elf: Remove prelink support

Prelinked binaries and libraries still work, the dynamic tags
DT_GNU_PRELINKED, DT_GNU_LIBLIST, DT_GNU_CONFLICT just ignored
(meaning the process is reallocated as default).

The loader environment variable TRACE_PRELINKING is also removed,
since it used solely on prelink.

Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

25 files changed, 117 insertions, 885 deletions

diff --git a/NEWS b/NEWS
index 7b8febcb72..9bef1058b5 100644
--- a/NEWS
+++ b/NEWS
@@ -13,7 +13,9 @@ Major new features:
 
 Deprecated and removed features, and other changes affecting compatibility:
 
-  [Add deprecations, removals and changes affecting compatibility here]
+* Support for prelink will be removed in the next release; this includes
+  removal of the LD_TRACE_PRELINKING, and LD_USE_LOAD_BIAS, environment
+  variables and their functionality in the dynamic loader.
 
 Changes to build and runtime requirements:
 
diff --git a/elf/Makefile b/elf/Makefile
index b2bd03a9f6..bff94954c9 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -127,7 +127,6 @@ rtld-routines = \
   $(all-dl-routines) \
   dl-audit \
   dl-compat \
-  dl-conflict \
   dl-diagnostics \
   dl-diagnostics-cpu \
   dl-diagnostics-kernel \
@@ -1103,14 +1102,6 @@ tests-special += $(objpfx)check-abi-ld.out
 update-abi: update-abi-ld
 update-all-abi: update-all-abi-ld
 
-ifeq ($(have-glob-dat-reloc),yes)
-tests += tst-prelink
-tests-internal += tst-prelink-cmp
-# Don't compile tst-prelink.c with PIE for GLOB_DAT relocation.
-CFLAGS-tst-prelink.c += -fno-pie
-tst-prelink-no-pie = yes
-endif
-
 # The test requires shared _and_ PIE because the executable
 # unit test driver must be able to link with the shared object
 # that is going to eventually go into an installed DSO.
@@ -2285,13 +2276,6 @@ $(objpfx)tst-tls-manydynamic: $(shared-thread-library)
 $(objpfx)tst-tls-manydynamic.out: \
   $(patsubst %,$(objpfx)%.so,$(tst-tls-many-dynamic-modules))
 
-tst-prelink-ENV = LD_TRACE_PRELINKING=1
-
-$(objpfx)tst-prelink-conflict.out: $(objpfx)tst-prelink.out
-	grep stdout $< | grep conflict | $(AWK) '{ print $$10, $$11 }' > $@
-
-$(objpfx)tst-prelink-cmp.out: $(objpfx)tst-prelink-conflict.out
-
 $(objpfx)tst-ldconfig-X.out : tst-ldconfig-X.sh $(objpfx)ldconfig
 	$(SHELL) $< '$(common-objpfx)' '$(test-wrapper-env)' \
 		 '$(run-program-env)' > $@; \
diff --git a/elf/dl-conflict.c b/elf/dl-conflict.c
deleted file mode 100644
index 769afd581b..0000000000
--- a/elf/dl-conflict.c
+++ /dev/null
@@ -1,77 +0,0 @@
-/* Resolve conflicts against already prelinked libraries.
-   Copyright (C) 2001-2022 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public License as
-   published by the Free Software Foundation; either version 2.1 of the
-   License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; see the file COPYING.LIB.  If
-   not, see <https://www.gnu.org/licenses/>.  */
-
-#include <assert.h>
-#include <errno.h>
-#include <libintl.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <ldsodefs.h>
-#include <sys/mman.h>
-#include <sys/param.h>
-#include <sys/types.h>
-#include "dynamic-link.h"
-
-/* Used at loading time solely for prelink executable.  It is not called
-   concurrently so it is be safe to defined as static.  */
-static struct link_map *resolve_conflict_map __attribute__ ((__unused__));
-
-    /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
-#define RESOLVE_MAP(map, scope, ref, version, flags) (*ref = NULL, NULL)
-#define RESOLVE(ref, version, flags) (*ref = NULL, 0)
-#define RESOLVE_CONFLICT_FIND_MAP(map, r_offset) \
-  do {									      \
-    while ((resolve_conflict_map->l_map_end < (ElfW(Addr)) (r_offset))	      \
-	   || (resolve_conflict_map->l_map_start > (ElfW(Addr)) (r_offset)))  \
-      resolve_conflict_map = resolve_conflict_map->l_next;		      \
-									      \
-    (map) = resolve_conflict_map;					      \
-  } while (0)
-
-#include "dynamic-link.h"
-
-void
-_dl_resolve_conflicts (struct link_map *l, ElfW(Rela) *conflict,
-		       ElfW(Rela) *conflictend)
-{
-#if ! ELF_MACHINE_NO_RELA
-  if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_RELOC))
-    _dl_debug_printf ("\nconflict processing: %s\n", DSO_FILENAME (l->l_name));
-
-  {
-    /* Do the conflict relocation of the object and library GOT and other
-       data.  */
-
-    /* Prelinking makes no sense for anything but the main namespace.  */
-    assert (l->l_ns == LM_ID_BASE);
-    resolve_conflict_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
-
-    /* Override these, defined in dynamic-link.h.  */
-#undef CHECK_STATIC_TLS
-#define CHECK_STATIC_TLS(ref_map, sym_map) ((void) 0)
-#undef TRY_STATIC_TLS
-#define TRY_STATIC_TLS(ref_map, sym_map) (0)
-
-    GL(dl_num_cache_relocations) += conflictend - conflict;
-
-    for (; conflict < conflictend; ++conflict)
-      elf_machine_rela (l, NULL, conflict, NULL, NULL,
-			(void *) conflict->r_offset, 0);
-  }
-#endif
-}
diff --git a/elf/dl-deps.c b/elf/dl-deps.c
index c8bab5cad5..a2fc278256 100644
--- a/elf/dl-deps.c
+++ b/elf/dl-deps.c
@@ -68,22 +68,6 @@ openaux (void *a)
 			      args->map->l_ns);
 }
 
