[PATCH v3 0/3] Add some linker namespaces conveniences

[PATCH v3 0/3] Add some linker namespaces conveniences

[Guinevere Larsen]

This series is a second step in improving the User Experience of
debugging inferiors with multiple namespaces. It adds 2 things to make
it more convenient for users to understand what the inferior is doing.

The first patch adds convenience variables, specifically
_active_linker_namespaces and _current_linker_namespaces. These can be
used to track where in the execution of an inferior the user is, and
could be used in breakpoint conditions to stop at a specific namespace.

The third patch adds a new command, "info linker-namespaces", to help the
user check what solibs are loaded, and where. To make the patch more
readable, the second patch is a minor refactor of the command "info
sharedlibrary".

The documentation changes have already been reviewed by Eli.

Changes for v3:
* Changed the final gdb.base/dlmopen-ns-ids.exp test to allow for linker
  namespaces that don't load libc and libm, since some systems may not
  do it.

Changes for v2:
* Renamed new command and variables to explicitly mention linker
  namespaces

Guinevere Larsen (3):
  gdb: add convenience variables around linker namespace debugging
  gdb: factor out printing a table of solibs for info sharedlibrary
  GDB: Introduce "info namespaces" command

 gdb/NEWS                                     |  11 +
 gdb/doc/gdb.texinfo                          |  28 ++
 gdb/solib-svr4.c                             |  55 ++++
 gdb/solib.c                                  | 267 ++++++++++++++-----
 gdb/solist.h                                 |   4 +
 gdb/testsuite/gdb.base/default.exp           |   2 +
 gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c |   6 +
 gdb/testsuite/gdb.base/dlmopen-ns-ids.exp    | 129 +++++++++
 8 files changed, 442 insertions(+), 60 deletions(-)


base-commit: 52c5091dfb18113156d645500ab86b600f1cdfe0
-- 
2.49.0

[PATCH v3 1/3] gdb: add convenience variables around linker namespace debugging

[Guinevere Larsen]

This commit adds 2 simple built-in convenience variables to help users
debug an inferior with multiple linker namespaces. The first is
$_active_linker_namespaces, which just counts how many namespaces have SOs
loaded onto them. The second is $_current_linker_namespace, and it tracks
which namespace does the current location in the inferior belongs to.

This commit also introduces a test ensuring that we track namespaces
correctly, and that a user can use the $_current_linker_namespace
variable to set a conditional breakpoint, while linespec changes aren't
finalized to make it more convenient.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---
 gdb/NEWS                                     |  6 +++
 gdb/doc/gdb.texinfo                          | 12 +++++
 gdb/solib-svr4.c                             |  6 +++
 gdb/solib.c                                  | 43 +++++++++++++++
 gdb/testsuite/gdb.base/default.exp           |  2 +
 gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c |  6 +++
 gdb/testsuite/gdb.base/dlmopen-ns-ids.exp    | 55 ++++++++++++++++++++
 7 files changed, 130 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 99ec392d4c4..053541683f1 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -40,6 +40,12 @@
   namespace into which the library was loaded, if more than one namespace
   is active.
 
+* New built-in convenience variables $_active_linker_namespaces and
+  $_current_linker_namespace.  These show the number of active linkage
+  namespaces, and the namespace to which the current location belongs to.
+  In systems that don't support linkage namespaces, these always return 1
+  and [[0]] respectively.
+
 * New commands
 
 maintenance check psymtabs
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index b251c8e1228..2dda8abd407 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -13046,6 +13046,18 @@ variable which may be @samp{truecolor} or @samp{24bit}. Other color spaces are
 determined by the "Co" termcap which in turn depends on the @env{TERM}
 environment variable.
 
+@vindex $_active_linker_namespaces@r{, convenience variable}
+@item $_active_linker_namespaces
+Number of active linkage namespaces in the inferior.  In systems with no
+support for linkage namespaces, this variable will always be set to @samp{1}.
+
+@vindex $_current_linker_namespace@r{, convenience variable}
+@item $_current_linker_namespace
+The namespace which contains the current location in the inferior.  This
+returns GDB's internal identifier for namespaces, which is @samp{[[@var{n}]]}
+where @var{n} is a zero-based namespace number.  In systems with no support
+for linkage namespaces, this variable will always be set to @samp{[[0]]}.
+
 @end table
 
 @node Convenience Funs
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index 83cb389dad5..148359a0227 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -451,6 +451,12 @@ svr4_maybe_add_namespace (svr4_info *info, CORE_ADDR lmid)
     info->namespace_id.push_back (lmid);
 
   info->active_namespaces.insert (i);
+
+  /* Create or update the convenience variable "active_namespaces".
+     It only needs to be updated here, as this only changes when a
+     dlmopen or dlclose call happens.  */
+  set_internalvar_integer (lookup_internalvar ("_active_linker_namespaces"),
+			   info->active_namespaces.size ());
 }
 
 /* Return whether DEBUG_BASE is the default namespace of INFO.  */
diff --git a/gdb/solib.c b/gdb/solib.c
index 4876f1a92ea..1ba98137f5e 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -1715,6 +1715,42 @@ default_find_solib_addr (solib &so)
   return {};
 }
 
