9d4ec9370a
Existing callers are checking for MAP_FAILED, so we should return that on error. Reported-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/*
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* Support for RAM backed by mmaped host memory.
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*
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* Copyright (c) 2015 Red Hat, Inc.
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*
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* Authors:
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* Michael S. Tsirkin <mst@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* later. See the COPYING file in the top-level directory.
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*/
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#include <qemu/mmap-alloc.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <assert.h>
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void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
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{
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/*
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* Note: this always allocates at least one extra page of virtual address
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* space, even if size is already aligned.
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*/
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size_t total = size + align;
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void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
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void *ptr1;
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if (ptr == MAP_FAILED) {
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return MAP_FAILED;
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}
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/* Make sure align is a power of 2 */
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assert(!(align & (align - 1)));
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/* Always align to host page size */
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assert(align >= getpagesize());
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ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
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MAP_FIXED |
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(fd == -1 ? MAP_ANONYMOUS : 0) |
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(shared ? MAP_SHARED : MAP_PRIVATE),
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fd, 0);
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if (ptr1 == MAP_FAILED) {
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munmap(ptr, total);
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return MAP_FAILED;
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}
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ptr += offset;
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total -= offset;
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if (offset > 0) {
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munmap(ptr - offset, offset);
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}
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/*
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* Leave a single PROT_NONE page allocated after the RAM block, to serve as
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* a guard page guarding against potential buffer overflows.
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*/
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if (total > size + getpagesize()) {
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munmap(ptr + size + getpagesize(), total - size - getpagesize());
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}
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return ptr;
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}
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void qemu_ram_munmap(void *ptr, size_t size)
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{
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if (ptr) {
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/* Unmap both the RAM block and the guard page */
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munmap(ptr, size + getpagesize());
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}
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}
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