runtime: ensure that asmsyscall6 follow AIX stack convention

The function asmsyscall6 must follow AIX stack layout. It means that its first local variable must be stored after its arguments area, ie after offset 112. Fixes golang#50185 Change-Id: I897731ddd2a9faad8218443a4c2f4b204ad7e173 Reviewed-on: https://go-review.googlesource.com/c/go/+/373074 Trust: Dmitri Shuralyov <[email protected]> Reviewed-by: Cherry Mui <[email protected]>
jproberts · Jun 21, 2022 · a713c0b · a713c0b
1 parent 9d3261e
commit a713c0b
Showing 1 changed file with 9 additions and 3 deletions.
diff --git a/src/runtime/sys_aix_ppc64.s b/src/runtime/sys_aix_ppc64.s
@@ -25,7 +25,12 @@ TEXT callCfunction<>(SB),	NOSPLIT|NOFRAME,$0
 // stored in libcall_fn and store the results in libcall struture
 // Up to 6 arguments can be passed to this C function
 // Called by runtime.asmcgocall
-// It reserves a stack of 288 bytes for the C function.
+// It reserves a stack of 288 bytes for the C function. It must
+// follow AIX convention, thus the first local variable must
+// be stored at the offset 112, after the linker area (48 bytes)
+// and the argument area (64).
+// The AIX convention is described here:
+// https://www.ibm.com/docs/en/aix/7.2?topic=overview-runtime-process-stack
 // NOT USING GO CALLING CONVENTION
 // runtime.asmsyscall6 is a function descriptor to the real asmsyscall6.
 DATA	runtime·asmsyscall6+0(SB)/8, $asmsyscall6<>(SB)
@@ -34,7 +39,8 @@ DATA	runtime·asmsyscall6+16(SB)/8, $0
 GLOBL	runtime·asmsyscall6(SB), NOPTR, $24
 
 TEXT asmsyscall6<>(SB),NOSPLIT,$256
-	MOVD	R3, 48(R1) // Save libcall for later
+	// Save libcall for later
+	MOVD	R3, 112(R1)
 	MOVD	libcall_fn(R3), R12
 	MOVD	libcall_args(R3), R9
 	MOVD	0(R9), R3
@@ -50,7 +56,7 @@ TEXT asmsyscall6<>(SB),NOSPLIT,$256
 	MOVD	40(R1), R2
 
 	// Store result in libcall
-	MOVD	48(R1), R5
+	MOVD	112(R1), R5
 	MOVD	R3, (libcall_r1)(R5)
 	MOVD	$-1, R6
 	CMP	R6, R3