signal: Simplify tracehook_report_syscall_exit

Replace user_single_step_siginfo with user_single_step_report
that allocates siginfo structure on the stack and sends it.

This allows tracehook_report_syscall_exit to become a simple
if statement that calls user_single_step_report or ptrace_report_syscall
depending on the value of step.

Update the default helper function now called user_single_step_report
to explicitly set si_code to SI_USER and to set si_uid and si_pid to 0.
The default helper has always been doing this (using memset) but it
was far from obvious.

The powerpc helper can now just call force_sig_fault.
The x86 helper can now just call send_sigtrap.

Unfortunately the default implementation of user_single_step_report
can not use force_sig_fault as it does not use a SIGTRAP si_code.
So it has to carefully setup the siginfo and use use force_sig_info.

The net result is code that is easier to understand and simpler
to maintain.

Ref: 85ec7fd9f8e5 ("ptrace: introduce user_single_step_siginfo() helper")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 4 insertions, 9 deletions

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 05589a3e37f4..40b0b4c1bf7b 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -123,15 +123,10 @@ static inline __must_check int tracehook_report_syscall_entry(
  */
 static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
 {
-	if (step) {
-		siginfo_t info;
-		clear_siginfo(&info);
-		user_single_step_siginfo(current, regs, &info);
-		force_sig_info(SIGTRAP, &info, current);
-		return;
-	}
-
-	ptrace_report_syscall(regs);
+	if (step)
+		user_single_step_report(regs);
+	else
+		ptrace_report_syscall(regs);
 }
 
 /**