gdb, gdbserver: support dlmopen()

In glibc, the r_debug structure contains (amongst others) the following
fields:

  int r_version:
    Version number for this protocol.  It should be greater than 0.

If r_version is 2, struct r_debug is extended to struct r_debug_extended
with one additional field:

  struct r_debug_extended *r_next;
    Link to the next r_debug_extended structure.  Each r_debug_extended
    structure represents a different namespace.  The first r_debug_extended
    structure is for the default namespace.

1. Change solib_svr4_r_map argument to take the debug base.
2. Add solib_svr4_r_next to find the link map in the next namespace from
the r_next field.
3. Update svr4_current_sos_direct to get the link map in the next namespace
from the r_next field.
4. Don't check shared libraries in other namespaces when updating shared
libraries in a new namespace.
5. Update svr4_same to check the load offset in addition to the name
6. Update svr4_default_sos to also set l_addr_inferior
7. Change the flat solib_list into a per-namespace list using the
namespace's r_debug address to identify the namespace.

Add gdb.base/dlmopen.exp to test this.

To remain backwards compatible with older gdbserver, we reserve the
namespace zero for a flat list of solibs from all namespaces.  Subsequent
patches will extend RSP to allow listing libraries grouped by namespace.

This fixes PR 11839.

Co-authored-by: Lu, Hongjiu  <hongjiu.lu@intel.com>

4 files changed, 336 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/dlmopen-lib.c b/gdb/testsuite/gdb.base/dlmopen-lib.c
new file mode 100644
index 0000000..616bf97
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dlmopen-lib.c
@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021-2022 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+__attribute__((visibility ("default")))
+int
+inc (int n)
+{
+  return n + 1;  /* bp.inc.  */
+}
diff --git a/gdb/testsuite/gdb.base/dlmopen.c b/gdb/testsuite/gdb.base/dlmopen.c
new file mode 100644
index 0000000..2dc2f2e
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dlmopen.c
@@ -0,0 +1,65 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <stddef.h>
+#include <assert.h>
+#include <unistd.h>
+
+volatile int wait_for_gdb = 1;
+
+int
+main (void)
+{
+  void *handle[4];
+  int (*fun) (int);
+  Lmid_t lmid;
+  int dl;
+
+  handle[0] = dlmopen (LM_ID_NEWLM, DSO1_NAME, RTLD_LAZY | RTLD_LOCAL);
+  assert (handle[0] != NULL);
+
+  dlinfo (handle[0], RTLD_DI_LMID, &lmid);
+
+  handle[1] = dlopen (DSO1_NAME, RTLD_LAZY | RTLD_LOCAL);
+  assert (handle[1] != NULL);
+
+  handle[2] = dlmopen (LM_ID_NEWLM, DSO1_NAME, RTLD_LAZY | RTLD_LOCAL);
+  assert (handle[2] != NULL);
+
+  handle[3] = dlmopen (lmid, DSO2_NAME, RTLD_LAZY | RTLD_LOCAL);
+  assert (handle[3] != NULL);
+
+  alarm (20);
+  while (wait_for_gdb != 0)
+    usleep (1);
+
+  for (dl = 0; dl < 4; ++dl)
+    {
+      fun = dlsym (handle[dl], "inc");
+      assert (fun != NULL);
+
+      fun (42);
+
+      dlclose (handle[dl]);
+    }
+
+  return 0;  /* bp.main  */
+}
diff --git a/gdb/testsuite/gdb.base/dlmopen.exp b/gdb/testsuite/gdb.base/dlmopen.exp
new file mode 100644
index 0000000..8e86d5d
--- /dev/null
+++ b/gdb/testsuite/gdb.base/dlmopen.exp
@@ -0,0 +1,150 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2021-2022 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+#
+# Test shared libraries loaded into different namespaces with dlmopen().
+#
+# We test that GDB shows the correct number of instances of the libraries
+# the test loaded while unloading them one-by-one.
+
+if { [skip_dlmopen_tests] } {
+    unsupported "target does not support dlmopen debugging"
+    return -1
+}
+
+standard_testfile
+
+set basename_lib dlmopen-lib
+set srcfile_lib $srcdir/$subdir/$basename_lib.c
+set binfile_lib1 [standard_output_file $basename_lib.1.so]
