* semantics of KSTK_ESP and friends
@ 2015-02-12 7:10 Vineet Gupta
2015-02-24 12:01 ` James Hogan
0 siblings, 1 reply; 2+ messages in thread
From: Vineet Gupta @ 2015-02-12 7:10 UTC (permalink / raw)
To: linux-arch@vger.kernel.org, james Hogan; +Cc: Alexey Brodkin, al Viro, lkml
Hi,
Is KSTK_ESP supposed to return the kernel mode SP of a sleeping task or is it supposed to provide the user mode SP at the time of last kernel entry ?
The 2 non arch users of the API expect the user mode SP semantics:
* vm_is_stack_for_task() - to annotate /proc/<pid>/maps stack vma - which is shere Alexey noted this.
* do_task_stat()
ARC port uses these for unwinding the task of a sleeping task (hence kernel mode SP semantics).
metag (from the looks of it) also seem to provide kernel mode value, while most others seem to provide the user mode variant.
I can fix ARC to work with expectation of generic code, but wanted to understand anyways.
Thx,
-Vineet
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: semantics of KSTK_ESP and friends
2015-02-12 7:10 semantics of KSTK_ESP and friends Vineet Gupta
@ 2015-02-24 12:01 ` James Hogan
0 siblings, 0 replies; 2+ messages in thread
From: James Hogan @ 2015-02-24 12:01 UTC (permalink / raw)
To: Vineet Gupta, linux-arch@vger.kernel.org; +Cc: Alexey Brodkin, al Viro, lkml
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Hi Vineet,
On 12/02/15 07:10, Vineet Gupta wrote:
> Hi,
>
> Is KSTK_ESP supposed to return the kernel mode SP of a sleeping task or is it supposed to provide the user mode SP at the time of last kernel entry ?
>
> The 2 non arch users of the API expect the user mode SP semantics:
> * vm_is_stack_for_task() - to annotate /proc/<pid>/maps stack vma - which is shere Alexey noted this.
> * do_task_stat()
Judging by both these uses, it would be the task's user mode SP that is
desired. Same for KSTK_EIP by the looks of it. Well spotted!
I'll look into fixing Metag.
Cheers
James
>
> ARC port uses these for unwinding the task of a sleeping task (hence kernel mode SP semantics).
> metag (from the looks of it) also seem to provide kernel mode value, while most others seem to provide the user mode variant.
>
> I can fix ARC to work with expectation of generic code, but wanted to understand anyways.
>
> Thx,
> -Vineet
>
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