tracehook_report_syscall_exit() && PT_PTRACED (Was: [PATCH 133] stepping, accommodate to utrace-cleanup changes)

[Oleg Nesterov]

On 11/16, Roland McGrath wrote:
>
> The change we talked about before seems simple enough and should cover this
> without new kludges in the ptrace layer.  I did this (commit f19442c).

I will reply to this in the next email, I'd like to discuss
another minor related issue first.

I noticed this change in your tree

	commit 2583b3267ed599cb25f6f893c24465204e06b3a6
	utrace: nit for utrace-ptrace

	--- a/include/linux/tracehook.h
	+++ b/include/linux/tracehook.h
	@@ -143,7 +143,7 @@ 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);
	 
	-	if (step && task_ptrace(current)) {
	+	if (step && (task_ptrace(current) & PT_PTRACED)) {
			siginfo_t info;
			user_single_step_siginfo(current, regs, &info);
			force_sig_info(SIGTRAP, &info, current);

Yes, and in fact I already had this change in my tree but didn't
send it to you yet.

But, I can't understand whats going on,

	-       if (step && task_ptrace(current)) {
	+       if (step && (task_ptrace(current) & PT_PTRACED)) {

The code after ptrace-change-tracehook_report_syscall_exit-to-handle-stepping.patch
is "if (step)", not "if (step && task_ptrace(current))", can't understand
where did this "&& task_ptrace(current)" come from. The previous commit in
your tree is

	462a57bb7a6a5c67b70e4388f97239f1e4da98df
	ptrace: change tracehook_report_syscall_exit() to handle stepping


Initially I was going to add the change below into
"tracehooks: prepare for utrace-ptrace",

	--- a/include/linux/tracehook.h
	+++ b/include/linux/tracehook.h
	@@ -134,6 +134,9 @@ static inline __must_check int tracehook
	  */
	 static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
	 {
	+	if (!(task_ptrace(current) & PT_PTRACED))
	+		return;
	+
		if (step) {
			siginfo_t info;
			user_single_step_siginfo(current, regs, &info);

but now I think perhaps it would be better to send
ptrace-change-tracehook_report_syscall_exit-to-handle-stepping_fix
to akpm right now:

	--- a/include/linux/tracehook.h
	+++ b/include/linux/tracehook.h
	@@ -134,7 +134,7 @@ static inline __must_check int tracehook
	  */
	 static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
	 {
	-	if (step) {
	+	if (step && (task_ptrace(current) & PT_PTRACED)) {
			siginfo_t info;
			user_single_step_siginfo(current, regs, &info);
			force_sig_info(SIGTRAP, &info, current);

What do you think?

Now, let's return to the original topic. Please note that utrace
does not need "int step" at all, see the next email.

Oleg.