+set binfile_lib2 [standard_output_file $basename_lib.2.so]
+
+if { [gdb_compile_shlib $srcfile_lib $binfile_lib1 {debug}] != "" } {
+    untested "failed to prepare shlib"
+    return -1
+}
+
+if { [gdb_compile_shlib $srcfile_lib $binfile_lib2 {debug}] != "" } {
+    untested "failed to prepare shlib"
+    return -1
+}
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile \
+	  [list additional_flags=-DDSO1_NAME=\"$binfile_lib1\" \
+	       additional_flags=-DDSO2_NAME=\"$binfile_lib2\" \
+	       libs=-ldl debug]] } {
+    return -1
+}
+
+if { ![runto_main] } {
+    return -1
+}
+
+# Check that 'info shared' show NUM occurrences of DSO.
+proc check_dso_count { dso num } {
+    global gdb_prompt hex
+
+    set count 0
+    gdb_test_multiple "info shared" "info shared" {
+	-re "$hex  $hex  Yes \[^\r\n\]*$dso\r\n" {
+	    # use longer form so debug remote does not interfere
+	    set count [expr $count + 1]
+	    exp_continue
+	}
+	-re "$gdb_prompt " {
+	    verbose -log "library: $dso, expected: $num, found: $count"
+	    gdb_assert {$count == $num} "$gdb_test_name"
+	}
+    }
+}
+
+# The DSO part of the test.  We run it once per DSO call.
+proc test_dlmopen_one { ndso1 ndso2 } {
+    global srcfile_lib srcfile_lib basename_lib bp_inc
+
+    # Try to reach the breakpoint in the dynamically loaded library.
+    gdb_continue_to_breakpoint "cont to bp.inc" \
+	".*$srcfile_lib:$bp_inc\r\n.*"
+
+    # We opened all DSOs initially and close them one by one.
+    with_test_prefix "dso 1" { check_dso_count $basename_lib.1.so $ndso1 }
+    with_test_prefix "dso 2" { check_dso_count $basename_lib.2.so $ndso2 }
+
+    # This might help debugging.
+    gdb_test "info breakpoints" ".*"
+    gdb_test "print \$pc" ".*"
+}
+
+# The actual test.  We run it twice.
+proc test_dlmopen {} {
+    global srcfile basename_lib bp_main
+
+    with_test_prefix "dlmopen 1" { test_dlmopen_one 3 1 }
+    with_test_prefix "dlmopen 2" { test_dlmopen_one 2 1 }
+    with_test_prefix "dlmopen 3" { test_dlmopen_one 1 1 }
+    with_test_prefix "dlmopen 4" { test_dlmopen_one 0 1 }
+
+    with_test_prefix "main" {
+	# Try to reach the breakpoint in the dynamically loaded library.
+	gdb_continue_to_breakpoint "cont to bp.main" \
+	    ".*$srcfile:$bp_main\r\n.*"
+
+	# The library should not be listed.
+	with_test_prefix "dso 1" { check_dso_count $basename_lib.1.so 0 }
+	with_test_prefix "dso 2" { check_dso_count $basename_lib.2.so 0 }
+    }
+}
+
+# Remove the pause.  We only need it for the attach test.
+gdb_test "print wait_for_gdb = 0" "\\\$1 = 0"
+
+# Break in the to-be-loaded library and at the end of main.
+set bp_inc [gdb_get_line_number "bp.inc" $srcfile_lib]
+set bp_main [gdb_get_line_number "bp.main" $srcfile]
+
+delete_breakpoints
+gdb_breakpoint $srcfile_lib:$bp_inc allow-pending
+gdb_breakpoint $srcfile:$bp_main
+
+test_dlmopen
+
+# Try the same again when attaching after dlmopen().
+if { ![can_spawn_for_attach] } {
+    unsupported "target does not support attach"
+    return -1
+}
+
+clean_restart $binfile
+
+# Start the test program.
+set test_spawn_id [spawn_wait_for_attach $binfile]
+set testpid [spawn_id_get_pid $test_spawn_id]
+
+# Attach.
+gdb_test "attach $testpid" "Attaching to program.*, process $testpid.*"
+
+with_test_prefix "attach" {
+    # Remove the pause.  We no longer need it.
+    gdb_test "print wait_for_gdb = 0" "\\\$1 = 0"
+
+    # Set the same breakpoints again.  This time, however, we do not allow the
+    # breakpoint to be pending since the library has already been loaded.
+    gdb_breakpoint $srcfile_lib:$bp_inc
+    gdb_breakpoint $srcfile:$bp_main
+
+    test_dlmopen
+}
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 36bcfac..c510ab2 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -2512,6 +2512,102 @@ proc skip_shlib_tests {} {
     return 1
 }
 