+/* Implementation of the current_linker_namespace convenience variable.
+   This returns the GDB internal identifier of the linker namespace,
+   for the current frame, in the form '[[<number>]]'.  If the inferior
+   doesn't support linker namespaces, this always returns [[0]].  */
+
+static value *
+current_linker_namespace_make_value (gdbarch *gdbarch, internalvar *var,
+				     void *ignore)
+{
+  const solib_ops *ops = gdbarch_so_ops (gdbarch);
+  const language_defn *lang = language_def (get_frame_language
+					      (get_current_frame ()));
+  std::string nsid = "[[0]]";
+  if (ops->find_solib_ns != nullptr)
+    {
+      CORE_ADDR curr_pc = get_frame_pc (get_current_frame ());
+      for (const solib &so : current_program_space->solibs ())
+	if (solib_contains_address_p (so, curr_pc))
+	  {
+	    nsid = string_printf ("[[%d]]", ops->find_solib_ns (so));
+	    break;
+	  }
+    }
+
+
+  /* If the PC is not in an SO, or the solib_ops doesn't support
+     linker namespaces, the inferior is in the default namespace.  */
+  return lang->value_string (gdbarch, nsid.c_str (), nsid.length ());
+}
+
+static const struct internalvar_funcs current_linker_namespace_funcs =
+{
+  current_linker_namespace_make_value,
+  nullptr,
+};
+
 void _initialize_solib ();
 
 void
@@ -1727,6 +1763,13 @@ _initialize_solib ()
   },
     "solib");
 
+  /* Convenience variables for debugging linker namespaces.  These are
+     set here, even if the solib_ops doesn't support them,
+     for consistency.  */
+  create_internalvar_type_lazy ("_current_linker_namespace",
+				&current_linker_namespace_funcs, nullptr);
+  set_internalvar_integer (lookup_internalvar ("_active_linker_namespaces"), 1);
+
   add_com (
     "sharedlibrary", class_files, sharedlibrary_command,
     _ ("Load shared object library symbols for files matching REGEXP."));
diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
index d4d6b208057..3abd0495387 100644
--- a/gdb/testsuite/gdb.base/default.exp
+++ b/gdb/testsuite/gdb.base/default.exp
@@ -699,6 +699,8 @@ set show_conv_list \
 	{$_gdb_minor = 1} \
 	{$_shell_exitsignal = void} \
 	{$_shell_exitcode = 0} \
+	{$_active_linker_namespaces = 1} \
+	{$_current_linker_namespace = <error: No registers.>}\
     }
 if [allow_python_tests] {
     append show_conv_list \
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c b/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
index 3bcd8196483..c7c038a08d1 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c
@@ -41,6 +41,12 @@ main (void)
   handle[2] = dlmopen (LM_ID_NEWLM, DSO_NAME, RTLD_LAZY | RTLD_LOCAL);
   assert (handle[2] != NULL);
 
+  for (dl = 2; dl >= 0; dl--)
+    {
+      fun = dlsym (handle[dl], "inc");
+      fun (dl);
+    }
+
   dlclose (handle[0]); /* TAG: first dlclose */
   dlclose (handle[1]); /* TAG: second dlclose */
   dlclose (handle[2]); /* TAG: third dlclose */
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 3ddc07e7773..1af57d13eb0 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -105,4 +105,59 @@ proc test_info_shared {} {
 	"after unloading everything"
 }
 
+# Run all tests related to the linkage namespaces convenience
+# variables, _active_namespaces and _current_namespaces.
+proc_with_prefix test_conv_vars {} {
+    clean_restart $::binfile
+
+    gdb_test "print \$_active_linker_namespaces" "1" \
+	"1 namespace before starting inferior"
+    gdb_test "print \$_current_linker_namespace" "No registers." \
+	"No current namespace before starting inferior"
+
+    if { ![runto_main] } {
+	return
+    }
+
+    gdb_test "print \$_active_linker_namespaces" "1" \
+	"Before activating namespaces"
+    gdb_test "print \$_current_linker_namespace" ".*\"\\\[\\\[0\\\]\\\]\"" \
+	"Still in the default namespace"
+
+    gdb_breakpoint "inc" allow-pending
+    gdb_breakpoint [gdb_get_line_number "TAG: first dlclose"]
+
+    foreach_with_prefix dl {3 2 1} {
+	gdb_continue_to_breakpoint "inc"
+
+	gdb_test "print \$_current_linker_namespace" ".*\"\\\[\\\[$dl\\\]\\\]\"" \
+	    "Verify we're in namespace $dl"
+    }
+
+    gdb_continue_to_breakpoint "first dlclose"
+    gdb_test "print \$_active_linker_namespaces" "4" "all SOs loaded"
+
+    gdb_test "next" ".*second dlclose.*" "close one SO"
+    gdb_test "print \$_active_linker_namespaces" "3" "one SOs unloaded"
+    gdb_test "next" ".*third dlclose.*" "close another SO"
+    gdb_test "print \$_active_linker_namespaces" "2" "two SOs unloaded"
+
+    # Restarting GDB so that we can test setting a breakpoint
+    # using the convenience variable, while a proper bp syntax
+    # isn't implemented for namespaces
+    clean_restart $::binfile
+    if {![runto_main]} {
+	return
+    }
+
+    # We need to load one SO because you can't have confitional
+    # breakpoints and pending breakpoints at the same time with
+    # gdb_breakpoint.
+    gdb_test "next" ".*assert.*" "load the first SO"
+    gdb_breakpoint "inc if \$_streq(\$_current_linker_namespace, \"\[\[2\]\]\")"
+    gdb_continue_to_breakpoint "inc"
+    gdb_continue_to_end "" continue 1
+}
+
 test_info_shared
+test_conv_vars
-- 
2.49.0

