commit 6e45d37decbbaf78ed4685213aebb1c9b5ccf8c2
author Christopher Ferris <cferris@google.com> Wed Apr 27 18:31:02 2016 -0700
committer Christopher Ferris <cferris@google.com> Wed Apr 27 18:31:02 2016 -0700
tree 7fc6d3f9efe6c96af6bc0cb51a83b8022474c349
parent f3158b94ab102b0f1066990683f08d283417cbba

Add unwind information for r7 in arm syscalls.

It turns out that clang can emit code where the sp is saved in the r7
register on arm. Unfortunately, a lot of our syscalls overwrite that
value while the syscall is executing, so unwinding through that syscall
fails.

Update the syscall generation code to add unwinding information for
these uses.

Bug: 28411713
Change-Id: Id51a5d43c058631bb50834527f93fa299bbcf759

libc/arch-arm/syscalls/sendfile.S

diff --git a/libc/arch-arm/syscalls/sendfile.S b/libc/arch-arm/syscalls/sendfile.S
index afae021..52e78d0 100644
--- a/libc/arch-arm/syscalls/sendfile.S
+++ b/libc/arch-arm/syscalls/sendfile.S
@@ -4,9 +4,11 @@
 
 ENTRY(sendfile)
     mov     ip, r7
+    .cfi_register r7, ip
     ldr     r7, =__NR_sendfile
     swi     #0
     mov     r7, ip
+    .cfi_restore r7
     cmn     r0, #(MAX_ERRNO + 1)
     bxls    lr
     neg     r0, r0