elf: Add glibc-hwcaps support for LD_LIBRARY_PATH

This hacks non-power-set processing into _dl_important_hwcaps.
Once the legacy hwcaps handling goes away, the subdirectory
handling needs to be reworked, but it is premature to do this
while both approaches are still supported.

ld.so supports two new arguments, --glibc-hwcaps-prepend and
--glibc-hwcaps-mask.  Each accepts a colon-separated list of
glibc-hwcaps subdirectory names.  The prepend option adds additional
subdirectories that are searched first, in the specified order.  The
mask option restricts the automatically selected subdirectories to
those listed in the option argument.  For example, on systems where
/usr/lib64 is on the library search path,
--glibc-hwcaps-prepend=valgrind:debug causes the dynamic loader to
search the directories /usr/lib64/glibc-hwcaps/valgrind and
/usr/lib64/glibc-hwcaps/debug just before /usr/lib64 is searched.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/elf/dl-load.c b/elf/dl-load.c
index f3201e7c14..9020f1646f 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -682,7 +682,9 @@ cache_rpath (struct link_map *l,
 
 
 void
-_dl_init_paths (const char *llp, const char *source)
+_dl_init_paths (const char *llp, const char *source,
+		const char *glibc_hwcaps_prepend,
+		const char *glibc_hwcaps_mask)
 {
   size_t idx;
   const char *strp;
@@ -697,7 +699,8 @@ _dl_init_paths (const char *llp, const char *source)
 
 #ifdef SHARED
   /* Get the capabilities.  */
-  capstr = _dl_important_hwcaps (&ncapstr, &max_capstrlen);
+  capstr = _dl_important_hwcaps (glibc_hwcaps_prepend, glibc_hwcaps_mask,
+				 &ncapstr, &max_capstrlen);
 #endif
 
   /* First set up the rest of the default search directory entries.  */