Re: [PATCH v3 1/3] gdb: add convenience variables around linker namespace debugging

[Tom Tromey]

>>>>> "Guinevere" == Guinevere Larsen <guinevere@redhat.com> writes:

Guinevere> +  In systems that don't support linkage namespaces, these always return 1
Guinevere> +  and [[0]] respectively.

What's the reason that this string syntax is chosen rather than, say, an
integer?

Tom

Re: [PATCH v3 1/3] gdb: add convenience variables around linker namespace debugging

[Guinevere Larsen]

On 4/18/25 4:15 PM, Tom Tromey wrote:
>>>>>> "Guinevere" == Guinevere Larsen <guinevere@redhat.com> writes:
> Guinevere> +  In systems that don't support linkage namespaces, these always return 1
> Guinevere> +  and [[0]] respectively.
>
> What's the reason that this string syntax is chosen rather than, say, an
> integer?
>
> Tom
>
I want to standardize it so whenever GDB prints a namespace identifier, 
we always use the same syntax that a user should use to find namespaces. 
This has the handy side-effect that, if we decide to use the convenience 
variable internally for something else (say, when printing a backtrace) 
there is no special handling, we'll only need to print the actual conv 
var string.

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

[PATCH v3 2/3] gdb: factor out printing a table of solibs for info sharedlibrary

[Guinevere Larsen]

The next patch will add a new command that will print libraries in a
manner very similar to the existing "info sharedlibrary" command. To
make that patch simpler to review, this commit does the bulk of
refactoring work, since it ends up being a non-trivial diff to review.

No functional changes are expected after this commit.
---
 gdb/solib.c | 137 ++++++++++++++++++++++++++++------------------------
 1 file changed, 74 insertions(+), 63 deletions(-)

diff --git a/gdb/solib.c b/gdb/solib.c
index 1ba98137f5e..d641a24dc86 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -1010,84 +1010,61 @@ solib_add (const char *pattern, int from_tty, int readsyms)
   }
 }
 
-/* Implement the "info sharedlibrary" command.  Walk through the
-   shared library list and print information about each attached
-   library matching PATTERN.  If PATTERN is elided, print them
-   all.  */
+/* Helper function for "info sharedlibrary" and "info namespace".
+   This receives a list of solibs to be printed, and prints a table
+   with all the relevant data.  If PRINT_NAMESPACE is true, figure out
+   the solib_ops of the current gdbarch, to calculate the namespace
+   that contains an solib.
+   Returns true if one or more solibs are missing debug information,
+   false otherwise.  */
 
 static void
-info_sharedlibrary_command (const char *pattern, int from_tty)
+print_solib_list_table (std::vector<const solib *> solib_list,
+			bool print_namespace)
 {
-  bool so_missing_debug_info = false;
-  int addr_width;
-  int nr_libs;
   gdbarch *gdbarch = current_inferior ()->arch ();
-  struct ui_out *uiout = current_uiout;
-
-  if (pattern)
-    {
-      char *re_err = re_comp (pattern);
-
-      if (re_err)
-	error (_ ("Invalid regexp: %s"), re_err);
-    }
-
   /* "0x", a little whitespace, and two hex digits per byte of pointers.  */
-  addr_width = 4 + (gdbarch_ptr_bit (gdbarch) / 4);
-
-  update_solib_list (from_tty);
-
-  /* ui_out_emit_table table_emitter needs to know the number of rows,
-     so we need to make two passes over the libs.  */
+  int addr_width = 4 + (gdbarch_ptr_bit (gdbarch) / 4);
+  const solib_ops *ops = gdbarch_so_ops (gdbarch);
+  struct ui_out *uiout = current_uiout;
+  bool so_missing_debug_info = false;
 
-  nr_libs = 0;
-  for (const solib &so : current_program_space->solibs ())
-    {
-      if (!so.so_name.empty ())
-	{
-	  if (pattern && !re_exec (so.so_name.c_str ()))
-	    continue;
-	  ++nr_libs;
-	}
-    }
+  /* There are 3 conditions for this command to print solib namespaces,
+     first PRINT_NAMESPACE has to be true, second the solib_ops has to
+     support multiple namespaces, and third there must be more than one
+     active namespace.  Fold all these into the PRINT_NAMESPACE condition.  */
+  print_namespace = print_namespace && ops->num_active_namespaces != nullptr
+		    && ops->num_active_namespaces () > 1;
 
