path: root/src/internal
diff options
authorRich Felker <>2015-11-11 17:34:17 -0500
committerRich Felker <>2015-11-11 17:40:27 -0500
commit9439ebd7668182a1c6213ad1a5011bdc71585b5f (patch)
tree5166f5c1b09e0c9115b582897633cc80331f4c81 /src/internal
parenta946e8117ed51dd771bd8cac3575fc28a0399a32 (diff)
fix dynamic loader library mapping for nommu systems
on linux/nommu, non-writable private mappings of files may actually use memory shared with other processes or the fs cache. the old nommu loader code (used when mmap with MAP_FIXED fails) simply wrote over top of the original file mapping, possibly clobbering this shared memory. no such breakage was observed in practice, but it should have been possible. the new code starts by mapping anonymous writable memory on archs that might support nommu, then maps load segments over top of it, falling back to read if MAP_FIXED fails. we use an anonymous map rather than a writable file map to avoid reading more data from disk than needed. since pages cannot be loaded lazily on fault, in case of large data/bss, mapping the full file may read a lot of data that will subsequently be thrown away when processing additional LOAD segments. as a result, we cannot skip the first LOAD segment when operating in this mode. these changes affect only non-FDPIC nommu support.
Diffstat (limited to 'src/internal')
1 files changed, 4 insertions, 0 deletions
diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h
index 86f379e6..9c494e43 100644
--- a/src/internal/dynlink.h
+++ b/src/internal/dynlink.h
@@ -64,6 +64,10 @@ struct fdpic_dummy_loadmap {
#define DL_FDPIC 0
#define IS_RELATIVE(x,s) ( \
(R_TYPE(x) == REL_RELATIVE) || \