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2005-10-17 Roland McGrath <roland@redhat.com> 

* elf/dl-load.c (MAP_COPY): When undefined, define to
	MAP_PRIVATE|MAP_DENYWRITE instead of just MAP_PRIVATE.
	(_dl_map_object_from_fd): Don't use MAP_DENYWRITE explicitly.
This commit is contained in:
Roland McGrath 2005-10-17 20:59:28 +00:00
parent 4fa64d66fe
commit a3fcd5e8a4
1 changed files with 12 additions and 10 deletions
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18
elf/dl-load.c
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@ -50,15 +50,17 @@
overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we
get is MAP_PRIVATE, which copies each page when it is modified; this get is MAP_PRIVATE, which copies each page when it is modified; this
means if the file is overwritten, we may at some point get some pages means if the file is overwritten, we may at some point get some pages
from the new version after starting with pages from the old version. */ from the new version after starting with pages from the old version.
To make up for the lack and avoid the overwriting problem,
what Linux does have is MAP_DENYWRITE. This prevents anyone
from modifying the file while we have it mapped. */
#ifndef MAP_COPY #ifndef MAP_COPY
# ifdef MAP_DENYWRITE
# define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE)
# else
# define MAP_COPY MAP_PRIVATE # define MAP_COPY MAP_PRIVATE
# endif # endif
/* We want to prevent people from modifying DSOs which are currently in
use. This is what MAP_DENYWRITE is for. */
#ifndef MAP_DENYWRITE
# define MAP_DENYWRITE 0
#endif #endif
/* Some systems link their relocatable objects for another base address /* Some systems link their relocatable objects for another base address
@ -1181,7 +1183,7 @@ cannot allocate TLS data structures for initial thread");
/* Remember which part of the address space this object uses. */ /* Remember which part of the address space this object uses. */
l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength, l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
c->prot, c->prot,
MAP_COPY|MAP_FILE|MAP_DENYWRITE, MAP_COPY|MAP_FILE,
fd, c->mapoff); fd, c->mapoff);
if (__builtin_expect ((void *) l->l_map_start == MAP_FAILED, 0)) if (__builtin_expect ((void *) l->l_map_start == MAP_FAILED, 0))
{ {
@ -1229,7 +1231,7 @@ cannot allocate TLS data structures for initial thread");
/* Map the segment contents from the file. */ /* Map the segment contents from the file. */
&& (__mmap ((void *) (l->l_addr + c->mapstart), && (__mmap ((void *) (l->l_addr + c->mapstart),
c->mapend - c->mapstart, c->prot, c->mapend - c->mapstart, c->prot,
MAP_FIXED|MAP_COPY|MAP_FILE|MAP_DENYWRITE, MAP_FIXED|MAP_COPY|MAP_FILE,
fd, c->mapoff) fd, c->mapoff)
== MAP_FAILED)) == MAP_FAILED))
goto map_error; goto map_error;