gdb was happy with what we had, but libgcc and libunwind weren't.
libgcc is happy with the kernel's restorer (because of the extra nop),
though libunwind looks like it's going to need code changes regardless.
We could make our restorer more like the kernel's one, but why bother
when we can just let the kernel supply the canonical one?
Bug: 17436734
Change-Id: I330fa5e68f23b1cf8133aa552896657b0b873ed3
* LP32 should use sa_restorer too. gdb expects this, and future (>= 3.15) x86
kernels will apparently stop supporting the case where SA_RESTORER isn't
set.
* gdb and libunwind care about the exact instruction sequences, so we need to
modify the code slightly in a few cases to match what they're looking for.
* gdb also cares about the exact function names (for some architectures),
so we need to use __restore and __restore_rt rather than __sigreturn and
__rt_sigreturn.
* It's possible that we don't have a VDSO; dl_iterate_phdr shouldn't assume
that getauxval(AT_SYSINFO_EHDR) will return a non-null pointer.
This fixes unwinding through a signal handler in gdb for all architectures.
It doesn't fix libunwind for arm and arm64. I'll keep investigating that...
Bug: 17436734
Change-Id: Ic1ea1184db6655c5d96180dc07bcc09628e647cb
Also clean up <signal.h> and revert the hacks that were necessary
for 64-bit in linker/debugger.cpp until now.
Change-Id: I3b0554ca8a49ee1c97cda086ce2c1954ebc11892
