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479872227c
The libc memmove and memclr don't reliably operate on full memory words. We already avoided them on PPC64, but the same problem can occur even on x86, where some processors use "rep movsb" and "rep stosb". Always use C code that stores full memory words. While we're here, clean up the C code. We don't need special handling if the memmove/memclr pointers are not pointer-aligned. Unfortunately, this will likely be slower. Perhaps some day we can have our own assembly code that operates a word at a time, or we can use different operations when we know there are no pointers. Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/685178
50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
/* go-memclr.c -- clear a memory buffer
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Copyright 2016 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file. */
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#include "runtime.h"
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void memclrNoHeapPointers(void *, uintptr)
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__asm__ (GOSYM_PREFIX "runtime.memclrNoHeapPointers")
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__attribute__ ((no_split_stack));
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void
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memclrNoHeapPointers(void *p1, uintptr len)
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{
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const uintptr ptr_size = sizeof(p1);
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uintptr rem,drem,i;
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uintptr offset;
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volatile uintptr *vp;
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if (len == 0) {
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return;
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}
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rem = len;
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offset = (uintptr)p1 % ptr_size;
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if (rem < ptr_size || offset > 0) {
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// This memset is OK since it can't contain
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// an pointer aligned pointer.
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__builtin_memset(p1, 0, rem);
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return;
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}
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drem = rem / ptr_size;
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vp = (volatile uintptr*)(p1);
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// Without the use of volatile here, the compiler
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// might convert the loop into a memset.
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for (i=0; i<drem; i++) {
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*vp = 0;
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vp++;
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rem -= ptr_size;
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}
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// Clear any remaining bytes.
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if (rem > 0) {
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p1 = (void*)((char*)p1 + ptr_size*drem);
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__builtin_memset(p1, 0, rem);
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}
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}
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