diff options
Diffstat (limited to 'linux-user/mmap.c')
| -rw-r--r-- | linux-user/mmap.c | 39 |
1 files changed, 37 insertions, 2 deletions
diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 888b491403..6f300a0400 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -24,6 +24,8 @@ #include <string.h> #include <unistd.h> #include <errno.h> +#include <sys/types.h> +#include <sys/stat.h> #include <sys/mman.h> #include <linux/mman.h> #include <linux/unistd.h> @@ -366,6 +368,36 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot, goto the_end; real_start = start & qemu_host_page_mask; + /* When mapping files into a memory area larger than the file, accesses + to pages beyond the file size will cause a SIGBUS. + + For example, if mmaping a file of 100 bytes on a host with 4K pages + emulating a target with 8K pages, the target expects to be able to + access the first 8K. But the host will trap us on any access beyond + 4K. + + When emulating a target with a larger page-size than the hosts, we + may need to truncate file maps at EOF and add extra anonymous pages + up to the targets page boundary. */ + + if ((qemu_real_host_page_size < TARGET_PAGE_SIZE) + && !(flags & MAP_ANONYMOUS)) { + struct stat sb; + + if (fstat (fd, &sb) == -1) + goto fail; + + /* Are we trying to create a map beyond EOF?. */ + if (offset + len > sb.st_size) { + /* If so, truncate the file map at eof aligned with + the hosts real pagesize. Additional anonymous maps + will be created beyond EOF. */ + len = (sb.st_size - offset); + len += qemu_real_host_page_size - 1; + len &= ~(qemu_real_host_page_size - 1); + } + } + if (!(flags & MAP_FIXED)) { abi_ulong mmap_start; void *p; @@ -381,13 +413,16 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot, especially important if qemu_host_page_size > qemu_real_host_page_size */ p = mmap(g2h(mmap_start), - host_len, prot, flags | MAP_FIXED, fd, host_offset); + host_len, prot, flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0); if (p == MAP_FAILED) goto fail; /* update start so that it points to the file position at 'offset' */ host_start = (unsigned long)p; - if (!(flags & MAP_ANONYMOUS)) + if (!(flags & MAP_ANONYMOUS)) { + p = mmap(g2h(mmap_start), len, prot, + flags | MAP_FIXED, fd, host_offset); host_start += offset - host_offset; + } start = h2g(host_start); } else { int flg; |