Enable arm64 .eh_frame terminator, align it to 4
Every architecture that uses .eh_frame needs a terminator at the end to
ensure that an unwinder library doesn't read past the end of the
section. This can happen when the unwinder looks up a PC that doesn't
have a matching FDE. Both LLVM libunwind and libgcc fall back to an
.eh_frame scan if the .eh_frame_hdr search table scan fails.
By convention, this terminator section is aligned to 4, even on 64-bit
targets. e.g. Both libgcc and compiler-rt have a crtend with 4-byte
.eh_frame alignment on arm64 and x86_64.
In practice, lld strips off the terminator from input object files and
adds one unconditionally to the output, but bfd/gold still require a
crtend with a terminator.
References:
- https://reviews.llvm.org/D86256
- https://reviews.llvm.org/D87750
- https://sourceware.org/bugzilla/show_bug.cgi?id=2655
Test: examine crtend.o and crtend_so.o with `readelf -SW` and \
`objdump -Wf`
Change-Id: Ib8478ee446ad806898aa7147a6208d384c7516d5
diff --git a/libc/arch-common/bionic/crtend.S b/libc/arch-common/bionic/crtend.S
index 87d1120..3af9883 100644
--- a/libc/arch-common/bionic/crtend.S
+++ b/libc/arch-common/bionic/crtend.S
@@ -43,11 +43,9 @@
#if defined(__linux__) && defined(__ELF__)
.section .note.GNU-stack,"",%progbits
#endif
-#if defined(__i386__) || defined(__x86_64__)
+#if !defined(__arm__)
.section .eh_frame,"a",@progbits
-#if defined(__i386__)
.balign 4
-#endif
.type __FRAME_END__, @object
.size __FRAME_END__, 4
__FRAME_END__: