diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/Makefile.objs | 1 | ||||
| -rw-r--r-- | util/mmap-alloc.c | 71 | ||||
| -rw-r--r-- | util/oslib-posix.c | 28 |
3 files changed, 76 insertions, 24 deletions
diff --git a/util/Makefile.objs b/util/Makefile.objs index 114d6578c4..f011b81dcb 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -1,6 +1,7 @@ util-obj-y = osdep.o cutils.o unicode.o qemu-timer-common.o util-obj-$(CONFIG_WIN32) += oslib-win32.o qemu-thread-win32.o event_notifier-win32.o util-obj-$(CONFIG_POSIX) += oslib-posix.o qemu-thread-posix.o event_notifier-posix.o qemu-openpty.o +util-obj-$(CONFIG_POSIX) += mmap-alloc.o util-obj-y += envlist.o path.o module.o util-obj-$(call lnot,$(CONFIG_INT128)) += host-utils.o util-obj-y += bitmap.o bitops.o hbitmap.o diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c new file mode 100644 index 0000000000..13942694cc --- /dev/null +++ b/util/mmap-alloc.c @@ -0,0 +1,71 @@ +/* + * Support for RAM backed by mmaped host memory. + * + * Copyright (c) 2015 Red Hat, Inc. + * + * Authors: + * Michael S. Tsirkin <mst@redhat.com> + * + * This work is licensed under the terms of the GNU GPL, version 2 or + * later. See the COPYING file in the top-level directory. + */ +#include <qemu/mmap-alloc.h> +#include <sys/types.h> +#include <sys/mman.h> +#include <assert.h> + +void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) +{ + /* + * Note: this always allocates at least one extra page of virtual address + * space, even if size is already aligned. + */ + size_t total = size + align; + void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; + void *ptr1; + + if (ptr == MAP_FAILED) { + return NULL; + } + + /* Make sure align is a power of 2 */ + assert(!(align & (align - 1))); + /* Always align to host page size */ + assert(align >= getpagesize()); + + ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE, + MAP_FIXED | + (fd == -1 ? MAP_ANONYMOUS : 0) | + (shared ? MAP_SHARED : MAP_PRIVATE), + fd, 0); + if (ptr1 == MAP_FAILED) { + munmap(ptr, total); + return NULL; + } + + ptr += offset; + total -= offset; + + if (offset > 0) { + munmap(ptr - offset, offset); + } + + /* + * Leave a single PROT_NONE page allocated after the RAM block, to serve as + * a guard page guarding against potential buffer overflows. + */ + if (total > size + getpagesize()) { + munmap(ptr + size + getpagesize(), total - size - getpagesize()); + } + + return ptr; +} + +void qemu_ram_munmap(void *ptr, size_t size) +{ + if (ptr) { + /* Unmap both the RAM block and the guard page */ + munmap(ptr, size + getpagesize()); + } +} diff --git a/util/oslib-posix.c b/util/oslib-posix.c index a0fcdc2ede..892d2d8ad2 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -72,6 +72,8 @@ extern int daemon(int, int); #include <sys/sysctl.h> #endif +#include <qemu/mmap-alloc.h> + int qemu_get_thread_id(void) { #if defined(__linux__) @@ -128,10 +130,7 @@ void *qemu_memalign(size_t alignment, size_t size) void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment) { size_t align = QEMU_VMALLOC_ALIGN; - size_t total = size + align; - void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); - size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; - void *ptr1; + void *ptr = qemu_ram_mmap(-1, size, align, false); if (ptr == MAP_FAILED) { return NULL; @@ -141,23 +140,6 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment) *alignment = align; } - ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); - if (ptr1 == MAP_FAILED) { - munmap(ptr, total); - return NULL; - } - - ptr += offset; - total -= offset; - - if (offset > 0) { - munmap(ptr - offset, offset); - } - if (total > size + getpagesize()) { - munmap(ptr + size + getpagesize(), total - size - getpagesize()); - } - trace_qemu_anon_ram_alloc(size, ptr); return ptr; } @@ -171,9 +153,7 @@ void qemu_vfree(void *ptr) void qemu_anon_ram_free(void *ptr, size_t size) { trace_qemu_anon_ram_free(ptr, size); - if (ptr) { - munmap(ptr, size + getpagesize()); - } + qemu_ram_munmap(ptr, size); } void qemu_set_block(int fd) |