diff mbox

[v9,09/10] Validate symbol file using build-id

Message ID 20150712192911.GB12553@host1.jankratochvil.net
State New
Headers show

Commit Message

Jan Kratochvil July 12, 2015, 7:29 p.m. UTC
On Sun, 12 Jul 2015 21:09:21 +0200, Jan Kratochvil wrote:
> On Wed, 08 Jul 2015 16:44:25 +0200, Pedro Alves wrote:
> > Doug Evans wrote:
> > > 
> > >> > If so, having solib in the option name is confusing.
> > >> > 
> > >> > set build-id-force
> > >> > or
> > >> > set require-build-id-match
> > >> > or some such would be clearer.
> > 
> > "build-id-force" sound odd to me.  The latter sounds OK,
> > as would "set build-id-validation on/off/...".
> 
> OK, I will change it to "set build-id-validation on/off/...".

It required some language changes as it reversed its on<->off meaning,
therefore Ccing Eli.


Jan
Hi,

consumer part of the "build-id" attribute.

Approved by:
	https://sourceware.org/ml/gdb-patches/2014-05/msg00424.html


Jan


gdb/ChangeLog
2014-02-26  Aleksandar Ristovski  <aristovski@qnx.com
	    Jan Kratochvil  <jan.kratochvil@redhat.com>

	Validate symbol file using build-id.
	* NEWS (Changes since GDB 7.9): Add 'set solib-build-id-validation'
	and 'show solib-build-id-validation'.  Add build-id attribute.
	* solib-darwin.c (_initialize_darwin_solib): Assign validate value.
	* solib-dsbt.c (_initialize_dsbt_solib): Ditto.
	* solib-frv.c (_initialize_frv_solib): Ditto.
	* solib-spu.c (set_spu_solib_ops): Ditto.
	* solib-svr4.c: Include rsp-low.h.
	(NOTE_GNU_BUILD_ID_NAME): New define.
	(svr4_validate): New function.
	(svr4_copy_library_list): Duplicate field build_id.
	(library_list_start_library): Parse 'build-id' attribute.
	(svr4_library_attributes): Add 'build-id' attribute.
	(_initialize_svr4_solib): Assign validate value.
	* solib-target.c (solib.h): Include.
	(_initialize_solib_target): Assign validate value.
	* solib.c (solib_build_id_validation, show_solib_build_id_validation):
	New.
	(solib_map_sections): Use ops->validate.
	(clear_so): Free build_id.
	(default_solib_validate): New function.
	(_initialize_solib): Add "solib-build-id-validation".
	* solib.h (default_solib_validate): New declaration.
	* solist.h (struct so_list): New fields 'build_idsz' and 'build_id'.
	(target_so_ops): New field 'validate'.

gdb/doc/ChangeLog
2014-03-02  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.texinfo (Files): Add 'set solib-build-id-validation'
	and 'show solib-build-id-validation'.
---
 gdb/NEWS            |  12 ++++++
 gdb/doc/gdb.texinfo |  38 +++++++++++++++++++
 gdb/solib-darwin.c  |   1 +
 gdb/solib-dsbt.c    |   1 +
 gdb/solib-frv.c     |   1 +
 gdb/solib-spu.c     |   1 +
 gdb/solib-svr4.c    | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/solib-target.c  |   2 +
 gdb/solib.c         |  64 +++++++++++++++++++++++++++++++-
 gdb/solib.h         |   4 ++
 gdb/solist.h        |  18 +++++++++
 11 files changed, 244 insertions(+), 1 deletion(-)

Comments

Eli Zaretskii July 12, 2015, 7:54 p.m. UTC | #1
> Date: Sun, 12 Jul 2015 21:29:11 +0200
> From: Jan Kratochvil <jan.kratochvil@redhat.com>
> Cc: Doug Evans <dje@google.com>, gdb-patches <gdb-patches@sourceware.org>,
>         Aleksandar Ristovski <ARistovski@qnx.com>,
>         Eli Zaretskii <eliz@gnu.org>
> 
> > > "build-id-force" sound odd to me.  The latter sounds OK,
> > > as would "set build-id-validation on/off/...".
> > 
> > OK, I will change it to "set build-id-validation on/off/...".
> 
> It required some language changes as it reversed its on<->off meaning,
> therefore Ccing Eli.