-static ptrdiff_t
-_dl_build_local_scope (struct link_map **list, struct link_map *map)
-{
-  struct link_map **p = list;
-  struct link_map **q;
-
-  *p++ = map;
-  map->l_reserved = 1;
-  if (map->l_initfini)
-    for (q = map->l_initfini + 1; *q; ++q)
-      if (! (*q)->l_reserved)
-	p += _dl_build_local_scope (p, *q);
-  return p - list;
-}
-
-
 /* We use a very special kind of list to track the path
    through the list of loaded shared objects.  We have to
    produce a flat list with unique members of all involved objects.
@@ -504,56 +488,6 @@ _dl_map_object_deps (struct link_map *map,
       runp->map->l_reserved = 0;
     }
 
-  if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK, 0) != 0
-      && map == GL(dl_ns)[LM_ID_BASE]._ns_loaded)
-    {
-      /* If we are to compute conflicts, we have to build local scope
-	 for each library, not just the ultimate loader.  */
-      for (i = 0; i < nlist; ++i)
-	{
-	  struct link_map *l = map->l_searchlist.r_list[i];
-	  unsigned int j, cnt;
-
-	  /* The local scope has been already computed.  */
-	  if (l == map
-	      || (l->l_local_scope[0]
-		  && l->l_local_scope[0]->r_nlist) != 0)
-	    continue;
-
-	  if (l->l_info[AUXTAG] || l->l_info[FILTERTAG])
-	    {
-	      /* As current DT_AUXILIARY/DT_FILTER implementation needs to be
-		 rewritten, no need to bother with prelinking the old
-		 implementation.  */
-	      _dl_signal_error (EINVAL, l->l_name, NULL, N_("\
-Filters not supported with LD_TRACE_PRELINKING"));
-	    }
-
-	  cnt = _dl_build_local_scope (l_initfini, l);
-	  assert (cnt <= nlist);
-	  for (j = 0; j < cnt; j++)
-	    {
-	      l_initfini[j]->l_reserved = 0;
-	      if (j && __builtin_expect (l_initfini[j]->l_info[DT_SYMBOLIC]
-					 != NULL, 0))
-		l->l_symbolic_in_local_scope = true;
-	    }
-
-	  l->l_local_scope[0] =
-	    (struct r_scope_elem *) malloc (sizeof (struct r_scope_elem)
-					    + (cnt
-					       * sizeof (struct link_map *)));
-	  if (l->l_local_scope[0] == NULL)
-	    _dl_signal_error (ENOMEM, map->l_name, NULL,
-			      N_("cannot allocate symbol search list"));
-	  l->l_local_scope[0]->r_nlist = cnt;
-	  l->l_local_scope[0]->r_list =
-	    (struct link_map **) (l->l_local_scope[0] + 1);
-	  memcpy (l->l_local_scope[0]->r_list, l_initfini,
-		  cnt * sizeof (struct link_map *));
-	}
-    }
-
   /* Maybe we can remove some relocation dependencies now.  */
   struct link_map_reldeps *l_reldeps = NULL;
   if (map->l_reldeps != NULL)
diff --git a/elf/dl-error-skeleton.c b/elf/dl-error-skeleton.c
index b4213ea3db..8abf437f87 100644
--- a/elf/dl-error-skeleton.c
+++ b/elf/dl-error-skeleton.c
