diff options
Diffstat (limited to 'src/lib/mmap-anon.c')
| -rw-r--r-- | src/lib/mmap-anon.c | 183 |
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 |