path: root/src/signal/powerpc64
diff options
authorBobby Bingham <>2017-08-04 00:12:32 -0500
committerRich Felker <>2017-08-11 20:31:33 -0400
commite31c8c2d796e8a9596503f079dc567c45f93c2ae (patch)
tree11d78ae147d030b5ead0e005cd470d8841b0c8fa /src/signal/powerpc64
parent52cf5c18f4ad3a7a59fb7113cf115c6fc05c7494 (diff)
ppc64: fix setjmp/longjmp handling of TOC pointer
The TOC pointer is constant within a single dso, but needs to be saved and restored around cross-dso calls. The PLT stub saves it to the caller's stack frame, and the linker adds code to the caller to restore it. With a local call, as within a single dso or with static linking, this doesn't happen and the TOC pointer is always in r2. Therefore, setjmp/longjmp need to save/restore the TOC pointer from/to different locations depending on whether the call to setjmp was a local or non-local call. It is always safe for longjmp to restore to both r2 and the caller's stack. If the call to setjmp was local, and only r2 matters and the stack location will be ignored, but is required by the ABI to be reserved for the TOC pointer. If the call was non-local, then only the stack location matters, and whatever is restored into r2 will be clobbered anyway when the caller reloads r2 from the stack. A little extra care is required for sigsetjmp, because it uses setjmp internally. After the second return from this setjmp call, r2 will contain the caller's TOC pointer instead of libc's TOC pointer. We need to save and restore the correct libc pointer before we can tail call to __sigsetjmp_tail.
Diffstat (limited to 'src/signal/powerpc64')
1 files changed, 14 insertions, 7 deletions
diff --git a/src/signal/powerpc64/sigsetjmp.s b/src/signal/powerpc64/sigsetjmp.s
index 52ac1d03..410c2831 100644
--- a/src/signal/powerpc64/sigsetjmp.s
+++ b/src/signal/powerpc64/sigsetjmp.s
@@ -2,29 +2,36 @@
.global __sigsetjmp
.type sigsetjmp,%function
.type __sigsetjmp,%function
- .hidden ___setjmp
+ .hidden __setjmp_toc
addis 2, 12, .TOC.-__sigsetjmp@ha
addi 2, 2, .TOC.-__sigsetjmp@l
+ ld 5, 24(1) # load from the TOC slot in the caller's stack frame
+ b 1f
.localentry sigsetjmp,.-sigsetjmp
.localentry __sigsetjmp,.-__sigsetjmp
+ mr 5, 2
cmpwi cr7, 4, 0
- beq- cr7, ___setjmp
+ beq- cr7, __setjmp_toc
- mflr 5
- std 5, 512(3)
- std 16, 512+8+8(3)
+ mflr 6
+ std 6, 512(3)
+ std 2, 512+16(3)
+ std 16, 512+24(3)
mr 16, 3
- bl ___setjmp
+ bl __setjmp_toc
mr 4, 3
mr 3, 16
ld 5, 512(3)
mtlr 5
- ld 16, 512+8+8(3)
+ ld 2, 512+16(3)
+ ld 16, 512+24(3)
.hidden __sigsetjmp_tail
b __sigsetjmp_tail