From: Jinjie Ruan <ruanjinjie@huawei.com>
To: <catalin.marinas@arm.com>, <will@kernel.org>,
<mark.rutland@arm.com>, <oleg@redhat.com>, <kees@kernel.org>,
<luto@amacapital.net>, <wad@chromium.org>, <peterz@infradead.org>,
<ada.coupriediaz@arm.com>, <linusw@kernel.org>,
<kevin.brodsky@arm.com>, <yeoreum.yun@arm.com>,
<thuth@redhat.com>, <james.morse@arm.com>,
<vladimir.murzin@arm.com>, <broonie@kernel.org>,
<pengcan@kylinos.cn>, <liqiang01@kylinos.cn>,
<ryan.roberts@arm.com>, <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>
Cc: <ruanjinjie@huawei.com>
Subject: [PATCH v18 12/14] arm64: ptrace: Make return type of arm64_syscall_trace_enter() bool
Date: Wed, 2 Sep 2026 17:55:35 +0800 [thread overview]
Message-ID: <20260902095537.602517-13-ruanjinjie@huawei.com> (raw)
In-Reply-To: <20260902095537.602517-1-ruanjinjie@huawei.com>
In preparation for migrating arm64 to the generic entry infrastructure,
decouple the decision to execute the syscall from the syscall number
itself. The ptrace and seccomp now returns a boolean flag rather than
overloading NO_SYSCALL (-1).
Changes:
- arm64_syscall_trace_enter() returns bool:
- false: abort syscall execution
- true: proceed, with syscall number reread from regs
- If we decide to execute the syscall, reread the syscall number
and check if it is NO_SYSCALL again. Because when a tracer sets
the syscall number to -1 and provides a custom return value in x0,
this avoids calling invoke_syscall() which would overwrite the custom
value with -ENOSYS by sys_ni_syscall().
Behavioral impact (unchanged):
- User-issued syscall(-1): unchanged, returns -ENOSYS.
- Tracer skip with custom x0: unchanged, returns custom x0
- Tracer skip without setting x0: unchanged, returns original
argument (garbage)
- Normal syscalls and seccomp rejects: unaffected
No functional changes.
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
arch/arm64/include/asm/syscall.h | 2 +-
arch/arm64/kernel/ptrace.c | 8 ++++----
arch/arm64/kernel/syscall.c | 6 +++++-
3 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 7cc872fde019..f19d4a8824ba 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -121,7 +121,7 @@ static inline int syscall_get_arch(struct task_struct *task)
return AUDIT_ARCH_AARCH64;
}
-int arm64_syscall_trace_enter(struct pt_regs *regs, unsigned long flags);
+bool arm64_syscall_trace_enter(struct pt_regs *regs, unsigned long flags);
void arm64_syscall_exit_work(struct pt_regs *regs, unsigned long flags);
static __always_inline void arm64_syscall_exit_to_user_mode_work(struct pt_regs *regs)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 08d2c39ae2ba..9825f4aff187 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2468,14 +2468,14 @@ static inline void syscall_enter_audit(struct pt_regs *regs)
}
#endif
-int arm64_syscall_trace_enter(struct pt_regs *regs, unsigned long flags)
+bool arm64_syscall_trace_enter(struct pt_regs *regs, 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;
+ return false;
/* ptrace might have changed thread flags */
flags = read_thread_flags();
@@ -2484,7 +2484,7 @@ int arm64_syscall_trace_enter(struct pt_regs *regs, unsigned long flags)
/* Do the secure computing after ptrace; failures should be fast. */
if (unlikely(flags & _TIF_SECCOMP)) {
if (!__seccomp_permit_syscall())
- return NO_SYSCALL;
+ return false;
}
if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
@@ -2493,7 +2493,7 @@ int arm64_syscall_trace_enter(struct pt_regs *regs, unsigned long flags)
if (unlikely(audit_context()))
syscall_enter_audit(regs);
- return syscall_get_nr(current, regs);
+ return true;
}
static inline bool report_single_step(unsigned long flags)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 3488afd45d20..72c6e8b7ab21 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -108,7 +108,11 @@ 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 = arm64_syscall_trace_enter(regs, read_thread_flags());
+ if (!arm64_syscall_trace_enter(regs, read_thread_flags()))
+ goto trace_exit;
+
+ /* Reread the syscall number as it might have been modified */
+ scno = syscall_get_nr(current, regs);
if (scno == NO_SYSCALL)
goto trace_exit;
}
--
2.34.1
next prev parent reply other threads:[~2026-09-02 9:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-02 9:55 [PATCH v18 00/14] arm64: entry: Convert to Generic Entry Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 01/14] arm64: ptrace: Fix redundant syscall exit stop for PTRACE_SYSEMU_SINGLESTEP Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 02/14] arm64: ptrace: Rework audit_syscall_entry() Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 03/14] arm64: ptrace: Open-code seccomp check in syscall_trace_enter() Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 04/14] arm64: ptrace: Rename and clean up syscall_trace_enter() Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 05/14] arm64: ptrace: Protect rseq_syscall() from tracer PC modifications Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 06/14] arm64: syscall: Rework the syscall exit path in el0_svc_common() Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 07/14] arm64: ptrace: Pass thread flags to trace enter/exit Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 08/14] arm64: ptrace: Extract arm64_syscall_exit_to_user_mode_work() helper Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 09/14] arm64: ptrace: Align syscall exit work semantics with generic entry Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 10/14] arm64: syscall: Use exit-specific flags check in el0_svc_common() Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 11/14] arm64: syscall: Simplify el0_svc_common() syscall exit path Jinjie Ruan
2026-09-02 9:55 ` Jinjie Ruan [this message]
2026-09-02 9:55 ` [PATCH v18 13/14] arm64: entry: Convert to generic entry Jinjie Ruan
2026-09-02 9:55 ` [PATCH v18 14/14] arm64: Inline el0_svc_common() Jinjie Ruan
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