if (ptrace_report_syscall_entry(regs))
+		forget_syscall(regs);
+	regs->regs[regno] = saved_reg;
+}
+
+static void report_syscall_exit(struct pt_regs *regs)
+{
+	unsigned long saved_reg;
+	int regno;
+
+	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, &regno);
+	if (!test_thread_flag(TIF_SINGLESTEP)) {
 		ptrace_report_syscall_exit(regs, 0);
 		regs->regs[regno] = saved_reg;
 	} else {
@@ -2392,7 +2409,7 @@ int syscall_trace_enter(struct pt_regs *regs)
 	unsigned long flags = read_thread_flags();
 
 	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
-		report_syscall(regs, PTRACE_SYSCALL_ENTER);
+		report_syscall_entry(regs);
 		if (flags & _TIF_SYSCALL_EMU)
 			return NO_SYSCALL;
 	}
@@ -2420,7 +2437,7 @@ void syscall_trace_exit(struct pt_regs *regs)
 		trace_sys_exit(regs, syscall_get_return_value(current, regs));
 
 	if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
-		report_syscall(regs, PTRACE_SYSCALL_EXIT);
+		report_syscall_exit(regs);
 
 	rseq_syscall(regs);
 }
-- 
2.34.1

[PATCH v10 03/16] arm64/ptrace: Return early for ptrace_report_syscall_entry() error

[Jinjie Ruan]

The generic entry abort the syscall_trace_enter() sequence if
ptrace_report_syscall_entry() errors out, but arm64 not.

When ptrace requests interception, it should prevent all subsequent
system-call processing, including audit and seccomp. In preparation for
moving arm64 over to the generic entry code, return early if
ptrace_report_syscall_entry() encounters an error.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/ptrace.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 03fe2f8a4d54..f333791ffba6 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2372,15 +2372,18 @@ static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
 	return saved_reg;
 }
 
-static void report_syscall_entry(struct pt_regs *regs)
+static int report_syscall_entry(struct pt_regs *regs)
 {
 	unsigned long saved_reg;
-	int regno;
+	int regno, ret;
 
 	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
-	if (ptrace_report_syscall_entry(regs))
+	ret = ptrace_report_syscall_entry(regs);
+	if (ret)
 		forget_syscall(regs);
 	regs->regs[regno] = saved_reg;
+
+	return ret;
 }
 
 static void report_syscall_exit(struct pt_regs *regs)
@@ -2407,10 +2410,11 @@ static void report_syscall_exit(struct pt_regs *regs)
 int syscall_trace_enter(struct pt_regs *regs)
 {
 	unsigned long flags = read_thread_flags();
+	int ret;
 
 	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
-		report_syscall_entry(regs);
-		if (flags & _TIF_SYSCALL_EMU)
+		ret = report_syscall_entry(regs);
+		if (ret || (flags & _TIF_SYSCALL_EMU))
 			return NO_SYSCALL;
 	}
 
-- 
2.34.1

[PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Jinjie Ruan]

The generic syscall entry code has the following form, which use
the input syscall work flag and syscall number:

| syscall_trace_enter(struct pt_regs *regs, long syscall,
|		      unsigned long work)
|
| syscall_exit_work(struct pt_regs *regs, unsigned long work)

In preparation for moving arm64 over to the generic entry code,
refactor syscall_trace_enter/exit() to also pass thread flags, and
get syscall number by syscall_get_nr() helper.

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/include/asm/syscall.h |  4 ++--
 arch/arm64/kernel/ptrace.c       | 25 ++++++++++++++++---------
 arch/arm64/kernel/syscall.c      |  5 +++--
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 5e4c7fc44f73..cef1d9ce6e1b 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -120,7 +120,7 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_AARCH64;
 }
 
-int syscall_trace_enter(struct pt_regs *regs);
-void syscall_trace_exit(struct pt_regs *regs);
+int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
+void syscall_trace_exit(struct pt_regs *regs, unsigned long flags);
 
 #endif	/* __ASM_SYSCALL_H */
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index f333791ffba6..79762ff33945 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2407,9 +2407,8 @@ static void report_syscall_exit(struct pt_regs *regs)
 	}
 }
 
-int syscall_trace_enter(struct pt_regs *regs)
+int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 {
-	unsigned long flags = read_thread_flags();
 	int ret;
 
 	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
@@ -2422,19 +2421,27 @@ int syscall_trace_enter(struct pt_regs *regs)
 	if (secure_computing() == -1)
 		return NO_SYSCALL;
 
-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
-		trace_sys_enter(regs, regs->syscallno);
+	/* Either of the above might have changed the syscall number */
+	syscall = syscall_get_nr(current, regs);
 
-	audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
+	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
+		trace_sys_enter(regs, syscall);
+
+		/*
+		 * Probes or BPF hooks in the tracepoint may have changed the
+		 * system call number as well.
+		 */
+		 syscall = syscall_get_nr(current, regs);
+	}
+
+	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
 			    regs->regs[2], regs->regs[3]);
 
-	return regs->syscallno;
+	return syscall;
 }
 
-void syscall_trace_exit(struct pt_regs *regs)
+void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 {
-	unsigned long flags = read_thread_flags();
-
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index c062badd1a56..5a103873de12 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -124,7 +124,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		 */
 		if (scno == NO_SYSCALL)
 			syscall_set_return_value(current, regs, -ENOSYS, 0);
-		scno = syscall_trace_enter(regs);
+		scno = syscall_trace_enter(regs, scno, flags);
 		if (scno == NO_SYSCALL)
 			goto trace_exit;
 	}
@@ -143,7 +143,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 	}
 
 trace_exit:
-	syscall_trace_exit(regs);
+	flags = read_thread_flags();
+	syscall_trace_exit(regs, flags);
 }
 
 void do_el0_svc(struct pt_regs *regs)
-- 
2.34.1

[PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Jinjie Ruan]

commit a9f3a74a29af ("entry: Provide generic syscall exit function")
introduce generic syscall exit function and call rseq_syscall()
before audit_syscall_exit() and arch_syscall_exit_tracehook().

And commit b74406f37737 ("arm: Add syscall detection for restartable
sequences") add rseq support for arm32, which also call rseq_syscall()
before audit_syscall_exit() and tracehook_report_syscall().

However, commit 409d5db49867c ("arm64: rseq: Implement backend rseq
calls and select HAVE_RSEQ") implement arm64 rseq and call
rseq_syscall() after audit_syscall_exit() and tracehook_report_syscall().

So compared to the generic entry and arm32 code, arm64 terminates
the process a bit later if the syscall is issued within
a restartable sequence.

But as commit b74406f37737 ("arm: Add syscall detection for restartable
sequences") said, syscalls are not allowed inside restartable sequences,
so should call rseq_syscall() at the very beginning of system call
exiting path for CONFIG_DEBUG_RSEQ=y kernel. This could help us to detect
whether there is a syscall issued inside restartable sequences.

It makes sense to raise SIGSEGV via rseq_syscall() before auditing
and ptrace syscall exit, because this guarantees that the process is
already in an error state with SIGSEGV pending when those later steps
run. Although it makes no practical difference to signal delivery (signals
are processed at the very end in arm64_exit_to_user_mode()), the ordering
is more logical: detect and flag the error first, then proceed with
the remaining work.

To make it more reasonable and in preparation for moving arm64 over to
the generic entry code, move rseq_syscall() ahead before
audit_syscall_exit().

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/ptrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 79762ff33945..983d8d1104df 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2442,6 +2442,8 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 
 void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 {
+	rseq_syscall(regs);
+
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
@@ -2449,8 +2451,6 @@ void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 
 	if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
 		report_syscall_exit(regs);
-
-	rseq_syscall(regs);
 }
 
 /*
-- 
2.34.1

[PATCH v10 06/16] arm64: syscall: Rework el0_svc_common()

[Jinjie Ruan]

The generic syscall syscall_exit_work() has the following content:

| audit_syscall_exit(regs)
| trace_sys_exit(regs, ...)
| ptrace_report_syscall_exit(regs, step)

The generic syscall syscall_exit_to_user_mode_work() has
the following form:

| unsigned long work = READ_ONCE(current_thread_info()->syscall_work)
| rseq_syscall()
| if (unlikely(work & SYSCALL_WORK_EXIT))
|	syscall_exit_work(regs, work)

In preparation for moving arm64 over to the generic entry code,
rework el0_svc_common() as below:

- Rename syscall_trace_exit() to syscall_exit_work().

- Add syscall_exit_to_user_mode_work_prepare() function to replace
  the combination of read_thread_flags() and syscall_exit_work(),
  also move the syscall exit check logic into it. Move has_syscall_work()
  helper into asm/syscall.h for reuse.

- As currently rseq_syscall() is always called and itself is controlled
  by the CONFIG_DEBUG_RSEQ macro, so the CONFIG_DEBUG_RSEQ check
  is removed.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/include/asm/syscall.h |  7 ++++++-
 arch/arm64/kernel/ptrace.c       | 14 +++++++++++---
 arch/arm64/kernel/syscall.c      | 20 +-------------------
 3 files changed, 18 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index cef1d9ce6e1b..b86b2ffa16ef 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -120,7 +120,12 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_AARCH64;
 }
 
+static inline bool has_syscall_work(unsigned long flags)
+{
+	return unlikely(flags & _TIF_SYSCALL_WORK);
+}
+
 int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
-void syscall_trace_exit(struct pt_regs *regs, unsigned long flags);
+void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs);
 
 #endif	/* __ASM_SYSCALL_H */
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 983d8d1104df..95f8ea21680a 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2440,10 +2440,8 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 	return syscall;
 }
 
-void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
+static void syscall_exit_work(struct pt_regs *regs, unsigned long flags)
 {
-	rseq_syscall(regs);
-
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
@@ -2453,6 +2451,16 @@ void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 		report_syscall_exit(regs);
 }
 
+void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
+{
+	unsigned long flags = read_thread_flags();
+
+	rseq_syscall(regs);
+
+	if (has_syscall_work(flags) || flags & _TIF_SINGLESTEP)
+		syscall_exit_work(regs, flags);
+}
+
 /*
  * SPSR_ELx bits which are always architecturally RES0 per ARM DDI 0487D.a.
  * We permit userspace to set SSBS (AArch64 bit 12, AArch32 bit 23) which is
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 5a103873de12..76c9c6fc1b30 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -65,11 +65,6 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	choose_random_kstack_offset(get_random_u16());
 }
 
-static inline bool has_syscall_work(unsigned long flags)
-{
-	return unlikely(flags & _TIF_SYSCALL_WORK);
-}
-
 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 			   const syscall_fn_t syscall_table[])
 {
@@ -130,21 +125,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 	}
 
 	invoke_syscall(regs, scno, sc_nr, syscall_table);
-
-	/*
-	 * The tracing status may have changed under our feet, so we have to
-	 * check again. However, if we were tracing entry, then we always trace
-	 * exit regardless, as the old entry assembly did.
-	 */
-	if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
-		flags = read_thread_flags();
-		if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP))
-			return;
-	}
-
 trace_exit:
-	flags = read_thread_flags();
-	syscall_trace_exit(regs, flags);
+	syscall_exit_to_user_mode_work_prepare(regs);
 }
 
 void do_el0_svc(struct pt_regs *regs)
-- 
2.34.1

[PATCH v10 07/16] arm64/ptrace: Not check _TIF_SECCOMP/SYSCALL_EMU for syscall_exit_work()

[Jinjie Ruan]

As syscall_exit_work() do not handle seccomp, so not check _TIF_SECCOMP
for syscall_exit_work().

And as the man manual of PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP
said, "For PTRACE_SYSEMU, continue and stop on entry to the next system
call, which will not be executed. For PTRACE_SYSEMU_SINGLESTEP, do the same
but also singlestep if not a system call.". So only the syscall entry need
to be reported for SYSCALL_EMU, so not check _TIF_SYSCALL_EMU for
syscall_exit_work().

