linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Qi Zheng <zhengqi.arch@bytedance.com>
To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	hpa@zytor.com, peterz@infradead.org, x86@kernel.org
Cc: linux-kernel@vger.kernel.org, songmuchun@bytedance.com,
	Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH] x86: fix get_wchan() not support the ORC unwinder
Date: Fri, 11 Jun 2021 20:46:42 +0800	[thread overview]
Message-ID: <20210611124642.72910-1-zhengqi.arch@bytedance.com> (raw)

Currently, the kernel CONFIG_UNWINDER_ORC option is enabled by
default on x86, but the implementation of get_wchan() is still
based on the frame pointer unwinder, so the /proc/<pid>/wchan
always return 0 regardless of whether the task <pid> is running.

We reimplement the get_wchan() by calling stack_trace_save_tsk(),
which is adapted to the ORC and frame pointer unwinders.

Fixes: ee9f8fce9964(x86/unwind: Add the ORC unwinder)
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 arch/x86/kernel/process.c | 51 +++--------------------------------------------
 1 file changed, 3 insertions(+), 48 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5e1f38179f49..976a36918ed7 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -928,58 +928,13 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
  */
 unsigned long get_wchan(struct task_struct *p)
 {
-	unsigned long start, bottom, top, sp, fp, ip, ret = 0;
-	int count = 0;
+	unsigned long entry = 0;
 
 	if (p == current || p->state == TASK_RUNNING)
 		return 0;
 
-	if (!try_get_task_stack(p))
-		return 0;
-
-	start = (unsigned long)task_stack_page(p);
-	if (!start)
-		goto out;
-
-	/*
-	 * Layout of the stack page:
-	 *
-	 * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
-	 * PADDING
-	 * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
-	 * stack
-	 * ----------- bottom = start
-	 *
-	 * The tasks stack pointer points at the location where the
-	 * framepointer is stored. The data on the stack is:
-	 * ... IP FP ... IP FP
-	 *
-	 * We need to read FP and IP, so we need to adjust the upper
-	 * bound by another unsigned long.
-	 */
-	top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
-	top -= 2 * sizeof(unsigned long);
-	bottom = start;
-
-	sp = READ_ONCE(p->thread.sp);
-	if (sp < bottom || sp > top)
-		goto out;
-
-	fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
-	do {
-		if (fp < bottom || fp > top)
-			goto out;
-		ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
-		if (!in_sched_functions(ip)) {
-			ret = ip;
-			goto out;
-		}
-		fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
-	} while (count++ < 16 && p->state != TASK_RUNNING);
-
-out:
-	put_task_stack(p);
-	return ret;
+	stack_trace_save_tsk(p, &entry, 1, 0);
+	return entry;
 }
 
 long do_arch_prctl_common(struct task_struct *task, int option,
-- 
2.11.0


             reply	other threads:[~2021-06-11 12:47 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-11 12:46 Qi Zheng [this message]
2021-06-14 16:21 ` Andy Lutomirski
2021-06-16  7:34   ` [External] " 郑琦

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210611124642.72910-1-zhengqi.arch@bytedance.com \
    --to=zhengqi.arch@bytedance.com \
    --cc=bp@alien8.de \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=songmuchun@bytedance.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] x86: fix get_wchan() not support the ORC unwinder' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).