On 28/01/2026 04:19, 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 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.
>
> 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), ptrace can not modify the "pc" on syscall exit
> path but 'only changes the return value', so calling rseq_syscall()
> before or after ptrace_report_syscall_exit() makes no difference.Let's update this as discussed on v10 - PC can be modified when ptrace_report_syscall_exit() is called. > And 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() also makes > no difference. > > In preparation for moving arm64 over to the generic entry code, move > rseq_syscall() ahead before audit_syscall_exit(). > > No functional changes. And naturally this is not the case. - Kevin > Reviewed-by: Kevin Brodsky <[email protected]> > Signed-off-by: Jinjie Ruan <[email protected]> > --- > 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 9f9aa3087c09..785280c76317 100644 > --- a/arch/arm64/kernel/ptrace.c > +++ b/arch/arm64/kernel/ptrace.c > @@ -2443,6 +2443,8 @@ 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) > @@ -2450,8 +2452,6 @@ 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); > } > > /*