It's OK, although I wonder whether solib-validate-build-id is perhaps
a better name.

Thanks.
Jan Kratochvil July 12, 2015, 8:01 p.m. UTC | #2
On Sun, 12 Jul 2015 21:54:17 +0200, Eli Zaretskii wrote:
> > > OK, I will change it to "set build-id-validation on/off/...".
> > 
> > It required some language changes as it reversed its on<->off meaning,
> > therefore Ccing Eli.
> 
> It's OK, although I wonder whether solib-validate-build-id is perhaps
> a better name.

I do not have an opinion on it so tell me if there is some settlement on
a change request.


Thanks,
Jan
Eli Zaretskii July 13, 2015, 2:30 a.m. UTC | #3
> Date: Sun, 12 Jul 2015 22:01:08 +0200
> From: Jan Kratochvil <jan.kratochvil@redhat.com>
> Cc: palves@redhat.com, dje@google.com, gdb-patches@sourceware.org,
>         ARistovski@qnx.com
> 
> On Sun, 12 Jul 2015 21:54:17 +0200, Eli Zaretskii wrote:
> > > > OK, I will change it to "set build-id-validation on/off/...".
> > > 
> > > It required some language changes as it reversed its on<->off meaning,
> > > therefore Ccing Eli.
> > 
> > It's OK, although I wonder whether solib-validate-build-id is perhaps
> > a better name.
> 
> I do not have an opinion on it so tell me if there is some settlement on
> a change request.

It was just a thought, feel free to disregard if you are okay with the
name you suggested.
Pedro Alves July 13, 2015, 10:34 a.m. UTC | #4
On 07/12/2015 08:54 PM, Eli Zaretskii wrote:
>> Date: Sun, 12 Jul 2015 21:29:11 +0200
>> From: Jan Kratochvil <jan.kratochvil@redhat.com>
>> Cc: Doug Evans <dje@google.com>, gdb-patches <gdb-patches@sourceware.org>,
>>         Aleksandar Ristovski <ARistovski@qnx.com>,
>>         Eli Zaretskii <eliz@gnu.org>
>>
>>>> "build-id-force" sound odd to me.  The latter sounds OK,
>>>> as would "set build-id-validation on/off/...".
>>>
>>> OK, I will change it to "set build-id-validation on/off/...".
>>
>> It required some language changes as it reversed its on<->off meaning,
>> therefore Ccing Eli.
> 
> It's OK, although I wonder whether solib-validate-build-id is perhaps
> a better name.

As the plan is for the feature to apply to the main executable too,
it's better that "solib" isn't part of the setting name.  I agree
that "validate-build-id" sounds better than "build-id-validation".

Thanks,
Pedro Alves
Jan Kratochvil July 13, 2015, 12:38 p.m. UTC | #5
On Mon, 13 Jul 2015 12:34:33 +0200, Pedro Alves wrote:
> As the plan is for the feature to apply to the main executable too,
> it's better that "solib" isn't part of the setting name.  I agree
> that "validate-build-id" sounds better than "build-id-validation".

OK, so validate-build-id or solib-validate-build-id.

Just this series being approved is still only for shlib and I do not yet have
completely finished the second series for all binaries; although 7.10 is
branched so till 7.11 there is now really enough time to have it all.

So I do not know if I should call it in this shlib-only first series as
validate-build-id or as solib-validate-build-id.


Jan
Doug Evans July 14, 2015, 4:13 p.m. UTC | #6
On Mon, Jul 13, 2015 at 5:38 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Mon, 13 Jul 2015 12:34:33 +0200, Pedro Alves wrote:
>> As the plan is for the feature to apply to the main executable too,
>> it's better that "solib" isn't part of the setting name.  I agree
>> that "validate-build-id" sounds better than "build-id-validation".
>
> OK, so validate-build-id or solib-validate-build-id.
>
> Just this series being approved is still only for shlib and I do not yet have
> completely finished the second series for all binaries; although 7.10 is
> branched so till 7.11 there is now really enough time to have it all.
>
> So I do not know if I should call it in this shlib-only first series as
> validate-build-id or as solib-validate-build-id.

