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Re: [PATCH v2] Improve IFUNC check
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Thu, 5 Mar 2020 15:43:40 -0300
- Subject: Re: [PATCH v2] Improve IFUNC check
- References: <20200205060922.5pbgm5hfj2r6vrl2@google.com> <20200206122422.GA1533826@aurel32.net> <20200206185300.7hfx7gfrrof63mda@google.com> <20200208093746.GA98572@aurel32.net> <20200210191425.52xvvdot7kunt2gc@google.com>
On 10/02/2020 16:14, Fangrui Song wrote:
> On 2020-02-08, Aurelien Jarno wrote:
>> On 2020-02-06 10:53, Fangrui Song wrote:
>>> On 2020-02-06, Aurelien Jarno wrote:
>>> > Hi,
>>> >
>>> > On 2020-02-04 22:09, Fangrui Song wrote:
>>> > > GNU ld's RISCV port does not support IFUNC. ld -no-pie produces no
>>> > > relocation and the test passed incorrectly. Be more rigid by testing
>>> > > IRELATIVE explicitly.
>>> >
>>> > Thanks for your patch and sorry for the time to answer, I was testing it
>>> > on many architectures. First of all I confirm it fixes the issue when
>>> > building glibc with PIE on mips* and riscv64. I also confirm it
>>> > introduces no regression on aarch64, armv5, armv7, hppa, m68k, powerpc,
>>> > ppc64, ppc64le, s390x and x86_64.
>>> >
>>> > However it wrongly detects that IFUNC is not supported on sparc64 when
>>> > PIE is not in use. Here is the output of of readelf for the non-PIE
>>> > case:
>>> >
>>> > | Relocation section '.rela.dyn' at offset 0x110 contains 1 entry:
>>> > | Offset Info Type Sym. Value Sym. Name + Addend
>>> > | 000000200280 0000000000f8 R_SPARC_JMP_IREL 100128
>>>
>>> sparc64 -no-pie does not produce an R_SPARC_IRELATIVE. This looks weird.
>>> All other archs emit an R_*_IRELATIVE.
>>>
>>> Can you dump the assembly (including .text and .[i]plt)?
>>> Or can someone with sparc64 experience answer why sparc64 is different
>>> here?
>>
>> Here is the dump of the .iplt section:
>> Disassembly of section .iplt:
>>
>> 0000000000200200 <.iplt>:
>> ...
>> 200280: 03 00 00 80 sethi %hi(0x20000), %g1
>> 200284: 30 6f ff e7 b,a %xcc, 200220 <__start+0x1000f8>
>> 200288: 01 00 00 00 nop
>> 20028c: 01 00 00 00 nop
>> 200290: 01 00 00 00 nop
>> 200294: 01 00 00 00 nop
>> 200298: 01 00 00 00 nop
>> 20029c: 01 00 00 00 nop
>>
>> There is no .text nor .plt section.
>>
>> --
>> Aurelien Jarno GPG: 4096R/1DDD8C9B
>> aurelien@aurel32.net http://www.aurel32.net
>
> Attached PATCH v2.
>
> sparc64 has a non-conventional R_SPARC_JMP_IREL, along with conventional
> R_SPARC_IRELATIVE.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>