revert "procfs: provide stack information for threads" and its fixup commits (34441427) · Commits · 戴 / test

Originally, commit ("procfs: provide stack information for threads") attempted to introduce a new feature for showing where the threadstack was located and how many pages are being utilized by the stack. Commit ("procfs: disable per-task stack usage on NOMMU") was applied to fix the NO_MMU case. Commit ("x86, fs: Fix x86 procfs stack information for threads on 64-bit") was applied to fix a bug in ia32 executables being loaded. Commit ("procfs: fix /proc/<pid>/stat stack pointer for kernel threads") was applied to fix a bug which had kernel threads printing a userland stack address. Commit ('proc: partially revert "procfs: provide stack information for threads"') was then applied to revert the stack pages being used to solve a significant performance regression. This patch nearly undoes the effect of all these patches. The reason for reverting these is it provides an unusable value in field 28. For x86_64, a fork will result in the task->stack_start value being updated to the current user top of stack and not the stack start address. This unpredictability of the stack_start value makes it worthless. That includes the intended use of showing how much stack space a thread has. Other architectures will get different values. As an example, ia64 gets 0. The do_fork() and copy_process() functions appear to treat the stack_start and stack_size parameters as architecture specific. I only partially reverted ("procfs: disable per-task stack usage on NOMMU") . If I had completely reverted it, I would have had to change mm/Makefile only build pagewalk.o when CONFIG_PROC_PAGE_MONITOR is configured. Since I could not test the builds without significant effort, I decided to not change mm/Makefile. I only partially reverted ("x86, fs: Fix x86 procfs stack information for threads on 64-bit") . I left the KSTK_ESP() change in place as that seemed worthwhile. Signed-off-by:

Robin Holt <holt@sgi.com> Cc: Stefani Seibold <stefani@seibold.net> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Michal Simek <monstr@monstr.eu> Cc: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/proc.txt

+1 −2

Original line number	Diff line number	Diff line
		@@ -316,7 +316,7 @@ address perms offset dev inode pathname
		08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
		0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
		a7cb1000-a7cb2000 ---p 00000000 00:00 0
		a7cb2000-a7eb2000 rw-p 00000000 00:00 0 [threadstack:001ff4b4]
		a7cb2000-a7eb2000 rw-p 00000000 00:00 0
		a7eb2000-a7eb3000 ---p 00000000 00:00 0
		a7eb3000-a7ed5000 rw-p 00000000 00:00 0
		a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
		@@ -352,7 +352,6 @@ is not associated with a file:
		[stack] = the stack of the main process
		[vdso] = the "virtual dynamic shared object",
		the kernel system call handler
		[threadstack:xxxxxxxx] = the stack of the thread, xxxxxxxx is the stack size

		or if empty, the mapping is anonymous.

fs/compat.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -1531,8 +1531,6 @@ int compat_do_execve(char * filename,
		if (retval < 0)
		goto out;

		current->stack_start = current->mm->start_stack;

		/* execve succeeded */
		current->fs->in_exec = 0;
		current->in_execve = 0;

fs/exec.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -1387,8 +1387,6 @@ int do_execve(char * filename,
		if (retval < 0)
		goto out;

		current->stack_start = current->mm->start_stack;

		/* execve succeeded */
		current->fs->in_exec = 0;
		current->in_execve = 0;

fs/proc/array.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -81,7 +81,6 @@
		#include <linux/pid_namespace.h>
		#include <linux/ptrace.h>
		#include <linux/tracehook.h>
		#include <linux/swapops.h>

		#include <asm/pgtable.h>
		#include <asm/processor.h>
		@@ -495,7 +494,7 @@ static int do_task_stat(struct seq_file m, struct pid_namespace ns,
		rsslim,
		mm ? mm->start_code : 0,
		mm ? mm->end_code : 0,
		(permitted && mm) ? task->stack_start : 0,
		(permitted && mm) ? mm->start_stack : 0,
		esp,
		eip,
		/* The signal information here is obsolete.

fs/proc/task_mmu.c

+0 −19

Original line number	Diff line number	Diff line
		@@ -247,25 +247,6 @@ static void show_map_vma(struct seq_file m, struct vm_area_struct vma)
		} else if (vma->vm_start <= mm->start_stack &&
		vma->vm_end >= mm->start_stack) {
		name = "[stack]";
		} else {
		unsigned long stack_start;
		struct proc_maps_private *pmp;

		pmp = m->private;
		stack_start = pmp->task->stack_start;

		if (vma->vm_start <= stack_start &&
		vma->vm_end >= stack_start) {
		pad_len_spaces(m, len);
		seq_printf(m,
		"[threadstack:%08lx]",
		#ifdef CONFIG_STACK_GROWSUP
		vma->vm_end - stack_start
		#else
		stack_start - vma->vm_start
		#endif
		);
		}
		}
		} else {
		name = "[vdso]";

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