After this, audit_syscall_exit() and report_syscall_exit() will
no longer be called if only SECCOMP and/or SYSCALL_EMU is set.

And remove has_syscall_work() by the way as currently it is only used in
el0_svc_common().

This is another preparation for moving arm64 over to the generic
entry code.

Link：https://man7.org/linux/man-pages/man2/ptrace.2.html
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/include/asm/syscall.h     | 5 -----
 arch/arm64/include/asm/thread_info.h | 3 +++
 arch/arm64/kernel/ptrace.c           | 2 +-
 arch/arm64/kernel/syscall.c          | 2 +-
 4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index b86b2ffa16ef..7746c8f0e045 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -120,11 +120,6 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_AARCH64;
 }
 
-static inline bool has_syscall_work(unsigned long flags)
-{
-	return unlikely(flags & _TIF_SYSCALL_WORK);
-}
-
 int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
 void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs);
 
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 24fcd6adaa33..ef1462b9b00b 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -110,6 +110,9 @@ void arch_setup_new_exec(void);
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
 				 _TIF_SYSCALL_EMU)
 
+#define _TIF_SYSCALL_EXIT_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+				 _TIF_SYSCALL_TRACEPOINT)
+
 #ifdef CONFIG_SHADOW_CALL_STACK
 #define INIT_SCS							\
 	.scs_base	= init_shadow_call_stack,			\
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 95f8ea21680a..ec818940114e 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2457,7 +2457,7 @@ void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
 
 	rseq_syscall(regs);
 
-	if (has_syscall_work(flags) || flags & _TIF_SINGLESTEP)
+	if (unlikely(flags & _TIF_SYSCALL_EXIT_WORK) || flags & _TIF_SINGLESTEP)
 		syscall_exit_work(regs, flags);
 }
 
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 76c9c6fc1b30..80b7fd67492e 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -101,7 +101,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		return;
 	}
 
-	if (has_syscall_work(flags)) {
+	if (unlikely(flags & _TIF_SYSCALL_WORK)) {
 		/*
 		 * The de-facto standard way to skip a system call using ptrace
 		 * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
-- 
2.34.1

[PATCH v10 08/16] arm64/ptrace: Do not report_syscall_exit() for PTRACE_SYSEMU_SINGLESTEP

[Jinjie Ruan]

The generic report_single_step() always returns false if SYSCALL_EMU
is set, but arm64 only checks _TIF_SINGLESTEP and does not check
_TIF_SYSCALL_EMU, which means that if both _TIF_SINGLESTEP and
_TIF_SYSCALL_EMU are set, the generic entry will not report
a single-step, whereas arm64 will do it.

As the man manual of PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP said,
"For PTRACE_SYSEMU, continue and stop on entry to the next system
call, which will not be executed. For PTRACE_SYSEMU_SINGLESTEP, do the
same but also singlestep if not a system call.". And as the generic entry
report_single_step() comment said, If SYSCALL_EMU is set, then the only
reason to report is when SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).
Because this syscall instruction has been already reported
in syscall_trace_enter(), there is no need to report the syscall
again in syscall_exit_work().

In preparation for moving arm64 over to the generic entry code,

- Add report_single_step() helper for arm64 to make it clear.

- Do not report_syscall_exit() if both _TIF_SYSCALL_EMU and
  _TIF_SINGLESTEP set.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/ptrace.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index ec818940114e..558d5553fd6b 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2440,14 +2440,25 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 	return syscall;
 }
 
+static inline bool report_single_step(unsigned long flags)
+{
+	if (flags & _TIF_SYSCALL_EMU)
+		return false;
+
+	return flags & _TIF_SINGLESTEP;
+}
+
 static void syscall_exit_work(struct pt_regs *regs, unsigned long flags)
 {
+	bool step;
+
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
 		trace_sys_exit(regs, syscall_get_return_value(current, regs));
 
-	if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
+	step = report_single_step(flags);
+	if (step || flags & _TIF_SYSCALL_TRACE)
 		report_syscall_exit(regs);
 }
 
-- 
2.34.1

[PATCH v10 09/16] arm64/ptrace: Expand secure_computing() in place

[Jinjie Ruan]

The generic entry expand secure_computing() in place and call
__secure_computing() directly.

In order to switch to the generic entry for arm64, refactor
secure_computing() for syscall_trace_enter().

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/ptrace.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 558d5553fd6b..a1922e4a6437 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2418,8 +2418,11 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 	}
 
 	/* Do the secure computing after ptrace; failures should be fast. */
-	if (secure_computing() == -1)
-		return NO_SYSCALL;
+	if (flags & _TIF_SECCOMP) {
+		ret = __secure_computing();
+		if (ret == -1)
+			return NO_SYSCALL;
+	}
 
 	/* Either of the above might have changed the syscall number */
 	syscall = syscall_get_nr(current, regs);
@@ -2437,7 +2440,7 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
 			    regs->regs[2], regs->regs[3]);
 
-	return syscall;
+	return ret ? : syscall;
 }
 
 static inline bool report_single_step(unsigned long flags)
-- 
2.34.1

[PATCH v10 10/16] arm64/ptrace: Use syscall_get_arguments() helper

[Jinjie Ruan]

The generic entry check audit context first and use
syscall_get_arguments() helper.

In order to switch to the generic entry for arm64,

- Also use syscall_get_arguments() to get audit_syscall_entry()'s
  last four parameters.

- Extract the syscall_enter_audit() helper to make it clear.

- Check audit context first, which saves an unnecessary memcpy when
  current process's audit_context is NULL.

Overall these changes make syscall_enter_audit() exactly equivalent
to the generic one.

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/ptrace.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index a1922e4a6437..2645ddf77369 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2407,6 +2407,16 @@ static void report_syscall_exit(struct pt_regs *regs)
 	}
 }
 
+static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
+{
+	if (unlikely(audit_context())) {
+		unsigned long args[6];
+
+		syscall_get_arguments(current, regs, args);
+		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
+	}
+}
+
 int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 {
 	int ret;
@@ -2437,8 +2447,7 @@ int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 		 syscall = syscall_get_nr(current, regs);
 	}
 
-	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
-			    regs->regs[2], regs->regs[3]);
+	syscall_enter_audit(regs, syscall);
 
 	return ret ? : syscall;
 }
-- 
2.34.1

[PATCH v10 11/16] entry: Split syscall_exit_to_user_mode_work() for arch reuse

[Jinjie Ruan]

In the generic entry code, the beginning of
syscall_exit_to_user_mode_work() can be reused on arm64 so it makes
sense to split it.

In preparation for moving arm64 over to the generic entry
code, split out syscall_exit_to_user_mode_work_prepare() helper from
syscall_exit_to_user_mode_work().

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 include/linux/entry-common.h | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 87efb38b7081..0de0e60630e1 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -121,20 +121,11 @@ static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, l
  */
 void syscall_exit_work(struct pt_regs *regs, unsigned long work);
 
-/**
- * syscall_exit_to_user_mode_work - Handle work before returning to user mode
- * @regs:	Pointer to currents pt_regs
- *
- * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
- * exit_to_user_mode() to perform the final transition to user mode.
- *
- * Calling convention is the same as for syscall_exit_to_user_mode() and it
- * returns with all work handled and interrupts disabled. The caller must
- * invoke exit_to_user_mode() before actually switching to user mode to
- * make the final state transitions. Interrupts must stay disabled between
- * return from this function and the invocation of exit_to_user_mode().
+/*
+ * Syscall specific exit to user mode preparation. Runs with interrupts
+ * enabled.
  */
-static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
+static __always_inline void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
 {
 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	unsigned long nr = syscall_get_nr(current, regs);
@@ -155,6 +146,24 @@ static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
 	 */
 	if (unlikely(work & SYSCALL_WORK_EXIT))
 		syscall_exit_work(regs, work);
+}
+
+/**
+ * syscall_exit_to_user_mode_work - Handle work before returning to user mode
+ * @regs:	Pointer to currents pt_regs
+ *
+ * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
+ * exit_to_user_mode() to perform the final transition to user mode.
+ *
+ * Calling convention is the same as for syscall_exit_to_user_mode() and it
+ * returns with all work handled and interrupts disabled. The caller must
+ * invoke exit_to_user_mode() before actually switching to user mode to
+ * make the final state transitions. Interrupts must stay disabled between
+ * return from this function and the invocation of exit_to_user_mode().
+ */
+static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+	syscall_exit_to_user_mode_work_prepare(regs);
 	local_irq_disable_exit_to_user();
 	syscall_exit_to_user_mode_prepare(regs);
 }
-- 
2.34.1

[PATCH v10 12/16] entry: Add arch_ptrace_report_syscall_entry/exit()

[Jinjie Ruan]

Differ from generic entry, due to historical reasons, ARM64 need to
save/restore during syscall entry/exit because ARM64 use a scratch
register (ip(r12) on AArch32, x7 on AArch64) to denote syscall entry/exit.

In preparation for moving arm64 over to the generic entry code,
add arch_ptrace_report_syscall_entry/exit() as the default
ptrace_report_syscall_entry/exit() implementation. This allows
arm64 to implement the architecture specific version.

This allows arm64 to implement the architecture specific version.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 include/linux/entry-common.h  | 39 +++++++++++++++++++++++++++++++++++
 kernel/entry/syscall-common.c |  4 ++--
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 0de0e60630e1..17171e8873fc 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -45,6 +45,25 @@
 				 SYSCALL_WORK_SYSCALL_EXIT_TRAP	|	\
 				 ARCH_SYSCALL_WORK_EXIT)
 
+/**
+ * arch_ptrace_report_syscall_entry - Architecture specific
+ *				      ptrace_report_syscall_entry().
+ *
+ * Invoked from syscall_trace_enter() to wrap ptrace_report_syscall_entry().
+ * Defaults to ptrace_report_syscall_entry.
+ *
+ * The main purpose is to support arch-specific ptrace_report_syscall_entry()
+ * implementation.
+ */
+static __always_inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs);
+
+#ifndef arch_ptrace_report_syscall_entry
+static __always_inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs)
+{
+	return ptrace_report_syscall_entry(regs);
+}
+#endif
+
 long syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long work);
 
 /**
@@ -112,6 +131,26 @@ static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, l
 	return ret;
 }
 
+/**
+ * arch_ptrace_report_syscall_exit - Architecture specific
+ *				     ptrace_report_syscall_exit.
+ *
+ * Invoked from syscall_exit_work() to wrap ptrace_report_syscall_exit().
+ *
+ * The main purpose is to support arch-specific ptrace_report_syscall_exit
+ * implementation.
+ */
+static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs,
+							    int step);
+
+#ifndef arch_ptrace_report_syscall_exit
+static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs,
+							    int step)
+{
+	ptrace_report_syscall_exit(regs, step);
+}
+#endif
+
 /**
  * syscall_exit_work - Handle work before returning to user mode
  * @regs:	Pointer to current pt_regs
diff --git a/kernel/entry/syscall-common.c b/kernel/entry/syscall-common.c
index 940a597ded40..fe38f84dfff3 100644
--- a/kernel/entry/syscall-common.c
+++ b/kernel/entry/syscall-common.c
@@ -34,7 +34,7 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall,
 
 	/* Handle ptrace */
 	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
-		ret = ptrace_report_syscall_entry(regs);
+		ret = arch_ptrace_report_syscall_entry(regs);
 		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
 			return -1L;
 	}
@@ -100,5 +100,5 @@ void syscall_exit_work(struct pt_regs *regs, unsigned long work)
 
 	step = report_single_step(work);
 	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
-		ptrace_report_syscall_exit(regs, step);
+		arch_ptrace_report_syscall_exit(regs, step);
 }
-- 
2.34.1

[PATCH v10 13/16] arm64: entry: Convert to generic entry

[Jinjie Ruan]

Currently, x86, Riscv, Loongarch use the generic entry which makes
maintainers' work easier and codes more elegant. arm64 has already
switched to the generic IRQ entry, so completely convert arm64 to use
the generic entry infrastructure from kernel/entry/*.

