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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.
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@ -1,3 +1,9 @@
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2018-03-09 Aurelien Jarno <aurelien@aurel32.net>
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[BZ #22919]
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* sysdeps/unix/sysv/linux/sparc/sparc32/setcontext.S (__startcontext):
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Add nop before __startcontext, add explaining comments.
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2018-03-07 Adhemerval Zanella <adhemerval.zanella@linaro.org>
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[BZ #22926]
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@ -95,6 +95,19 @@ END(__setcontext)
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weak_alias (__setcontext, setcontext)
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/* We add an NOP here to separate between __setcontext/__startcontext. The
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wanted behavior that happens is: when unwinding from a function called
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inside a makecontext() context, FDE lookup will use '&__startcontext - 1',
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then returns NULL for no FDE found, and immediately ends the unwind, in
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a normal fashion.
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If this NOP word does not exist, FDE lookup just repeatedly finds
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__setcontext's FDE in an infinite loop, due to the convention of using
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'address - 1' for FDE lookup. Modifiying/deleting the below
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__startcontext's FDE has no help on this. */
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nop
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/* This is the helper code which gets called if a function which is
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registered with 'makecontext' returns. In this case we have to
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install the context listed in the uc_link element of the context
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