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54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
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/* go-trampoline.c -- allocate a trampoline for a nested function.
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Copyright 2009 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 "config.h"
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#include <stddef.h>
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#include <stdint.h>
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#include <unistd.h>
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#ifdef HAVE_SYS_MMAN_H
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#include <sys/mman.h>
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#endif
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#include "go-alloc.h"
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#include "go-assert.h"
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/* In order to build a trampoline we need space which is both writable
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and executable. We currently just allocate a whole page. This
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needs to be more system dependent. */
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void *
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__go_allocate_trampoline (uintptr_t size, void *closure)
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{
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unsigned int page_size;
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void *ret;
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size_t off;
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page_size = getpagesize ();
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__go_assert (page_size >= size);
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ret = __go_alloc (2 * page_size - 1);
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ret = (void *) (((uintptr_t) ret + page_size - 1)
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& ~ ((uintptr_t) page_size - 1));
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/* Because the garbage collector only looks at correct address
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offsets, we need to ensure that it will see the closure
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address. */
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off = ((size + sizeof (void *) - 1) / sizeof (void *)) * sizeof (void *);
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__go_assert (size + off + sizeof (void *) <= page_size);
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__builtin_memcpy (ret + off, &closure, sizeof (void *));
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#ifdef HAVE_SYS_MMAN_H
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{
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int i;
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i = mprotect (ret, size, PROT_READ | PROT_WRITE | PROT_EXEC);
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__go_assert (i == 0);
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}
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#endif
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return ret;
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}
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