summaryrefslogtreecommitdiffstats
path: root/src/lib/mmap-anon.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 09:51:24 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 09:51:24 +0000
commitf7548d6d28c313cf80e6f3ef89aed16a19815df1 (patch)
treea3f6f2a3f247293bee59ecd28e8cd8ceb6ca064a /src/lib/mmap-anon.c
parentInitial commit. (diff)
downloaddovecot-upstream.tar.xz
dovecot-upstream.zip
Adding upstream version 1:2.3.19.1+dfsg1.upstream/1%2.3.19.1+dfsg1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--src/lib/mmap-anon.c183
1 files changed, 183 insertions, 0 deletions
diff --git a/src/lib/mmap-anon.c b/src/lib/mmap-anon.c
new file mode 100644
index 0000000..fbb2c47
--- /dev/null
+++ b/src/lib/mmap-anon.c
@@ -0,0 +1,183 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+/* @UNSAFE: whole file */
+
+#include "lib.h"
+#include "mmap-util.h"
+
+#include <fcntl.h>
+
+#ifndef MAP_ANONYMOUS
+# ifdef MAP_ANON
+# define MAP_ANONYMOUS MAP_ANON
+# else
+# define MAP_ANONYMOUS 0
+# endif
+#endif
+
+#ifndef HAVE_LINUX_MREMAP
+
+#include <sys/mman.h>
+
+#define MMAP_SIGNATURE 0xdeadbeef
+
+#define PAGE_ALIGN(size) \
+ (((size) + (size_t)page_size-1) & ~(size_t)(page_size-1))
+
+struct anon_header {
+ unsigned int signature;
+ size_t size;
+};
+
+static int page_size = 0;
+static int header_size = 0;
+static int zero_fd = -1;
+
+static void movable_mmap_init(void)
+{
+#if MAP_ANONYMOUS == 0
+ /* mmap()ing /dev/zero should be the same with some platforms */
+ zero_fd = open("/dev/zero", O_RDWR);
+ if (zero_fd == -1)
+ i_fatal("Can't open /dev/zero for creating anonymous mmap: %m");
+ fd_close_on_exec(zero_fd, TRUE);
+#endif
+
+ page_size = getpagesize();
+ header_size = page_size;
+}
+
+void *mmap_anon(size_t length)
+{
+ struct anon_header *hdr;
+ void *base;
+
+ if (header_size == 0)
+ movable_mmap_init();
+
+ /* we need extra page to store the pieces which construct
+ the full mmap. also allocate only page-aligned mmap sizes. */
+ length = PAGE_ALIGN(length + header_size);
+
+ base = mmap(NULL, length, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, zero_fd, 0);
+ if (base == MAP_FAILED)
+ return MAP_FAILED;
+
+ /* initialize the header */
+ hdr = base;
+ hdr->signature = MMAP_SIGNATURE;
+ hdr->size = length - header_size;
+
+ return (char *) hdr + header_size;
+}
+
+static void *mremap_move(struct anon_header *hdr, size_t new_size)
+{
+ void *new_base;
+ char *p;
+ size_t block_size, old_size;
+
+ new_base = mmap_anon(new_size);
+ if (new_base == MAP_FAILED)
+ return MAP_FAILED;
+
+ /* If we're moving large memory areas, it takes less memory to
+ copy the memory pages in smaller blocks. */
+ old_size = hdr->size;
+ block_size = 1024*1024;
+
+ p = (char *) hdr + header_size + hdr->size;
+ do {
+ if (block_size > old_size)
+ block_size = old_size;
+ p -= block_size;
+ old_size -= block_size;
+
+ memcpy((char *) new_base + old_size, p, block_size);
+ if (munmap((void *) p, block_size) < 0)
+ i_panic("munmap() failed: %m");
+ } while (old_size != 0);
+
+ if (munmap((void *) hdr, header_size) < 0)
+ i_panic("munmap() failed: %m");
+
+ return new_base;
+}
+
+void *mremap_anon(void *old_address, size_t old_size ATTR_UNUSED,
+ size_t new_size, unsigned long flags)
+{
+ struct anon_header *hdr;
+
+ if (old_address == NULL || old_address == MAP_FAILED) {
+ errno = EINVAL;
+ return MAP_FAILED;
+ }
+
+ hdr = (struct anon_header *) ((char *) old_address - header_size);
+ if (hdr->signature != MMAP_SIGNATURE)
+ i_panic("movable_mremap(): Invalid old_address");
+
+ new_size = PAGE_ALIGN(new_size);
+
+ if (new_size > hdr->size) {
+ /* grow */
+ if ((flags & MREMAP_MAYMOVE) == 0) {
+ errno = ENOMEM;
+ return MAP_FAILED;
+ }
+
+ return mremap_move(hdr, new_size);
+ }
+
+ if (new_size < hdr->size) {
+ /* shrink */
+ if (munmap((void *) ((char *) hdr + header_size + new_size),
+ hdr->size - new_size) < 0)
+ i_panic("munmap() failed: %m");
+ hdr->size = new_size;
+ }
+
+ return old_address;
+}
+
+int munmap_anon(void *start, size_t length ATTR_UNUSED)
+{
+ struct anon_header *hdr;
+
+ if (start == NULL || start == MAP_FAILED) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ hdr = (struct anon_header *) ((char *) start - header_size);
+ if (hdr->signature != MMAP_SIGNATURE)
+ i_panic("movable_munmap(): Invalid address");
+
+ if (munmap((void *) hdr, hdr->size + header_size) < 0)
+ i_panic("munmap() failed: %m");
+
+ return 0;
+}
+
+#else
+
+void *mmap_anon(size_t length)
+{
+ return mmap(NULL, length, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+}
+
+void *mremap_anon(void *old_address, size_t old_size, size_t new_size,
+ unsigned long flags)
+{
+ return mremap(old_address, old_size, new_size, flags);
+}
+
+int munmap_anon(void *start, size_t length)
+{
+ return munmap(start, length);
+}
+
+#endif