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, 11 insertions, 6 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 4f36431c380b..1de2235511c8 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -336,14 +336,19 @@ static inline void user_enable_block_step(struct task_struct *task)
 extern void user_enable_block_step(struct task_struct *);
 #endif  /* arch_has_block_step */
 
-#ifdef ARCH_HAS_USER_SINGLE_STEP_INFO
-extern void user_single_step_siginfo(struct task_struct *tsk,
-                                struct pt_regs *regs, siginfo_t *info);
+#ifdef ARCH_HAS_USER_SINGLE_STEP_REPORT
+extern void user_single_step_report(struct pt_regs *regs);
 #else
-static inline void user_single_step_siginfo(struct task_struct *tsk,
-                                struct pt_regs *regs, siginfo_t *info)
+static inline void user_single_step_report(struct pt_regs *regs)
 {
-        info->si_signo = SIGTRAP;
+        siginfo_t info;
+        clear_siginfo(&info);
+        info.si_signo = SIGTRAP;
+        info.si_errno = 0;
+        info.si_code = SI_USER;
+        info.si_pid = 0;
+        info.si_uid = 0;
+        force_sig_info(info.si_signo, &info, current);
 }
 #endif