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 #50185

Change-Id: I897731ddd2a9faad8218443a4c2f4b204ad7e173
Reviewed-on: https://go-review.googlesource.com/c/go/+/373074
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/runtime/sys_aix_ppc64.s b/src/runtime/sys_aix_ppc64.s
index c171c191c0e5ecf4a21e4c6271a20ba5fb3051d9..217ebb8878eba664ea2411268882458c023ee13e 100644 (file)
--- 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