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 calls rseq_syscall() a bit later. 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. To align the order of the calls with generic entry, move rseq_syscall() ahead before audit_syscall_exit(). As for the impact of raising SIGSEGV via rseq_syscall(), it makes no practical difference to signal delivery because signals are processed in arm64_exit_to_user_mode() at the very end. As for the "regs", rseq_syscall() only checks and update instruction_pointer(regs) when CONFIG_DEBUG_RSEQ=y, audit_syscall_exit() only checks the return value (x0 for arm64), so calling rseq_syscall() before or after audit syscall exit makes no difference. trace_sys_exit() only uses syscallno and the return value, so calling rseq_syscall() before or after trace_sys_exit() makes no difference. But ptrace can also modify the "pc" on syscall exit path. So when CONFIG_DEBUG_RSEQ=y, before this patch, rseq could observe the PC modified by ptrace on the syscall exit path; after this patch, rseq no longer sees modifications made by ptrace. 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 e3dcadf13e99..50344a2d7b88 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -2455,6 +2455,8 @@ int syscall_trace_enter(struct pt_regs *regs, 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) @@ -2462,8 +2464,6 @@ 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