-  /* How many columns the table should have.  If the inferior has
-     more than one namespace active, we need a column to show that.  */
   int num_cols = 4;
-  const solib_ops *ops = gdbarch_so_ops (gdbarch);
-  if (ops->num_active_namespaces != nullptr
-      && ops->num_active_namespaces () > 1)
+  if (print_namespace)
     num_cols++;
 
   {
-    ui_out_emit_table table_emitter (uiout, num_cols, nr_libs,
+    ui_out_emit_table table_emitter (uiout, num_cols, solib_list.size (),
 				     "SharedLibraryTable");
 
     /* The "- 1" is because ui_out adds one space between columns.  */
     uiout->table_header (addr_width - 1, ui_left, "from", "From");
     uiout->table_header (addr_width - 1, ui_left, "to", "To");
-    if (ops->num_active_namespaces != nullptr
-	&& ops->num_active_namespaces () > 1)
+    if (print_namespace)
       uiout->table_header (5, ui_left, "namespace", "NS");
     uiout->table_header (12 - 1, ui_left, "syms-read", "Syms Read");
     uiout->table_header (0, ui_noalign, "name", "Shared Object Library");
 
     uiout->table_body ();
 
-    for (const solib &so : current_program_space->solibs ())
+    for (const solib *so : solib_list)
       {
-	if (so.so_name.empty ())
-	  continue;
-
-	if (pattern && !re_exec (so.so_name.c_str ()))
+	if (so->so_name.empty ())
 	  continue;
 
 	ui_out_emit_tuple tuple_emitter (uiout, "lib");
 
-	if (so.addr_high != 0)
+	if (so->addr_high != 0)
 	  {
-	    uiout->field_core_addr ("from", gdbarch, so.addr_low);
-	    uiout->field_core_addr ("to", gdbarch, so.addr_high);
+	    uiout->field_core_addr ("from", gdbarch, so->addr_low);
+	    uiout->field_core_addr ("to", gdbarch, so->addr_high);
 	  }
 	else
 	  {
@@ -1095,12 +1072,11 @@ info_sharedlibrary_command (const char *pattern, int from_tty)
 	    uiout->field_skip ("to");
 	  }
 
-	if (ops->num_active_namespaces != nullptr
-	    && ops->num_active_namespaces ()> 1)
+	if (print_namespace)
 	  {
 	    try
 	      {
-		uiout->field_fmt ("namespace", "[[%d]]", ops->find_solib_ns (so));
+		uiout->field_fmt ("namespace", "[[%d]]", ops->find_solib_ns (*so));
 	      }
 	    catch (const gdb_exception_error &er)
 	      {
@@ -1109,33 +1085,68 @@ info_sharedlibrary_command (const char *pattern, int from_tty)
 	  }
 
 	if (!top_level_interpreter ()->interp_ui_out ()->is_mi_like_p ()
-	    && so.symbols_loaded && !objfile_has_symbols (so.objfile))
+	    && so->symbols_loaded && !objfile_has_symbols (so->objfile))
 	  {
 	    so_missing_debug_info = true;
 	    uiout->field_string ("syms-read", "Yes (*)");
 	  }
 	else
-	  uiout->field_string ("syms-read", so.symbols_loaded ? "Yes" : "No");
+	  uiout->field_string ("syms-read", so->symbols_loaded ? "Yes" : "No");
 
-	uiout->field_string ("name", so.so_name, file_name_style.style ());
+	uiout->field_string ("name", so->so_name, file_name_style.style ());
 
 	uiout->text ("\n");
       }
   }
 
-  if (nr_libs == 0)
+  if (so_missing_debug_info)
+    uiout->message (_ ("(*): Shared library is missing "
+		       "debugging information.\n"));
+}
+
+/* Implement the "info sharedlibrary" command.  Walk through the
+   shared library list and print information about each attached
+   library matching PATTERN.  If PATTERN is elided, print them
+   all.  */
+
+static void
+info_sharedlibrary_command (const char *pattern, int from_tty)
+{
+  struct ui_out *uiout = current_uiout;
+
+  if (pattern)
+    {
+      char *re_err = re_comp (pattern);
+
+      if (re_err)
+	error (_ ("Invalid regexp: %s"), re_err);
+    }
+
+  update_solib_list (from_tty);
+
+  /* ui_out_emit_table table_emitter needs to know the number of rows,
+     so we need to make two passes over the libs.  */
+
+  std::vector<const solib *> print_libs;
+  for (const solib &so : current_program_space->solibs ())
+    {
+      if (!so.so_name.empty ())
+	{
+	  if (pattern && !re_exec (so.so_name.c_str ()))
+	    continue;
+	  print_libs.push_back (&so);
+	}
+    }
+
+  print_solib_list_table (print_libs, true);
+
+  if (print_libs.size () == 0)
     {
       if (pattern)
 	uiout->message (_ ("No shared libraries matched.\n"));
       else
 	uiout->message (_ ("No shared libraries loaded at this time.\n"));
     }
-  else
-    {
-      if (so_missing_debug_info)
-	uiout->message (_ ("(*): Shared library is missing "
-			   "debugging information.\n"));
-    }
 }
 
 /* See solib.h.  */
-- 
2.49.0

[PATCH v3 3/3] GDB: Introduce "info namespaces" command

[Guinevere Larsen]

Continuing to improve GDB's ability to debug linker namespaces, this
commit adds the command "info linker- namespaces". The command is
similar to "info sharedlibrary" but focused on improved readability
when the inferior has multiple linker namespaces active. This command
can be used in 2 different ways, with or without an argument.

