diff mbox series

[v3,21/32] elf: _dl_rtld_map should not exist in static builds

Message ID 6515a7c0cae19a148a3eb745aeb9f309e77d73fe.1701944612.git.fweimer@redhat.com
State New
Headers show
Series RELRO linkmaps | expand

Commit Message

Florian Weimer Dec. 7, 2023, 10:32 a.m. UTC 
We have separate objects for SHARED and !SHARED, so there is no need
to make the rtld link map equality check somehow work in static
builds.  Instead, hide the _dl_rtld_map reference in the new
is_rtld_link_map function, and simply define that to return false
for !SHARED because the static linked loader does not have a link
map.
---
 elf/do-rel.h                           | 11 +----------
 elf/dynamic-link.h                     |  2 +-
 sysdeps/arm/dl-machine.h               | 11 +----------
 sysdeps/generic/ldsodefs.h             | 14 ++++++++++++++
 sysdeps/mips/dl-machine.h              | 16 +++-------------
 sysdeps/powerpc/powerpc64/dl-machine.h |  4 ++--
 sysdeps/sh/dl-machine.h                |  7 ++-----
 7 files changed, 24 insertions(+), 41 deletions(-)

Comments

Joseph Myers Feb. 28, 2024, 12:38 p.m. UTC | #1 
On Thu, 7 Dec 2023, Florian Weimer wrote:

> We have separate objects for SHARED and !SHARED, so there is no need
> to make the rtld link map equality check somehow work in static
> builds.  Instead, hide the _dl_rtld_map reference in the new
> is_rtld_link_map function, and simply define that to return false
> for !SHARED because the static linked loader does not have a link
> map.

Probably this should replace all comparisons with &GL(dl_rtld_map) with 
calls to is_rtld_link_map (unless there's a specific reason such a 
replacement is problematic in a given case), even if no SHARED conditional 
is involved?  I don't think it does at present.  Maybe patch 11 (which I 
still need to review) was meant to remove dl-dst.h (which it doesn't; nor 
does it remove the include of dl-dst.h from elf/dl-origin.c), which would 
deal with IS_RTLD there.  But what about sysdeps/x86/dl-prop.h and 
sysdeps/x86_64/dl-cet.c, or a few such comparisons in rtld.c itself?
diff mbox series

Patch

diff --git a/elf/do-rel.h b/elf/do-rel.h
index 8083cb4162..78b5ddfe87 100644
--- a/elf/do-rel.h
+++ b/elf/do-rel.h
@@ -102,16 +102,7 @@  elf_dynamic_do_Rel (struct link_map_private *map, struct r_scope_elem *scope[],
   else
 #endif
     {
-      /* This is defined in rtld.c, but nowhere in the static libc.a; make
-	 the reference weak so static programs can still link.  This
-	 declaration cannot be done when compiling rtld.c (i.e. #ifdef
-	 RTLD_BOOTSTRAP) because rtld.c contains the common defn for
-	 _dl_rtld_map, which is incompatible with a weak decl in the same
-	 file.  */
-# ifndef SHARED
-      weak_extern (GL(dl_rtld_map));
-# endif
-      if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.  */
+      if (!is_rtld_link_map (map)) /* Already done in rtld itself.  */
 # if !defined DO_RELA || defined ELF_MACHINE_REL_RELATIVE
 	/* Rela platforms get the offset from r_addend and this must
 	   be copied in the relocation address.  Therefore we can skip
diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index 2f72240b6a..8f4d096182 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -190,7 +190,7 @@  elf_machine_lazy_rel (struct link_map_private *map,
   do {									      \
     int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy),	      \
 					      (consider_profile));	      \
-    if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP))		      \
+    if ((!is_rtld_link_map (map) || DO_RTLD_BOOTSTRAP))			      \
       ELF_DYNAMIC_DO_RELR (map);					      \
     ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc);		      \
     ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc);		      \
diff --git a/sysdeps/arm/dl-machine.h b/sysdeps/arm/dl-machine.h
index b138596252..99bf9656b2 100644
--- a/sysdeps/arm/dl-machine.h
+++ b/sysdeps/arm/dl-machine.h
@@ -356,16 +356,7 @@  elf_machine_rel (struct link_map_private *map, struct r_scope_elem *scope[],
 		Elf32_Addr x;
 	      } __attribute__ ((packed, may_alias));
 # ifndef RTLD_BOOTSTRAP
-	   /* This is defined in rtld.c, but nowhere in the static
-	      libc.a; make the reference weak so static programs can
-	      still link.  This declaration cannot be done when
-	      compiling rtld.c (i.e.  #ifdef RTLD_BOOTSTRAP) because
-	      rtld.c contains the common defn for _dl_rtld_map, which
-	      is incompatible with a weak decl in the same file.  */
-#  ifndef SHARED
-	    weak_extern (_dl_rtld_map);
-#  endif
-	    if (map == &GL(dl_rtld_map))
+	    if (is_rtld_link_map (map))
 	      /* Undo the relocation done here during bootstrapping.
 		 Now we will relocate it anew, possibly using a
 		 binding found in the user program or a loaded library
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 9f2022d43e..c5d49cae62 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -406,8 +406,10 @@  struct rtld_global
   /* List of search directories.  */
   EXTERN struct r_search_path_elem *_dl_all_dirs;
 
+#ifdef SHARED
   /* Structure describing the dynamic linker itself.  */
   EXTERN struct link_map_private _dl_rtld_map;
+#endif
 
 #if !PTHREAD_IN_LIBC && defined SHARED \
     && defined __rtld_lock_default_lock_recursive
@@ -1326,6 +1328,18 @@  dl_init_static_tls (struct link_map_private *map)
 void __rtld_static_init (struct link_map_private *map) attribute_hidden;
 #endif
 
