From: Michael Ellerman <mpe@ellerman•id.au>
To: "Naveen N. Rao" <naveen.n.rao@linux•ibm.com>,
linuxppc-dev@lists•ozlabs.org
Cc: amodra@gmail•com
Subject: Re: [PATCH] powerpc/vdso: Fix incorrect CFI in gettimeofday.S
Date: Tue, 17 May 2022 22:32:09 +1000 [thread overview]
Message-ID: <877d6kpcfq.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <1652772528.r6qrwbbda5.naveen@linux.ibm.com>
"Naveen N. Rao" <naveen.n.rao@linux•ibm.com> writes:
> Michael Ellerman wrote:
>>
>> diff --git a/arch/powerpc/kernel/vdso/gettimeofday.S b/arch/powerpc/kernel/vdso/gettimeofday.S
>> index eb9c81e1c218..0aee255e9cbb 100644
>> --- a/arch/powerpc/kernel/vdso/gettimeofday.S
>> +++ b/arch/powerpc/kernel/vdso/gettimeofday.S
>> @@ -22,12 +22,15 @@
>> .macro cvdso_call funct call_time=0
>> .cfi_startproc
>> PPC_STLU r1, -PPC_MIN_STKFRM(r1)
>> + .cfi_adjust_cfa_offset PPC_MIN_STKFRM
>> mflr r0
>> - .cfi_register lr, r0
>> PPC_STLU r1, -PPC_MIN_STKFRM(r1)
>> + .cfi_adjust_cfa_offset PPC_MIN_STKFRM
>> PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
>
> <snip>
>
>> @@ -46,6 +50,7 @@
>> mtlr r0
>> .cfi_restore lr
>> addi r1, r1, 2 * PPC_MIN_STKFRM
>> + .cfi_def_cfa_offset 0
>
> Should this be .cfi_adjust_cfa_offset, given that we used that at the
> start of the function?
AIUI "adjust x" is offset += x, whereas "def x" is offset = x.
So we could use adjust here, but we'd need to adjust by -(2 * PPC_MIN_STKFRM).
It seemed clearer to just set the offset back to 0, which is what it is
at the start of the function.
But I'm not a CFI expert at all, so I'll defer to anyone else who has an
opinion :)
cheers
next prev parent reply other threads:[~2022-05-17 12:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-02 12:50 [PATCH] powerpc/vdso: Fix incorrect CFI in gettimeofday.S Michael Ellerman
2022-05-02 14:27 ` Segher Boessenkool
2022-05-02 23:53 ` Alan Modra
2022-05-04 12:34 ` Michael Ellerman
2022-05-04 12:27 ` Michael Ellerman
2022-05-04 14:08 ` Segher Boessenkool
2022-05-08 11:11 ` Michael Ellerman
2022-05-17 7:33 ` Naveen N. Rao
2022-05-17 12:32 ` Michael Ellerman [this message]
2022-05-18 9:38 ` Naveen N. Rao
2022-05-19 1:30 ` Alan Modra
2022-05-20 12:14 ` Naveen N. Rao
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