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syscall, runtime/internal/syscall: zero r2 before mips linux syscalls

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All mips variant perform syscalls similarly. R2 (v0) holds r1 and R3
(v1) holds r2 of a syscall. The latter is only used by 2-ret syscalls.
A 1-ret syscall would not touch R3 but keeps it as is, making r2 be a
random value. Always reset it to 0 before SYSCALL to fix the issue.

Fixes #56426

Change-Id: Ie49965c0c3c224c4a895703ac659205cd040ff56
Reviewed-on: https://go-review.googlesource.com/c/go/+/452975
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Meng Zhuo <mzh@golangcn.org>
This commit is contained in:
Rongrong 2022-11-21 14:05:40 +08:00 committed by Meng Zhuo
parent 7a9ce74655
commit 2c7c98c3ad
4 changed files with 7 additions and 2 deletions
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1
src/runtime/internal/syscall/asm_linux_mips64x.s
View file

@ -15,6 +15,7 @@ TEXT ·Syscall6(SB),NOSPLIT,$0-80
MOVV a4+32(FP), R7
MOVV a5+40(FP), R8
MOVV a6+48(FP), R9
MOVV R0, R3 // reset R3 to 0 as 1-ret SYSCALL keeps it
SYSCALL
BEQ R7, ok
MOVV $-1, R1

1
src/runtime/internal/syscall/asm_linux_mipsx.s
View file

@ -20,6 +20,7 @@ TEXT ·Syscall6(SB),NOSPLIT,$20-40
MOVW a6+24(FP), R9
MOVW R8, 16(R29)
MOVW R9, 20(R29)
MOVW R0, R3 // reset R3 to 0 as 1-ret SYSCALL keeps it
SYSCALL
BEQ R7, ok
MOVW $-1, R1

5
src/syscall/asm_linux_mips64x.s
View file

@ -38,7 +38,8 @@ TEXT ·rawSyscallNoError(SB),NOSPLIT,$0-48
MOVV R0, R8
MOVV R0, R9
MOVV trap+0(FP), R2 // syscall entry
MOVV R0, R3 // reset R3 to zero as 1-ret SYSCALL keeps it
SYSCALL
MOVV R2, r1+32(FP)
MOVV R3, r2+40(FP)
MOVV R2, r1+32(FP) // r1
MOVV R3, r2+40(FP) // r2
RET

2
src/syscall/asm_linux_mipsx.s
View file

@ -29,6 +29,7 @@ TEXT ·Syscall9(SB),NOSPLIT,$28-52
MOVW R10, 24(R29)
MOVW R11, 28(R29)
MOVW trap+0(FP), R2 // syscall entry
MOVW R0, R3 // reset R3 to zero as 1-ret SYSCALL keeps it
SYSCALL
BEQ R7, ok9
MOVW $-1, R1
@ -66,6 +67,7 @@ TEXT ·rawSyscallNoError(SB),NOSPLIT,$20-24
MOVW a2+8(FP), R5
MOVW a3+12(FP), R6
MOVW trap+0(FP), R2 // syscall entry
MOVW R0, R3 // reset R3 to zero as 1-ret SYSCALL keeps it
SYSCALL
MOVW R2, r1+16(FP) // r1
MOVW R3, r2+20(FP) // r2