Introduce _TIF_SYSCALL_EXIT_WORK to filter out entry-only flags
during the syscall exit path. This aligns arm64 with the generic
entry framework's SYSCALL_WORK_EXIT semantics.
[Rationale]
The current syscall exit path uses _TIF_SYSCALL_WORK to decide whether
to invoke syscall_exit_work(). However, _TIF_SYSCALL_WORK includes
flags that are only relevant during syscall entry:
1. _TIF_SECCOMP: Seccomp filtering (__secure_computing) only runs
on entry. There is no seccomp callback for syscall exit.
2. _TIF_SYSCALL_EMU: In PTRACE_SYSEMU mode, the syscall is
intercepted and skipped on entry. Since the syscall is never
executed, reporting a syscall exit stop is unnecessary.
[Changes]
- Define _TIF_SYSCALL_EXIT_WORK: A new mask containing only flags
requiring exit processing: _TIF_SYSCALL_TRACE, _TIF_SYSCALL_AUDIT,
and _TIF_SYSCALL_TRACEPOINT.
- Update exit path: Use _TIF_SYSCALL_EXIT_WORK in
syscall_exit_to_user_mode_work() to avoid redundant calls to
audit and ptrace reporting when only entry-flags are set.
- Cleanup: Remove the has_syscall_work() helper as it is no longer
needed. Direct flag comparison is now used to distinguish between
entry and exit work requirements.
[Impact]
audit_syscall_exit() and report_syscall_exit() will no longer be
triggered for seccomp-only or emu-only syscalls. This matches the
generic entry behavior and improves efficiency by skipping unnecessary
exit processing.
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
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 c469d09a7964..dea392c081ca 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, unsigned long flags);
void syscall_exit_to_user_mode_work(struct pt_regs *regs);
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 7942478e4065..4ae83cb620bb 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -109,6 +109,9 @@ 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 35efa2062408..3cac9668aaa8 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2471,7 +2471,7 @@ void syscall_exit_to_user_mode_work(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 66d4da641d97..ec478fc37a9f 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