One of the important bits for me is to not add an option knowing
we're going to rename it later.

We've just branched 7.10 and I'm guessing all of this will be
present for 7.11.

So I'd be ok with just adding a simple note somewhere saying
the option only applies to solibs at the moment and will
eventually also apply to exes.
Jan Kratochvil July 15, 2015, 8:21 a.m. UTC | #7
On Tue, 14 Jul 2015 18:13:26 +0200, Doug Evans wrote:
> So I'd be ok with just adding a simple note somewhere saying
> the option only applies to solibs at the moment and will
> eventually also apply to exes.

So the option is now called 'validate-build-id'.

Its description everywhere (NEWS+gdb.texinfo+'help set validate-build-id')
talks about shared library now.  Is it OK this way or should it be changed?


Jan
Doug Evans July 15, 2015, 2:59 p.m. UTC | #8
On Wed, Jul 15, 2015 at 1:21 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Tue, 14 Jul 2015 18:13:26 +0200, Doug Evans wrote:
>> So I'd be ok with just adding a simple note somewhere saying
>> the option only applies to solibs at the moment and will
>> eventually also apply to exes.
>
> So the option is now called 'validate-build-id'.
>
> Its description everywhere (NEWS+gdb.texinfo+'help set validate-build-id')
> talks about shared library now.  Is it OK this way or should it be changed?

fine by me.  thanks!
diff mbox

Patch

diff --git a/gdb/NEWS b/gdb/NEWS
index 7ce9758..b07c973 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -194,6 +194,12 @@  maint set|show btrace pt skip-pad
   Set and show whether PAD packets are skipped when computing the
   packet history.
 
+set solib-build-id-validation (on|off)
+show solib-build-id-validation
+  Inferior shared library and symbol file may contain unique build-id.
+  If both build-ids are present but they do not match then this setting
+  enables (off) or disables (on) loading of such symbol file.
+
 * The command 'thread apply all' can now support new option '-ascending'
   to call its specified command for all threads in ascending order.
 
@@ -277,6 +283,12 @@  fork-events and vfork-events features in qSupported
 * GDB now supports access to vector registers on S/390 GNU/Linux
   targets.
 
+* New features in the GDB remote stub, GDBserver
+
+  ** library-list-svr4 contains also optional attribute 'build-id' for
+     each library.  GDB does not load library with build-id that
+     does not match such attribute.
+
 * Removed command line options
 
 -xdb  HP-UX XDB compatibility mode.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 932c38d..b017a6d 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -17950,6 +17950,44 @@  libraries that were loaded by explicit user requests are not
 discarded.
 @end table
 
