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| author | Aurelien Jarno <aurelien@aurel32.net> | 2018-03-09 00:14:27 +0100 |
|---|---|---|
| committer | Aurelien Jarno <aurelien@aurel32.net> | 2018-03-09 00:14:27 +0100 |
| commit | 9aa5c222b9e0409143410a02b6364a3b25dbf028 (patch) | |
| tree | cab255c55954064b17343fdb8d5f600b2d289f61 | |
| parent | e921c89e01389161c036ec09112da6e18aeaa688 (diff) | |
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sparc32: Add nop before __startcontext to stop unwinding [BZ #22919]
On sparc32 tst-makecontext fails, as backtrace called within a context
created by makecontext to yield infinite backtrace.
Fix that the same way than nios2 by adding a nop just before
__startcontext. This is needed as otherwise FDE lookup just repeatedly
finds __setcontext's FDE in an infinite loop, due to the convention of
using 'address - 1' for FDE lookup.
Changelog:
[BZ #22919]
* sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S (__startcontext):
Add nop before __startcontext, add explaining comments.
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S | 13 |
2 files changed, 19 insertions, 0 deletions
@@ -1,3 +1,9 @@ +2018-03-09 Aurelien Jarno <aurelien@aurel32.net> + + [BZ #22919] + * sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S (__startcontext): + Add nop before __startcontext, add explaining comments. + 2018-03-07 Adhemerval Zanella <adhemerval.zanella@linaro.org> [BZ #22926] diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S b/sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S index 695f172c63..283aef1b30 100644 --- a/sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S @@ -95,6 +95,19 @@ END(__setcontext) weak_alias (__setcontext, setcontext) +/* We add an NOP here to separate between __setcontext/__startcontext. The + wanted behavior that happens is: when unwinding from a function called + inside a makecontext() context, FDE lookup will use '&__startcontext - 1', + then returns NULL for no FDE found, and immediately ends the unwind, in + a normal fashion. + + If this NOP word does not exist, FDE lookup just repeatedly finds + __setcontext's FDE in an infinite loop, due to the convention of using + 'address - 1' for FDE lookup. Modifiying/deleting the below + __startcontext's FDE has no help on this. */ + + nop + /* This is the helper code which gets called if a function which is registered with 'makecontext' returns. In this case we have to install the context listed in the uc_link element of the context |