From fad5a6c66e73d3df20846906121d52159e1f6bf4 Mon Sep 17 00:00:00 2001 From: Michal Schmidt Date: Fri, 12 Dec 2014 17:57:22 +0100 Subject: journal: add debug mode for mmap-cache (--enable-debug=mmap-cache) 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 */ --- src/journal/mmap-cache.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'src/journal/mmap-cache.c') diff --git a/src/journal/mmap-cache.c b/src/journal/mmap-cache.c index b7db6f1da5..c57c1623c5 100644 --- a/src/journal/mmap-cache.c +++ b/src/journal/mmap-cache.c @@ -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 } } -- cgit v1.2.3-54-g00ecf