+@table @code
+@kindex set solib-build-id-validation
+@cindex override @value{GDBN} build-id check
+@item set solib-build-id-validation @var{mode}
+Setting to override @value{GDBN} build-id check.
+
+Inferior shared libraries and symbol files may contain unique build-id.
+By default @value{GDBN} will ignore symbol files with non-matching build-id
+while printing:
+
+@smallexample
+  warning: Shared object "libfoo.so.1" could not be validated (remote
+  build ID 2bc1745e does not match local build ID a08f8767) and will be
+  ignored; or use 'set solib-build-id-validation off'.
+@end smallexample
+
+Turning off this setting would load such symbol file while still printing:
+
+@smallexample
+  warning: Shared object "libfoo.so.1" could not be validated (remote
+  build ID 2bc1745e does not match local build ID a08f8767) but it is
+  being loaded due to 'set solib-build-id-validation off'.
+@end smallexample
+
+If remote build-id is present but it does not match local build-id (or local
+build-id is not present) then this setting enables (@var{mode} is @code{off}) or
+disables (@var{mode} is @code{on}) loading of such symbol file.  On systems
+where build-id is not present in the remote system this setting has no effect.
+The default value is @code{on}.
+
+Loading non-matching symbol file may confuse debugging including breakage
+of backtrace output.
+
+@kindex show solib-build-id-validation
+@item show solib-build-id-validation
+Display the current mode of build-id check override.
+@end table
+
 Sometimes you may wish that @value{GDBN} stops and gives you control
 when any of shared library events happen.  The best way to do this is
 to use @code{catch load} and @code{catch unload} (@pxref{Set
diff --git a/gdb/solib-darwin.c b/gdb/solib-darwin.c
index f96841f..9309c35 100644
--- a/gdb/solib-darwin.c
+++ b/gdb/solib-darwin.c
@@ -634,4 +634,5 @@  _initialize_darwin_solib (void)
   darwin_so_ops.in_dynsym_resolve_code = darwin_in_dynsym_resolve_code;
   darwin_so_ops.lookup_lib_global_symbol = darwin_lookup_lib_symbol;
   darwin_so_ops.bfd_open = darwin_bfd_open;
+  darwin_so_ops.validate = default_solib_validate;
 }
diff --git a/gdb/solib-dsbt.c b/gdb/solib-dsbt.c
index 7da5833..9fe6533 100644
--- a/gdb/solib-dsbt.c
+++ b/gdb/solib-dsbt.c
@@ -1080,6 +1080,7 @@  _initialize_dsbt_solib (void)
   dsbt_so_ops.open_symbol_file_object = open_symbol_file_object;
   dsbt_so_ops.in_dynsym_resolve_code = dsbt_in_dynsym_resolve_code;
   dsbt_so_ops.bfd_open = solib_bfd_open;
+  dsbt_so_ops.validate = default_solib_validate;
 
   /* Debug this file's internals.  */
   add_setshow_zuinteger_cmd ("solib-dsbt", class_maintenance,
diff --git a/gdb/solib-frv.c b/gdb/solib-frv.c
index f7ef38b..b768146 100644
--- a/gdb/solib-frv.c
+++ b/gdb/solib-frv.c
@@ -1183,6 +1183,7 @@  _initialize_frv_solib (void)
   frv_so_ops.open_symbol_file_object = open_symbol_file_object;
   frv_so_ops.in_dynsym_resolve_code = frv_in_dynsym_resolve_code;
   frv_so_ops.bfd_open = solib_bfd_open;
+  frv_so_ops.validate = default_solib_validate;
 
   /* Debug this file's internals.  */
   add_setshow_zuinteger_cmd ("solib-frv", class_maintenance,
diff --git a/gdb/solib-spu.c b/gdb/solib-spu.c
index 44fbf91..d162884 100644
--- a/gdb/solib-spu.c
+++ b/gdb/solib-spu.c
@@ -519,6 +519,7 @@  set_spu_solib_ops (struct gdbarch *gdbarch)
       spu_so_ops.current_sos = spu_current_sos;
       spu_so_ops.bfd_open = spu_bfd_open;
       spu_so_ops.lookup_lib_global_symbol = spu_lookup_lib_symbol;
+      spu_so_ops.validate = default_solib_validate;
     }
 
   set_solib_ops (gdbarch, &spu_so_ops);
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index 909dfb7..71522c6 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -45,6 +45,9 @@ 
 #include "auxv.h"
 #include "gdb_bfd.h"
 #include "probe.h"
+#include "rsp-low.h"
+
+#define NOTE_GNU_BUILD_ID_NAME  ".note.gnu.build-id"
 
 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
 static int svr4_have_link_map_offsets (void);
@@ -970,6 +973,64 @@  svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
   return (name_lm >= vaddr && name_lm < vaddr + size);
 }
 
