Re: [PATCH] elf: Fix rtld-audit trampoline for aarch64

[Vladislav Khmelevsky via Libc-alpha <libc-alpha@sourceware.org>]

Thanks! But I would need some guidance from you if you don't mind. First of all I don't have write access to the repo, I would very appreciate if you or somebody would help me to merge this :)

> 17 нояб. 2022 г., в 22:36, Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> написал(а):
> 
> 
> 
> On 17/11/22 15:23, Vladislav Khmelevsky wrote:
>> 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.
>> 
> 
> Fair enough, although we might want to backport this.
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
> 
>>> 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]
>>