commit f5a9123d9f365e3a72ac9f2a3921f439541a87e8
author Christopher Ferris <cferris@google.com> Wed Apr 27 18:31:02 2016 -0700
committer Christopher Ferris <cferris@google.com> Wed Apr 27 20:34:47 2016 -0700
tree 22f028385c21a408bd228a79a94f02024cb3f39b
parent b3c1ff69d293d095c36371ecc21e0505c6156db7

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
(cherry picked from commit 6e45d37decbbaf78ed4685213aebb1c9b5ccf8c2)

Change-Id: Ib775effc44c4113735fe9032b0602b9d63e3e390

libc/tools/gensyscalls.py

diff --git a/libc/tools/gensyscalls.py b/libc/tools/gensyscalls.py
index f7785d6..04ccf39 100755
--- a/libc/tools/gensyscalls.py
+++ b/libc/tools/gensyscalls.py
@@ -62,9 +62,11 @@
 
 arm_eabi_call_default = syscall_stub_header + """\
     mov     ip, r7
+    .cfi_register r7, ip
     ldr     r7, =%(__NR_name)s
     swi     #0
     mov     r7, ip
+    .cfi_restore r7
     cmn     r0, #(MAX_ERRNO + 1)
     bxls    lr
     neg     r0, r0