[glibc/fw/glibc-hwcaps] elf: Do not search HWCAP subdirectories in statically linked binaries

[glibc/fw/glibc-hwcaps] elf: Do not search HWCAP subdirectories in statically linked binaries

[Florian Weimer]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=75fdede6bc2db8a3638c1402855b2c5245f4b545

commit 75fdede6bc2db8a3638c1402855b2c5245f4b545
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Jun 19 14:59:09 2020 +0200

    elf: Do not search HWCAP subdirectories in statically linked binaries
    
    This functionality does not seem to be useful since static dlopen
    is mostly used for iconv/character set conversion and NSS support.
    gconv modules are loaded with full paths anyway, so that the
    HWCAP subdirectory logic does not apply.

Diff:
---
 NEWS          |  4 ++++
 elf/Makefile  |  4 ++--
 elf/dl-load.c | 14 ++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index ce05d05b16..902fa3a7f8 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,10 @@ Deprecated and removed features, and other changes affecting compatibility:
 * The mallinfo function is marked deprecated.  Callers should call
   mallinfo2 instead.
 
+* When dlopen is used in statically linked programs, alternative library
+  implementations from HWCAP subdirectories are no longer loaded.
+  Instead, the default implementation is used.
+
 Changes to build and runtime requirements:
 
   [Add changes to build and runtime requirements here]
diff --git a/elf/Makefile b/elf/Makefile
index c587e9f06e..e0a8bf2998 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -29,7 +29,7 @@ routines	= $(all-dl-routines) dl-support dl-iteratephdr \
 
 # The core dynamic linking functions are in libc for the static and
 # profiled libraries.
-dl-routines	= $(addprefix dl-,load lookup object reloc deps hwcaps \
+dl-routines	= $(addprefix dl-,load lookup object reloc deps \
 				  runtime init fini debug misc \
 				  version profile tls origin scope \
 				  execstack open close trampoline \
@@ -59,7 +59,7 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
 # ld.so uses those routines, plus some special stuff for being the program
 # interpreter and operating independent of libc.
 rtld-routines	= rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \
-  dl-error-minimal dl-conflict
+  dl-error-minimal dl-conflict dl-hwcaps
 all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
 
 CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 646c5dca40..5ba117d597 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -101,9 +101,13 @@ int __stack_prot attribute_hidden attribute_relro
 static struct r_search_path_struct env_path_list attribute_relro;
 
 /* List of the hardware capabilities we might end up using.  */
+#ifdef SHARED
 static const struct r_strlenpair *capstr attribute_relro;
 static size_t ncapstr attribute_relro;
 static size_t max_capstrlen attribute_relro;
+#else
+enum { ncapstr = 1, max_capstrlen = 0 };
+#endif
 
 
 /* Get the generated information about the trusted directories.  Use
@@ -691,9 +695,11 @@ _dl_init_paths (const char *llp)
   /* Fill in the information about the application's RPATH and the
      directories addressed by the LD_LIBRARY_PATH environment variable.  */
 
+#ifdef SHARED
   /* Get the capabilities.  */
   capstr = _dl_important_hwcaps (GLRO(dl_platform), GLRO(dl_platformlen),
 				 &ncapstr, &max_capstrlen);
+#endif
 
   /* First set up the rest of the default search directory entries.  */
   aelem = rtld_search_dirs.dirs = (struct r_search_path_elem **)
@@ -1521,11 +1527,15 @@ print_search_path (struct r_search_path_elem **list,
       for (cnt = 0; cnt < ncapstr; ++cnt)
 	if ((*list)->status[cnt] != nonexisting)
 	  {
+#ifdef SHARED
 	    char *cp = __mempcpy (endp, capstr[cnt].str, capstr[cnt].len);
 	    if (cp == buf || (cp == buf + 1 && buf[0] == '/'))
 	      cp[0] = '\0';
 	    else
 	      cp[-1] = '\0';
+#else
+	    *endp = '\0';
+#endif
 
 	    _dl_debug_printf_c (first ? "%s" : ":%s", buf);
 	    first = 0;
@@ -1886,11 +1896,15 @@ open_path (const char *name, size_t namelen, int mode,
 	  if (this_dir->status[cnt] == nonexisting)
 	    continue;
 
+#ifdef SHARED
 	  buflen =
 	    ((char *) __mempcpy (__mempcpy (edp, capstr[cnt].str,
 					    capstr[cnt].len),
 				 name, namelen)
 	     - buf);
+#else
+	  buflen = (char *) __mempcpy (edp, name, namelen) - buf;
+#endif
 
 	  /* Print name we try if this is wanted.  */
 	  if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS))