When cross-compiling libunwind with optimizations (-O1 or higher),
gcc-4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) optimizes away the memory
writes prior to the inline asm() statement in arm_local_resume() in the
non-signal-frame path, causing the `regs' array to be only allocated on
the stack, but not populated. This means that we are restoring garbage
to the registers.
As suggested in the GCC docs, add a fixed size input memory constraint
for the array content. This is enough to get the desired code to be
generated.
Adding __builtin_unreachable() to the point that we should never reach
was also in itself enough to inhibit the optimization. It also reduces
the function size by a few instructions.
Define unw_tdep_context rather than using ucontext_t in order to support
systems that lack ucontext.h. Note that POSIX.1-2008 removed getcontext,
makecontext and swapcontext from its specification.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
This patch add support for resuming at a certain stack frame even if signal
frames are involved. For restoring the registers the trampoline (sigreturn)
is used. RT and non-RT signal frames are handled for both >=2.6.18 and
<2.6.18 kernels.
Signed-off-by: Ken Werner <ken.werner@linaro.org>
