shaba/systemd
1
0
Fork 0
mirror of https://github.com/systemd/systemd.git synced 2024-10-27 10:25:37 +03:00
Code

journal: add debug mode for mmap-cache (--enable-debug=mmap-cache)

Browse Source 
This is useful for exposing unsafe access to mmapped objects after
the context that they were mapped in was already moved.

For example:
journal_file_move_to_object(f1, OBJECT_DATA, p1, &o1);
journal_file_move_to_object(f2, OBJECT_DATA, p2, &o2);
t = o1->object.type; /* this usually works, but is unsafe */
This commit is contained in:
Michal Schmidt 2014-12-12 17:57:22 +01:00
parent fc86aa0ed2
commit fad5a6c66e
2 changed files with 21 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
configure.ac
View File

@ -1328,9 +1328,9 @@ AC_ARG_ENABLE(tests,
AM_CONDITIONAL(ENABLE_TESTS, [test x$enable_tests = xyes])
AC_ARG_ENABLE(debug,
[AC_HELP_STRING([--enable-debug@<:@=LIST@:>@], [enable extra debugging (hashmap)])],
[AC_HELP_STRING([--enable-debug@<:@=LIST@:>@], [enable extra debugging (hashmap,mmap-cache)])],
[if test "x$enableval" = "xyes"; then
enableval="hashmap"
enableval="hashmap,mmap-cache"
fi
saved_ifs="$IFS"
IFS="$IFS$PATH_SEPARATOR,"
@ -1339,6 +1339,9 @@ AC_ARG_ENABLE(debug,
hashmap)
enable_debug_hashmap=yes
;;
mmap-cache)
enable_debug_mmap_cache=yes
;;
esac
done
IFS="$saved_ifs"],[])
@ -1348,6 +1351,9 @@ AS_IF([test x$enable_debug_hashmap = xyes], [
AC_DEFINE(ENABLE_DEBUG_HASHMAP, 1, [Define if hashmap debugging is to be enabled])
enable_debug="hashmap $enable_debug"
])
AS_IF([test x$enable_debug_mmap_cache = xyes], [
AC_DEFINE(ENABLE_DEBUG_MMAP_CACHE, 1, [Define if mmap cache debugging is to be enabled])
enable_debug="mmap-cache $enable_debug"
])
test -z "$enable_debug" && enable_debug="none"

14
src/journal/mmap-cache.c
View File

@ -83,7 +83,13 @@ struct MMapCache {
};
#define WINDOWS_MIN 64
#define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
#ifdef ENABLE_DEBUG_MMAP_CACHE
/* Tiny windows increase mmap activity and the chance of exposing unsafe use. */
# define WINDOW_SIZE (page_size())
#else
# define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
#endif
MMapCache* mmap_cache_new(void) {
MMapCache *m;
@ -187,11 +193,17 @@ static void context_detach_window(Context *c) {
if (!w->contexts && w->keep_always == 0) {
/* Not used anymore? */
#ifdef ENABLE_DEBUG_MMAP_CACHE
/* Unmap unused windows immediately to expose use-after-unmap
* by SIGSEGV. */
window_free(w);
#else
LIST_PREPEND(unused, c->cache->unused, w);
if (!c->cache->last_unused)
c->cache->last_unused = w;
w->in_unused = true;
#endif
}
}