+/* Returns true if MAP is the dynamic loader itself.  Statically
+   linked binaries do not have a dynamic loader, so return false.  */
+static inline bool
+is_rtld_link_map (const struct link_map_private *map)
+{
+#ifdef SHARED
+  return map == &GL (dl_rtld_map);
+#else
+  return false;
+#endif
+}
+
 /* Return true if the ld.so copy in this namespace is actually active
    and working.  If false, the dl_open/dlfcn hooks have to be used to
    call into the outer dynamic linker (which happens after static
diff --git a/sysdeps/mips/dl-machine.h b/sysdeps/mips/dl-machine.h
index b7b1705f65..2eb01ca7cb 100644
--- a/sysdeps/mips/dl-machine.h
+++ b/sysdeps/mips/dl-machine.h
@@ -436,16 +436,6 @@  elf_machine_reloc (struct link_map_private *map, struct r_scope_elem *scope[],
   const unsigned long int r_type = ELFW(R_TYPE) (r_info);
   ElfW(Addr) *addr_field = (ElfW(Addr) *) reloc_addr;
 
-#if !defined RTLD_BOOTSTRAP && !defined SHARED
-  /* This is defined in rtld.c, but nowhere in the static libc.a;
-     make the reference weak so static programs can still link.  This
-     declaration cannot be done when compiling rtld.c (i.e.  #ifdef
-     RTLD_BOOTSTRAP) because rtld.c contains the common defn for
-     _dl_rtld_map, which is incompatible with a weak decl in the same
-     file.  */
-  weak_extern (GL(dl_rtld_map));
-#endif
-
   switch (r_type)
     {
 #if !defined (RTLD_BOOTSTRAP)
@@ -534,7 +524,7 @@  elf_machine_reloc (struct link_map_private *map, struct r_scope_elem *scope[],
 		   though it's not ABI compliant.  Some day we should
 		   bite the bullet and stop doing this.  */
 #ifndef RTLD_BOOTSTRAP
-		if (map != &GL(dl_rtld_map))
+		if (!is_rtld_link_map (map))
 #endif
 		  reloc_value += SYMBOL_ADDRESS (map, sym, true);
 	      }
@@ -553,7 +543,7 @@  elf_machine_reloc (struct link_map_private *map, struct r_scope_elem *scope[],
 	  }
 	else
 #ifndef RTLD_BOOTSTRAP
-	  if (map != &GL(dl_rtld_map))
+	  if (!is_rtld_link_map (map))
 #endif
 	    reloc_value += map->l_public.l_addr;
 
@@ -752,7 +742,7 @@  elf_machine_got_rel (struct link_map_private *map,
 
   n = map->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;
   /* The dynamic linker's local got entries have already been relocated.  */
-  if (map != &GL(dl_rtld_map))
+  if (!is_rtld_link_map (map))
     {
       /* got[0] is reserved. got[1] is also reserved for the dynamic object
 	 generated by gnu ld. Skip these reserved entries from relocation.  */
diff --git a/sysdeps/powerpc/powerpc64/dl-machine.h b/sysdeps/powerpc/powerpc64/dl-machine.h
index 6104d6ae9c..80754546b4 100644
--- a/sysdeps/powerpc/powerpc64/dl-machine.h
+++ b/sysdeps/powerpc/powerpc64/dl-machine.h
@@ -519,7 +519,7 @@  elf_machine_fixup_plt (struct link_map_private *map, lookup_t sym_map,
   if (finaladdr != 0 && map != sym_map && !sym_map->l_relocated
 #if !defined RTLD_BOOTSTRAP && defined SHARED
       /* Bootstrap map doesn't have l_relocated set for it.  */
-      && sym_map != &GL(dl_rtld_map)
+      && !is_rtld_link_map (sym_map)
 #endif
       )
     offset = sym_map->l_public.l_addr;
@@ -645,7 +645,7 @@  resolve_ifunc (Elf64_Addr value,
   if (map != sym_map
 # if !defined RTLD_BOOTSTRAP && defined SHARED
       /* Bootstrap map doesn't have l_relocated set for it.  */
-      && sym_map != &GL(dl_rtld_map)
+      && !is_rtld_link_map (sym_map)
 # endif
       && !sym_map->l_relocated)
     {
diff --git a/sysdeps/sh/dl-machine.h b/sysdeps/sh/dl-machine.h
index 786cd00cab..f76254cca8 100644
--- a/sysdeps/sh/dl-machine.h
+++ b/sysdeps/sh/dl-machine.h
@@ -285,7 +285,7 @@  elf_machine_rela (struct link_map_private *map, struct r_scope_elem *scope[],
   if (__glibc_unlikely (r_type == R_SH_RELATIVE))
     {
 #ifndef RTLD_BOOTSTRAP
-      if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.	 */
+      if (!is_rtld_link_map (map)) /* Already done in rtld itself.  */
 #endif
 	{
 	  if (reloc->r_addend)
@@ -388,10 +388,7 @@  elf_machine_rela (struct link_map_private *map, struct r_scope_elem *scope[],
 	      compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP) because
 	      rtld.c contains the common defn for _dl_rtld_map, which
 	      is incompatible with a weak decl in the same file.  */
-# ifndef SHARED
-	    weak_extern (_dl_rtld_map);
-# endif
-	    if (map == &GL(dl_rtld_map))
+	    if (is_rtld_link_map (map))
 	      /* Undo the relocation done here during bootstrapping.
 		 Now we will relocate it anew, possibly using a
 		 binding found in the user program or a loaded library