@@ -132,7 +132,7 @@ _dl_signal_cexception (int errcode, struct dl_exception *exception,
 		       const char *occasion)
 {
   if (__builtin_expect (GLRO(dl_debug_mask)
-			& ~(DL_DEBUG_STATISTICS|DL_DEBUG_PRELINK), 0))
+			& ~(DL_DEBUG_STATISTICS), 0))
     _dl_debug_printf ("%s: error: %s: %s (%s)\n",
 		      exception->objname, occasion,
 		      exception->errstring, receiver ? "continued" : "fatal");
@@ -153,7 +153,7 @@ _dl_signal_cerror (int errcode, const char *objname, const char *occation,
 		   const char *errstring)
 {
   if (__builtin_expect (GLRO(dl_debug_mask)
-			& ~(DL_DEBUG_STATISTICS|DL_DEBUG_PRELINK), 0))
+			& ~(DL_DEBUG_STATISTICS), 0))
     _dl_debug_printf ("%s: error: %s: %s (%s)\n", objname, occation,
 		      errstring, receiver ? "continued" : "fatal");
 
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 5b0ff41ee1..892e8ef2f6 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -2263,8 +2263,7 @@ _dl_map_object (struct link_map *loader, const char *name,
 
   if (__glibc_unlikely (fd == -1))
     {
-      if (trace_mode
-	  && __glibc_likely ((GLRO(dl_debug_mask) & DL_DEBUG_PRELINK) == 0))
+      if (trace_mode)
 	{
 	  /* We haven't found an appropriate library.  But since we
 	     are only interested in the list of libraries this isn't
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index cbf46fda62..7b2a6622be 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -296,19 +296,6 @@ do_lookup_unique (const char *undef_name, uint_fast32_t new_hash,
       assert (!RTLD_CHECK_FOREIGN_CALL);
 #endif
 
-#ifdef SHARED
-      /* If tab->entries is NULL, but tab->size is not, it means
-	 this is the second, conflict finding, lookup for
-	 LD_TRACE_PRELINKING in _dl_debug_bindings.  Don't
-	 allocate anything and don't enter anything into the
-	 hash table.  */
-      if (__glibc_unlikely (tab->size))
-	{
-	  assert (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK);
-	  goto success;
-	}
-#endif
-
 #define INITIAL_NUNIQUE_SYM_TABLE 31
       size = INITIAL_NUNIQUE_SYM_TABLE;
       entries = calloc (sizeof (struct unique_sym), size);
@@ -341,9 +328,6 @@ marking %s [%lu] as NODELETE due to unique symbol\n",
     }
   ++tab->n_elements;
 
-#ifdef SHARED
- success:
-#endif
   __rtld_lock_unlock_recursive (tab->lock);
 
   result->s = sym;
@@ -818,12 +802,6 @@ marking %s [%lu] as NODELETE due to memory allocation failure\n",
   goto out;
 }
 
-static void
-_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
-		    const ElfW(Sym) **ref, struct sym_val *value,
-		    const struct r_found_version *version, int type_class,
-		    int protected);
-
 
