Add stack unwinding directives to assembly leaf functions.
So that the real culprit of native crashes can surface in the stack trace.
diff --git a/libc/arch-arm/bionic/atomics_arm.S b/libc/arch-arm/bionic/atomics_arm.S
index b2da09f..f8b23e6 100644
--- a/libc/arch-arm/bionic/atomics_arm.S
+++ b/libc/arch-arm/bionic/atomics_arm.S
@@ -41,6 +41,8 @@
.equ kernel_cmpxchg, 0xFFFF0FC0
.equ kernel_atomic_base, 0xFFFF0FFF
__atomic_dec:
+ .fnstart
+ .save {r4, lr}
stmdb sp!, {r4, lr}
mov r2, r0
1: @ atomic_dec
@@ -53,8 +55,11 @@
add r0, r1, #1
ldmia sp!, {r4, lr}
bx lr
+ .fnend
__atomic_inc:
+ .fnstart
+ .save {r4, lr}
stmdb sp!, {r4, lr}
mov r2, r0
1: @ atomic_inc
@@ -67,9 +72,12 @@
sub r0, r1, #1
ldmia sp!, {r4, lr}
bx lr
+ .fnend
/* r0(old) r1(new) r2(addr) -> r0(zero_if_succeeded) */
__atomic_cmpxchg:
+ .fnstart
+ .save {r4, lr}
stmdb sp!, {r4, lr}
mov r4, r0 /* r4 = save oldvalue */
1: @ atomic_cmpxchg
@@ -84,6 +92,7 @@
2: @ atomic_cmpxchg
ldmia sp!, {r4, lr}
bx lr
+ .fnend
#else
#define KUSER_CMPXCHG 0xffffffc0