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Re: [PATCH 1/3] New --inhibit-ldcache option to ld.so to prevent itform reading ld.so.cache


On Fri,  6 Apr 2012 09:37:05 -0700 (PDT)
Roland McGrath <roland@hack.frob.com> wrote:
> Call the option just --inhibit-cache and the variable
> _dl_inhibit_cache. Use string concatenation to use LD_SO_CACHE rather
> than a hard-coded name in the help text.
> 

Thanks, updated patch attached.

--
Siddhesh

ChangeLog:

2012-04-09  Siddhesh Poyarekar  <siddhesh@redhat.com>

	* elf/dl-support.c (_dl_inhibit_cache): New variable.
	* elf/rtld.c (_rtld_global_ro): New member
	_dl_inhibit_cache. (dl_main): Handle --inhibit-cache.
	* sysdeps/generic/ldsodefs.h (struct rtld_global_ro): New
	member _dl_inhibit_cache
	* elf/dl-load.c (_dl_map_object): Use it.
	* elf/Makefile: Define SYSCONFDIR when building rtld.c.
---
 elf/Makefile               |    1 +
 elf/dl-load.c              |    3 ++-
 elf/dl-support.c           |    2 ++
 elf/rtld.c                 |    9 +++++++++
 sysdeps/generic/ldsodefs.h |    3 +++
 5 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/elf/Makefile b/elf/Makefile
index 59a3936..7453f17 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -419,6 +419,7 @@ CFLAGS-ldconfig.c = $(SYSCONF-FLAGS) -D'LIBDIR="$(libdir)"' \
 		    -D'SLIBDIR="$(slibdir)"' -DIS_IN_ldconfig=1
 CFLAGS-dl-cache.c = $(SYSCONF-FLAGS)
 CFLAGS-cache.c = $(SYSCONF-FLAGS)
+CFLAGS-rtld.c = $(SYSCONF-FLAGS)
 
 CPPFLAGS-.os += $(if $(filter $(@F),$(patsubst %,%.os,$(all-rtld-routines))),-DNOT_IN_libc=1 -DIS_IN_rtld=1)
 
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 41d48ee..d005244 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -2194,7 +2194,8 @@ _dl_map_object (struct link_map *loader, const char *name,
 
       if (fd == -1
 	  && (__builtin_expect (! (mode & __RTLD_SECURE), 1)
-	      || ! INTUSE(__libc_enable_secure)))
+	      || ! INTUSE(__libc_enable_secure))
+	  && __builtin_expect (GLRO(dl_inhibit_cache) == 0, 1))
 	{
 	  /* Check the list of libraries in the file /etc/ld.so.cache,
 	     for compatibility with Linux's ldconfig program.  */
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 565f342..5d5ab4a 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -107,6 +107,8 @@ void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 
 size_t _dl_pagesize = EXEC_PAGESIZE;
 
+int _dl_inhibit_cache;
+
 unsigned int _dl_osversion;
 
 /* All known directories in sorted order.  */
diff --git a/elf/rtld.c b/elf/rtld.c
index 0362b14..88a340d 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -161,6 +161,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
     ._dl_fpu_control = _FPU_DEFAULT,
     ._dl_pointer_guard = 1,
     ._dl_pagesize = EXEC_PAGESIZE,
+    ._dl_inhibit_cache = 0,
 
     /* Function pointers.  */
     ._dl_debug_printf = _dl_debug_printf,
@@ -973,6 +974,13 @@ dl_main (const ElfW(Phdr) *phdr,
 	    --_dl_argc;
 	    ++INTUSE(_dl_argv);
 	  }
+	else if (! strcmp (INTUSE(_dl_argv)[1], "--inhibit-cache"))
+	  {
+	    GLRO(dl_inhibit_cache) = 1;
+	    ++_dl_skip_args;
+	    --_dl_argc;
+	    ++INTUSE(_dl_argv);
+	  }
 	else if (! strcmp (INTUSE(_dl_argv)[1], "--library-path")
 		 && _dl_argc > 2)
 	  {
@@ -1022,6 +1030,7 @@ of this helper program; chances are you did not intend to run this program.\n\
   --list                list all dependencies and how they are resolved\n\
   --verify              verify that given object really is a dynamically linked\n\
 			object we can handle\n\
+  --inhibit-cache       Do not use " LD_SO_CACHE "\n\
   --library-path PATH   use given PATH instead of content of the environment\n\
 			variable LD_LIBRARY_PATH\n\
   --inhibit-rpath LIST  ignore RUNPATH and RPATH information in object names\n\
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 9955430..c9e17b9 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -560,6 +560,9 @@ struct rtld_global_ro
   /* Cached value of `getpagesize ()'.  */
   EXTERN size_t _dl_pagesize;
 
+  /* Do we read from ld.so.cache?  */
+  EXTERN int _dl_inhibit_cache;
+
   /* Copy of the content of `_dl_main_searchlist' at startup time.  */
   EXTERN struct r_scope_elem _dl_initial_searchlist;
 
-- 
1.7.7.6


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