mmap-alloc: unfold qemu_ram_mmap()
Unfold parts of qemu_ram_mmap() for the sake of understanding, moving declarations to the top, and keeping architecture-specifics in the ifdef-else blocks. No changes in the function behaviour. Give ptr and ptr1 meaningful names: ptr -> guardptr : pointer to the PROT_NONE guard region ptr1 -> ptr : pointer to the mapped memory returned to caller Signed-off-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Greg Kurz <groug@kaod.org>
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@ -77,11 +77,19 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
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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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int flags;
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int guardfd;
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size_t offset;
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size_t total;
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void *guardptr;
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void *ptr;
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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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total = size + align;
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#if defined(__powerpc64__) && defined(__linux__)
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/* On ppc64 mappings in the same segment (aka slice) must share the same
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* page size. Since we will be re-allocating part of this segment
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@ -91,16 +99,22 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
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* We do this unless we are using the system page size, in which case
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* anonymous memory is OK.
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*/
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int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
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int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
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void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
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flags = MAP_PRIVATE;
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if (fd == -1 || qemu_fd_getpagesize(fd) == getpagesize()) {
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guardfd = -1;
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flags |= MAP_ANONYMOUS;
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} else {
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guardfd = fd;
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flags |= MAP_NORESERVE;
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}
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#else
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void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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guardfd = -1;
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flags = MAP_PRIVATE | MAP_ANONYMOUS;
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#endif
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size_t offset;
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void *ptr1;
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if (ptr == MAP_FAILED) {
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guardptr = mmap(0, total, PROT_NONE, flags, guardfd, 0);
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if (guardptr == MAP_FAILED) {
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return MAP_FAILED;
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}
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@ -108,19 +122,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
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/* Always align to host page size */
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assert(align >= getpagesize());
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offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
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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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flags = MAP_FIXED;
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flags |= fd == -1 ? MAP_ANONYMOUS : 0;
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flags |= shared ? MAP_SHARED : MAP_PRIVATE;
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offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
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ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, flags, fd, 0);
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if (ptr == MAP_FAILED) {
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munmap(guardptr, total);
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return MAP_FAILED;
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}
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if (offset > 0) {
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munmap(ptr, offset);
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munmap(guardptr, offset);
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}
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/*
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@ -129,10 +144,10 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
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*/
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total -= offset;
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if (total > size + getpagesize()) {
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munmap(ptr1 + size + getpagesize(), total - size - getpagesize());
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munmap(ptr + size + getpagesize(), total - size - getpagesize());
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}
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return ptr1;
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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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