+/* Validate SO by comparing build-id from the associated bfd and
+   corresponding build-id from target memory.  Return NULL for success
+   or a string for error.  Caller must call xfree for the error string.  */
+
+static char *
+svr4_validate (const struct so_list *const so)
+{
+  const bfd_byte *local_id;
+  size_t local_idsz;
+
+  gdb_assert (so != NULL);
+
+  /* Target doesn't support reporting the build ID or the remote shared library
+     does not have build ID.  */
+  if (so->build_id == NULL)
+    return NULL;
+
+  /* Build ID may be present in the local file, just GDB is unable to retrieve
+     it.  As it has been reported by gdbserver it is not FSF gdbserver.  */
+  if (so->abfd == NULL
+      || !bfd_check_format (so->abfd, bfd_object))
+    return NULL;
+
+  /* GDB has verified the local file really does not contain the build ID.  */
+  if (so->abfd->build_id == NULL)
+    {
+      char *remote_hex;
+
+      remote_hex = alloca (so->build_idsz * 2 + 1);
+      bin2hex (so->build_id, remote_hex, so->build_idsz);
+
+      return xstrprintf (_("remote build ID is %s "
+			   "but local file does not have build ID"),
+			 remote_hex);
+    }
+
+  local_id = so->abfd->build_id->data;
+  local_idsz = so->abfd->build_id->size;
+
+  if (so->build_idsz != local_idsz
+      || memcmp (so->build_id, local_id, so->build_idsz) != 0)
+    {
+      char *remote_hex, *local_hex;
+
+      remote_hex = alloca (so->build_idsz * 2 + 1);
+      bin2hex (so->build_id, remote_hex, so->build_idsz);
+      local_hex = alloca (local_idsz * 2 + 1);
+      bin2hex (local_id, local_hex, local_idsz);
+
+      return xstrprintf (_("remote build ID %s "
+			   "does not match local build ID %s"),
+			 remote_hex, local_hex);
+    }
+
+  /* Both build IDs are present and they match.  */
+  return NULL;
+}
+
 /* Implement the "open_symbol_file_object" target_so_ops method.
 
    If no open symbol file, attempt to locate and open the main symbol
@@ -1108,6 +1169,12 @@  svr4_copy_library_list (struct so_list *src)
       newobj->lm_info = xmalloc (sizeof (struct lm_info));
       memcpy (newobj->lm_info, src->lm_info, sizeof (struct lm_info));
 
+      if (newobj->build_id != NULL)
+	{
+	  newobj->build_id = xmalloc (src->build_idsz);
+	  memcpy (newobj->build_id, src->build_id, src->build_idsz);
+	}
+
       newobj->next = NULL;
       *link = newobj;
       link = &newobj->next;
@@ -1135,6 +1202,9 @@  library_list_start_library (struct gdb_xml_parser *parser,
   ULONGEST *lmp = xml_find_attribute (attributes, "lm")->value;
   ULONGEST *l_addrp = xml_find_attribute (attributes, "l_addr")->value;
   ULONGEST *l_ldp = xml_find_attribute (attributes, "l_ld")->value;
+  const struct gdb_xml_value *const att_build_id
+    = xml_find_attribute (attributes, "build-id");
+  const char *const hex_build_id = att_build_id ? att_build_id->value : NULL;
   struct so_list *new_elem;
 
   new_elem = XCNEW (struct so_list);
@@ -1146,6 +1216,37 @@  library_list_start_library (struct gdb_xml_parser *parser,
   strncpy (new_elem->so_name, name, sizeof (new_elem->so_name) - 1);
   new_elem->so_name[sizeof (new_elem->so_name) - 1] = 0;
   strcpy (new_elem->so_original_name, new_elem->so_name);
+  if (hex_build_id != NULL)
+    {
+      const size_t hex_build_id_len = strlen (hex_build_id);
+
+      if (hex_build_id_len == 0)
+	warning (_("Shared library \"%s\" received empty build-id "
+	           "from gdbserver"), new_elem->so_original_name);
+      else if ((hex_build_id_len & 1U) != 0)
+	warning (_("Shared library \"%s\" received odd number "
+		   "of build-id \"%s\" hex characters from gdbserver"),
+		 new_elem->so_original_name, hex_build_id);
+      else
+	{
+	  const size_t build_idsz = hex_build_id_len / 2;
+
+	  new_elem->build_id = xmalloc (build_idsz);
+	  new_elem->build_idsz = hex2bin (hex_build_id, new_elem->build_id,
+					  build_idsz);
+	  if (new_elem->build_idsz != build_idsz)
+	    {
+	      warning (_("Shared library \"%s\" received invalid "
+			 "build-id \"%s\" hex character at encoded byte "
+			 "position %s (first as 0) from gdbserver"),
+		       new_elem->so_original_name, hex_build_id,
+		       pulongest (new_elem->build_idsz));
+	      xfree (new_elem->build_id);
+	      new_elem->build_id = NULL;
+	      new_elem->build_idsz = 0;
+	    }
+	}
+    }
 
