Re: [PATCH dwarves v2 0/3] pahole: Fix arm64 argument register allocation

[Alan Maguire <alan.maguire@oracle.com>]

On 24/09/2026 17:20, Alexei Starovoitov wrote:
> 
> On Thu Sep 24, 2026 at 4:15 PM UTC, Alan Maguire wrote:
>> On 17/09/2026 17:40, Yonghong Song wrote:
>>> 
>>> The arm64 ABI starts an argument twice the register size on an even-numbered
>>> argument register, leaving a hole when the next free register is an odd one:
>>> 
>>>   u64 f(u64 a, __int128 v, u64 b);
>>> 
>>> passes a in x0, v in x2:x3 -- skipping x1 -- and b in x4.  pahole did not
>>> model the hole, so b looked like it was in an unexpected register and the
>>> whole function was dropped from BTF.  Patch 1 skips the register the ABI
>>> leaves behind, patch 3 adds a test for it.  Only arm64 has this rule; the
>>> other architectures are unaffected.
>>> 
>>> Patch 2 is a small follow-up.  Floating point and vector arguments are
>>> allocated from a register bank of their own -- v0-v7 on arm64, xmm0-xmm7 on
>>> x86-64 -- so a wide one never occupies a general purpose register pair and
>>> must not trigger the even-register rule either.  It does not change the BTF
>>> emitted today, because such an argument still advances the general purpose
>>> register index by its own size, so it comes with no test of its own; it
>>> keeps the alignment rule scoped to the bank it applies to.
>>>
>>
>> one small issue here; we record alignment for structs from DW_AT_align
>> in associated tags; we should ensure that we utilize that alignment
>> where available. However it's a bit broken in that we don't appear
>> to record alignment for typedefs, just structs.
>>
>> I think we can tackle that with a followup though; unless anyone objects I'll
>> land these patches later today.
> 
> Pls go ahead.
> Also pls land LOC* things too, so you can post the rest of LOC* kernel bits.
> So that everything lands and ready for the merge window in a couple weeks.
> 
> People will be traveling soon, so the sooner the better.
> 

Sure; this series is applied; location patches will go out shortly. We will need a
libbpf sync commit with latest libbpf for pahole too; Andrii would you mind doing
that when you get a chance? (The pahole stuff will still build without latest libbpf
but the inline feature will not work without the APIs to add location data).