[glibc] Add wait-for-debugger test harness hooks

[DJ Delorie <dj at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4052fa22f69c0964bb42c0f13daa791617253de5

commit 4052fa22f69c0964bb42c0f13daa791617253de5
Author: DJ Delorie <dj@redhat.com>
Date:   Wed Oct 2 14:46:46 2019 -0400

    Add wait-for-debugger test harness hooks
    
    If WAIT_FOR_DEBUGGER is set to a non-zero value in the environment,
    any test that runs will print some useful gdb information and wait
    for gdb to attach to it and clear the "wait_for_debugger" variable.
    
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 support/support_test_main.c | 53 +++++++++++++++++++++++++++++++++++++++++++++
 support/test-container.c    | 22 +++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/support/support_test_main.c b/support/support_test_main.c
index 05ad92e..0be1bd3 100644
--- a/support/support_test_main.c
+++ b/support/support_test_main.c
@@ -19,6 +19,7 @@
 #include <support/test-driver.h>
 #include <support/check.h>
 #include <support/temp_file-internal.h>
+#include <support/support.h>
 
 #include <assert.h>
 #include <errno.h>
@@ -36,6 +37,8 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <xstdio.h>
+
 static const struct option default_options[] =
 {
   TEST_DEFAULT_OPTIONS
@@ -176,10 +179,55 @@ signal_handler (int sig)
   exit (1);
 }
 
+/* This must be volatile as it will be modified by the debugger.  */
+static volatile int wait_for_debugger = 0;
+
 /* Run test_function or test_function_argv.  */
 static int
 run_test_function (int argc, char **argv, const struct test_config *config)
 {
+  const char *wfd = getenv("WAIT_FOR_DEBUGGER");
+  if (wfd != NULL)
+    wait_for_debugger = atoi (wfd);
+  if (wait_for_debugger)
+    {
+      pid_t mypid;
+      FILE *gdb_script;
+      char *gdb_script_name;
+      int inside_container = 0;
+
+      mypid = getpid();
+      if (mypid < 3)
+	{
+	  const char *outside_pid = getenv("PID_OUTSIDE_CONTAINER");
+	  if (outside_pid)
+	    {
+	      mypid = atoi (outside_pid);
+	      inside_container = 1;
+	    }
+	}
+
+      gdb_script_name = (char *) xmalloc (strlen (argv[0]) + strlen (".gdb") + 1);
+      sprintf (gdb_script_name, "%s.gdb", argv[0]);
+      gdb_script = xfopen (gdb_script_name, "w");
+
+      fprintf (stderr, "Waiting for debugger, test process is pid %d\n", mypid);
+      fprintf (stderr, "gdb -x %s\n", gdb_script_name);
+      if (inside_container)
+	fprintf (gdb_script, "set sysroot %s/testroot.root\n", support_objdir_root);
+      fprintf (gdb_script, "file\n");
+      fprintf (gdb_script, "file %s\n", argv[0]);
+      fprintf (gdb_script, "symbol-file %s\n", argv[0]);
+      fprintf (gdb_script, "exec-file %s\n", argv[0]);
+      fprintf (gdb_script, "attach %ld\n", (long int) mypid);
+      fprintf (gdb_script, "set wait_for_debugger = 0\n");
+      fclose (gdb_script);
+    }
+
+  /* Wait for the debugger to set wait_for_debugger to zero.  */
+  while (wait_for_debugger)
+    usleep (1000);
+
   if (config->test_function != NULL)
     return config->test_function ();
   else if (config->test_function_argv != NULL)
@@ -229,6 +277,11 @@ support_test_main (int argc, char **argv, const struct test_config *config)
   unsigned int timeoutfactor = 1;
   pid_t termpid;
 
+  /* If we're debugging the test, we need to disable timeouts and use
+     the initial pid (esp if we're running inside a container).  */
+  if (getenv("WAIT_FOR_DEBUGGER") != NULL)
+    direct = 1;
+
   if (!config->no_mallopt)
     {
       /* Make uses of freed and uninitialized memory known.  Do not
diff --git a/support/test-container.c b/support/test-container.c
index 9c42d3a..5d08979 100644
--- a/support/test-container.c
+++ b/support/test-container.c
@@ -676,6 +676,9 @@ main (int argc, char **argv)
   char *so_base;
   int do_postclean = 0;
 
+  int pipes[2];
+  char pid_buf[20];
+
   uid_t original_uid;
   gid_t original_gid;
   /* If set, the test runs as root instead of the user running the testsuite.  */
@@ -999,6 +1002,11 @@ main (int argc, char **argv)
   if (chdir (new_cwd_path) < 0)
     FAIL_EXIT1 ("Can't cd to new %s - ", new_cwd_path);
 
+  /* This is to pass the "outside" PID to the child, which will be PID
+     1.  */
+  if (pipe2 (pipes, O_CLOEXEC) < 0)
+    FAIL_EXIT1 ("Can't create pid pipe");
+
   /* To complete the containerization, we need to fork () at least
      once.  We can't exec, nor can we somehow link the new child to
      our parent.  So we run the child and propogate it's exit status
@@ -1010,6 +1018,12 @@ main (int argc, char **argv)
     {
       /* Parent.  */
       int status;
+
+      /* Send the child's "outside" pid to it.  */
+      write (pipes[1], &child, sizeof(child));
+      close (pipes[0]);
+      close (pipes[1]);
+
       waitpid (child, &status, 0);
 
       if (WIFEXITED (status))
@@ -1028,6 +1042,14 @@ main (int argc, char **argv)
   /* The rest is the child process, which is now PID 1 and "in" the
      new root.  */
 
+  /* Get our "outside" pid from our parent.  We use this to help with
+     debugging from outside the container.  */
+  read (pipes[0], &child, sizeof(child));
+  close (pipes[0]);
+  close (pipes[1]);
+  sprintf (pid_buf, "%lu", (long unsigned)child);
+  setenv ("PID_OUTSIDE_CONTAINER", pid_buf, 0);
+
   maybe_xmkdir ("/tmp", 0755);
 
   /* Now that we're pid 1 (effectively "root") we can mount /proc  */