When called without argument, the command will print the number of
namespaces, and for each active namespace, it's identifier, how many
libraries are loaded in it, and all the libraries (in a similar table to
what "info sharedlibrary" shows). As an example, this is what GDB's
output could look like:

  (gdb) info linker-namespaces
  There are 2 linker namespaces loaded
  There are 3 libraries loaded in linker namespace [[0]]
  Displaying libraries for linker namespace [[0]]:
  From                To                  Syms Read   Shared Object Library
  0x00007ffff7fc6000  0x00007ffff7fff000  Yes         /lib64/ld-linux-x86-64.so.2
  0x00007ffff7ebc000  0x00007ffff7fa2000  Yes (*)     /lib64/libm.so.6
  0x00007ffff7cc9000  0x00007ffff7ebc000  Yes (*)     /lib64/libc.so.6
  (*): Shared library is missing debugging information.

  There are 4 libraries loaded in linker namespace [[1]]
  Displaying libraries for linker namespace [[1]]:
  From                To                  Syms Read   Shared Object Library
  0x00007ffff7fc6000  0x00007ffff7fff000  Yes         /lib64/ld-linux-x86-64.so.2
  0x00007ffff7fb9000  0x00007ffff7fbe000  Yes         gdb.base/dlmopen-ns-ids/dlmopen-lib.so
  0x00007ffff7bc4000  0x00007ffff7caa000  Yes (*)     /lib64/libm.so.6
  0x00007ffff79d1000  0x00007ffff7bc4000  Yes (*)     /lib64/libc.so.6
  (*): Shared library is missing debugging information.

When called with an argument, the argument must be a namespace
identifier (either with or without the square brackets decorators). In
this situation, the command will truncate the output to only show the
relevant information for the requested namespace. For example:

  (gdb) info linker-namespaces 0
  There are 3 libraries loaded in linker namespace [[0]]
  Displaying libraries for linker namespace [[0]]:
  From                To                  Syms Read   Shared Object Library
  0x00007ffff7fc6000  0x00007ffff7fff000  Yes         /lib64/ld-linux-x86-64.so.2
  0x00007ffff7ebc000  0x00007ffff7fa2000  Yes (*)     /lib64/libm.so.6
  0x00007ffff7cc9000  0x00007ffff7ebc000  Yes (*)     /lib64/libc.so.6
  (*): Shared library is missing debugging information.

The test gdb.base/dlmopen-ns-id.exp has been extended to test this new
command.  Because some gcc and glibc defaults can change between
systems, we are not guaranteed to always have libc and libm loaded in a
namespace, so we can't guarantee the number of libraries, but the range
of the result is 2, so we can still check for glaring issues.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---
 gdb/NEWS                                  |  5 ++
 gdb/doc/gdb.texinfo                       | 16 ++++
 gdb/solib-svr4.c                          | 49 ++++++++++++
 gdb/solib.c                               | 93 +++++++++++++++++++++++
 gdb/solist.h                              |  4 +
 gdb/testsuite/gdb.base/dlmopen-ns-ids.exp | 78 +++++++++++++++++++
 6 files changed, 245 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 053541683f1..17a16db2341 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -60,6 +60,11 @@ show riscv numeric-register-names
   (e.g 'x1') or their abi names (e.g. 'ra').
   Defaults to 'off', matching the old behaviour (abi names).
 
+info linker-namespaces
+info linker-namespaces [[N]]
+  Print information about the given linker namespace (identified as N),
+  or about all the namespaces if no argument is given.
+
 * Changed commands
 
 info sharedlibrary
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 2dda8abd407..b1c13d6dbd0 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -22223,6 +22223,22 @@ command for this.  This command exists for historical reasons.  It is
 less useful than setting a catchpoint, because it does not allow for
 conditions or commands as a catchpoint does.
 
+@table @code
+@kindex info linker-namespaces
+@item info linker-namespaces
+@item info linker-namespaces @code{[[@var{n}]]}
+
+With no argument, print the number of linker namespaces which are
+currently active --- that is, namespaces that have libraries loaded
+into them.  Then, it prints the number of libraries loaded into each
+namespace, and all the libraries loaded into them, in the same way
+as @code{info sharedlibrary}.
+
+If an argument @code{[[@var{n}]]} is provided, only prints the
+library count and the libraried for the provided namespace @var{n}.
+The surrounding square brackets are optional.
+@end table
+
 @table @code
 @item set stop-on-solib-events
 @kindex set stop-on-solib-events
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index 148359a0227..2a2745dc271 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -3558,6 +3558,54 @@ svr4_num_active_namespaces ()
   return info->active_namespaces.size ();
 }
 
