public inbox for binutils@sourceware.org
 help / color / mirror / Atom feed
* [PATCH] aarch64: Disallow copy relocations on protected data
@ 2022-05-24  5:10 Fangrui Song
  2022-05-27 22:43 ` Fangrui Song
       [not found] ` <CAN30aBHDJM4KJAJJ_=4=vKgJL-yow2roUEUa7LFaAFaivkVswg@mail.gmail.com>
  0 siblings, 2 replies; 8+ messages in thread
From: Fangrui Song @ 2022-05-24  5:10 UTC (permalink / raw)
  To: binutils, Adhemerval Zanella, Szabolcs Nagy

The behavior matches ld.lld which has been used on many aarch64 OSes.

Rationale: copy relocations indicate that the executable and the shared object
would access different copies, if the shared object does not reference the
variable with GLOB_DAT.

Note: x86 requires GNU_PROPERTY_NO_COPY_ON_PROTECTED to have the error.
This is to largely due to GCC 5's
"x86-64: Optimize access to globals in PIE with copy reloc" which started to use
direct access relocations for external data symbols in -fpie mode.

GCC's aarch64 port does not have the change. Nowadays with most builds switching
to -fpie/-fpic, aarch64 mostly doesn't need to worry about copy relocations. So
for aarch64 we simply don't check GNU_PROPERTY_NO_COPY_ON_PROTECTED.
---
 bfd/elfnn-aarch64.c                           | 28 ++++++++++++++++++-
 ld/testsuite/ld-aarch64/aarch64-elf.exp       |  9 ++++++
 .../ld-aarch64/copy-reloc-protected.d         |  2 ++
 ld/testsuite/ld-aarch64/protected.s           |  8 ++++++
 4 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 ld/testsuite/ld-aarch64/copy-reloc-protected.d
 create mode 100644 ld/testsuite/ld-aarch64/protected.s

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 4926bab9cf2..8896b0f78dd 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2579,6 +2579,9 @@ struct elf_aarch64_link_hash_entry
      this symbol.  */
   unsigned int got_type;
 
+  /* TRUE if symbol is defined as a protected symbol.  */
+  unsigned int def_protected : 1;
+
   /* A pointer to the most recently used stub hash entry against this
      symbol.  */
   struct elf_aarch64_stub_hash_entry *stub_cache;
@@ -2855,9 +2858,16 @@ elfNN_aarch64_copy_indirect_symbol (struct bfd_link_info *info,
 static void
 elfNN_aarch64_merge_symbol_attribute (struct elf_link_hash_entry *h,
 				      unsigned int st_other,
-				      bool definition ATTRIBUTE_UNUSED,
+				      bool definition,
 				      bool dynamic ATTRIBUTE_UNUSED)
 {
+  if (definition)
+    {
+      struct elf_aarch64_link_hash_entry *eh
+	= (struct elf_aarch64_link_hash_entry *) h;
+      eh->def_protected = ELF_ST_VISIBILITY (st_other) == STV_PROTECTED;
+    }
+
   unsigned int isym_sto = st_other & ~ELF_ST_VISIBILITY (-1);
   unsigned int h_sto = h->other & ~ELF_ST_VISIBILITY (-1);
 
@@ -8701,6 +8711,22 @@ elfNN_aarch64_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
   if (h->dyn_relocs == NULL)
     return true;
 
+  for (p = h->dyn_relocs; p != NULL; p = p->next)
+    if (eh->def_protected)
+      {
+	/* Disallow copy relocations against protected symbol.  */
+	asection *s = p->sec->output_section;
+	if (s != NULL && (s->flags & SEC_READONLY) != 0)
+	  {
+	    info->callbacks->einfo
+		/* xgettext:c-format */
+		(_ ("%F%P: %pB: copy relocation against non-copyable "
+		    "protected symbol `%s'\n"),
+		 p->sec->owner, h->root.root.string);
+	    return false;
+	  }
+      }
+
   /* In the shared -Bsymbolic case, discard space allocated for
      dynamic pc-relative relocs against symbols which turn out to be
      defined in regular objects.  For the normal shared case, discard
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 64476f111e0..31162277bd9 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -407,6 +407,8 @@ set aarch64elflinktests {
     {copy-reloc-exe-2.s} {{objdump -R copy-reloc-2.d}} "copy-reloc-2"}
   {"ld-aarch64/exe with copy relocation elimination" "-e0 tmpdir/copy-reloc-so.so" "" ""
     {copy-reloc-exe-eliminate.s} {{objdump -R copy-reloc-eliminate.d}} "copy-reloc-elimination"}
+  {"Build .so with protected data" "-shared" "" "" {protected.s}
+    {} "protected.so"}
   {"ld-aarch64/so with global func" "-shared" "" "" {func-in-so.s}
     {} "func-in-so.so"}
   {"ld-aarch64/func sym hash opt for exe"
@@ -416,8 +418,15 @@ set aarch64elflinktests {
     {} "libbti-plt-so.so"}
 }
 
+set aarch64elfcclinktests [list \
+  [list "copy relocation on protected data" \
+    "-no-pie tmpdir/copy-reloc-exe.o tmpdir/protected.so" "" \
+    {} {{error_output copy-reloc-protected.d}} "copy-reloc-protected"]
+]
+
 if [check_shared_lib_support] {
     run_ld_link_tests $aarch64elflinktests
+    run_cc_link_tests $aarch64elfcclinktests
 }
 
 run_dump_test "bti-plt-3"
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-protected.d b/ld/testsuite/ld-aarch64/copy-reloc-protected.d
new file mode 100644
index 00000000000..99a356a3df6
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-protected.d
@@ -0,0 +1,2 @@
+.*: tmpdir/copy-reloc-exe.o: copy relocation against non-copyable protected symbol `global_a'
+#...
diff --git a/ld/testsuite/ld-aarch64/protected.s b/ld/testsuite/ld-aarch64/protected.s
new file mode 100644
index 00000000000..eb3fb402dc4
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/protected.s
@@ -0,0 +1,8 @@
+.global global_a
+.protected global_a
+.type global_a, %object
+.size global_a, 4
+
+.data
+global_a:
+.word 0xcafedead
-- 
2.36


^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-07-01 11:16 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-05-24  5:10 [PATCH] aarch64: Disallow copy relocations on protected data Fangrui Song
2022-05-27 22:43 ` Fangrui Song
     [not found] ` <CAN30aBHDJM4KJAJJ_=4=vKgJL-yow2roUEUa7LFaAFaivkVswg@mail.gmail.com>
2022-06-01  5:53   ` PING: " Fangrui Song
     [not found]   ` <CAN30aBH68jT8ArEPEx_X-zVzuOmN3u_KV5HKc-Vgc2tVohJADw@mail.gmail.com>
2022-06-15 22:28     ` Fangrui Song
2022-06-21 19:27       ` Fangrui Song
     [not found]       ` <DS7PR12MB57658D646BB4944D4BECAF84CBB39@DS7PR12MB5765.namprd12.prod.outlook.com>
2022-06-22 10:55         ` Nick Clifton
2022-06-22 11:15           ` Szabolcs Nagy
2022-07-01 11:16             ` Matthias Klose

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).