The changes are below:
 - Remove TIF_SYSCALL_* flag.

 - Remove _TIF_SYSCALL_WORK/EXIT_WORK as they are equal with
   SYSCALL_WORK_ENTER/EXIT.

 - Implement arch_ptrace_report_syscall_entry/exit() with
   report_syscall_entry/exit() to do arm64-specific save/restore
   during syscall entry/exit.

 - Remove arm64 syscall_trace_enter() and related sub-functions
   including syscall_enter_audit(), by calling generic entry's
   functions with similar functionality.

 - Set/clear SYSCALL_EXIT_TRAP flag when enable/disable single_step,
   So _TIF_SINGLESTEP can be replaced with generic SYSCALL_EXIT_TRAP,
   _TIF_SYSCALL_EXIT_WORK and _TIF_SINGLESTEP can be replaced
   with generic SYSCALL_WORK_EXIT, arm64's report_single_step() can be
   replaced with generic version.

 - Remove arm64's syscall_exit_to_user_mode_work_prepare() and
   syscall_exit_work() etc. by using generic entry's similar same name
   functions.

 - Implement arch_syscall_is_vdso_sigreturn() to support "Syscall User
   Dispatch".

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Suggested-by: Kevin Brodsky <kevin.brodsky@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/Kconfig                    |   2 +-
 arch/arm64/include/asm/entry-common.h |  76 +++++++++++++
 arch/arm64/include/asm/syscall.h      |  19 +++-
 arch/arm64/include/asm/thread_info.h  |  19 +---
 arch/arm64/kernel/debug-monitors.c    |   7 ++
 arch/arm64/kernel/ptrace.c            | 153 --------------------------
 arch/arm64/kernel/signal.c            |   2 +-
 arch/arm64/kernel/syscall.c           |   6 +-
 8 files changed, 107 insertions(+), 177 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 93173f0a09c7..f50b49ce8b65 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -153,9 +153,9 @@ config ARM64
 	select GENERIC_CPU_DEVICES
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
+	select GENERIC_ENTRY
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IOREMAP
-	select GENERIC_IRQ_ENTRY
 	select GENERIC_IRQ_IPI
 	select GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
 	select GENERIC_IRQ_PROBE
diff --git a/arch/arm64/include/asm/entry-common.h b/arch/arm64/include/asm/entry-common.h
index cab8cd78f693..d8bf4bf342e8 100644
--- a/arch/arm64/include/asm/entry-common.h
+++ b/arch/arm64/include/asm/entry-common.h
@@ -3,14 +3,21 @@
 #ifndef _ASM_ARM64_ENTRY_COMMON_H
 #define _ASM_ARM64_ENTRY_COMMON_H
 
+#include <linux/ptrace.h>
 #include <linux/thread_info.h>
 
+#include <asm/compat.h>
 #include <asm/cpufeature.h>
 #include <asm/daifflags.h>
 #include <asm/fpsimd.h>
 #include <asm/mte.h>
 #include <asm/stacktrace.h>
 
+enum ptrace_syscall_dir {
+	PTRACE_SYSCALL_ENTER = 0,
+	PTRACE_SYSCALL_EXIT,
+};
+
 #define ARCH_EXIT_TO_USER_MODE_WORK (_TIF_MTE_ASYNC_FAULT | _TIF_FOREIGN_FPSTATE)
 
 static __always_inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
@@ -54,4 +61,73 @@ static inline bool arch_irqentry_exit_need_resched(void)
 
 #define arch_irqentry_exit_need_resched arch_irqentry_exit_need_resched
 
+static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
+						     enum ptrace_syscall_dir dir,
+						     int *regno)
+{
+	unsigned long saved_reg;
+
+	/*
+	 * We have some ABI weirdness here in the way that we handle syscall
+	 * exit stops because we indicate whether or not the stop has been
+	 * signalled from syscall entry or syscall exit by clobbering a general
+	 * purpose register (ip/r12 for AArch32, x7 for AArch64) in the tracee
+	 * and restoring its old value after the stop. This means that:
+	 *
+	 * - Any writes by the tracer to this register during the stop are
+	 *   ignored/discarded.
+	 *
+	 * - The actual value of the register is not available during the stop,
+	 *   so the tracer cannot save it and restore it later.
+	 *
+	 * - Syscall stops behave differently to seccomp and pseudo-step traps
+	 *   (the latter do not nobble any registers).
+	 */
+	*regno = (is_compat_task() ? 12 : 7);
+	saved_reg = regs->regs[*regno];
+	regs->regs[*regno] = dir;
+
+	return saved_reg;
+}
+
+static __always_inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs)
+{
+	unsigned long saved_reg;
+	int regno, ret;
+
+	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
+	ret = ptrace_report_syscall_entry(regs);
+	if (ret)
+		forget_syscall(regs);
+	regs->regs[regno] = saved_reg;
+
+	return ret;
+}
+
+#define arch_ptrace_report_syscall_entry arch_ptrace_report_syscall_entry
+
+static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs,
+							    int step)
+{
+	unsigned long saved_reg;
+	int regno;
+
+	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, &regno);
+	if (!step) {
+		ptrace_report_syscall_exit(regs, 0);
+		regs->regs[regno] = saved_reg;
+	} else {
+		regs->regs[regno] = saved_reg;
+
+		/*
+		 * Signal a pseudo-step exception since we are stepping but
+		 * tracer modifications to the registers may have rewound the
+		 * state machine.
+		 */
+		ptrace_report_syscall_exit(regs, 1);
+	}
+}
+
+#define arch_ptrace_report_syscall_exit arch_ptrace_report_syscall_exit
+
 #endif /* _ASM_ARM64_ENTRY_COMMON_H */
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 7746c8f0e045..240d45735cc5 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -9,6 +9,9 @@
 #include <linux/compat.h>
 #include <linux/err.h>
 
+#include <asm/compat.h>
+#include <asm/vdso.h>
+
 typedef long (*syscall_fn_t)(const struct pt_regs *regs);
 
 extern const syscall_fn_t sys_call_table[];
@@ -120,7 +123,19 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_AARCH64;
 }
 
-int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
-void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs);
+static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
+{
+	unsigned long sigtramp;
+
+#ifdef CONFIG_COMPAT
+	if (is_compat_task()) {
+		unsigned long sigpage = (unsigned long)current->mm->context.sigpage;
+
+		return regs->pc >= sigpage && regs->pc < (sigpage + PAGE_SIZE);
+	}
+#endif
+	sigtramp = (unsigned long)VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+	return regs->pc == (sigtramp + 8);
+}
 
 #endif	/* __ASM_SYSCALL_H */
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index ef1462b9b00b..90be0c590b86 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -43,6 +43,7 @@ struct thread_info {
 	void			*scs_sp;
 #endif
 	u32			cpu;
+	unsigned long		syscall_work;   /* SYSCALL_WORK_ flags */
 };
 
 #define thread_saved_pc(tsk)	\
@@ -65,11 +66,6 @@ void arch_setup_new_exec(void);
 #define TIF_UPROBE		5	/* uprobe breakpoint or singlestep */
 #define TIF_MTE_ASYNC_FAULT	6	/* MTE Asynchronous Tag Check Fault */
 #define TIF_NOTIFY_SIGNAL	7	/* signal notifications exist */
-#define TIF_SYSCALL_TRACE	8	/* syscall trace active */
-#define TIF_SYSCALL_AUDIT	9	/* syscall auditing */
-#define TIF_SYSCALL_TRACEPOINT	10	/* syscall tracepoint for ftrace */
-#define TIF_SECCOMP		11	/* syscall secure computing */
-#define TIF_SYSCALL_EMU		12	/* syscall emulation active */
 #define TIF_PATCH_PENDING	13	/* pending live patching update */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_FREEZE		19
@@ -92,27 +88,14 @@ void arch_setup_new_exec(void);
 #define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_FOREIGN_FPSTATE	(1 << TIF_FOREIGN_FPSTATE)
-#define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
-#define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
-#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
-#define _TIF_SECCOMP		(1 << TIF_SECCOMP)
-#define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)
 #define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
-#define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
 #define _TIF_32BIT		(1 << TIF_32BIT)
 #define _TIF_SVE		(1 << TIF_SVE)
 #define _TIF_MTE_ASYNC_FAULT	(1 << TIF_MTE_ASYNC_FAULT)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_TSC_SIGSEGV	(1 << TIF_TSC_SIGSEGV)
 
-#define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
-				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
-				 _TIF_SYSCALL_EMU)
-
-#define _TIF_SYSCALL_EXIT_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
-				 _TIF_SYSCALL_TRACEPOINT)
-
 #ifdef CONFIG_SHADOW_CALL_STACK
 #define INIT_SCS							\
 	.scs_base	= init_shadow_call_stack,			\
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 29307642f4c9..e67643a70405 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -385,11 +385,18 @@ void user_enable_single_step(struct task_struct *task)
 
 	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
 		set_regs_spsr_ss(task_pt_regs(task));
+
+	/*
+	 * Ensure that a trap is triggered once stepping out of a system
+	 * call prior to executing any user instruction.
+	 */
+	set_task_syscall_work(task, SYSCALL_EXIT_TRAP);
 }
 NOKPROBE_SYMBOL(user_enable_single_step);
 
 void user_disable_single_step(struct task_struct *task)
 {
 	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
+	clear_task_syscall_work(task, SYSCALL_EXIT_TRAP);
 }
 NOKPROBE_SYMBOL(user_disable_single_step);
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 2645ddf77369..f575b30b2dc4 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -8,7 +8,6 @@
  * Copyright (C) 2012 ARM Ltd.
  */
 
-#include <linux/audit.h>
 #include <linux/compat.h>
 #include <linux/kernel.h>
 #include <linux/sched/signal.h>
@@ -18,7 +17,6 @@
 #include <linux/smp.h>
 #include <linux/ptrace.h>
 #include <linux/user.h>
-#include <linux/seccomp.h>
 #include <linux/security.h>
 #include <linux/init.h>
 #include <linux/signal.h>
@@ -28,7 +26,6 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/regset.h>
 #include <linux/elf.h>
-#include <linux/rseq.h>
 
 #include <asm/compat.h>
 #include <asm/cpufeature.h>
@@ -38,13 +35,9 @@
 #include <asm/mte.h>
 #include <asm/pointer_auth.h>
 #include <asm/stacktrace.h>
-#include <asm/syscall.h>
 #include <asm/traps.h>
 #include <asm/system_misc.h>
 
-#define CREATE_TRACE_POINTS
-#include <trace/events/syscalls.h>
-
 struct pt_regs_offset {
 	const char *name;
 	int offset;
@@ -2338,152 +2331,6 @@ long arch_ptrace(struct task_struct *child, long request,
 	return ptrace_request(child, request, addr, data);
 }
 
