syscall: fix system calls with misaligned arguments on freebsd/arm

This CL enables the current tree to work with FreeBSD 10-STABLE
on ARM EABI platforms, though there are still a few test fails.

Also updates documentation.

LGTM=iant
R=iant, dave
CC=golang-codereviews
https://golang.org/cl/61060044

diff --git a/src/pkg/syscall/asm_freebsd_arm.s b/src/pkg/syscall/asm_freebsd_arm.s
index 9283d079b8b116b3e301365da55021d07c707e54..c01ce6febf5dac274e74da4bf23ffe64fe1d9f47 100644 (file)
--- a/src/pkg/syscall/asm_freebsd_arm.s
+++ b/src/pkg/syscall/asm_freebsd_arm.s
@@ -8,13 +8,13 @@
 // System call support for ARM, FreeBSD
 //
 
-// func Syscall(trap int32, a1, a2, a3 int32) (r1, r2, err int32);
-// func Syscall6(trap int32, a1, a2, a3, a4, a5, a6 int32) (r1, r2, err int32);
-// func Syscall9(trap int32, a1, a2, a3, a4, a5, a6, a7, a8, a9 int64) (r1, r2, err int32)
+// func Syscall(trap, a1, a2, a3 uintptr) (r1, r2, errno uintptr);
+// func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr);
+// func Syscall9(trap, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, errno uintptr)
 
 TEXT   ·Syscall(SB),NOSPLIT,$0-28
        BL runtime·entersyscall(SB)
-       MOVW 0(FP), R7 // sigcall num
+       MOVW 0(FP), R7 // syscall number
        MOVW 4(FP), R0 // a1
        MOVW 8(FP), R1 // a2
        MOVW 12(FP), R2 // a3
@@ -23,69 +23,71 @@ TEXT        ·Syscall(SB),NOSPLIT,$0-28
        BCS error
        MOVW R0, 16(FP) // r1
        MOVW R1, 20(FP) // r2
-       MOVW R2, 24(FP) // err
+       MOVW R2, 24(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 error:
        MOVW $-1, R3
        MOVW R3, 16(FP) // r1
        MOVW R2, 20(FP) // r2
-       MOVW R0, 24(FP) // err
+       MOVW R0, 24(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 
 TEXT   ·Syscall6(SB),NOSPLIT,$0-40
        BL runtime·entersyscall(SB)
-       MOVW 0(FP), R7 // sigcall num
+       MOVW 0(FP), R7 // syscall number
        MOVW 4(FP), R0 // a1
        MOVW 8(FP), R1 // a2
        MOVW 12(FP), R2 // a3
        MOVW 16(FP), R3 // a4
-       ADD $24, R13 // a5 to a6 are passed on stack
+       MOVW R13, R4
+       MOVW $20(FP), R13 // a5 to a6 are passed on stack
        SWI $0 // syscall
-       SUB $24, R13
+       MOVW R4, R13
        MOVW $0, R2
        BCS error6
        MOVW R0, 28(FP) // r1
        MOVW R1, 32(FP) // r2
-       MOVW R2, 36(FP) // err
+       MOVW R2, 36(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 error6:
        MOVW $-1, R3
        MOVW R3, 28(FP) // r1
        MOVW R2, 32(FP) // r2
-       MOVW R0, 36(FP) // err
+       MOVW R0, 36(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 
 TEXT   ·Syscall9(SB),NOSPLIT,$0-52
        BL runtime·entersyscall(SB)
-       MOVW 0(FP), R7 // sigcall num
+       MOVW 0(FP), R7 // syscall number
        MOVW 4(FP), R0 // a1
        MOVW 8(FP), R1 // a2
        MOVW 12(FP), R2 // a3
        MOVW 16(FP), R3 // a4
-       ADD $24, R13 // a5 to a9 are passed on stack
+       MOVW R13, R4
+       MOVW $20(FP), R13 // a5 to a9 are passed on stack
        SWI $0 // syscall
-       SUB $24, R13
+       MOVW R4, R13
        MOVW $0, R2
        BCS error9
        MOVW R0, 40(FP) // r1
        MOVW R1, 44(FP) // r2
-       MOVW R2, 48(FP) // err
+       MOVW R2, 48(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 error9:
        MOVW $-1, R3
        MOVW R3, 40(FP) // r1
        MOVW R2, 44(FP) // r2
-       MOVW R0, 48(FP) // err
+       MOVW R0, 48(FP) // errno
        BL runtime·exitsyscall(SB)
        RET
 
 TEXT   ·RawSyscall(SB),NOSPLIT,$0-28
-       MOVW 0(FP), R7 // sigcall num
+       MOVW 0(FP), R7 // syscall number
        MOVW 4(FP), R0 // a1
        MOVW 8(FP), R1 // a2
        MOVW 12(FP), R2 // a3
@@ -94,33 +96,34 @@ TEXT        ·RawSyscall(SB),NOSPLIT,$0-28
        BCS errorr
        MOVW R0, 16(FP) // r1
        MOVW R1, 20(FP) // r2
-       MOVW R2, 24(FP) // err
+       MOVW R2, 24(FP) // errno
        RET
 errorr:
        MOVW $-1, R3
        MOVW R3, 16(FP) // r1
        MOVW R2, 20(FP) // r2
-       MOVW R0, 24(FP) // err
+       MOVW R0, 24(FP) // errno
        RET
 
 TEXT   ·RawSyscall6(SB),NOSPLIT,$0-40
-       MOVW 0(FP), R7 // sigcall num
+       MOVW 0(FP), R7 // syscall number
        MOVW 4(FP), R0 // a1
        MOVW 8(FP), R1 // a2
        MOVW 12(FP), R2 // a3
        MOVW 16(FP), R3 // a4
-       ADD $24, R13 // a5 to a6 are passed on stack
+       MOVW R13, R4
+       MOVW $20(FP), R13 // a5 to a6 are passed on stack
        SWI $0 // syscall
-       SUB $24, R13
+       MOVW R4, R13
        MOVW $0, R2
        BCS errorr6
        MOVW R0, 28(FP) // r1
        MOVW R1, 32(FP) // r2
-       MOVW R2, 36(FP) // err
+       MOVW R2, 36(FP) // errno
        RET
 errorr6:
        MOVW $-1, R3
        MOVW R3, 28(FP) // r1
        MOVW R2, 32(FP) // r2
-       MOVW R0, 36(FP) // err
+       MOVW R0, 36(FP) // errno
        RET