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, 5 insertions, 6 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index e2ee403865eb..94bd6e89129a 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1382,12 +1382,6 @@ static void fill_sigtrap_info(struct task_struct *tsk,
         info->si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
 }
 
-void user_single_step_siginfo(struct task_struct *tsk,
-                                struct pt_regs *regs,
-                                struct siginfo *info)
-{
-        fill_sigtrap_info(tsk, regs, 0, TRAP_BRKPT, info);
-}
 
 void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
                                          int error_code, int si_code)
@@ -1399,3 +1393,8 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
         /* Send us the fake SIGTRAP */
         force_sig_info(SIGTRAP, &info, tsk);
 }
+
+void user_single_step_report(struct pt_regs *regs)
+{
+        send_sigtrap(current, regs, 0, TRAP_BRKPT);
+}