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Add an ugly hack to libgcc's unwind code, to make it behave properly at

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runtime on amd64, when it is compiled by clang.  Some versions of clang
don't save and restore all callee registers, if a __builtin_eh_return()
intrinsic is used in a function.  This is particularly bad on amd64.

Until the problem gets fixed by upstream, use an asm statement to force
clang to assume the registers in question are clobbered, when invoking
__builtin_eh_return(), so it will emit code to save and restore them.

This should fix the crashes reported on -current with some C++ programs,
particularly those that throw exceptions over multiple function
boundaries.

Reported by:	stefanf
MFC after:	3 days
This commit is contained in:
Dimitry Andric 2013-01-10 23:36:02 +00:00
parent 3da2132e52
commit bfd6a1d202
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=245272
1 changed files with 12 additions and 0 deletions
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12
contrib/gcc/unwind-dw2.c
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@ -1438,6 +1438,17 @@ uw_init_context_1 (struct _Unwind_Context *context,
context->ra = __builtin_extract_return_addr (outer_ra);
}
#if defined(__clang__) && defined(__amd64__)
/* Some versions of clang don't save and restore all callee registers, if a
__builtin_eh_return() intrinsic is used in a function. This is particularly
bad on amd64. For now, use the following ugly hack to force it to assume
those registers are clobbered, when invoking __builtin_eh_return(), so it
will emit code to save and restore them. */
#define CLOBBER_REGS_HACK \
__asm __volatile(" " : : : "r15", "r14", "r13", "r12", "rbx", "rdx", "rax");
#else
#define CLOBBER_REGS_HACK
#endif /* __clang__ */
/* Install TARGET into CURRENT so that we can return to it. This is a
macro because __builtin_eh_return must be invoked in the context of
@ -1448,6 +1459,7 @@ uw_init_context_1 (struct _Unwind_Context *context,
{ \
long offset = uw_install_context_1 ((CURRENT), (TARGET)); \
void *handler = __builtin_frob_return_addr ((TARGET)->ra); \
CLOBBER_REGS_HACK \
__builtin_eh_return (offset, handler); \
} \
while (0)