[RFC 1/2] arm64: Implement arch_stack_walk_reliable

[RFC 1/2] arm64: Implement arch_stack_walk_reliable

[Song Liu]

Let do_kunwind() and kunwind_stack_walk() return the state of stack walk
properly to the caller, and use them in arch_stack_walk_reliable(). This
can be used to enable livepatching for arm64.

Signed-off-by: Song Liu <song@kernel.org>
---
 arch/arm64/Kconfig             |  2 +-
 arch/arm64/kernel/stacktrace.c | 35 +++++++++++++++++++++++++++-------
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 213f42d5ca27..f5af6faf9e2b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -271,6 +271,7 @@ config ARM64
 	select HAVE_SOFTIRQ_ON_OWN_STACK
 	select USER_STACKTRACE_SUPPORT
 	select VDSO_GETRANDOM
+	select HAVE_RELIABLE_STACKTRACE
 	help
 	  ARM 64-bit (AArch64) Linux support.
 
@@ -2495,4 +2496,3 @@ endmenu # "CPU Power Management"
 source "drivers/acpi/Kconfig"
 
 source "arch/arm64/kvm/Kconfig"
-
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 1d9d51d7627f..280dd6839a18 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -277,22 +277,28 @@ kunwind_next(struct kunwind_state *state)
 
 typedef bool (*kunwind_consume_fn)(const struct kunwind_state *state, void *cookie);
 
-static __always_inline void
+static __always_inline int
 do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state,
 	   void *cookie)
 {
+	int ret;
+
 	if (kunwind_recover_return_address(state))
-		return;
+		return -EINVAL;
 
 	while (1) {
-		int ret;
 
-		if (!consume_state(state, cookie))
+		ret = consume_state(state, cookie);
+		if (!ret)
 			break;
 		ret = kunwind_next(state);
 		if (ret < 0)
 			break;
 	}
+	/* Unwind terminated successfully */
+	if (ret == -ENOENT)
+		ret = 0;
+	return ret;
 }
 
 /*
@@ -324,7 +330,7 @@ do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state,
 			: stackinfo_get_unknown();		\
 	})
 
-static __always_inline void
+static __always_inline int
 kunwind_stack_walk(kunwind_consume_fn consume_state,
 		   void *cookie, struct task_struct *task,
 		   struct pt_regs *regs)
@@ -352,7 +358,7 @@ kunwind_stack_walk(kunwind_consume_fn consume_state,
 
 	if (regs) {
 		if (task != current)
-			return;
+			return -EINVAL;
 		kunwind_init_from_regs(&state, regs);
 	} else if (task == current) {
 		kunwind_init_from_caller(&state);
@@ -360,7 +366,7 @@ kunwind_stack_walk(kunwind_consume_fn consume_state,
 		kunwind_init_from_task(&state, task);
 	}
 
-	do_kunwind(&state, consume_state, cookie);
+	return do_kunwind(&state, consume_state, cookie);
 }
 
 struct kunwind_consume_entry_data {
@@ -387,6 +393,21 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
 	kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs);
 }
 
+noinline noinstr int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
+			void *cookie, struct task_struct *task)
+{
+	int ret;
+
+	struct kunwind_consume_entry_data data = {
+		.consume_entry = consume_entry,
+		.cookie = cookie,
+	};
+
+	ret = kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, NULL);
+
+	return ret;
+}
+
 struct bpf_unwind_consume_entry_data {
 	bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp);
 	void *cookie;
-- 
2.43.5

[RFC 2/2] arm64: Implement HAVE_LIVEPATCH

[Song Liu]

This is largely based on [1] by Suraj Jitindar Singh.

Test coverage:

- Passed manual tests with samples/livepatch.
- Passed all but test-kprobe.sh in selftests/livepatch.
  test-kprobe.sh is expected to fail, because arm64 doesn't have
  KPROBES_ON_FTRACE.
- Passed tests with kpatch-build [2]. (This version includes commits that
  are not merged to upstream kpatch yet).

[1] https://lore.kernel.org/all/20210604235930.603-1-surajjs@amazon.com/
[2] https://github.com/liu-song-6/kpatch/tree/fb-6.13
Cc: Suraj Jitindar Singh <surajjs@amazon.com>
Cc: Torsten Duwe <duwe@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
---
 arch/arm64/Kconfig                   | 3 +++
 arch/arm64/include/asm/thread_info.h | 4 +++-
 arch/arm64/kernel/entry-common.c     | 4 ++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index f5af6faf9e2b..475caa57c94a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -272,6 +272,7 @@ config ARM64
 	select USER_STACKTRACE_SUPPORT
 	select VDSO_GETRANDOM
 	select HAVE_RELIABLE_STACKTRACE
+	select HAVE_LIVEPATCH
 	help
 	  ARM 64-bit (AArch64) Linux support.
 
@@ -2496,3 +2497,5 @@ endmenu # "CPU Power Management"
 source "drivers/acpi/Kconfig"
 
 source "arch/arm64/kvm/Kconfig"
+
+source "kernel/livepatch/Kconfig"
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 1114c1c3300a..01623c471beb 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -69,6 +69,7 @@ void arch_setup_new_exec(void);
 #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
 #define TIF_RESTORE_SIGMASK	20
@@ -92,6 +93,7 @@ void arch_setup_new_exec(void);
 #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)
@@ -103,7 +105,7 @@ void arch_setup_new_exec(void);
 #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
 				 _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
 				 _TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
-				 _TIF_NOTIFY_SIGNAL)
+				 _TIF_NOTIFY_SIGNAL | _TIF_PATCH_PENDING)
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index b260ddc4d3e9..b537af333b42 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -8,6 +8,7 @@
 #include <linux/context_tracking.h>
 #include <linux/kasan.h>
 #include <linux/linkage.h>
+#include <linux/livepatch.h>
 #include <linux/lockdep.h>
 #include <linux/ptrace.h>
 #include <linux/resume_user_mode.h>
@@ -144,6 +145,9 @@ static void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
 				       (void __user *)NULL, current);
 		}
 
+		if (thread_flags & _TIF_PATCH_PENDING)
+			klp_update_patch_state(current);
+
 		if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 			do_signal(regs);
 
-- 
2.43.5