+/* See solib_ops::get_solibs_in_ns in solist.h.  */
+static std::vector<const solib *>
+svr4_get_solibs_in_ns (int nsid)
+{
+  std::vector<const solib*> ns_solibs;
+  svr4_info *info = get_svr4_info (current_program_space);
+
+  /* If the namespace ID is inactive, there will be no active
+     libraries, so we can have an early exit, as a treat.  */
+  if (info->active_namespaces.count (nsid) != 1)
+    return ns_solibs;
+
+  /* Since we only have the names of solibs in a given namespace,
+     we'll need to walk through the solib list of the inferior and
+     find which solib objects correspond to which svr4_so.  We create
+     an unordered map with the names and lm_info to check things
+     faster, and to be able to remove SOs from the map, to avoid
+     returning the dynamic linker multiple times.  */
+  CORE_ADDR debug_base = info->namespace_id[nsid];
+  std::unordered_map<std::string, const lm_info_svr4 *> namespace_solibs;
+  for (svr4_so &so : info->solib_lists[debug_base])
+    {
+      namespace_solibs[so.name]
+	= gdb::checked_static_cast<const lm_info_svr4 *>
+	    (so.lm_info.get ());
+    }
+  for (const solib &so: current_program_space->solibs ())
+    {
+      auto *lm_inferior
+	= gdb::checked_static_cast<const lm_info_svr4 *> (so.lm_info.get ());
+
+      /* This is inspired by the svr4_same, by finding the svr4_so object
+	 in the map, and then double checking if the lm_info is considered
+	 the same.  */
+      if (namespace_solibs.count (so.so_original_name) > 0
+	  && namespace_solibs[so.so_original_name]->l_addr_inferior
+	      == lm_inferior->l_addr_inferior)
+	{
+	  ns_solibs.push_back (&so);
+	  /* Remove the SO from the map, so that we don't end up
+	     printing the dynamic linker multiple times.  */
+	  namespace_solibs.erase (so.so_original_name);
+	}
+    }
+
+  return ns_solibs;
+}
+
 const struct solib_ops svr4_so_ops =
 {
   svr4_relocate_section_addresses,
@@ -3575,6 +3623,7 @@ const struct solib_ops svr4_so_ops =
   svr4_find_solib_addr,
   svr4_find_solib_ns,
   svr4_num_active_namespaces,
+  svr4_get_solibs_in_ns,
 };
 
 void _initialize_svr4_solib ();
diff --git a/gdb/solib.c b/gdb/solib.c
index d641a24dc86..4c0a79cc14e 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -1149,6 +1149,96 @@ info_sharedlibrary_command (const char *pattern, int from_tty)
     }
 }
 
+/* Implement the "info linker-namespaces" command.  If the current
+   gdbarch's solib_ops object does not support multiple namespaces,
+   this command would just look like "info sharedlibrary", so point
+   the user to that command instead.
+   If solib_ops does support multiple namespaces, this command
+   will group the libraries by linker namespace, or only print the
+   libraries in the supplied namespace.  */
+static void
+info_linker_namespace_command (const char *pattern, int from_tty)
+{
+  const solib_ops *ops = gdbarch_so_ops (current_inferior ()->arch ());
+  /* This command only really makes sense for inferiors that support
+     linker namespaces, so we can leave early.  */
+  if (ops->num_active_namespaces == nullptr)
+    error (_("Current inferior does not support linker namespaces." \
+	     "Use \"info sharedlibrary\" instead"));
+
+  struct ui_out *uiout = current_uiout;
+  std::vector<std::pair<int, std::vector<const solib *>>> all_solibs_to_print;
+
+  if (pattern != nullptr)
+    while (*pattern == ' ')
+      pattern++;
+
+  if (pattern == nullptr || pattern[0] == '\0')
+    {
+      uiout->message (_ ("There are %d linker namespaces loaded\n"),
+		      ops->num_active_namespaces ());
+
+      int printed = 0;
+      for (int i = 0; printed < ops->num_active_namespaces (); i++)
+	{
+	  std::vector<const solib *> solibs_to_print
+	    = ops->get_solibs_in_ns (i);
+	  if (solibs_to_print.size () > 0)
+	    {
+	      all_solibs_to_print.push_back (std::make_pair
+					      (i, solibs_to_print));
+	      printed++;
+	    }
+	}
+    }
+  else
+    {
+      int ns;
+      /* Check if the pattern includes the optional [[ and ]] decorators.
+	 To match multiple occurrences, '+' needs to be escaped, and every
+	 escape sequence must be doubled to survive the compiler pass.  */
+      re_comp ("^\\[\\[[0-9]\\+\\]\\]$");
+      if (re_exec (pattern))
+	ns = strtol (pattern+2, nullptr, 10);
+      else
+	{
+	  char * end = nullptr;
+	  ns = strtol (pattern, &end, 10);
+	  if (end[0] != '\0')
+	    error (_ ("Invalid linker namespace identifier: %s"), pattern);
+	}
+
+      all_solibs_to_print.push_back
+	(std::make_pair (ns, ops->get_solibs_in_ns (ns)));
+    }
+
+  bool ns_separator = false;
+
+  for (auto &solibs_pair : all_solibs_to_print)
+    {
+      if (ns_separator)
+	uiout->message ("\n\n");
+      else
+	ns_separator = true;
+      int ns = solibs_pair.first;
+      std::vector<const solib *> solibs_to_print = solibs_pair.second;
+      if (solibs_to_print.size () == 0)
+	{
+	  uiout->message (_("Linker namespace [[%d]] is not active.\n"), ns);
+	  /* If we got here, a specific namespace was requested, so there
+	     will only be one vector.  We can leave early.  */
+	  break;
+	}
+      uiout->message
+	(_ ("There are %ld libraries loaded in linker namespace [[%d]]\n"),
+	 solibs_to_print.size (), ns);
+      uiout->message
+	(_ ("Displaying libraries for linker namespace [[%d]]:\n"), ns);
+
+      print_solib_list_table (solibs_to_print, false);
+    }
+}
+
 /* See solib.h.  */
 
