[ARM] Fix ld.so crash when built using Binutils 2.29

There is bug report that ld.so in GLIBC 2.24 built by Binutils 2.29 will crash
on arm-linux-gnueabihf.  This is confirmed, and the details is at:

   https://sourceware.org/bugzilla/show_bug.cgi?id=21725.

As analyzed in the PR, the old code was with the assumption that assembler
won't set bit0 of thumb function address if it comes from PC-relative
instructions and the calculation can be finished during assembling.  This
assumption however does not hold after PR gas/21458.

	* sysdeps/arm/dl-machine.h (elf_machine_load_address):  Also strip bit 0
	of pcrel_address under Thumb mode.
This commit is contained in:
Jiong Wang 2017-07-13 15:48:41 +01:00 committed by Szabolcs Nagy
parent 1dd577fd33
commit 5ba6405338
2 changed files with 17 additions and 4 deletions

View File

@ -1,3 +1,8 @@
2017-07-12 Jiong Wang <jiong.wang@arm.com>
* sysdeps/arm/dl-machine.h (elf_machine_load_address): Also strip bit 0
of pcrel_address under Thumb mode.
2017-07-12 Akhilesh Kumar <akhilesh.k@samsung.com>
[BZ #21207]

View File

@ -56,11 +56,19 @@ elf_machine_load_address (void)
extern Elf32_Addr internal_function __dl_start (void *) asm ("_dl_start");
Elf32_Addr got_addr = (Elf32_Addr) &__dl_start;
Elf32_Addr pcrel_addr;
#ifdef __thumb__
/* Clear the low bit of the funciton address. */
got_addr &= ~(Elf32_Addr) 1;
#endif
asm ("adr %0, _dl_start" : "=r" (pcrel_addr));
#ifdef __thumb__
/* Clear the low bit of the function address.
NOTE: got_addr is from GOT table whose lsb is always set by linker if it's
Thumb function address. PCREL_ADDR comes from PC-relative calculation
which will finish during assembling. GAS assembler before the fix for
PR gas/21458 was not setting the lsb but does after that. Always do the
strip for both, so the code works with various combinations of glibc and
Binutils. */
got_addr &= ~(Elf32_Addr) 1;
pcrel_addr &= ~(Elf32_Addr) 1;
#endif
return pcrel_addr - got_addr;
}