https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727
Kewen Lin <linkw at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amodra at gcc dot gnu.org,
| |amodra at gmail dot com,
| |segher at gcc dot gnu.org
--- Comment #2 from Kewen Lin <linkw at gcc dot gnu.org> ---
This is one bug in libgcc morestack support (powerpc64 elfv1 ABI specific):
The segfault happens on:
Dump of assembler code for function 00000000.plt_call._Unwind_Resume:
=> 0x0000000010003580 <+0>: std r2,40(r1)
0x0000000010003584 <+4>: ld r12,-31760(r2)
0x0000000010003588 <+8>: mtctr r12
0x000000001000358c <+12>: ld r2,-31752(r2)
0x0000000010003590 <+16>: cmpldi r2,0
0x0000000010003594 <+20>: bnectr+
0x0000000010003598 <+24>: b 0x100031a4 <_Unwind_Resume@plt>
0x000000001000359c <+28>: .long 0x0
The target address of std at 0x0000000010003580 is 0x7ffff72e0008, which isn't
writable as the following mappings:
0x7ffff40f0000 0x7ffff72e0000 0x31f0000 0x0 rw-p
0x7ffff72e0000 0x7ffff72f0000 0x10000 0x0 ---p
For the stack segment returned from __generic_morestack, we adjust it by 32
bytes:
bl JUMP_TARGET(__generic_morestack)
# Start using new stack
stdu %r29,-32(%r3) # back-chain
mr %r1,%r3
but it isn't enough for powerpc64 elfv1 ABI as the TOC base save slot is with
offset 40.
The fix can be to use PARAMS like:
diff --git a/libgcc/config/rs6000/morestack.S
b/libgcc/config/rs6000/morestack.S
index 5e7ad133303..f2fea6abb10 100644
--- a/libgcc/config/rs6000/morestack.S
+++ b/libgcc/config/rs6000/morestack.S
@@ -205,12 +205,12 @@ ENTRY0(__morestack)
bl JUMP_TARGET(__generic_morestack)
# Start using new stack
- stdu %r29,-32(%r3) # back-chain
+ stdu %r29,-PARAMS(%r3) # back-chain
mr %r1,%r3
# Set __private_ss stack guard for the new stack.
ld %r12,NEWSTACKSIZE_SAVE(%r29) # modified size
- addi %r3,%r3,BACKOFF-32
+ addi %r3,%r3,BACKOFF-PARAMS
sub %r3,%r3,%r12
# Note that a signal frame has $pc pointing at the instruction
# where the signal occurred. For something like a timer
============================================================
Hi Alan, does the above fix look reasonable to you?
