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>

1 files changed, 96 insertions, 0 deletions

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 {} {