-enum ptrace_syscall_dir {
-	PTRACE_SYSCALL_ENTER = 0,
-	PTRACE_SYSCALL_EXIT,
-};
-
-static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
-						     enum ptrace_syscall_dir dir,
-						     int *regno)
-{
-	unsigned long saved_reg;
-
-	/*
-	 * We have some ABI weirdness here in the way that we handle syscall
-	 * exit stops because we indicate whether or not the stop has been
-	 * signalled from syscall entry or syscall exit by clobbering a general
-	 * purpose register (ip/r12 for AArch32, x7 for AArch64) in the tracee
-	 * and restoring its old value after the stop. This means that:
-	 *
-	 * - Any writes by the tracer to this register during the stop are
-	 *   ignored/discarded.
-	 *
-	 * - The actual value of the register is not available during the stop,
-	 *   so the tracer cannot save it and restore it later.
-	 *
-	 * - Syscall stops behave differently to seccomp and pseudo-step traps
-	 *   (the latter do not nobble any registers).
-	 */
-	*regno = (is_compat_task() ? 12 : 7);
-	saved_reg = regs->regs[*regno];
-	regs->regs[*regno] = dir;
-
-	return saved_reg;
-}
-
-static int report_syscall_entry(struct pt_regs *regs)
-{
-	unsigned long saved_reg;
-	int regno, ret;
-
-	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
-	ret = ptrace_report_syscall_entry(regs);
-	if (ret)
-		forget_syscall(regs);
-	regs->regs[regno] = saved_reg;
-
-	return ret;
-}
-
-static void report_syscall_exit(struct pt_regs *regs)
-{
-	unsigned long saved_reg;
-	int regno;
-
-	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, &regno);
-	if (!test_thread_flag(TIF_SINGLESTEP)) {
-		ptrace_report_syscall_exit(regs, 0);
-		regs->regs[regno] = saved_reg;
-	} else {
-		regs->regs[regno] = saved_reg;
-
-		/*
-		 * Signal a pseudo-step exception since we are stepping but
-		 * tracer modifications to the registers may have rewound the
-		 * state machine.
-		 */
-		ptrace_report_syscall_exit(regs, 1);
-	}
-}
-
-static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
-{
-	if (unlikely(audit_context())) {
-		unsigned long args[6];
-
-		syscall_get_arguments(current, regs, args);
-		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
-	}
-}
-
-int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
-{
-	int ret;
-
-	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
-		ret = report_syscall_entry(regs);
-		if (ret || (flags & _TIF_SYSCALL_EMU))
-			return NO_SYSCALL;
-	}
-
-	/* Do the secure computing after ptrace; failures should be fast. */
-	if (flags & _TIF_SECCOMP) {
-		ret = __secure_computing();
-		if (ret == -1)
-			return NO_SYSCALL;
-	}
-
-	/* Either of the above might have changed the syscall number */
-	syscall = syscall_get_nr(current, regs);
-
-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
-		trace_sys_enter(regs, syscall);
-
-		/*
-		 * Probes or BPF hooks in the tracepoint may have changed the
-		 * system call number as well.
-		 */
-		 syscall = syscall_get_nr(current, regs);
-	}
-
-	syscall_enter_audit(regs, syscall);
-
-	return ret ? : syscall;
-}
-
-static inline bool report_single_step(unsigned long flags)
-{
-	if (flags & _TIF_SYSCALL_EMU)
-		return false;
-
-	return flags & _TIF_SINGLESTEP;
-}
-
-static void syscall_exit_work(struct pt_regs *regs, unsigned long flags)
-{
-	bool step;
-
-	audit_syscall_exit(regs);
-
-	if (flags & _TIF_SYSCALL_TRACEPOINT)
-		trace_sys_exit(regs, syscall_get_return_value(current, regs));
-
-	step = report_single_step(flags);
-	if (step || flags & _TIF_SYSCALL_TRACE)
-		report_syscall_exit(regs);
-}
-
-void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
-{
-	unsigned long flags = read_thread_flags();
-
-	rseq_syscall(regs);
-
-	if (unlikely(flags & _TIF_SYSCALL_EXIT_WORK) || flags & _TIF_SINGLESTEP)
-		syscall_exit_work(regs, flags);
-}
-
 /*
  * SPSR_ELx bits which are always architecturally RES0 per ARM DDI 0487D.a.
  * We permit userspace to set SSBS (AArch64 bit 12, AArch32 bit 23) which is
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 1110eeb21f57..d3ec1892b3c7 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -8,8 +8,8 @@
 
 #include <linux/cache.h>
 #include <linux/compat.h>
+#include <linux/entry-common.h>
 #include <linux/errno.h>
-#include <linux/irq-entry-common.h>
 #include <linux/kernel.h>
 #include <linux/signal.h>
 #include <linux/freezer.h>
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 80b7fd67492e..c440ccb2af62 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -2,6 +2,7 @@
 
 #include <linux/compiler.h>
 #include <linux/context_tracking.h>
+#include <linux/entry-common.h>
 #include <linux/errno.h>
 #include <linux/nospec.h>
 #include <linux/ptrace.h>
@@ -68,6 +69,7 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 			   const syscall_fn_t syscall_table[])
 {
+	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	unsigned long flags = read_thread_flags();
 
 	regs->orig_x0 = regs->regs[0];
@@ -101,7 +103,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		return;
 	}
 
-	if (unlikely(flags & _TIF_SYSCALL_WORK)) {
+	if (unlikely(work & SYSCALL_WORK_ENTER)) {
 		/*
 		 * The de-facto standard way to skip a system call using ptrace
 		 * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
@@ -119,7 +121,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		 */
 		if (scno == NO_SYSCALL)
 			syscall_set_return_value(current, regs, -ENOSYS, 0);
-		scno = syscall_trace_enter(regs, scno, flags);
+		scno = syscall_trace_enter(regs, scno, work);
 		if (scno == NO_SYSCALL)
 			goto trace_exit;
 	}
-- 
2.34.1

[PATCH v10 14/16] arm64: Inline el0_svc_common()

[Jinjie Ruan]

After switch arm64 to Generic Entry, the compiler no longer inlines
el0_svc_common() into do_el0_svc(). So inline el0_svc_common() and it
has 1% performance uplift on perf bench basic syscall on kunpeng920
as below.

| Metric     | W/O this patch | With this patch | Change    |
| ---------- | -------------- | --------------- | --------- |
| Total time | 2.195 [sec]    | 2.171 [sec]     |  ↓1.1%   |
| usecs/op   | 0.219575       | 0.217192        |  ↓1.1%   |
| ops/sec    | 4,554,260      | 4,604,225       |  ↑1.1%    |

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/syscall.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index c440ccb2af62..45ceb8c4316a 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -66,8 +66,8 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 	choose_random_kstack_offset(get_random_u16());
 }
 
-static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
-			   const syscall_fn_t syscall_table[])
+static __always_inline void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
+					   const syscall_fn_t syscall_table[])
 {
 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	unsigned long flags = read_thread_flags();
-- 
2.34.1

[PATCH v10 15/16] entry: Inline syscall_exit_work() and syscall_trace_enter()

[Jinjie Ruan]

After switch arm64 to Generic Entry, a new hotspot syscall_exit_work()
appeared because syscall_exit_work() is not inlined, so inline
syscall_exit_work(). Also inline syscall_trace_enter() to align with
syscall_exit_work().

On v6.19-rc1 with audit on, inline both syscall_trace_enter() and
syscall_exit_work() has 4% performance uplift on perf bench basic
syscall on kunpeng920 as below:

    | Metric     | W/O this patch | With this patch | Change  |
    | ---------- | -------------- | --------------- | ------  |
    | Total time | 2.353 [sec]    | 2.264 [sec]     |  ↓3.8%  |
    | usecs/op   | 0.235374       | 0.226472        |  ↓3.8%  |
    | ops/sec    | 4,248,588      | 4,415,554       |  ↑3.9%  |

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 include/linux/entry-common.h         | 102 ++++++++++++++++++++++++++-
 kernel/entry/common.h                |   7 --
 kernel/entry/syscall-common.c        |  96 ++-----------------------
 kernel/entry/syscall_user_dispatch.c |   4 +-
 4 files changed, 106 insertions(+), 103 deletions(-)
 delete mode 100644 kernel/entry/common.h

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 17171e8873fc..ad61a13bf24f 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -2,6 +2,7 @@
 #ifndef __LINUX_ENTRYCOMMON_H
 #define __LINUX_ENTRYCOMMON_H
 
+#include <linux/audit.h>
 #include <linux/irq-entry-common.h>
 #include <linux/livepatch.h>
 #include <linux/ptrace.h>
@@ -64,7 +65,64 @@ static __always_inline int arch_ptrace_report_syscall_entry(struct pt_regs *regs
 }
 #endif
 
-long syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long work);
+static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
+{
+	if (unlikely(audit_context())) {
+		unsigned long args[6];
+
+		syscall_get_arguments(current, regs, args);
+		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
+	}
+}
+
+void __trace_sys_enter(struct pt_regs *regs, long syscall);
+bool syscall_user_dispatch(struct pt_regs *regs);
+
+static __always_inline long syscall_trace_enter(struct pt_regs *regs, long syscall,
+						unsigned long work)
+{
+	long ret = 0;
+
+	/*
+	 * Handle Syscall User Dispatch.  This must comes first, since
+	 * the ABI here can be something that doesn't make sense for
+	 * other syscall_work features.
+	 */
+	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
+		if (syscall_user_dispatch(regs))
+			return -1L;
+	}
+
+	/* Handle ptrace */
+	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
+		ret = arch_ptrace_report_syscall_entry(regs);
+		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
+			return -1L;
+	}
+
+	/* Do seccomp after ptrace, to catch any tracer changes. */
+	if (work & SYSCALL_WORK_SECCOMP) {
+		ret = __secure_computing();
+		if (ret == -1L)
+			return ret;
+	}
+
+	/* Either of the above might have changed the syscall number */
+	syscall = syscall_get_nr(current, regs);
+
+	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) {
+		__trace_sys_enter(regs, syscall);
+		/*
+		 * Probes or BPF hooks in the tracepoint may have changed the
+		 * system call number as well.
+		 */
+		syscall = syscall_get_nr(current, regs);
+	}
+
+	syscall_enter_audit(regs, syscall);
+
+	return ret ? : syscall;
+}
 
 /**
  * syscall_enter_from_user_mode_work - Check and handle work before invoking
@@ -131,6 +189,19 @@ static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, l
 	return ret;
 }
 
+/*
+ * If SYSCALL_EMU is set, then the only reason to report is when
+ * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
+ * instruction has been already reported in syscall_enter_from_user_mode().
+ */
+static __always_inline bool report_single_step(unsigned long work)
+{
+	if (work & SYSCALL_WORK_SYSCALL_EMU)
+		return false;
+
+	return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
+}
+
 /**
  * arch_ptrace_report_syscall_exit - Architecture specific
  *				     ptrace_report_syscall_exit.
@@ -151,6 +222,8 @@ static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs
 }
 #endif
 
+void __trace_sys_exit(struct pt_regs *regs, long ret);
+
 /**
  * syscall_exit_work - Handle work before returning to user mode
  * @regs:	Pointer to current pt_regs
@@ -158,7 +231,32 @@ static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs *regs
  *
  * Do one-time syscall specific work.
  */
-void syscall_exit_work(struct pt_regs *regs, unsigned long work);
+static __always_inline void syscall_exit_work(struct pt_regs *regs, unsigned long work)
+{
+	bool step;
+
+	/*
+	 * If the syscall was rolled back due to syscall user dispatching,
+	 * then the tracers below are not invoked for the same reason as
+	 * the entry side was not invoked in syscall_trace_enter(): The ABI
+	 * of these syscalls is unknown.
+	 */
+	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
+		if (unlikely(current->syscall_dispatch.on_dispatch)) {
+			current->syscall_dispatch.on_dispatch = false;
+			return;
+		}
+	}
+
+	audit_syscall_exit(regs);
+
+	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
+		__trace_sys_exit(regs, syscall_get_return_value(current, regs));
+
+	step = report_single_step(work);
+	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
+		arch_ptrace_report_syscall_exit(regs, step);
+}
 
 /*
  * Syscall specific exit to user mode preparation. Runs with interrupts
diff --git a/kernel/entry/common.h b/kernel/entry/common.h
deleted file mode 100644
index f6e6d02f07fe..000000000000
--- a/kernel/entry/common.h
+++ /dev/null
@@ -1,7 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _COMMON_H
-#define _COMMON_H
-
-bool syscall_user_dispatch(struct pt_regs *regs);
-
-#endif
diff --git a/kernel/entry/syscall-common.c b/kernel/entry/syscall-common.c
index fe38f84dfff3..10231d30405e 100644
--- a/kernel/entry/syscall-common.c
+++ b/kernel/entry/syscall-common.c
@@ -1,104 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0
 
-#include <linux/audit.h>
 #include <linux/entry-common.h>
-#include "common.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/syscalls.h>
 
