From: Vladislav Khmelevsky <och95@yandex.ru>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org, woodard@redhat.com
Subject: Re: [PATCH] elf: Fix rtld-audit trampoline for aarch64
Date: Thu, 17 Nov 2022 22:23:07 +0400 [thread overview]
Message-ID: <B57E427D-D92F-4726-9DF7-599A8EE012F8@yandex.ru> (raw)
In-Reply-To: <8c6d9a21-464b-3b8d-661a-a3b3733e1bb7@linaro.org>
Thank you for reviewing!
Yes, it is true tat inly x0/x1 are used as return register. But I have a specific audit library code that was storing some metadata in a free registers during plt entrer and reading it during plt exit :) As for a normal use cases both problems doesn't really affect anything.
> 17 нояб. 2022 г., в 22:15, Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> написал(а):
>
>
>
> On 17/11/22 05:47, Vladislav Khmelevsky wrote:
>> This patch fixes two problems with audit:
>> 1. The DL_OFFSET_RV_VPCS offset was mixed up with DL_OFFSET_RG_VPCS,
>> resulting in x2 register value nulling in RG structure.
>> 2. We need to preserve the x8 register before function call, but don't have
>> to save it's new value and restore it before return. Anyway the final
>> restore was using OFFSET_RV instead of OFFSET_RG value which is wrong (althoug doesn't affect anything).
>
> Patch looks ok, although I think currently the ABI only uses x0 and/or x1
> to return value (for __int128_t for instance). So I think it should not
> be a user-visible issue (at least tst-audit26 does check that lr_vpcs
> and lrv_vpcs are zeroed). Are you seeing any issue with current code?
> If so could you open a bug please?
>
>> ---
>> sysdeps/aarch64/dl-trampoline.S | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/sysdeps/aarch64/dl-trampoline.S b/sysdeps/aarch64/dl-trampoline.S
>> index 909b208578..d66f0b9c45 100644
>> --- a/sysdeps/aarch64/dl-trampoline.S
>> +++ b/sysdeps/aarch64/dl-trampoline.S
>> @@ -298,12 +298,11 @@ _dl_runtime_profile:
>> stp x2, x3, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*1]
>> stp x4, x5, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*2]
>> stp x6, x7, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*3]
>> - str x8, [x29, #OFFSET_RG + DL_OFFSET_RG_X0 + 16*4]
>> stp q0, q1, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*0]
>> stp q2, q3, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*1]
>> stp q4, q5, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*2]
>> stp q6, q7, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*3]
>> - str xzr, [X29, #OFFSET_RV + DL_OFFSET_RG_VPCS]
>> + str xzr, [X29, #OFFSET_RV + DL_OFFSET_RV_VPCS]
>>
>> /* Setup call to pltexit */
>> ldp x0, x1, [x29, #OFFSET_SAVED_CALL_X0]
>> @@ -315,7 +314,6 @@ _dl_runtime_profile:
>> ldp x2, x3, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*1]
>> ldp x4, x5, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*2]
>> ldp x6, x7, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*3]
>> - ldr x8, [x29, #OFFSET_RV + DL_OFFSET_RV_X0 + 16*4]
>> ldp q0, q1, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*0]
>> ldp q2, q3, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*1]
>> ldp q4, q5, [x29, #OFFSET_RV + DL_OFFSET_RV_V0 + 32*2]
next prev parent reply other threads:[~2022-11-17 18:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-17 8:47 Vladislav Khmelevsky
2022-11-17 18:15 ` Adhemerval Zanella Netto
2022-11-17 18:23 ` Vladislav Khmelevsky [this message]
2022-11-17 18:36 ` Adhemerval Zanella Netto
2022-11-17 18:51 ` Vladislav Khmelevsky
2022-12-02 18:20 ` Carlos O'Donell
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