+# Return 1 if we should skip dlmopen tests, 0 if we should not.
+
+gdb_caching_proc skip_dlmopen_tests {
+    global srcdir subdir gdb_prompt inferior_exited_re
+
+    # We need shared library support.
+    if { [skip_shlib_tests] } {
+	return 1
+    }
+
+    set me "skip_dlmopen_tests"
+    set lib {
+	int foo (void) {
+	    return 42;
+	}
+    }
+    set src {
+	#define _GNU_SOURCE
+	#include <dlfcn.h>
+	#include <link.h>
+	#include <stdio.h>
+	#include <errno.h>
+
+	int  main (void) {
+	    struct r_debug *r_debug;
+	    ElfW(Dyn) *dyn;
+	    void *handle;
+
+	    /* The version is kept at 1 until we create a new namespace.  */
+	    handle = dlmopen (LM_ID_NEWLM, DSO_NAME, RTLD_LAZY | RTLD_LOCAL);
+	    if (!handle) {
+		printf ("dlmopen failed: %s.\n", dlerror ());
+		return 1;
+	    }
+
+	    r_debug = 0;
+	    /* Taken from /usr/include/link.h.  */
+	    for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
+	        if (dyn->d_tag == DT_DEBUG)
+	            r_debug = (struct r_debug *) dyn->d_un.d_ptr;
+
+	    if (!r_debug) {
+	        printf ("r_debug not found.\n");
+		return 1;
+	    }
+	    if (r_debug->r_version < 2) {
+	        printf ("dlmopen debug not supported.\n");
+		return 1;
+	    }
+	    printf ("dlmopen debug supported.\n");
+	    return 0;
+	}
+    }
+
+    set libsrc [standard_temp_file "libfoo.c"]
+    set libout [standard_temp_file "libfoo.so"]
+    gdb_produce_source $libsrc $lib
+
+    if { [gdb_compile_shlib $libsrc $libout {debug}] != "" } {
+	verbose -log "failed to build library"
+	return 1
+    }
+    if { ![gdb_simple_compile $me $src executable \
+	       [list shlib_load debug \
+		    additional_flags=-DDSO_NAME=\"$libout\"]] } {
+	verbose -log "failed to build executable"
+        return 1
+    }
+
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load $obj
+
+    if { [gdb_run_cmd] != 0 } {
+	verbose -log "failed to start skip test"
+	return 1
+    }
+    gdb_expect {
+        -re "$inferior_exited_re normally.*${gdb_prompt} $" {
+            set skip_dlmopen_tests 0
+        }
+        -re "$inferior_exited_re with code.*${gdb_prompt} $" {
+            set skip_dlmopen_tests 1
+        }
+        default {
+	    warning "\n$me: default case taken"
+            set skip_dlmopen_tests 1
+        }
+    }
+    gdb_exit
+
+    verbose "$me:  returning $skip_dlmopen_tests" 2
+    return $skip_dlmopen_tests
+}
+
 # Return 1 if we should skip tui related tests.
 
 proc skip_tui_tests {} {