When dynamically linking, ifunc resolvers are called before TLS is
initialized, so they cannot be safely stack-protected.
We avoid disabling stack-protection on large numbers of files by
using __attribute__ ((__optimize__ ("-fno-stack-protector")))
to turn it off just for the resolvers themselves. (We provide
the attribute even when statically linking, because we will later
use it elsewhere too.)
As pointer out on the mailing list, the inline assembly code in
sysdeps/powerpc/ifunc-sel.h doesn't have a list of clobbered registers
and used wrong constraints.
This patch fixes that. I verified it doesn't introduce any change in the
generated code.
Changelog:
* sysdeps/powerpc/ifunc-sel.h (ifunc_sel): Add "11", "12", "cr0" to the
clobber list. Use "i" constraint instead of "X".
(ifunc_one): Add "12" to the clobber list. Use "i" constraint instead
of "X".
On 32-bit PowerPC GCC 6 always saves the PIC register on the stack in
the prologue and adjust the stack in the epilogue. It is therefore not
possible anymore to just exit the function in the inline asm code,
otherwise it corrupts the stack pointer. This causes the following tests
to fail when using GCC 6:
FAIL: elf/ifuncmain1
FAIL: elf/ifuncmain1pic
FAIL: elf/ifuncmain1picstatic
FAIL: elf/ifuncmain1pie
FAIL: elf/ifuncmain1staticpic
FAIL: elf/ifuncmain1staticpie
FAIL: elf/ifuncmain1vis
FAIL: elf/ifuncmain1vispic
FAIL: elf/ifuncmain1vispie
FAIL: elf/ifuncmain2pic
FAIL: elf/ifuncmain2picstatic
FAIL: elf/ifuncmain3
FAIL: elf/ifuncmain4picstatic
FAIL: elf/ifuncmain5
FAIL: elf/ifuncmain5picstatic
FAIL: elf/ifuncmain5staticpic
The solution is to replace the beqlr instructions by a beq to the end
of the inline asm code. This fixes all the above failures.
ChangeLog:
* sysdeps/powerpc/ifunc-sel.h (ifunc_sel): Replace beqlr instructions
by beq instructions jumping to the end of the function.
* sysdeps/powerpc/elf/ifunc-sel.h: Moved to ...
* sysdeps/powerpc/ifunc-sel.h: ... here.
* sysdeps/powerpc/elf/rtld-global-offsets.sym: Moved to ...
* sysdeps/powerpc/rtld-global-offsets.sym: ... here.
Nick Alcock
Aurelien Jarno
Andreas Jaeger