-static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
+void __trace_sys_enter(struct pt_regs *regs, long syscall)
 {
-	if (unlikely(audit_context())) {
-		unsigned long args[6];
-
-		syscall_get_arguments(current, regs, args);
-		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
-	}
+	trace_sys_enter(regs, syscall);
 }
 
-long syscall_trace_enter(struct pt_regs *regs, long syscall,
-				unsigned long work)
+void __trace_sys_exit(struct pt_regs *regs, long ret)
 {
-	long ret = 0;
-
-	/*
-	 * Handle Syscall User Dispatch.  This must comes first, since
-	 * the ABI here can be something that doesn't make sense for
-	 * other syscall_work features.
-	 */
-	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
-		if (syscall_user_dispatch(regs))
-			return -1L;
-	}
-
-	/* Handle ptrace */
-	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
-		ret = arch_ptrace_report_syscall_entry(regs);
-		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
-			return -1L;
-	}
-
-	/* Do seccomp after ptrace, to catch any tracer changes. */
-	if (work & SYSCALL_WORK_SECCOMP) {
-		ret = __secure_computing();
-		if (ret == -1L)
-			return ret;
-	}
-
-	/* Either of the above might have changed the syscall number */
-	syscall = syscall_get_nr(current, regs);
-
-	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) {
-		trace_sys_enter(regs, syscall);
-		/*
-		 * Probes or BPF hooks in the tracepoint may have changed the
-		 * system call number as well.
-		 */
-		syscall = syscall_get_nr(current, regs);
-	}
-
-	syscall_enter_audit(regs, syscall);
-
-	return ret ? : syscall;
-}
-
-/*
- * If SYSCALL_EMU is set, then the only reason to report is when
- * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
- * instruction has been already reported in syscall_enter_from_user_mode().
- */
-static inline bool report_single_step(unsigned long work)
-{
-	if (work & SYSCALL_WORK_SYSCALL_EMU)
-		return false;
-
-	return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
-}
-
-void syscall_exit_work(struct pt_regs *regs, unsigned long work)
-{
-	bool step;
-
-	/*
-	 * If the syscall was rolled back due to syscall user dispatching,
-	 * then the tracers below are not invoked for the same reason as
-	 * the entry side was not invoked in syscall_trace_enter(): The ABI
-	 * of these syscalls is unknown.
-	 */
-	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
-		if (unlikely(current->syscall_dispatch.on_dispatch)) {
-			current->syscall_dispatch.on_dispatch = false;
-			return;
-		}
-	}
-
-	audit_syscall_exit(regs);
-
-	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
-		trace_sys_exit(regs, syscall_get_return_value(current, regs));
-
-	step = report_single_step(work);
-	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
-		arch_ptrace_report_syscall_exit(regs, step);
+	trace_sys_exit(regs, ret);
 }
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index a9055eccb27e..d89dffcc2d64 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -2,6 +2,8 @@
 /*
  * Copyright (C) 2020 Collabora Ltd.
  */
+
+#include <linux/entry-common.h>
 #include <linux/sched.h>
 #include <linux/prctl.h>
 #include <linux/ptrace.h>
@@ -15,8 +17,6 @@
 
 #include <asm/syscall.h>
 
-#include "common.h"
-
 static void trigger_sigsys(struct pt_regs *regs)
 {
 	struct kernel_siginfo info;
-- 
2.34.1

[PATCH v10 16/16] selftests: sud_test: Support aarch64

[Jinjie Ruan]

From: kemal <kmal@cock.li>

Support aarch64 to test "Syscall User Dispatch" with sud_test
selftest testcase.

Signed-off-by: kemal <kmal@cock.li>
---
 tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c | 2 +-
 tools/testing/selftests/syscall_user_dispatch/sud_test.c      | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
index 073a03702ff5..6059abe75cb3 100644
--- a/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
+++ b/tools/testing/selftests/syscall_user_dispatch/sud_benchmark.c
@@ -41,7 +41,7 @@
  * out of the box, but don't enable them until they support syscall user
  * dispatch.
  */
-#if defined(__x86_64__) || defined(__i386__)
+#if defined(__x86_64__) || defined(__i386__) || defined(__aarch64__)
 #define TEST_BLOCKED_RETURN
 #endif
 
diff --git a/tools/testing/selftests/syscall_user_dispatch/sud_test.c b/tools/testing/selftests/syscall_user_dispatch/sud_test.c
index b855c6000287..3ffea2f4a66d 100644
--- a/tools/testing/selftests/syscall_user_dispatch/sud_test.c
+++ b/tools/testing/selftests/syscall_user_dispatch/sud_test.c
@@ -192,6 +192,10 @@ static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
 	((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A0] =
 			((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A7];
 #endif
+#ifdef __aarch64__
+	((ucontext_t *)ucontext)->uc_mcontext.regs[0] = (unsigned int)
+			((ucontext_t *)ucontext)->uc_mcontext.regs[8];
+#endif
 }
 
 int setup_sigsys_handler(void)
-- 
2.34.1

Re: [PATCH v10 11/16] entry: Split syscall_exit_to_user_mode_work() for arch reuse

[Kevin Brodsky]

On 22/12/2025 12:47, Jinjie Ruan wrote:
> In the generic entry code, the beginning of
> syscall_exit_to_user_mode_work() can be reused on arm64 so it makes
> sense to split it.
>
> In preparation for moving arm64 over to the generic entry
> code, split out syscall_exit_to_user_mode_work_prepare() helper from
> syscall_exit_to_user_mode_work().
>
> No functional changes.
>
> Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  include/linux/entry-common.h | 35 ++++++++++++++++++++++-------------
>  1 file changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index 87efb38b7081..0de0e60630e1 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -121,20 +121,11 @@ static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, l
>   */
>  void syscall_exit_work(struct pt_regs *regs, unsigned long work);
>  
> -/**
> - * syscall_exit_to_user_mode_work - Handle work before returning to user mode
> - * @regs:	Pointer to currents pt_regs
> - *
> - * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
> - * exit_to_user_mode() to perform the final transition to user mode.
> - *
> - * Calling convention is the same as for syscall_exit_to_user_mode() and it
> - * returns with all work handled and interrupts disabled. The caller must
> - * invoke exit_to_user_mode() before actually switching to user mode to
> - * make the final state transitions. Interrupts must stay disabled between
> - * return from this function and the invocation of exit_to_user_mode().
> +/*
> + * Syscall specific exit to user mode preparation. Runs with interrupts
> + * enabled.
>   */
> -static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
> +static __always_inline void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
>  {
>  	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
>  	unsigned long nr = syscall_get_nr(current, regs);
> @@ -155,6 +146,24 @@ static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
>  	 */
>  	if (unlikely(work & SYSCALL_WORK_EXIT))
>  		syscall_exit_work(regs, work);
> +}
> +
> +/**
> + * syscall_exit_to_user_mode_work - Handle work before returning to user mode
> + * @regs:	Pointer to currents pt_regs
> + *
> + * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
> + * exit_to_user_mode() to perform the final transition to user mode.
> + *
> + * Calling convention is the same as for syscall_exit_to_user_mode() and it
> + * returns with all work handled and interrupts disabled. The caller must
> + * invoke exit_to_user_mode() before actually switching to user mode to
> + * make the final state transitions. Interrupts must stay disabled between
> + * return from this function and the invocation of exit_to_user_mode().
> + */
> +static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
> +{
> +	syscall_exit_to_user_mode_work_prepare(regs);

The naming is getting awfully confusing, with the separate introduction
of syscall_exit_to_user_mode_prepare().

Having had a closer look, do we really need
syscall_exit_to_user_mode_work() as it currently stands? Nothing calls
it except the generic syscall_exit_to_user_mode(). Which makes me think:
how about moving the two lines below into syscall_exit_to_user_mode()
instead of creating a new helper? IOW:

@@ -155,8 +155,6 @@ static __always_inline void
syscall_exit_to_user_mode_work(struct pt_regs *regs)
      */
     if (unlikely(work & SYSCALL_WORK_EXIT))
         syscall_exit_work(regs, work);
-    local_irq_disable_exit_to_user();
-    syscall_exit_to_user_mode_prepare(regs);
 }
 
 /**
@@ -192,6 +190,8 @@ static __always_inline void
syscall_exit_to_user_mode(struct pt_regs *regs)
 {
     instrumentation_begin();
     syscall_exit_to_user_mode_work(regs);
+    local_irq_disable_exit_to_user();
+    syscall_exit_to_user_mode_prepare(regs);
     instrumentation_end();
     exit_to_user_mode();
 }

- Kevin

>  	local_irq_disable_exit_to_user();
>  	syscall_exit_to_user_mode_prepare(regs);
>  }

Re: [PATCH v10 11/16] entry: Split syscall_exit_to_user_mode_work() for arch reuse

[Jinjie Ruan]

On 2025/12/30 2:03, Kevin Brodsky wrote:
> On 22/12/2025 12:47, Jinjie Ruan wrote:
>> In the generic entry code, the beginning of
>> syscall_exit_to_user_mode_work() can be reused on arm64 so it makes
>> sense to split it.
>>
>> In preparation for moving arm64 over to the generic entry
>> code, split out syscall_exit_to_user_mode_work_prepare() helper from
>> syscall_exit_to_user_mode_work().
>>
>> No functional changes.
>>
>> Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
>> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
>> ---
>>  include/linux/entry-common.h | 35 ++++++++++++++++++++++-------------
>>  1 file changed, 22 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
>> index 87efb38b7081..0de0e60630e1 100644
>> --- a/include/linux/entry-common.h
>> +++ b/include/linux/entry-common.h
>> @@ -121,20 +121,11 @@ static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, l
>>   */
>>  void syscall_exit_work(struct pt_regs *regs, unsigned long work);
>>  
>> -/**
>> - * syscall_exit_to_user_mode_work - Handle work before returning to user mode
>> - * @regs:	Pointer to currents pt_regs
>> - *
>> - * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
>> - * exit_to_user_mode() to perform the final transition to user mode.
>> - *
>> - * Calling convention is the same as for syscall_exit_to_user_mode() and it
>> - * returns with all work handled and interrupts disabled. The caller must
>> - * invoke exit_to_user_mode() before actually switching to user mode to
>> - * make the final state transitions. Interrupts must stay disabled between
>> - * return from this function and the invocation of exit_to_user_mode().
>> +/*
>> + * Syscall specific exit to user mode preparation. Runs with interrupts
>> + * enabled.
>>   */
>> -static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
>> +static __always_inline void syscall_exit_to_user_mode_work_prepare(struct pt_regs *regs)
>>  {
>>  	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
>>  	unsigned long nr = syscall_get_nr(current, regs);
>> @@ -155,6 +146,24 @@ static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
>>  	 */
>>  	if (unlikely(work & SYSCALL_WORK_EXIT))
>>  		syscall_exit_work(regs, work);
>> +}
>> +
>> +/**
>> + * syscall_exit_to_user_mode_work - Handle work before returning to user mode
>> + * @regs:	Pointer to currents pt_regs
>> + *
>> + * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
>> + * exit_to_user_mode() to perform the final transition to user mode.
>> + *
>> + * Calling convention is the same as for syscall_exit_to_user_mode() and it
>> + * returns with all work handled and interrupts disabled. The caller must
>> + * invoke exit_to_user_mode() before actually switching to user mode to
>> + * make the final state transitions. Interrupts must stay disabled between
>> + * return from this function and the invocation of exit_to_user_mode().
>> + */
>> +static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
>> +{
>> +	syscall_exit_to_user_mode_work_prepare(regs);
> 
> The naming is getting awfully confusing, with the separate introduction
> of syscall_exit_to_user_mode_prepare().
> 
> Having had a closer look, do we really need
> syscall_exit_to_user_mode_work() as it currently stands? Nothing calls
> it except the generic syscall_exit_to_user_mode(). Which makes me think:
> how about moving the two lines below into syscall_exit_to_user_mode()
> instead of creating a new helper? IOW:

It looks fine to me, this will make the change less. The comment also
need to be updated.

