Fix signal trampolines.
* 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...
(cherry picked from commit 36f451a6d93b6807944d99fa23396e039c47e845)
Bug: 17436734
Change-Id: Ic1ea1184db6655c5d96180dc07bcc09628e647cb
diff --git a/libc/bionic/dl_iterate_phdr_static.cpp b/libc/bionic/dl_iterate_phdr_static.cpp
index 155a7a0..2196ac8 100644
--- a/libc/bionic/dl_iterate_phdr_static.cpp
+++ b/libc/bionic/dl_iterate_phdr_static.cpp
@@ -62,6 +62,11 @@
// Try the VDSO if that didn't work.
ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(getauxval(AT_SYSINFO_EHDR));
+ if (ehdr_vdso == nullptr) {
+ // There is no VDSO, so there's nowhere left to look.
+ return rc;
+ }
+
struct dl_phdr_info vdso_info;
vdso_info.dlpi_addr = 0;
vdso_info.dlpi_name = NULL;