ptrace: change tracehook_report_syscall_exit() to handle stepping

Suggested by Roland.

Change tracehook_report_syscall_exit() to look at step flag and send the trap signal if needed.

This change affects ia64, microblaze, parisc, powerpc, sh. They pass nonzero "step" argument to tracehook but since it was ignored the tracee reports via ptrace_notify(), this is not right and not consistent.

- PTRACE_SETSIGINFO doesn't work

- if the tracer resumes the tracee with signr != 0 the new signal is generated rather than delivering it

- If PT_TRACESYSGOOD is set the tracee reports the wrong exit_code

I don't have a powerpc machine, but I think this test-case should see the difference:

	#include <unistd.h>
	#include <sys/ptrace.h>
	#include <sys/wait.h>
	#include <assert.h>
	#include <stdio.h>

	int main(void)
	{
		int pid, status;

		if (!(pid = fork())) {
			assert(ptrace(PTRACE_TRACEME) == 0);
			kill(getpid(), SIGSTOP);

			getppid();

			return 0;
		}

		assert(pid == wait(&status));
		assert(ptrace(PTRACE_SETOPTIONS, pid, 0, PTRACE_O_TRACESYSGOOD) == 0);

		assert(ptrace(PTRACE_SYSCALL, pid, 0,0) == 0);
		assert(pid == wait(&status));

		assert(ptrace(PTRACE_SINGLESTEP, pid, 0,0) == 0);
		assert(pid == wait(&status));

		if (status == 0x57F)
			return 0;

		printf("kernel bug: status=%X shouldn't have 0x80\n", status);
		return 1;
	}

---

 include/linux/tracehook.h |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -134,6 +134,13 @@ static inline __must_check int tracehook
  */
 static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
 {
+	if (step) {
+		siginfo_t info;
+		user_single_step_siginfo(current, regs, &info);
+		force_sig_info(SIGTRAP, &info, current);
+		return;
+	}
+
 	ptrace_report_syscall(regs);
 }
 

This patch conflicts with utrace-core.patch a bit:

***************
*** 134,139 ****
*/
static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)

  {
        ptrace_report_syscall(regs);

}

--- 140,147 ----
*/
static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) {
+ if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT))

+               utrace_report_syscall_exit(regs);
        ptrace_report_syscall(regs);

}

I did this:

  static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
  {
        if (step) {
                siginfo_t info;
                user_single_step_siginfo(current, regs, &info);
                force_sig_info(SIGTRAP, &info, current);
                return;
        }

+ if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT))

+               utrace_report_syscall_exit(regs);
        ptrace_report_syscall(regs);

}

utrace-core.patch is getting rather old. What is its status?

Ah, indeed, sorry...

Roland, given that you are going to send the updated utrace patch, perhaps it makes sense to drop this old utrace-core.patch from -mm?

Oleg.

Yes, I think that's the easiest thing to do. When we send new utrace and ptrace code, we can make that relative to -mm or at least relative to the all ptrace-related patches you've already submitted in this cycle.

Thanks,
Roland