> 
> @@ -155,8 +155,6 @@ static __always_inline void
> syscall_exit_to_user_mode_work(struct pt_regs *regs)
>       */
>      if (unlikely(work & SYSCALL_WORK_EXIT))
>          syscall_exit_work(regs, work);
> -    local_irq_disable_exit_to_user();
> -    syscall_exit_to_user_mode_prepare(regs);
>  }
>  
>  /**
> @@ -192,6 +190,8 @@ static __always_inline void
> syscall_exit_to_user_mode(struct pt_regs *regs)
>  {
>      instrumentation_begin();
>      syscall_exit_to_user_mode_work(regs);
> +    local_irq_disable_exit_to_user();
> +    syscall_exit_to_user_mode_prepare(regs);
>      instrumentation_end();
>      exit_to_user_mode();
>  }
> 
> - Kevin
> 
>>  	local_irq_disable_exit_to_user();
>>  	syscall_exit_to_user_mode_prepare(regs);
>>  }
> 

Re: [PATCH v10 00/16] arm64: entry: Convert to Generic Entry

[Jinjie Ruan]

On 2025/12/22 19:47, Jinjie Ruan wrote:
> Currently, x86, Riscv, Loongarch use the Generic Entry which makes
> maintainers' work easier and codes more elegant. arm64 has already
> successfully switched to the Generic IRQ Entry in commit
> b3cf07851b6c ("arm64: entry: Switch to generic IRQ entry"), it is
> time to completely convert arm64 to Generic Entry.
> 
> The goal is to bring arm64 in line with other architectures that already
> use the generic entry infrastructure, reducing duplicated code and
> making it easier to share future changes in entry/exit paths, such as
> "Syscall User Dispatch".

Gentle ping.

Hi Catalin, Will and everyone,if there is any new feedback or if the
preparatory refactor parts are mature enough to be considered for merging.

Please let me know if any further changes are needed, or if I should
respin with a different approach. I'm happy to address any additional
comments whenever you have time.

> 
> This patch set is rebased on v6.19-rc1. And the performance was measured
> on Kunpeng 920 using "perf bench basic syscall" with "arm64.nopauth
> selinux=0 audit=1".
> 
> After switch to Generic Entry, the performance are below:
> 
> | Metric     | W/O Generic Framework | With Generic Framework | Change |
> | ---------- | --------------------- | ---------------------- | ------ |
> | Total time | 2.487 [sec]           |  2.393[sec]            | ↓3.8% |
> | usecs/op   | 0.248780              |  0.239361              | ↓3.8% |
> | ops/sec    | 4,019,620             |  4,177,789             | ↑3.9% |
> 
> Compared to earlier with arch specific handling, the performance improved
> by approximately 3.9%.
> 
> On the basis of optimizing syscall_get_arguments()[1], el0_svc_common()
> and syscall_exit_work(), the performance are below:
> 
> | Metric     | W/O Generic Entry | With Generic Entry opt| Change |
> | ---------- | ----------------- | ------------------    | ------ |
> | Total time | 2.487 [sec]       | 2.264 [sec]           | ↓9.0% |
> | usecs/op   | 0.248780          | 0.226481              | ↓9.0% |
> | ops/sec    | 4,019,620         | 4,415,383             | ↑9.8% |
> 
> Therefore, after the optimization, ARM64 System Call performance improved
> by approximately 9%.
> 
> It was tested ok with following test cases on kunpeng920 and QEMU
> virt platform:
>  - Perf tests.
>  - Different `dynamic preempt` mode switch.
>  - Pseudo NMI tests.
>  - Stress-ng CPU stress test.
>  - Hackbench stress test.
>  - MTE test case in Documentation/arch/arm64/memory-tagging-extension.rst
>    and all test cases in tools/testing/selftests/arm64/mte/*.
>  - "sud" selftest testcase.
>  - get_set_sud, get_syscall_info, set_syscall_info, peeksiginfo
>    in tools/testing/selftests/ptrace.
>  - breakpoint_test_arm64 in selftests/breakpoints.
>  - syscall-abi and ptrace in tools/testing/selftests/arm64/abi
>  - fp-ptrace, sve-ptrace, za-ptrace in selftests/arm64/fp.
>  - vdso_test_getrandom in tools/testing/selftests/vDSO
>  - Strace tests.
> 
> The test QEMU configuration is as follows:
> 
> 	qemu-system-aarch64 \
> 		-M virt,gic-version=3,virtualization=on,mte=on \
> 		-cpu max,pauth-impdef=on \
> 		-kernel Image \
> 		-smp 8,sockets=1,cores=4,threads=2 \
> 		-m 512m \
> 		-nographic \
> 		-no-reboot \
> 		-device virtio-rng-pci \
> 		-append "root=/dev/vda rw console=ttyAMA0 kgdboc=ttyAMA0,115200 \
> 			earlycon preempt=voluntary irqchip.gicv3_pseudo_nmi=1" \
> 		-drive if=none,file=images/rootfs.ext4,format=raw,id=hd0 \
> 		-device virtio-blk-device,drive=hd0 \
> 
> [1]: https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm/+/89bf683c9507c280e20c3e17b4ea15e19696ed63%5E%21/#F0
> 
> Changes in v10:
> - Rebased on v6.19-rc1, rename syscall_exit_to_user_mode_prepare() to
>   syscall_exit_to_user_mode_work_prepare() to avoid conflict.
> - Also inline syscall_trace_enter().
> - Support aarch64 for sud_benchmark.
> - Update and correct the commit message.
> - Add Reviewed-by.
> - Link to v9: https://lore.kernel.org/all/20251204082123.2792067-1-ruanjinjie@huawei.com/
> 
> Changes in v9:
> - Move "Return early for ptrace_report_syscall_entry() error" patch ahead
>   to make it not introduce a regression.
> - Not check _TIF_SECCOMP/SYSCALL_EMU for syscall_exit_work() in
>   a separate patch.
> - Do not report_syscall_exit() for PTRACE_SYSEMU_SINGLESTEP in a separate
>   patch.
> - Add two performance patch to improve the arm64 performance.
> - Add Reviewed-by.
> - Link to v8: https://lore.kernel.org/all/20251126071446.3234218-1-ruanjinjie@huawei.com/
> 
> Changes in v8:
> - Rename "report_syscall_enter()" to "report_syscall_entry()".
> - Add ptrace_save_reg() to avoid duplication.
> - Remove unused _TIF_WORK_MASK in a standalone patch.
> - Align syscall_trace_enter() return value with the generic version.
> - Use "scno" instead of regs->syscallno in el0_svc_common().
> - Move rseq_syscall() ahead in a standalone patch to clarify it clearly.
> - Rename "syscall_trace_exit()" to "syscall_exit_work()".
> - Keep the goto in el0_svc_common().
> - No argument was passed to __secure_computing() and check -1 not -1L.
> - Remove "Add has_syscall_work() helper" patch.
> - Move "Add syscall_exit_to_user_mode_prepare() helper" patch later.
> - Add miss header for asm/entry-common.h.
> - Update the implementation of arch_syscall_is_vdso_sigreturn().
> - Add "ARCH_SYSCALL_WORK_EXIT" to be defined as "SECCOMP | SYSCALL_EMU"
>   to keep the behaviour unchanged.
> - Add more testcases test.
> - Add Reviewed-by.
> - Update the commit message.
> - Link to v7: https://lore.kernel.org/all/20251117133048.53182-1-ruanjinjie@huawei.com/
> 
> Chanegs in v7:
> - Support "Syscall User Dispatch" by implementing
>   arch_syscall_is_vdso_sigreturn() as kemal suggested.
> - Add aarch64 support for "sud" selftest testcase, which tested ok with
>   the patch series.
> - Fix the kernel test robot warning for arch_ptrace_report_syscall_entry()
>   and arch_ptrace_report_syscall_exit() in asm/entry-common.h.
> - Add perf syscall performance test.
> - Link to v6: https://lore.kernel.org/all/20250916082611.2972008-1-ruanjinjie@huawei.com/
> 
> Changes in v6:
> - Rebased on v6.17-rc5-next as arm64 generic irq entry has merged.
> - Update the commit message.
> - Link to v5: https://lore.kernel.org/all/20241206101744.4161990-1-ruanjinjie@huawei.com/
> 
> Changes in v5:
> - Not change arm32 and keep inerrupts_enabled() macro for gicv3 driver.
> - Move irqentry_state definition into arch/arm64/kernel/entry-common.c.
> - Avoid removing the __enter_from_*() and __exit_to_*() wrappers.
> - Update "irqentry_state_t ret/irq_state" to "state"
>   to keep it consistently.
> - Use generic irq entry header for PREEMPT_DYNAMIC after split
>   the generic entry.
> - Also refactor the ARM64 syscall code.
> - Introduce arch_ptrace_report_syscall_entry/exit(), instead of
>   arch_pre/post_report_syscall_entry/exit() to simplify code.
> - Make the syscall patches clear separation.
> - Update the commit message.
> - Link to v4: https://lore.kernel.org/all/20241025100700.3714552-1-ruanjinjie@huawei.com/
> 
> Changes in v4:
> - Rework/cleanup split into a few patches as Mark suggested.
> - Replace interrupts_enabled() macro with regs_irqs_disabled(), instead
>   of left it here.
> - Remove rcu and lockdep state in pt_regs by using temporary
>   irqentry_state_t as Mark suggested.
> - Remove some unnecessary intermediate functions to make it clear.
> - Rework preempt irq and PREEMPT_DYNAMIC code
>   to make the switch more clear.
> - arch_prepare_*_entry/exit() -> arch_pre_*_entry/exit().
> - Expand the arch functions comment.
> - Make arch functions closer to its caller.
> - Declare saved_reg in for block.
> - Remove arch_exit_to_kernel_mode_prepare(), arch_enter_from_kernel_mode().
> - Adjust "Add few arch functions to use generic entry" patch to be
>   the penultimate.
> - Update the commit message.
> - Add suggested-by.
> - Link to v3: https://lore.kernel.org/all/20240629085601.470241-1-ruanjinjie@huawei.com/
> 
> Changes in v3:
> - Test the MTE test cases.
> - Handle forget_syscall() in arch_post_report_syscall_entry()
> - Make the arch funcs not use __weak as Thomas suggested, so move
>   the arch funcs to entry-common.h, and make arch_forget_syscall() folded
>   in arch_post_report_syscall_entry() as suggested.
> - Move report_single_step() to thread_info.h for arm64
> - Change __always_inline() to inline, add inline for the other arch funcs.
> - Remove unused signal.h for entry-common.h.
> - Add Suggested-by.
> - Update the commit message.
> 
> Changes in v2:
> - Add tested-by.
> - Fix a bug that not call arch_post_report_syscall_entry() in
>   syscall_trace_enter() if ptrace_report_syscall_entry() return not zero.
> - Refactor report_syscall().
> - Add comment for arch_prepare_report_syscall_exit().
> - Adjust entry-common.h header file inclusion to alphabetical order.
> - Update the commit message.
> 
> Jinjie Ruan (15):
>   arm64: Remove unused _TIF_WORK_MASK
>   arm64/ptrace: Split report_syscall()
>   arm64/ptrace: Return early for ptrace_report_syscall_entry() error
>   arm64/ptrace: Refactor syscall_trace_enter/exit()
>   arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()
>   arm64: syscall: Rework el0_svc_common()
>   arm64/ptrace: Not check _TIF_SECCOMP/SYSCALL_EMU for
>     syscall_exit_work()
>   arm64/ptrace: Do not report_syscall_exit() for
>     PTRACE_SYSEMU_SINGLESTEP
>   arm64/ptrace: Expand secure_computing() in place
>   arm64/ptrace: Use syscall_get_arguments() helper
>   entry: Split syscall_exit_to_user_mode_work() for arch reuse
>   entry: Add arch_ptrace_report_syscall_entry/exit()
>   arm64: entry: Convert to generic entry
>   arm64: Inline el0_svc_common()
>   entry: Inline syscall_exit_work() and syscall_trace_enter()
> 
> kemal (1):
>   selftests: sud_test: Support aarch64
> 
>  arch/arm64/Kconfig                            |   2 +-
>  arch/arm64/include/asm/entry-common.h         |  76 ++++++++
>  arch/arm64/include/asm/syscall.h              |  19 +-
>  arch/arm64/include/asm/thread_info.h          |  22 +--
>  arch/arm64/kernel/debug-monitors.c            |   7 +
>  arch/arm64/kernel/ptrace.c                    |  94 ----------
>  arch/arm64/kernel/signal.c                    |   2 +-
>  arch/arm64/kernel/syscall.c                   |  29 +--
>  include/linux/entry-common.h                  | 176 ++++++++++++++++--
>  kernel/entry/common.h                         |   7 -
>  kernel/entry/syscall-common.c                 |  96 +---------
>  kernel/entry/syscall_user_dispatch.c          |   4 +-
>  .../syscall_user_dispatch/sud_benchmark.c     |   2 +-
>  .../syscall_user_dispatch/sud_test.c          |   4 +
>  14 files changed, 282 insertions(+), 258 deletions(-)
>  delete mode 100644 kernel/entry/common.h
> 