   *list->tailp = new_elem;
   list->tailp = &new_elem->next;
@@ -1180,6 +1281,7 @@  static const struct gdb_xml_attribute svr4_library_attributes[] =
   { "lm", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
   { "l_addr", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
   { "l_ld", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
+  { "build-id", GDB_XML_AF_OPTIONAL, NULL, NULL },
   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 };
 
@@ -3258,4 +3360,5 @@  _initialize_svr4_solib (void)
   svr4_so_ops.keep_data_in_core = svr4_keep_data_in_core;
   svr4_so_ops.update_breakpoints = svr4_update_solib_event_breakpoints;
   svr4_so_ops.handle_event = svr4_handle_solib_event;
+  svr4_so_ops.validate = svr4_validate;
 }
diff --git a/gdb/solib-target.c b/gdb/solib-target.c
index f14363a..13cbd26 100644
--- a/gdb/solib-target.c
+++ b/gdb/solib-target.c
@@ -25,6 +25,7 @@ 
 #include "target.h"
 #include "vec.h"
 #include "solib-target.h"
+#include "solib.h"
 
 /* Private data for each loaded library.  */
 struct lm_info
@@ -506,6 +507,7 @@  _initialize_solib_target (void)
   solib_target_so_ops.in_dynsym_resolve_code
     = solib_target_in_dynsym_resolve_code;
   solib_target_so_ops.bfd_open = solib_bfd_open;
+  solib_target_so_ops.validate = default_solib_validate;
 
   /* Set current_target_so_ops to solib_target_so_ops if not already
      set.  */
diff --git a/gdb/solib.c b/gdb/solib.c
index eb933c0..2ab8b80 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -518,6 +518,20 @@  solib_bfd_open (char *pathname)
   return abfd;
 }
 
+/* Boolean for command 'set solib-build-id-validation'.  */
+static int solib_build_id_validation = 1;
+
+/* Implement 'show solib-build-id-validation'.  */
+
+static void
+show_solib_build_id_validation (struct ui_file *file, int from_tty,
+				struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Validation a build-id matches to load a shared "
+			    "library is %s.\n"),
+		    value);
+}
+
 /* Given a pointer to one of the shared objects in our list of mapped
    objects, use the recorded name to open a bfd descriptor for the
    object, build a section table, relocate all the section addresses
@@ -534,7 +548,7 @@  static int
 solib_map_sections (struct so_list *so)
 {
   const struct target_so_ops *ops = solib_ops (target_gdbarch ());
-  char *filename;
+  char *filename, *validate_error;
   struct target_section *p;
   struct cleanup *old_chain;
   bfd *abfd;
@@ -550,6 +564,29 @@  solib_map_sections (struct so_list *so)
   /* Leave bfd open, core_xfer_memory and "info files" need it.  */
   so->abfd = abfd;
 
