commit 36783141cf090412e3e6f042f25f7f6c63d6a14a

Author: Florian Weimer <fweimer@redhat.com>

Date:   Thu Apr 22 11:07:43 2021 +0200

    nptl: Check for compatible GDB in nptl/tst-pthread-gdb-attach

    Also do not clear the subprocess environment, in case running

    GDB needs certain environment variables.

    (cherry picked from commit f553dc066071a4465321fbc122bed8a75afd996b)

diff --git a/nptl/tst-pthread-gdb-attach.c b/nptl/tst-pthread-gdb-attach.c

index 0603ad844defb8de..901a12003426d342 100644

--- a/nptl/tst-pthread-gdb-attach.c

+++ b/nptl/tst-pthread-gdb-attach.c

@@ -20,8 +20,12 @@

    whether libthread_db can be loaded, and that access to thread-local

    variables works.  */

+#include <elf.h>

 #include <errno.h>

+#include <fcntl.h>

+#include <stdbool.h>

 #include <stdlib.h>

+#include <string.h>

 #include <support/check.h>

 #include <support/support.h>

 #include <support/temp_file.h>

@@ -35,6 +39,49 @@

    the thread.  */

 __thread volatile int altered_by_debugger;

+/* Common prefix between 32-bit and 64-bit ELF.  */

+struct elf_prefix

+{

+  unsigned char e_ident[EI_NIDENT];

+  uint16_t e_type;

+  uint16_t e_machine;

+  uint32_t e_version;

+};

+_Static_assert (sizeof (struct elf_prefix) == EI_NIDENT + 8,

+                "padding in struct elf_prefix");

+

+/* Reads the ELF header from PATH.  Returns true if the header can be

+   read, false if the file is too short.  */

+static bool

+read_elf_header (const char *path, struct elf_prefix *elf)

+{

+  int fd = xopen (path, O_RDONLY, 0);

+  bool result = read (fd, elf, sizeof (*elf)) == sizeof (*elf);

+  xclose (fd);

+  return result;

+}

+

+/* Searches for "gdb" alongside the path variable.  See execvpe.  */

+static char *

+find_gdb (void)

+{

+  const char *path = getenv ("PATH");

+  if (path == NULL)

+    return NULL;

+  while (true)

+    {

+      const char *colon = strchrnul (path, ':');

+      char *candidate = xasprintf ("%.*s/gdb", (int) (colon - path), path);

+      if (access (candidate, X_OK) == 0)

+        return candidate;

+      free (candidate);

+      if (*colon == '\0')

+        break;

+      path = colon + 1;

+    }

+  return NULL;

+}

+

 /* Writes the GDB script to run the test to PATH.  */

 static void

 write_gdbscript (const char *path, int tested_pid)

@@ -105,6 +152,33 @@ in_subprocess (void)

 static int

 do_test (void)

 {

+  char *gdb_path = find_gdb ();

+  if (gdb_path == NULL)

+    FAIL_UNSUPPORTED ("gdb command not found in PATH: %s", getenv ("PATH"));

+

+  /* Check that libthread_db is compatible with the gdb architecture

+     because gdb loads it via dlopen.  */

+  {

+    char *threaddb_path = xasprintf ("%s/nptl_db/libthread_db.so",

+                                     support_objdir_root);

+    struct elf_prefix elf_threaddb;

+    TEST_VERIFY_EXIT (read_elf_header (threaddb_path, &elf_threaddb));

+    struct elf_prefix elf_gdb;

+    /* If the ELF header cannot be read or "gdb" is not an ELF file,

+       assume this is a wrapper script that can run.  */

+    if (read_elf_header (gdb_path, &elf_gdb)

+        && memcmp (&elf_gdb, ELFMAG, SELFMAG) == 0)

+      {

+        if (elf_gdb.e_ident[EI_CLASS] != elf_threaddb.e_ident[EI_CLASS])

+          FAIL_UNSUPPORTED ("GDB at %s has wrong class", gdb_path);

+        if (elf_gdb.e_ident[EI_DATA] != elf_threaddb.e_ident[EI_DATA])

+          FAIL_UNSUPPORTED ("GDB at %s has wrong data", gdb_path);

+        if (elf_gdb.e_machine != elf_threaddb.e_machine)

+          FAIL_UNSUPPORTED ("GDB at %s has wrong machine", gdb_path);

+      }

+    free (threaddb_path);

+  }

+

   pid_t tested_pid = xfork ();

   if (tested_pid == 0)

     in_subprocess ();

@@ -117,9 +191,8 @@ do_test (void)

   pid_t gdb_pid = xfork ();

   if (gdb_pid == 0)

     {

-      clearenv ();

       xdup2 (STDOUT_FILENO, STDERR_FILENO);

-      execlp ("gdb", "gdb", "-nx", "-batch", "-x", gdbscript, NULL);

+      execl (gdb_path, "gdb", "-nx", "-batch", "-x", gdbscript, NULL);

       if (errno == ENOENT)

         _exit (EXIT_UNSUPPORTED);

       else

@@ -137,6 +210,7 @@ do_test (void)

   free (tested_pid_string);

   free (gdbscript);

+  free (gdb_path);

   return 0;

 }