Re: [PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Will Deacon]

On Mon, Dec 22, 2025 at 07:47:25PM +0800, Jinjie Ruan wrote:
> The generic syscall entry code has the following form, which use
> the input syscall work flag and syscall number:
> 
> | syscall_trace_enter(struct pt_regs *regs, long syscall,
> |		      unsigned long work)
> |
> | syscall_exit_work(struct pt_regs *regs, unsigned long work)
> 
> In preparation for moving arm64 over to the generic entry code,
> refactor syscall_trace_enter/exit() to also pass thread flags, and
> get syscall number by syscall_get_nr() helper.
> 
> No functional changes.
> 
> Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  arch/arm64/include/asm/syscall.h |  4 ++--
>  arch/arm64/kernel/ptrace.c       | 25 ++++++++++++++++---------
>  arch/arm64/kernel/syscall.c      |  5 +++--
>  3 files changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
> index 5e4c7fc44f73..cef1d9ce6e1b 100644
> --- a/arch/arm64/include/asm/syscall.h
> +++ b/arch/arm64/include/asm/syscall.h
> @@ -120,7 +120,7 @@ static inline int syscall_get_arch(struct task_struct *task)
>  	return AUDIT_ARCH_AARCH64;
>  }
>  
> -int syscall_trace_enter(struct pt_regs *regs);
> -void syscall_trace_exit(struct pt_regs *regs);
> +int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
> +void syscall_trace_exit(struct pt_regs *regs, unsigned long flags);
>  
>  #endif	/* __ASM_SYSCALL_H */
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index f333791ffba6..79762ff33945 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -2407,9 +2407,8 @@ static void report_syscall_exit(struct pt_regs *regs)
>  	}
>  }
>  
> -int syscall_trace_enter(struct pt_regs *regs)
> +int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
>  {
> -	unsigned long flags = read_thread_flags();
>  	int ret;
>  
>  	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
> @@ -2422,19 +2421,27 @@ int syscall_trace_enter(struct pt_regs *regs)
>  	if (secure_computing() == -1)
>  		return NO_SYSCALL;
>  
> -	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> -		trace_sys_enter(regs, regs->syscallno);
> +	/* Either of the above might have changed the syscall number */
> +	syscall = syscall_get_nr(current, regs);

I understand that you're gradually making the arch code more similar to
the core code so that we can switch over to it, but I'm struggling to
understand why syscall_trace_enter() takes the 'syscall' argument.

Even the core code just seems to use it as a local variable, which it
overrides before it ever uses it. What am I missing?

Will

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Will Deacon]

On Mon, Dec 22, 2025 at 07:47:26PM +0800, Jinjie Ruan wrote:
> commit a9f3a74a29af ("entry: Provide generic syscall exit function")
> introduce generic syscall exit function and call rseq_syscall()
> before audit_syscall_exit() and arch_syscall_exit_tracehook().
> 
> And commit b74406f37737 ("arm: Add syscall detection for restartable
> sequences") add rseq support for arm32, which also call rseq_syscall()
> before audit_syscall_exit() and tracehook_report_syscall().
> 
> However, commit 409d5db49867c ("arm64: rseq: Implement backend rseq
> calls and select HAVE_RSEQ") implement arm64 rseq and call
> rseq_syscall() after audit_syscall_exit() and tracehook_report_syscall().
> 
> So compared to the generic entry and arm32 code, arm64 terminates
> the process a bit later if the syscall is issued within
> a restartable sequence.

Given that signals are processed until later, is this actually true?

> But as commit b74406f37737 ("arm: Add syscall detection for restartable
> sequences") said, syscalls are not allowed inside restartable sequences,
> so should call rseq_syscall() at the very beginning of system call
> exiting path for CONFIG_DEBUG_RSEQ=y kernel. This could help us to detect
> whether there is a syscall issued inside restartable sequences.
> 
> It makes sense to raise SIGSEGV via rseq_syscall() before auditing
> and ptrace syscall exit, because this guarantees that the process is
> already in an error state with SIGSEGV pending when those later steps
> run. Although it makes no practical difference to signal delivery (signals
> are processed at the very end in arm64_exit_to_user_mode()), the ordering
> is more logical: detect and flag the error first, then proceed with
> the remaining work.
> 
> To make it more reasonable and in preparation for moving arm64 over to
> the generic entry code, move rseq_syscall() ahead before
> audit_syscall_exit().

I've been struggling a bit to see how this helps to align with the
generic code. I'm also concerned that rseq_debug_update_user_cs()
operates on instruction_pointer(regs) which is something that can be
chaned by ptrace.

So, I'm not saying this is wrong, but it feels like a user-visible
change that needs better justification.

Will

Re: [PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Jinjie Ruan]

On 2026/1/27 0:42, Will Deacon wrote:
> On Mon, Dec 22, 2025 at 07:47:25PM +0800, Jinjie Ruan wrote:
>> The generic syscall entry code has the following form, which use
>> the input syscall work flag and syscall number:
>>
>> | syscall_trace_enter(struct pt_regs *regs, long syscall,
>> |		      unsigned long work)
>> |
>> | syscall_exit_work(struct pt_regs *regs, unsigned long work)
>>
>> In preparation for moving arm64 over to the generic entry code,
>> refactor syscall_trace_enter/exit() to also pass thread flags, and
>> get syscall number by syscall_get_nr() helper.
>>
>> No functional changes.
>>
>> Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
>> ---
>>  arch/arm64/include/asm/syscall.h |  4 ++--
>>  arch/arm64/kernel/ptrace.c       | 25 ++++++++++++++++---------
>>  arch/arm64/kernel/syscall.c      |  5 +++--
>>  3 files changed, 21 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
>> index 5e4c7fc44f73..cef1d9ce6e1b 100644
>> --- a/arch/arm64/include/asm/syscall.h
>> +++ b/arch/arm64/include/asm/syscall.h
>> @@ -120,7 +120,7 @@ static inline int syscall_get_arch(struct task_struct *task)
>>  	return AUDIT_ARCH_AARCH64;
>>  }
>>  
>> -int syscall_trace_enter(struct pt_regs *regs);
>> -void syscall_trace_exit(struct pt_regs *regs);
>> +int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
>> +void syscall_trace_exit(struct pt_regs *regs, unsigned long flags);
>>  
>>  #endif	/* __ASM_SYSCALL_H */
>> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
>> index f333791ffba6..79762ff33945 100644
>> --- a/arch/arm64/kernel/ptrace.c
>> +++ b/arch/arm64/kernel/ptrace.c
>> @@ -2407,9 +2407,8 @@ static void report_syscall_exit(struct pt_regs *regs)
>>  	}
>>  }
>>  
>> -int syscall_trace_enter(struct pt_regs *regs)
>> +int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
>>  {
>> -	unsigned long flags = read_thread_flags();
>>  	int ret;
>>  
>>  	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
>> @@ -2422,19 +2421,27 @@ int syscall_trace_enter(struct pt_regs *regs)
>>  	if (secure_computing() == -1)
>>  		return NO_SYSCALL;
>>  
>> -	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
>> -		trace_sys_enter(regs, regs->syscallno);
>> +	/* Either of the above might have changed the syscall number */
>> +	syscall = syscall_get_nr(current, regs);
> 
> I understand that you're gradually making the arch code more similar to
> the core code so that we can switch over to it, but I'm struggling to
> understand why syscall_trace_enter() takes the 'syscall' argument.
> 
> Even the core code just seems to use it as a local variable, which it
> overrides before it ever uses it. What am I missing?

Hi,

You're absolutely right. The 'syscall' parameter is indeed treated as a
local variable and gets overridden before any real use. Should we
refactor to remove the parameter entirely in generic entry?

Regards,
Jinjie

> 
> Will
> 

Re: [PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Kevin Brodsky]

On 27/01/2026 04:01, Jinjie Ruan wrote:
>> I understand that you're gradually making the arch code more similar to
>> the core code so that we can switch over to it, but I'm struggling to
>> understand why syscall_trace_enter() takes the 'syscall' argument.
>>
>> Even the core code just seems to use it as a local variable, which it
>> overrides before it ever uses it. What am I missing?
> Hi,
>
> You're absolutely right. The 'syscall' parameter is indeed treated as a
> local variable and gets overridden before any real use. Should we
> refactor to remove the parameter entirely in generic entry?

I noticed this as well, removing it from the generic function would make
sense. AFAICT that removal could be propagated quite far in fact:
syscall_enter_from_user_mode_work(), syscall_enter_from_user_mode(),
even arch implementation (do_syscall_64() on x86).

- Kevin

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Kevin Brodsky]

On 26/01/2026 20:02, Will Deacon wrote:
> On Mon, Dec 22, 2025 at 07:47:26PM +0800, Jinjie Ruan wrote:
>> [...]
>>
>> To make it more reasonable and in preparation for moving arm64 over to
>> the generic entry code, move rseq_syscall() ahead before
>> audit_syscall_exit().
> I've been struggling a bit to see how this helps to align with the
> generic code.

rseq_syscall(), or rather rseq_debug_syscall_return() since eaa9088d568c
("rseq: Use static branch for syscall exit debug when
GENERIC_IRQ_ENTRY=y"), is called first in the generic
syscall_exit_to_user_mode_work(), so the aim of that patch is to align
the order of calls with generic entry.

>  I'm also concerned that rseq_debug_update_user_cs()
> operates on instruction_pointer(regs) which is something that can be
> chaned by ptrace.

Isn't that true regardless of where rseq_syscall() is called on the
syscall exit path, though?

> So, I'm not saying this is wrong, but it feels like a user-visible
> change that needs better justification.

This seems to hang on whether the force_sig(SIGSEGV) that rseq_syscall()
might issue interacts in any way with the tracing calls. My feeling is
that it doesn't, but I haven't confirmed it. Worth noting this is only
relevant if rseq debugging is enabled, so any potential user-visible
effect is limited.

- Kevin

Re: [PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Jinjie Ruan]

On 2026/1/27 17:43, Kevin Brodsky wrote:
> On 27/01/2026 04:01, Jinjie Ruan wrote:
>>> I understand that you're gradually making the arch code more similar to
>>> the core code so that we can switch over to it, but I'm struggling to
>>> understand why syscall_trace_enter() takes the 'syscall' argument.
>>>
>>> Even the core code just seems to use it as a local variable, which it
>>> overrides before it ever uses it. What am I missing?
>> Hi,
>>
>> You're absolutely right. The 'syscall' parameter is indeed treated as a
>> local variable and gets overridden before any real use. Should we
>> refactor to remove the parameter entirely in generic entry?
> 
> I noticed this as well, removing it from the generic function would make
> sense. AFAICT that removal could be propagated quite far in fact:
> syscall_enter_from_user_mode_work(), syscall_enter_from_user_mode(),
> even arch implementation (do_syscall_64() on x86).

