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util/mmap-alloc: Factor out calculation of the pagesize for the guard page

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Let's factor out calculating the size of the guard page and rename the
variable to make it clearer that this pagesize only applies to the
guard page.

Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine core
Cc: Igor Kotrasinski <i.kotrasinsk@partner.samsung.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-2-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Hildenbrand 2021-05-10 13:43:14 +02:00 committed by Paolo Bonzini
parent dbb92eea38
commit adad0b3ae8
1 changed files with 16 additions and 15 deletions
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31
util/mmap-alloc.c
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@ -82,6 +82,16 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
return qemu_real_host_page_size;
}
static inline size_t mmap_guard_pagesize(int fd)
{
#if defined(__powerpc64__) && defined(__linux__)
/* Mappings in the same segment must share the same page size */
return qemu_fd_getpagesize(fd);
#else
return qemu_real_host_page_size;
#endif
}
void *qemu_ram_mmap(int fd,
size_t size,
size_t align,
@ -90,12 +100,12 @@ void *qemu_ram_mmap(int fd,
bool is_pmem,
off_t map_offset)
{
const size_t guard_pagesize = mmap_guard_pagesize(fd);
int prot;
int flags;
int map_sync_flags = 0;
int guardfd;
size_t offset;
size_t pagesize;
size_t total;
void *guardptr;
void *ptr;
@ -116,8 +126,7 @@ void *qemu_ram_mmap(int fd,
* anonymous memory is OK.
*/
flags = MAP_PRIVATE;
pagesize = qemu_fd_getpagesize(fd);
if (fd == -1 || pagesize == qemu_real_host_page_size) {
if (fd == -1 || guard_pagesize == qemu_real_host_page_size) {
guardfd = -1;
flags |= MAP_ANONYMOUS;
} else {
@ -126,7 +135,6 @@ void *qemu_ram_mmap(int fd,
}
#else
guardfd = -1;
pagesize = qemu_real_host_page_size;
flags = MAP_PRIVATE | MAP_ANONYMOUS;
#endif
@ -138,7 +146,7 @@ void *qemu_ram_mmap(int fd,
assert(is_power_of_2(align));
/* Always align to host page size */
assert(align >= pagesize);
assert(align >= guard_pagesize);
flags = MAP_FIXED;
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
@ -193,8 +201,8 @@ void *qemu_ram_mmap(int fd,
* a guard page guarding against potential buffer overflows.
*/
total -= offset;
if (total > size + pagesize) {
munmap(ptr + size + pagesize, total - size - pagesize);
if (total > size + guard_pagesize) {
munmap(ptr + size + guard_pagesize, total - size - guard_pagesize);
}
return ptr;
@ -202,15 +210,8 @@ void *qemu_ram_mmap(int fd,
void qemu_ram_munmap(int fd, void *ptr, size_t size)
{
size_t pagesize;
if (ptr) {
/* Unmap both the RAM block and the guard page */
#if defined(__powerpc64__) && defined(__linux__)
pagesize = qemu_fd_getpagesize(fd);
#else
pagesize = qemu_real_host_page_size;
#endif
munmap(ptr, size + pagesize);
munmap(ptr, size + mmap_guard_pagesize(fd));
}
}