[BFD][AARCH64]Disallow R_AARCH64_ABS32(LP64) & R_AARCH64_ABS16 in const section of shared object

[Renlin Li]

Hi Matthias,

Sorry for the break, I am currently looking into it.

Regards,
Renlin

On 02/02/18 16:45, Matthias Klose wrote:
> This seems to break kernel builds, and linking systemd against gnu-efi
> libraries.  Now reported in PR22764.
> 
> Matthias
> 
> On 18.10.2017 12:40, Renlin Li wrote:
>> Hi all,
>>
>> R_AARCH64_ABS64, R_AARCH64_ABS32 and R_AARCH64_ABS16 are data relocations
>> supported in AArch64 elf ABI.
>>
>> R_AARCH64_ABS64 under LP64 is allowed in shared object and a dynamic relocation
>> entry
>> will be generated. This allows the dynamic linker to do further symbol resolution.
>>
>> R_AARCH64_ABS32 likewise is allowed in shared object, however under ILP32 abi.
>>
>> The original behavior for R_AARCH64_ABS32 under LP64 is that, it's allowed
>> in shared object and silently resolved at static linking time.
>> No dynamic relocation entry is generate for it.
>>
>> R_AARCH64_ABS16 is allowed in shared object under both L64 and ILP32.
>> It's resolved at static linking time as well.
>>
>> Under LP64, the address should be 64-bit. R_AARCH64_ABS32 relocation indicates
>> an address that is only sized 32 bits which is not correct in LP64 shared object.
>> It's useful to error out.
>>
>> I have checked glibc dynamic linker code, R_AARCH64_ABS16 is not supported at
>> all. So
>> R_AARCH64_ABS16 should be reject in shared object completely.
>>
>>
>> In this patch, R_AARCH64_ABS32 is rejected under LP64 in read-only section of
>> shared object.
>> R_AARCH64_ABS16 is rejected in constant section of shared object in both ABI.
>>
>> This will sometimes provide useful information for buggy code.
>>
>> By the way, glibc aarch64 elf_machine_load_address is using R_AARCH64_ABS32 to
>> hold an address even in LP64. I had a discussion here sometime ago. The change
>> here will break the glibc build. This patch will not be committed until glibc
>> has been fixed.
>> https://sourceware.org/ml/libc-alpha/2017-10/msg00816.html
>>
>> testcases are also added. Binutils regression checked OK.
>> Linux kernel linked OK with new binutils. OK for trunk?
>>
>>
>> Regards,
>> Renlin Li
>>
>>
>> ld/ChangeLog:
>>
>> 2017-10-18  Renlin Li  <renlin.li@arm.com>
>>
>>  Â Â Â Â * testsuite/ld-aarch64/aarch64-elf.exp: Run new test cases.
>>  Â Â Â Â * testsuite/ld-aarch64/emit-relocs-258-dyn-bad.d: New.
>>  Â Â Â Â * testsuite/ld-aarch64/emit-relocs-258.s: New.
>>  Â Â Â Â * testsuite/ld-aarch64/emit-relocs-259-dyn-bad.d: New.
>>  Â Â Â Â * testsuite/ld-aarch64/emit-relocs-259.s: New.
>>  Â Â Â Â * testsuite/ld-aarch64/gc-relocs-257.s: Put R_AARCH64_ABS32,
>>  Â Â Â Â R_AARCH64_ABS16 data into data section.
>>
>> bfd/ChangeLog:
>>
>> 2017-10-18  Renlin Li  <renlin.li@arm.com>
>>
>>  Â Â Â Â * elfnn-aarch64.c (elfNN_aarch64_check_relocs): Disallow
>>  Â Â Â Â BFD_RELOC_AARCH64_16 in shared object const section. Disallow
>>  Â Â Â Â BFD_RELOC_AARCH64_32 in shared object const section under LP64.
>>
>>
>>
>