diff options
Diffstat (limited to 'pkg/safecopy/memclr_arm64.s')
| -rw-r--r-- | pkg/safecopy/memclr_arm64.s | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/pkg/safecopy/memclr_arm64.s b/pkg/safecopy/memclr_arm64.s new file mode 100644 index 000000000..7361b9067 --- /dev/null +++ b/pkg/safecopy/memclr_arm64.s @@ -0,0 +1,74 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +#include "textflag.h" + +// handleMemclrFault returns (the value stored in R0, the value stored in R1). +// Control is transferred to it when memclr below receives SIGSEGV or SIGBUS, +// with the faulting address stored in R0 and the signal number stored in R1. +// +// It must have the same frame configuration as memclr so that it can undo any +// potential call frame set up by the assembler. +TEXT handleMemclrFault(SB), NOSPLIT, $0-28 + MOVD R0, addr+16(FP) + MOVW R1, sig+24(FP) + RET + +// See the corresponding doc in safecopy_unsafe.go +// +// The code is derived from runtime.memclrNoHeapPointers. +// +// func memclr(ptr unsafe.Pointer, n uintptr) (fault unsafe.Pointer, sig int32) +TEXT ·memclr(SB), NOSPLIT, $0-28 + // Store 0 as the returned signal number. If we run to completion, + // this is the value the caller will see; if a signal is received, + // handleMemclrFault will store a different value in this address. + MOVW $0, sig+24(FP) + MOVD ptr+0(FP), R0 + MOVD n+8(FP), R1 + + // If size is less than 16 bytes, use tail_zero to zero what remains + CMP $16, R1 + BLT tail_zero + // Get buffer offset into 16 byte aligned address for better performance + ANDS $15, R0, ZR + BNE unaligned_to_16 +aligned_to_16: + LSR $4, R1, R2 +zero_by_16: + STP.P (ZR, ZR), 16(R0) // Store pair with post index. + SUBS $1, R2, R2 + BNE zero_by_16 + ANDS $15, R1, R1 + BEQ end + + // Zero buffer with size=R1 < 16 +tail_zero: + TBZ $3, R1, tail_zero_4 + MOVD.P ZR, 8(R0) +tail_zero_4: + TBZ $2, R1, tail_zero_2 + MOVW.P ZR, 4(R0) +tail_zero_2: + TBZ $1, R1, tail_zero_1 + MOVH.P ZR, 2(R0) +tail_zero_1: + TBZ $0, R1, end + MOVB ZR, (R0) +end: + RET + +unaligned_to_16: + MOVD R0, R2 +head_loop: + MOVBU.P ZR, 1(R0) + ANDS $15, R0, ZR + BNE head_loop + // Adjust length for what remains + SUB R2, R0, R3 + SUB R3, R1 + // If size is less than 16 bytes, use tail_zero to zero what remains + CMP $16, R1 + BLT tail_zero + B aligned_to_16 |