Not really, it is the default return value of
syscall_enter_from_user_mode_work() as below, so we only need to remove
the parameter in syscall_trace_enter().

static __always_inline long syscall_enter_from_user_mode_work(struct
pt_regs *regs, long syscall)
{
	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);

       if (work & SYSCALL_WORK_ENTER)
            syscall = syscall_trace_enter(regs, work);

      return syscall;
}


> 
> - Kevin
> 

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Jinjie Ruan]

On 2026/1/27 17:44, Kevin Brodsky wrote:
> On 26/01/2026 20:02, Will Deacon wrote:
>> On Mon, Dec 22, 2025 at 07:47:26PM +0800, Jinjie Ruan wrote:
>>> [...]
>>>
>>> To make it more reasonable and in preparation for moving arm64 over to
>>> the generic entry code, move rseq_syscall() ahead before
>>> audit_syscall_exit().
>> I've been struggling a bit to see how this helps to align with the
>> generic code.
> 
> rseq_syscall(), or rather rseq_debug_syscall_return() since eaa9088d568c
> ("rseq: Use static branch for syscall exit debug when
> GENERIC_IRQ_ENTRY=y"), is called first in the generic
> syscall_exit_to_user_mode_work(), so the aim of that patch is to align
> the order of calls with generic entry.
> 
>>  I'm also concerned that rseq_debug_update_user_cs()
>> operates on instruction_pointer(regs) which is something that can be
>> chaned by ptrace.
> 
> Isn't that true regardless of where rseq_syscall() is called on the
> syscall exit path, though?

My understanding is that if instruction_pointer(regs) is hijacked and
modified via ptrace at the syscall exit (ptrace_report_syscall_exit()),
this modification will not be observed by rseq. Specifically, in the
generic entry syscall exit path, rseq_syscall() is unable to detect such
a PC modification.


Regards,
Jinjie

> 
>> So, I'm not saying this is wrong, but it feels like a user-visible
>> change that needs better justification.
> 
> This seems to hang on whether the force_sig(SIGSEGV) that rseq_syscall()
> might issue interacts in any way with the tracing calls. My feeling is
> that it doesn't, but I haven't confirmed it. Worth noting this is only
> relevant if rseq debugging is enabled, so any potential user-visible
> effect is limited.
> 
> - Kevin
> 

Re: [PATCH v10 00/16] arm64: entry: Convert to Generic Entry

[Will Deacon]

On Mon, 22 Dec 2025 19:47:21 +0800, Jinjie Ruan wrote:
> Currently, x86, Riscv, Loongarch use the Generic Entry which makes
> maintainers' work easier and codes more elegant. arm64 has already
> successfully switched to the Generic IRQ Entry in commit
> b3cf07851b6c ("arm64: entry: Switch to generic IRQ entry"), it is
> time to completely convert arm64 to Generic Entry.
> 
> The goal is to bring arm64 in line with other architectures that already
> use the generic entry infrastructure, reducing duplicated code and
> making it easier to share future changes in entry/exit paths, such as
> "Syscall User Dispatch".
> 
> [...]

Applied first three to arm64 (for-next/entry), thanks!

[01/16] arm64: Remove unused _TIF_WORK_MASK
        https://git.kernel.org/arm64/c/e7e7afdc7c14
[02/16] arm64/ptrace: Split report_syscall()
        https://git.kernel.org/arm64/c/741a9000173a
[03/16] arm64/ptrace: Return early for ptrace_report_syscall_entry() error
        https://git.kernel.org/arm64/c/a3386301667e

I know it's a drop in the ocean, but they look good to me and it saves
you from having to carry them over.

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

Re: [PATCH v10 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

[Kevin Brodsky]

On 27/01/2026 12:02, Jinjie Ruan wrote:
>
> On 2026/1/27 17:43, Kevin Brodsky wrote:
>> On 27/01/2026 04:01, Jinjie Ruan wrote:
>>>> I understand that you're gradually making the arch code more similar to
>>>> the core code so that we can switch over to it, but I'm struggling to
>>>> understand why syscall_trace_enter() takes the 'syscall' argument.
>>>>
>>>> Even the core code just seems to use it as a local variable, which it
>>>> overrides before it ever uses it. What am I missing?
>>> Hi,
>>>
>>> You're absolutely right. The 'syscall' parameter is indeed treated as a
>>> local variable and gets overridden before any real use. Should we
>>> refactor to remove the parameter entirely in generic entry?
>> I noticed this as well, removing it from the generic function would make
>> sense. AFAICT that removal could be propagated quite far in fact:
>> syscall_enter_from_user_mode_work(), syscall_enter_from_user_mode(),
>> even arch implementation (do_syscall_64() on x86).
> Not really, it is the default return value of
> syscall_enter_from_user_mode_work() as below, so we only need to remove
> the parameter in syscall_trace_enter().
>
> static __always_inline long syscall_enter_from_user_mode_work(struct
> pt_regs *regs, long syscall)
> {
> 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
>
>        if (work & SYSCALL_WORK_ENTER)
>             syscall = syscall_trace_enter(regs, work);
>
>       return syscall;
> }

You're right, hadn't realised the call to syscall_trace_enter() was
conditional.

- Kevin

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Kevin Brodsky]

On 27/01/2026 12:34, Jinjie Ruan wrote:
>> [...]
>>
>>>  I'm also concerned that rseq_debug_update_user_cs()
>>> operates on instruction_pointer(regs) which is something that can be
>>> chaned by ptrace.
>> Isn't that true regardless of where rseq_syscall() is called on the
>> syscall exit path, though?
> My understanding is that if instruction_pointer(regs) is hijacked and
> modified via ptrace at the syscall exit (ptrace_report_syscall_exit()),
> this modification will not be observed by rseq. Specifically, in the
> generic entry syscall exit path, rseq_syscall() is unable to detect such
> a PC modification.

Good point. So concretely that means that currently on arm64, one could
make the rseq debug check pass/fail by using the syscall exit trap to
modify PC. OTOH this is impossible with generic entry because the rseq
check is performed first. I'm not sure this is a feature anyone has even
noticed, but it is a user-visible change indeed.

- Kevin

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Jinjie Ruan]

On 2026/1/27 23:06, Kevin Brodsky wrote:
> On 27/01/2026 12:34, Jinjie Ruan wrote:
>>> [...]
>>>
>>>>  I'm also concerned that rseq_debug_update_user_cs()
>>>> operates on instruction_pointer(regs) which is something that can be
>>>> chaned by ptrace.
>>> Isn't that true regardless of where rseq_syscall() is called on the
>>> syscall exit path, though?
>> My understanding is that if instruction_pointer(regs) is hijacked and
>> modified via ptrace at the syscall exit (ptrace_report_syscall_exit()),
>> this modification will not be observed by rseq. Specifically, in the
>> generic entry syscall exit path, rseq_syscall() is unable to detect such
>> a PC modification.
> 
> Good point. So concretely that means that currently on arm64, one could
> make the rseq debug check pass/fail by using the syscall exit trap to
> modify PC. OTOH this is impossible with generic entry because the rseq
> check is performed first. I'm not sure this is a feature anyone has even
> noticed, but it is a user-visible change indeed.

After digging into the ptrace code, I found that ptrace does not modify
instruction_pointer(regs) on the syscall exit path; it only changes the
return value as below.
Therefore, if my understanding is correct, Will's concern does not apply
here.

ptrace_set_syscall_info()
  -> ptrace_set_syscall_info_exit()
     -> syscall_set_return_value(child, regs, 0, rval)


Regards,
Jinjie

> 
> - Kevin
> 

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Kevin Brodsky]

On 28/01/2026 02:09, Jinjie Ruan wrote:
>
> On 2026/1/27 23:06, Kevin Brodsky wrote:
>> On 27/01/2026 12:34, Jinjie Ruan wrote:
>>>> [...]
>>>>
>>>>>  I'm also concerned that rseq_debug_update_user_cs()
>>>>> operates on instruction_pointer(regs) which is something that can be
>>>>> chaned by ptrace.
>>>> Isn't that true regardless of where rseq_syscall() is called on the
>>>> syscall exit path, though?
>>> My understanding is that if instruction_pointer(regs) is hijacked and
>>> modified via ptrace at the syscall exit (ptrace_report_syscall_exit()),
>>> this modification will not be observed by rseq. Specifically, in the
>>> generic entry syscall exit path, rseq_syscall() is unable to detect such
>>> a PC modification.
>> Good point. So concretely that means that currently on arm64, one could
>> make the rseq debug check pass/fail by using the syscall exit trap to
>> modify PC. OTOH this is impossible with generic entry because the rseq
>> check is performed first. I'm not sure this is a feature anyone has even
>> noticed, but it is a user-visible change indeed.
> After digging into the ptrace code, I found that ptrace does not modify
> instruction_pointer(regs) on the syscall exit path; it only changes the
> return value as below.
> Therefore, if my understanding is correct, Will's concern does not apply
> here.
>
> ptrace_set_syscall_info()
>   -> ptrace_set_syscall_info_exit()
>      -> syscall_set_return_value(child, regs, 0, rval)

I'm not following, how is that related to the call to
ptrace_report_syscall_exit()? That eventually results in a call to
ptrace_stop() (via ptrace_notify()), which synchronously causes the
tracee to sleep and allows the tracer to issue ptrace commands, e.g.
setting PC.

- Kevin

Re: [PATCH v10 05/16] arm64: ptrace: Move rseq_syscall() before audit_syscall_exit()

[Jinjie Ruan]

On 2026/1/28 22:53, Kevin Brodsky wrote:
> On 28/01/2026 02:09, Jinjie Ruan wrote:
>>
>> On 2026/1/27 23:06, Kevin Brodsky wrote:
>>> On 27/01/2026 12:34, Jinjie Ruan wrote:
>>>>> [...]
>>>>>
>>>>>>  I'm also concerned that rseq_debug_update_user_cs()
>>>>>> operates on instruction_pointer(regs) which is something that can be
>>>>>> chaned by ptrace.
>>>>> Isn't that true regardless of where rseq_syscall() is called on the
>>>>> syscall exit path, though?
>>>> My understanding is that if instruction_pointer(regs) is hijacked and
>>>> modified via ptrace at the syscall exit (ptrace_report_syscall_exit()),
>>>> this modification will not be observed by rseq. Specifically, in the
>>>> generic entry syscall exit path, rseq_syscall() is unable to detect such
>>>> a PC modification.
>>> Good point. So concretely that means that currently on arm64, one could
>>> make the rseq debug check pass/fail by using the syscall exit trap to
>>> modify PC. OTOH this is impossible with generic entry because the rseq
>>> check is performed first. I'm not sure this is a feature anyone has even
>>> noticed, but it is a user-visible change indeed.
>> After digging into the ptrace code, I found that ptrace does not modify
>> instruction_pointer(regs) on the syscall exit path; it only changes the
>> return value as below.
>> Therefore, if my understanding is correct, Will's concern does not apply
>> here.
>>
>> ptrace_set_syscall_info()
>>   -> ptrace_set_syscall_info_exit()
>>      -> syscall_set_return_value(child, regs, 0, rval)
> 
> I'm not following, how is that related to the call to
> ptrace_report_syscall_exit()? That eventually results in a call to
> ptrace_stop() (via ptrace_notify()), which synchronously causes the
> tracee to sleep and allows the tracer to issue ptrace commands, e.g.
> setting PC.

I realize I had a misunderstanding — PTRACE_SET_SYSCALL_INFO is only one
possible ptrace command. What I actually tried was to modify regs->pc on
the syscall return path using PTRACE_SETREGSET, and the result shows
that I can indeed change regs->pc to make the tracee segment fault.

> 
> - Kevin
>