 bool
@@ -1791,6 +1881,9 @@ _initialize_solib ()
   add_com ("nosharedlibrary", class_files, no_shared_libraries_command,
 	   _ ("Unload all shared object library symbols."));
 
+  add_info ("linker-namespaces", info_linker_namespace_command,
+      _ ("Get information about linker namespaces in the inferior."));
+
   add_setshow_boolean_cmd ("auto-solib-add", class_support, &auto_solib_add,
 			   _ ("\
 Set autoloading of shared library symbols."),
diff --git a/gdb/solist.h b/gdb/solist.h
index 0b7bbf9bd18..6ab5a06ccc9 100644
--- a/gdb/solist.h
+++ b/gdb/solist.h
@@ -194,6 +194,10 @@ struct solib_ops
 
   /* Returns the number of active namespaces in the inferior.  */
   int (*num_active_namespaces) ();
+
+  /* Returns all solibs for a given namespace.  If the namespace is not
+     active, returns an empty vector.  */
+  std::vector<const solib *> (*get_solibs_in_ns) (int ns);
 };
 
 /* A unique pointer to a so_list.  */
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 1af57d13eb0..8f521992bd1 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -159,5 +159,83 @@ proc_with_prefix test_conv_vars {} {
     gdb_continue_to_end "" continue 1
 }
 
+# Run several tests relating to the command "info namespaces".
+proc test_info_linker_namespaces {} {
+    clean_restart $::binfile
+
+    if { ![runto_main] } {
+	return
+    }
+
+    with_test_prefix "info linker-namespaces" {
+	gdb_breakpoint [gdb_get_line_number "TAG: first dlclose"]
+	gdb_continue_to_breakpoint "TAG: first dlclose"
+    }
+
+    # First, test printing a single namespace, and ensure all of
+    # them are correct, using both syntaxes.
+    set found_all_libs false
+    gdb_test_multiple "info linker-namespaces \[\[0\]\]" "print namespace 0" -lbl {
+	-re "^\r\nThere are ($::decimal) libraries loaded in linker namespace \\\[\\\[0\\\]\\\]" {
+	    # Some systems may add libc and libm to every loaded namespace,
+	    # others may load only one or neither, because the SO doesn't
+	    # actually use either library.  The best we can do is check if
+	    # we found the dynamic linker, and up to 2 more libraries.
+	    set libs $expect_out(1,string)
+	    set found_all_libs [expr $libs - 1 <= 2]
+	    exp_continue
+	}
+	-re "^\r\n$::gdb_prompt $" {
+	    gdb_assert $found_all_libs "the correct number of libraries was reported"
+	}
+	-re "(^\r\n)?\[^\r\n\]+(?=\r\n)" {
+	    exp_continue
+	}
+    }
+    foreach_with_prefix ns {1 2 3} {
+	set found_test_so false
+	set found_all_libs false
+	gdb_test_multiple "info linker-namespaces $ns" "print namespace $ns" -lbl {
+	    -re "^\r\nThere are ($::decimal) libraries loaded in linker namespace \\\[\\\[$ns\\\]\\\]" {
+		set libs $expect_out(1,string)
+		# Some systems may add libc and libm to every loaded namespace,
+		# others may load only one or neither, because the SO doesn't
+		# actually use either library.  The best we can do is check if
+		# we found the dynamic linker, the test SO, and maybe up to 2
+		# more libraries.
+		set found_all_libs [expr $libs - 2 <= 2]
+		exp_continue
+	    }
+	    -re "^\r\n\[^\r\n\]+${::binfile_lib}\[^\r\n\]*(?=\r\n)" {
+		set found_test_so true
+		exp_continue
+	    }
+	    -re "^\r\n$::gdb_prompt $" {
+		gdb_assert $found_test_so "this testfle's SO was reported"
+		gdb_assert $found_all_libs "the correct number of libraries was reported"
+	    }
+	    -re "(^\r\n)?\[^\r\n\]+(?=\r\n)" {
+		exp_continue
+	    }
+	}
+    }
+
+    # These patterns are simpler, and purposefully glob multiple lines.
+    # The point is to ensure that we find and display all the namespaces,
+    # without worrying about the libraries printed, since that was tested
+    # above.
+    gdb_test "info linker-namespaces" \
+	[multi_line "There are 4 linker namespaces loaded" \
+		    "There are $::decimal libraries loaded in linker namespace ..0.." \
+		    ".*" \
+		    "There are $::decimal libraries loaded in linker namespace ..1.." \
+		    ".*" \
+		    "There are $::decimal libraries loaded in linker namespace ..2.." \
+		    ".*" \
+		    "There are $::decimal libraries loaded in linker namespace ..3.." \
+		    ".*" ] "print namespaces with no argument"
+}
+
 test_info_shared
 test_conv_vars
+test_info_linker_namespaces
-- 
2.49.0