+  gdb_assert (ops->validate != NULL);
+
+  validate_error = ops->validate (so);
+  if (validate_error != NULL)
+    {
+      if (solib_build_id_validation)
+	{
+	  warning (_("Shared object \"%s\" could not be validated (%s) and "
+	             "will be ignored; "
+		     "or use 'set solib-build-id-validation off'."),
+		   so->so_name, validate_error);
+	  xfree (validate_error);
+	  gdb_bfd_unref (so->abfd);
+	  so->abfd = NULL;
+	  return 0;
+	}
+      warning (_("Shared object \"%s\" could not be validated (%s) "
+		 "but it is being loaded due to "
+		 "'set solib-build-id-validation off'."),
+	       so->so_name, validate_error);
+      xfree (validate_error);
+    }
+
   /* Copy the full path name into so_name, allowing symbol_file_add
      to find it later.  This also affects the =library-loaded GDB/MI
      event, and in particular the part of that notification providing
@@ -626,6 +663,9 @@  clear_so (struct so_list *so)
      of the symbol file.  */
   strcpy (so->so_name, so->so_original_name);
 
+  xfree (so->build_id);
+  so->build_id = NULL;
+
   /* Do the same for target-specific data.  */
   if (ops->clear_so != NULL)
     ops->clear_so (so);
@@ -1657,6 +1697,14 @@  remove_user_added_objfile (struct objfile *objfile)
     }
 }
 
+/* Default implementation does not perform any validation.  */
+
+char *
+default_solib_validate (const struct so_list *const so)
+{
+  return NULL; /* No validation.  */
+}
+
 extern initialize_file_ftype _initialize_solib; /* -Wmissing-prototypes */
 
 void
@@ -1714,4 +1762,18 @@  PATH and LD_LIBRARY_PATH."),
 				     reload_shared_libraries,
 				     show_solib_search_path,
 				     &setlist, &showlist);
+
+  add_setshow_boolean_cmd ("solib-build-id-validation", class_support,
+			   &solib_build_id_validation, _("\
+Set validation a build-id matches to load a shared library."), _("\
+SHow validation a build-id matches to load a shared library."), _("\
+Inferior shared library and symbol file may contain unique build-id.\n\
+If both build-ids are present but they do not match then this setting\n\
+enables (off) or disables (on) loading of such symbol file.\n\
+Loading non-matching symbol file may confuse debugging including breakage\n\
+of backtrace output."),
+			   NULL,
+			   show_solib_build_id_validation,
+			   &setlist, &showlist);
+
 }
diff --git a/gdb/solib.h b/gdb/solib.h
index 336971d..c3bf529 100644
--- a/gdb/solib.h
+++ b/gdb/solib.h
@@ -98,4 +98,8 @@  extern void update_solib_breakpoints (void);
 
 extern void handle_solib_event (void);
 
+/* Default validation always returns 1.  */
+
+extern char *default_solib_validate (const struct so_list *so);
+
 #endif /* SOLIB_H */
diff --git a/gdb/solist.h b/gdb/solist.h
index 7021f5c..e6e74af 100644
--- a/gdb/solist.h
+++ b/gdb/solist.h
@@ -75,6 +75,19 @@  struct so_list
        There may not be just one (e.g. if two segments are relocated
        differently); but this is only used for "info sharedlibrary".  */
     CORE_ADDR addr_low, addr_high;
+
+    /* Build id decoded from .note.gnu.build-id without note header.  This is
+       actual BUILD_ID which comes either from the remote target via qXfer
+       packet or via reading target memory.  Note that if there's a
+       mismatch with the associated bfd then so->abfd will be cleared.
+       Reading target memory should be done by following execution view
+       of the binary (following program headers in the case of ELF).
+       Computing address from the linking view (following ELF section
+       headers) may give incorrect build-id memory address despite the
+       symbols still match.
+       Such an example is a prelinked vs. unprelinked i386 ELF file.  */
+    size_t build_idsz;
+    gdb_byte *build_id;
   };
 
 struct target_so_ops
@@ -168,6 +181,11 @@  struct target_so_ops
        NULL, in which case no specific preprocessing is necessary
        for this target.  */
     void (*handle_event) (void);
+
+    /* Return NULL if SO does match target SO it is supposed to
+       represent.  Otherwise return string describing why it does not match.
+       Caller has to free the string.  */
+    char *(*validate) (const struct so_list *so);
   };
 
 /* Free the memory associated with a (so_list *).  */