 /* Search loaded objects' symbol tables for a definition of the symbol
    UNDEF_NAME, perhaps with a requested version for the symbol.
@@ -943,145 +921,6 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
   if (__glibc_unlikely (current_value.m->l_used == 0))
     current_value.m->l_used = 1;
 
-  if (__glibc_unlikely (GLRO(dl_debug_mask)
-			& (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK)))
-    _dl_debug_bindings (undef_name, undef_map, ref,
-			&current_value, version, type_class, protected);
-
   *ref = current_value.s;
   return LOOKUP_VALUE (current_value.m);
 }
-
-
-static void
-_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
-		    const ElfW(Sym) **ref, struct sym_val *value,
-		    const struct r_found_version *version, int type_class,
-		    int protected)
-{
-  const char *reference_name = undef_map->l_name;
-
-  if (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
-    {
-      _dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
-			DSO_FILENAME (reference_name),
-			undef_map->l_ns,
-			DSO_FILENAME (value->m->l_name),
-			value->m->l_ns,
-			protected ? "protected" : "normal", undef_name);
-      if (version)
-	_dl_debug_printf_c (" [%s]\n", version->name);
-      else
-	_dl_debug_printf_c ("\n");
-    }
-#ifdef SHARED
-  if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK)
-    {
-/* ELF_RTYPE_CLASS_XXX must match RTYPE_CLASS_XXX used by prelink with
-   LD_TRACE_PRELINKING.  */
-#define RTYPE_CLASS_VALID	8
-#define RTYPE_CLASS_PLT		(8|1)
-#define RTYPE_CLASS_COPY	(8|2)
-#define RTYPE_CLASS_TLS		(8|4)
-#if ELF_RTYPE_CLASS_PLT != 0 && ELF_RTYPE_CLASS_PLT != 1
-# error ELF_RTYPE_CLASS_PLT must be 0 or 1!
-#endif
-#if ELF_RTYPE_CLASS_COPY != 0 && ELF_RTYPE_CLASS_COPY != 2
-# error ELF_RTYPE_CLASS_COPY must be 0 or 2!
-#endif
-      int conflict = 0;
-      struct sym_val val = { NULL, NULL };
-
-      if ((GLRO(dl_trace_prelink_map) == NULL
-	   || GLRO(dl_trace_prelink_map) == GL(dl_ns)[LM_ID_BASE]._ns_loaded)
-	  && undef_map != GL(dl_ns)[LM_ID_BASE]._ns_loaded)
-	{
-	  const uint_fast32_t new_hash = dl_new_hash (undef_name);
-	  unsigned long int old_hash = 0xffffffff;
-	  struct unique_sym *saved_entries
-	    = GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries;
-
-	  GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries = NULL;
-	  do_lookup_x (undef_name, new_hash, &old_hash, *ref, &val,
-		       undef_map->l_local_scope[0], 0, version, 0, NULL,
-		       type_class, undef_map);
-	  if (val.s != value->s || val.m != value->m)
-	    conflict = 1;
-	  else if (__glibc_unlikely (undef_map->l_symbolic_in_local_scope)
-		   && val.s
-		   && __glibc_unlikely (ELFW(ST_BIND) (val.s->st_info)
-					== STB_GNU_UNIQUE))
-	    {
-	      /* If it is STB_GNU_UNIQUE and undef_map's l_local_scope
-		 contains any DT_SYMBOLIC libraries, unfortunately there
-		 can be conflicts even if the above is equal.  As symbol
-		 resolution goes from the last library to the first and
-		 if a STB_GNU_UNIQUE symbol is found in some late DT_SYMBOLIC
-		 library, it would be the one that is looked up.  */
-	      struct sym_val val2 = { NULL, NULL };
-	      size_t n;
-	      struct r_scope_elem *scope = undef_map->l_local_scope[0];
-
-	      for (n = 0; n < scope->r_nlist; n++)