Re: [PATCH v3 0/3] Add some linker namespaces conveniences

[Kevin Buettner]

On Fri, 11 Apr 2025 14:50:19 -0300
Guinevere Larsen <guinevere@redhat.com> wrote:

> This series is a second step in improving the User Experience of
> debugging inferiors with multiple namespaces. It adds 2 things to make
> it more convenient for users to understand what the inferior is doing.
> 
> The first patch adds convenience variables, specifically
> _active_linker_namespaces and _current_linker_namespaces. These can be
> used to track where in the execution of an inferior the user is, and
> could be used in breakpoint conditions to stop at a specific namespace.
> 
> The third patch adds a new command, "info linker-namespaces", to help the
> user check what solibs are loaded, and where. To make the patch more
> readable, the second patch is a minor refactor of the command "info
> sharedlibrary".
> 
> The documentation changes have already been reviewed by Eli.
> 
> Changes for v3:
> * Changed the final gdb.base/dlmopen-ns-ids.exp test to allow for linker
>   namespaces that don't load libc and libm, since some systems may not
>   do it.
> 
> Changes for v2:
> * Renamed new command and variables to explicitly mention linker
>   namespaces
> 
> Guinevere Larsen (3):
>   gdb: add convenience variables around linker namespace debugging
>   gdb: factor out printing a table of solibs for info sharedlibrary
>   GDB: Introduce "info namespaces" command
> 
>  gdb/NEWS                                     |  11 +
>  gdb/doc/gdb.texinfo                          |  28 ++
>  gdb/solib-svr4.c                             |  55 ++++
>  gdb/solib.c                                  | 267 ++++++++++++++-----
>  gdb/solist.h                                 |   4 +
>  gdb/testsuite/gdb.base/default.exp           |   2 +
>  gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c |   6 +
>  gdb/testsuite/gdb.base/dlmopen-ns-ids.exp    | 129 +++++++++
>  8 files changed, 442 insertions(+), 60 deletions(-)

I'm still comfortable with the approvals that I provided earlier for
the v2 series.

Approved-by: Kevin Buettner <kevinb@redhat.com>

Re: [PATCH v3 0/3] Add some linker namespaces conveniences

[Guinevere Larsen]

On 4/17/25 8:43 PM, Kevin Buettner wrote:
> On Fri, 11 Apr 2025 14:50:19 -0300
> Guinevere Larsen <guinevere@redhat.com> wrote:
>
>> This series is a second step in improving the User Experience of
>> debugging inferiors with multiple namespaces. It adds 2 things to make
>> it more convenient for users to understand what the inferior is doing.
>>
>> The first patch adds convenience variables, specifically
>> _active_linker_namespaces and _current_linker_namespaces. These can be
>> used to track where in the execution of an inferior the user is, and
>> could be used in breakpoint conditions to stop at a specific namespace.
>>
>> The third patch adds a new command, "info linker-namespaces", to help the
>> user check what solibs are loaded, and where. To make the patch more
>> readable, the second patch is a minor refactor of the command "info
>> sharedlibrary".
>>
>> The documentation changes have already been reviewed by Eli.
>>
>> Changes for v3:
>> * Changed the final gdb.base/dlmopen-ns-ids.exp test to allow for linker
>>    namespaces that don't load libc and libm, since some systems may not
>>    do it.
>>
>> Changes for v2:
>> * Renamed new command and variables to explicitly mention linker
>>    namespaces
>>
>> Guinevere Larsen (3):
>>    gdb: add convenience variables around linker namespace debugging
>>    gdb: factor out printing a table of solibs for info sharedlibrary
>>    GDB: Introduce "info namespaces" command
>>
>>   gdb/NEWS                                     |  11 +
>>   gdb/doc/gdb.texinfo                          |  28 ++
>>   gdb/solib-svr4.c                             |  55 ++++
>>   gdb/solib.c                                  | 267 ++++++++++++++-----
>>   gdb/solist.h                                 |   4 +
>>   gdb/testsuite/gdb.base/default.exp           |   2 +
>>   gdb/testsuite/gdb.base/dlmopen-ns-ids-main.c |   6 +
>>   gdb/testsuite/gdb.base/dlmopen-ns-ids.exp    | 129 +++++++++
>>   8 files changed, 442 insertions(+), 60 deletions(-)
> I'm still comfortable with the approvals that I provided earlier for
> the v2 series.
>
> Approved-by: Kevin Buettner <kevinb@redhat.com>
>
I pushed this patch.

There was some conversation on IRC about details, but since Simon said 
he didn't have the time to review in depth, and didn't show interest in 
me delaying pushing, I figured I could push it. And anyway, in my 
opinion, as long as we haven't branched for GDB 17 yet, I think we 
should be ok with changing those details, so if the changes are 
requested, I think a future patch could change with little overhead (for 
now).

-- 
Cheers,
Guinevere Larsen
She/Her/Hers