linux-kernel - [PATCH 11/16] ptrace: Use si_sino as the signal number to resume with

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Date:   Wed, 18 May 2022 17:53:50 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     rjw@...ysocki.net, Oleg Nesterov <oleg@...hat.com>,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        bigeasy@...utronix.de, Will Deacon <will@...nel.org>,
        tj@...nel.org, linux-pm@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, linux-ia64@...r.kernel.org,
        Robert OCallahan <roc@...nos.co>, Kyle Huey <khuey@...nos.co>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 11/16] ptrace: Use si_sino as the signal number to resume with

The signal number to resume with is already in si_signo.  So instead
of placing an extra copy in tsk->exit_code and later reading the extra
copy from tsk->exit_code just read si_signo.

Read si_signo in ptrace_do_notify where it is easy as the siginfo is a
local variable.  Only ptrace_report_syscall cares about the signal to
resume with from ptrace_stop and it calls ptrace_notify which calls
ptrace_do_notify so moving the actual work into ptrace_do_notify where
it is easier is not a problem.

With ptrace_stop not being involved in returning the signal to tracer
asked the tracee to resume with remove the comment and the return
code from ptrace_stop.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/ptrace.c |  1 -
 kernel/signal.c | 13 ++++---------
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index a0a07d140751..e0ecb1536dfc 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -530,7 +530,6 @@ static void ptrace_set_signr(struct task_struct *child, unsigned int signr)
 {
 	struct kernel_siginfo *info = child->last_siginfo;
 
-	child->exit_code = signr;
 	/*
 	 * Update the siginfo structure if the signal has
 	 * changed.  If the debugger wanted something
diff --git a/kernel/signal.c b/kernel/signal.c
index 3d955c23b13d..2cc45e8448e2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2186,12 +2186,8 @@ static void do_notify_parent_cldstop(struct task_struct *tsk,
  * We always set current->last_siginfo while stopped here.
  * That makes it a way to test a stopped process for
  * being ptrace-stopped vs being job-control-stopped.
- *
- * Returns the signal the ptracer requested the code resume
- * with.  If the code did not stop because the tracer is gone,
- * the stop signal remains unchanged unless clear_code.
  */
-static int ptrace_stop(int exit_code, int why, unsigned long message,
+static void ptrace_stop(int exit_code, int why, unsigned long message,
 		       kernel_siginfo_t *info)
 	__releases(&current->sighand->siglock)
 	__acquires(&current->sighand->siglock)
@@ -2219,7 +2215,7 @@ static int ptrace_stop(int exit_code, int why, unsigned long message,
 	 * signals here to prevent ptrace_stop sleeping in schedule.
 	 */
 	if (!current->ptrace || __fatal_signal_pending(current))
-		return exit_code;
+		return;
 
 	set_special_state(TASK_TRACED);
 	current->jobctl |= JOBCTL_TRACED;
@@ -2302,7 +2298,6 @@ static int ptrace_stop(int exit_code, int why, unsigned long message,
 	 * any signal-sending on another CPU that wants to examine it.
 	 */
 	spin_lock_irq(&current->sighand->siglock);
-	exit_code = current->exit_code;
 	current->last_siginfo = NULL;
 	current->ptrace_message = 0;
 	current->exit_code = 0;
@@ -2316,7 +2311,6 @@ static int ptrace_stop(int exit_code, int why, unsigned long message,
 	 * This sets TIF_SIGPENDING, but never clears it.
 	 */
 	recalc_sigpending_tsk(current);
-	return exit_code;
 }
 
 static int ptrace_do_notify(int signr, int exit_code, int why, unsigned long message)
@@ -2330,7 +2324,8 @@ static int ptrace_do_notify(int signr, int exit_code, int why, unsigned long mes
 	info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
 
 	/* Let the debugger run.  */
-	return ptrace_stop(exit_code, why, message, &info);
+	ptrace_stop(exit_code, why, message, &info);
+	return info.si_signo;
 }
 
 int ptrace_notify(int exit_code, unsigned long message)
-- 
2.35.3