runtime: preserve R11 in darwin/arm entrypoint
The _rt0_arm_darwin_lib entrypoint has to conform to the darwin ARMv7
calling convention, which requires functions to preserve the value of
R11. Go uses R11 as the liblink REGTMP register, so save it manually.
Also avoid using R4, which is also callee-save.
Fixes #12590
Change-Id: I9c3b374e330f81ff8fc9c01fa20505a33ddcf39a
Reviewed-on: https://go-review.googlesource.com/14603
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/runtime/rt0_darwin_arm.s b/src/runtime/rt0_darwin_arm.s
index 95a2b17..d609850 100644
--- a/src/runtime/rt0_darwin_arm.s
+++ b/src/runtime/rt0_darwin_arm.s
@@ -16,27 +16,34 @@
//
// Note that all currently shipping darwin/arm platforms require
// cgo and do not support c-shared.
-TEXT _rt0_arm_darwin_lib(SB),NOSPLIT,$12
+TEXT _rt0_arm_darwin_lib(SB),NOSPLIT,$0
+ // R11 is REGTMP, reserved for liblink. It is used below to
+ // move R0/R1 into globals. However in the darwin ARMv7 calling
+ // convention, it is a callee-saved register. So we save it to a
+ // temporary register.
+ MOVW R11, R2
MOVW R0, _rt0_arm_darwin_lib_argc<>(SB)
MOVW R1, _rt0_arm_darwin_lib_argv<>(SB)
// Create a new thread to do the runtime initialization and return.
- MOVW _cgo_sys_thread_create(SB), R4
- CMP $0, R4
+ MOVW _cgo_sys_thread_create(SB), R3
+ CMP $0, R3
B.EQ nocgo
MOVW $_rt0_arm_darwin_lib_go(SB), R0
MOVW $0, R1
- BL (R4)
+ MOVW R2, R11
+ BL (R3)
RET
nocgo:
MOVW $0x400000, R0
- MOVW $_rt0_arm_darwin_lib_go(SB), R1
- MOVW $0, R2
- MOVW R0, (R13) // stacksize
- MOVW R1, 4(R13) // fn
- MOVW R2, 8(R13) // fnarg
- MOVW $runtime·newosproc0(SB), R4
- BL (R4)
+ MOVW R0, (R13) // stacksize
+ MOVW $_rt0_arm_darwin_lib_go(SB), R0
+ MOVW R0, 4(R13) // fn
+ MOVW $0, R0
+ MOVW R0, 8(R13) // fnarg
+ MOVW $runtime·newosproc0(SB), R3
+ MOVW R2, R11
+ BL (R3)
RET
TEXT _rt0_arm_darwin_lib_go(SB),NOSPLIT,$0
