linux-kernel - Re: [PATCH] update fix X86_64 procfs provide stack information for threads

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Date:	Tue, 3 Nov 2009 09:28:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Americo Wang <xiyou.wangcong@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] update fix X86_64 procfs provide stack information for
	threads


* Stefani Seibold <stefani@...bold.net> wrote:

> This patch fix two issues in the procfs stack information on X86_64
> linux. 
> 
> The 32 bit loader compat_do_execve did not store stack start (this was
> figured out by alexey).
> 
> The stack information on a X64_64 kernel always show 0 kbyte stack
> usage, because of a miss implemented KSTK_ESP macro which always return
> -1. The new implementation returns now the right value. 
> 
> The patch is against 2.6.32-rc5-git5.
> 
> Andrew would you so kind to apply this patch?
> 
> Greetings,
> Stefani
> 
> Signed-off-by: Stefani Seibold <stefani@...bold.net>
> ---
>  arch/x86/include/asm/processor.h |    8 +++++++-
>  arch/x86/kernel/process_64.c     |    8 ++++++++
>  fs/compat.c                      |    2 ++
>  3 files changed, 17 insertions(+), 1 deletion(-)
> 
> --- linux-2.6.32-rc5/fs/compat.c	2009-10-16 02:41:50.000000000 +0200
> +++ linux-2.6.32-rc5.new/fs/compat.c	2009-11-02 09:00:52.871909633 +0100
> @@ -1532,6 +1532,8 @@
>  	if (retval < 0)
>  		goto out;
>  
> +	current->stack_start = current->mm->start_stack;
> +
>  	/* execve succeeded */
>  	current->fs->in_exec = 0;
>  	current->in_execve = 0;
> --- linux-2.6.32-rc5/arch/x86/include/asm/processor.h	2009-10-16 02:41:50.000000000 +0200
> +++ linux-2.6.32-rc5.new/arch/x86/include/asm/processor.h	2009-11-02 10:39:47.177909657 +0100
> @@ -1000,7 +1001,13 @@
>  #define thread_saved_pc(t)	(*(unsigned long *)((t)->thread.sp - 8))
>  
>  #define task_pt_regs(tsk)	((struct pt_regs *)(tsk)->thread.sp0 - 1)
> -#define KSTK_ESP(tsk)		-1 /* sorry. doesn't work for syscall. */
> +
> +#ifdef CONFIG_IA32_EMULATION
> +extern unsigned long KSTK_ESP(struct task_struct *task);
> +#else
> +#define KSTK_ESP(task)		((task)->thread.usersp)
> +#endif
> +
>  #endif /* CONFIG_X86_64 */
>  
>  extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
> --- linux-2.6.32-rc5/arch/x86/kernel/process_64.c	2009-10-16 02:41:50.000000000 +0200
> +++ linux-2.6.32-rc5.new/arch/x86/kernel/process_64.c	2009-11-02 10:48:23.614936810 +0100
> @@ -664,3 +669,11 @@
>  	return do_arch_prctl(current, code, addr);
>  }
>  
> +#ifdef CONFIG_IA32_EMULATION
> +unsigned long KSTK_ESP(struct task_struct *task)
> +{
> +	return (test_tsk_thread_flag(task, TIF_IA32)) ? \
> +			(task_pt_regs(task)->sp) : \
> +			((task)->thread.usersp);
> +}
> +#endif

That's quite ugly. The KSTK_ESP() function should be unconditional and 
the #ifdef should be eliminated. If CONFIG_IA32_EMULATION is turned off 
(whichis rare) then TIF_IA32 wont be set so the function should work 
fine.

Thanks,

	Ingo
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