runtime: remove OABI check from ARM startup

The code in question is trying to print a nice error message
when a Go EABI binary runs on an OABI machine.
Unfortunately, the only way to do that is to use
ARM Thumb instructions, which we otherwise don't use.

There exist ARM EABI machines that do not support Thumb.
We could run on them if not for this OABI check, so disable it.

Fixes #5685.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/13234050

diff --git a/src/pkg/runtime/rt0_linux_arm.s b/src/pkg/runtime/rt0_linux_arm.s
index 63133e9aded30f656897616cfa3b8a00054dff18..309fa2f79de1febbe49ec99284c842afed023a3d 100644 (file)
--- a/src/pkg/runtime/rt0_linux_arm.s
+++ b/src/pkg/runtime/rt0_linux_arm.s
@@ -22,31 +22,36 @@ TEXT _rt0_arm_linux1(SB),NOSPLIT,$-4
 
        // Save argc and argv
        MOVM.DB.W [R0-R1], (R13)
-       // set up sa_handler
-       MOVW    $bad_abi<>(SB), R0 // sa_handler
-       MOVW    $0, R1 // sa_flags
-       MOVW    $0, R2 // sa_restorer
-       MOVW    $0, R3 // sa_mask
-       MOVM.DB.W [R0-R3], (R13)
-       MOVW    $4, R0 // SIGILL
-       MOVW    R13, R1 // sa
-       SUB     $16, R13
-       MOVW    R13, R2 // old_sa
-       MOVW    $8, R3 // c
-       MOVW    $174, R7 // sys_sigaction
-       BL      oabi_syscall<>(SB)
+
+       // Thumb mode OABI check disabled because there are some
+       // EABI systems that do not support Thumb execution.
+       // We can run on them except for this check!
+
+       // // set up sa_handler
+       // MOVW $bad_abi<>(SB), R0 // sa_handler
+       // MOVW $0, R1 // sa_flags
+       // MOVW $0, R2 // sa_restorer
+       // MOVW $0, R3 // sa_mask
+       // MOVM.DB.W [R0-R3], (R13)
+       // MOVW $4, R0 // SIGILL
+       // MOVW R13, R1 // sa
+       // SUB  $16, R13
+       // MOVW R13, R2 // old_sa
+       // MOVW $8, R3 // c
+       // MOVW $174, R7 // sys_sigaction
+       // BL   oabi_syscall<>(SB)
 
        // do an EABI syscall
        MOVW    $20, R7 // sys_getpid
        SWI     $0 // this will trigger SIGILL on OABI systems
        
-       MOVW    $4, R0  // SIGILL
-       MOVW    R13, R1 // sa
-       MOVW    $0, R2 // old_sa
-       MOVW    $8, R3 // c
-       MOVW    $174, R7 // sys_sigaction
-       SWI     $0 // restore signal handler
-       ADD     $32, R13
+       // MOVW $4, R0  // SIGILL
+       // MOVW R13, R1 // sa
+       // MOVW $0, R2 // old_sa
+       // MOVW $8, R3 // c
+       // MOVW $174, R7 // sys_sigaction
+       // SWI  $0 // restore signal handler
+       // ADD  $32, R13
 
        SUB     $4, R13 // fake a stack frame for runtime·setup_auxv
        BL      runtime·setup_auxv(SB)