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[Bug ld/16017] LD creates invalid PLT instructions on CORTEX-M3
From: |
cvs-commit at gcc dot gnu.org |
Subject: |
[Bug ld/16017] LD creates invalid PLT instructions on CORTEX-M3 |
Date: |
Wed, 08 Apr 2020 17:56:25 +0000 |
https://sourceware.org/bugzilla/show_bug.cgi?id=16017
--- Comment #31 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot
gnu.org> ---
The binutils-2_34-branch branch has been updated by Tamar Christina
<address@hidden>:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=aaf3f0599a210699a76767c07a7d7f62d7633d71
commit aaf3f0599a210699a76767c07a7d7f62d7633d71
Author: Tamar Christina <address@hidden>
Date: Wed Apr 1 10:47:18 2020 +0100
Arm: Fix LSB of GOT for Thumb2 only PLT.
When you have a Thumb only PLT then the address in the GOT for PLT0 needs
to
have the Thumb bit set since the instruction used in PLTn to get there is
`ldr.w pc` which is an inter-working instruction:
the PLT sequence in question is
00000120 <foo@plt>:
120: f240 0c98 movw ip, #152 ; 0x98
124: f2c0 0c01 movt ip, #1
128: 44fc add ip, pc
12a: f8dc f000 ldr.w pc, [ip]
12e: e7fc b.n 12a <foo@plt+0xa>
Disassembly of section .text:
00000130 <bar>:
130: b580 push {r7, lr}
132: af00 add r7, sp, #0
134: f7ff fff4 bl 120 <foo@plt>
and previously the linker would generate
Hex dump of section '.got':
...
0x000101b8 40010100 00000000 00000000 10010000 @...............
Which would make it jump and transition out of thumb mode and crash since
you
only have thumb mode on such cores.
Now it correctly generates
Hex dump of section '.got':
...
0x000101b8 40010100 00000000 00000000 11010000 @...............
Thanks to Amol for testing patch and to rgujju for reporting it.
bfd/ChangeLog:
PR ld/16017
* elf32-arm.c (elf32_arm_populate_plt_entry): Set LSB of the PLT0
address in the GOT if in thumb only mode.
ld/ChangeLog:
PR ld/16017
* testsuite/ld-arm/arm-elf.exp (thumb-plt-got): New.
* testsuite/ld-arm/thumb-plt-got.d: New test.
(cherry picked from commit a7618269b727da9cf56727c22cb538ff5f0e4d25)
(cherry picked from commit 3ce23ca1de4c769c4b7247f0724a10ef5fb24a11)
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