-		if (scope->r_list[n] == val.m)
-		  break;
-
-	      for (n++; n < scope->r_nlist; n++)
-		if (scope->r_list[n]->l_info[DT_SYMBOLIC] != NULL
-		    && do_lookup_x (undef_name, new_hash, &old_hash, *ref,
-				    &val2,
-				    &scope->r_list[n]->l_symbolic_searchlist,
-				    0, version, 0, NULL, type_class,
-				    undef_map) > 0)
-		  {
-		    conflict = 1;
-		    val = val2;
-		    break;
-		  }
-	    }
-	  GL(dl_ns)[LM_ID_BASE]._ns_unique_sym_table.entries = saved_entries;
-	}
-
-      if (value->s)
-	{
-	  /* Keep only ELF_RTYPE_CLASS_PLT and ELF_RTYPE_CLASS_COPY
-	     bits since since prelink only uses them.  */
-	  type_class &= ELF_RTYPE_CLASS_PLT | ELF_RTYPE_CLASS_COPY;
-	  if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
-				== STT_TLS))
-	    /* Clear the RTYPE_CLASS_VALID bit in RTYPE_CLASS_TLS.  */
-	    type_class = RTYPE_CLASS_TLS & ~RTYPE_CLASS_VALID;
-	  else if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
-				     == STT_GNU_IFUNC))
-	    /* Set the RTYPE_CLASS_VALID bit.  */
-	    type_class |= RTYPE_CLASS_VALID;
-	}
-
-      if (conflict
-	  || GLRO(dl_trace_prelink_map) == undef_map
-	  || GLRO(dl_trace_prelink_map) == NULL
-	  || type_class >= 4)
-	{
-	  _dl_printf ("%s 0x%0*Zx 0x%0*Zx -> 0x%0*Zx 0x%0*Zx ",
-		      conflict ? "conflict" : "lookup",
-		      (int) sizeof (ElfW(Addr)) * 2,
-		      (size_t) undef_map->l_map_start,
-		      (int) sizeof (ElfW(Addr)) * 2,
-		      (size_t) (((ElfW(Addr)) *ref) - undef_map->l_map_start),
-		      (int) sizeof (ElfW(Addr)) * 2,
-		      (size_t) (value->s ? value->m->l_map_start : 0),
-		      (int) sizeof (ElfW(Addr)) * 2,
-		      (size_t) (value->s ? value->s->st_value : 0));
-
-	  if (conflict)
-	    _dl_printf ("x 0x%0*Zx 0x%0*Zx ",
-			(int) sizeof (ElfW(Addr)) * 2,
-			(size_t) (val.s ? val.m->l_map_start : 0),
-			(int) sizeof (ElfW(Addr)) * 2,
-			(size_t) (val.s ? val.s->st_value : 0));
-
-	  _dl_printf ("/%x %s\n", type_class, undef_name);
-	}
-    }
-#endif
-}
diff --git a/elf/do-rel.h b/elf/do-rel.h
index 60d5dce8f2..d3e022267b 100644
--- a/elf/do-rel.h
+++ b/elf/do-rel.h
@@ -105,9 +105,6 @@ elf_dynamic_do_Rel (struct link_map *map, struct r_scope_elem *scope[],
 	   relocations or rela relocations if they are computed as
 	   memory_loc += l_addr...  */
 	if (l_addr != 0)
-# else
-	/* ...or we know the object has been prelinked.  */
-	if (l_addr != 0 || ! map->l_info[VALIDX(DT_GNU_PRELINKED)])
 # endif
 #endif
 	  for (; relative < r; ++relative)
diff --git a/elf/rtld.c b/elf/rtld.c
index 8dafaf61f4..5f089038e1 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -565,7 +565,7 @@ _dl_start (void *arg)
   ELF_MACHINE_BEFORE_RTLD_RELOC (&bootstrap_map, bootstrap_map.l_info);
 #endif
 
-  if (bootstrap_map.l_addr || ! bootstrap_map.l_info[VALIDX(DT_GNU_PRELINKED)])
+  if (bootstrap_map.l_addr)
     {
       /* Relocate ourselves so we can do normal function calls and
 	 data access using the global offset table.  */
@@ -1322,7 +1322,6 @@ dl_main (const ElfW(Phdr) *phdr,
   size_t file_size;
   char *file;
   unsigned int i;
-  bool prelinked = false;
   bool rtld_is_main = false;
   void *tcbp = NULL;
 
@@ -2055,37 +2054,7 @@ dl_main (const ElfW(Phdr) *phdr,
 	 after relocation.  */
       struct link_map *l;
 
-      if (GLRO(d