[PATCH][gold][aarch64][pr23870] Check whether symbols with MOVW_.ABS relocations require PLT entries

[Egeyar Bagcioglu]

Hello,

The following patch on upstream glibc

https://sourceware.org/ml/libc-alpha/2017-09/msg00282.html

is causing crt1.o to contain R_AARCH64_MOVW_UABS_G* relocations for the 
symbol "main". AArch64 backend of gold currently does not check whether 
such symbols require a PLT entry.

This is causing pr 23870:
When a non-pie referring to a "main" symbol in a shared library is being 
linked using a recent crt1.o, gold is failing to create a dynamic symbol 
for "main". Therefore, upon calling "main", such an executable seg-faults.

I added a test case mimicking what _start and __libc_start_main does: 
The former gives an undefined symbol as an argument to the latter where 
it is called as a function. Therefore, the symbol does not become a 
global symbol in either .o and the linker needs to arrange the dynamic 
relocation.

The attached patch checks if a symbol with R_AARCH64_MOVW_.ABS_G* 
relocations needs a PLT entry and creates it if necessary. It is tested 
on aarch64-unknown-linux-gnu and caused no regressions.

gold/ChangeLog entry:

2019-01-28  Egeyar Bagcioglu  <egeyar.bagcioglu@oracle.com>

 Â Â Â  PR 23870
 Â Â Â  * aarch64.cc (Target_aarch64::Scan::global): Check if a symbol with
 Â Â Â  R_AARCH64_MOVW_.ABS_* relocations requires a PLT entry.
 Â Â Â  * testsuite/Makefile.am: Add aarch64_pr23870 test case.
 Â Â Â  * testsuite/Makefile.in: Regenerate.
 Â Â Â  * testsuite/aarch64_pr23870_bar.c: New file.
 Â Â Â  * testsuite/aarch64_pr23870_foo.c: New file.
 Â Â Â  * testsuite/aarch64_pr23870_main.S: New file.


Please take a look and apply if legitimate.

Regards,
Egeyar
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