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Date: Tue, 24 Feb 2015 12:01:55 +0000
From: James Hogan <james.hogan@imgtec.com>
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To: Vineet Gupta <Vineet.Gupta1@synopsys.com>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
CC: Alexey Brodkin <Alexey.Brodkin@synopsys.com>,
        al Viro <viro@ZenIV.linux.org.uk>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: semantics of KSTK_ESP and friends
References: <C2D7FE5348E1B147BCA15975FBA230756658D08C@IN01WEMBXB.internal.synopsys.com>
In-Reply-To: <C2D7FE5348E1B147BCA15975FBA230756658D08C@IN01WEMBXB.internal.synopsys.com>
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Hi Vineet,

On 12/02/15 07:10, Vineet Gupta wrote:
> Hi,
>=20
> 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 en=
try ?
>=20
> 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 - whi=
ch 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

>=20
> ARC port uses these for unwinding the task of a sleeping task (hence ke=
rnel mode SP semantics).
> metag (from the looks of it) also seem to provide kernel mode value, wh=
ile most others seem to provide the user mode variant.
>=20
>  I can fix ARC to work with expectation of generic code, but wanted to =
understand anyways.
>=20
> Thx,
> -Vineet
>=20


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