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.
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.
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);
}
/*
--
2.34.1
