Add debugging code to the com_err library

If the environment variable COMERR_DEBUG is set to 1, print out debugging
messages as error tables are added and removed from the com_err library.
If the COMERR_DEBUG_FILE environment variable is set (and the process is
not setuid) the debugging messages may be redirected to a file.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/et/ChangeLog b/lib/et/ChangeLog
index a43245cf7c12a2e06db7cf85a3de72aeb5f17f91..8940dd7c9cd80d7b0f9f279792a26ce96d6e324c 100644 (file)
--- a/lib/et/ChangeLog
+++ b/lib/et/ChangeLog
@@ -1,3 +1,9 @@
+2006-12-22  Theodore Tso  <tytso@mit.edu>
+
+       * error_message.c (add_error_table, remove_error_table): Add
+               debugging so we can see what happens when various shared
+               libraries are loading and unloading error tables.
+
 2006-11-12  Theodore Tso  <tytso@mit.edu>
 
        * compile_et.sh.in: Make sure locale environment variables are set to

diff --git a/lib/et/error_message.c b/lib/et/error_message.c
index 90d63c417f1a6ada35bc568b48314f5f1fd3564d..469ea964af4317786ed1a35b0eb3ea5b189265ca 100644 (file)
--- a/lib/et/error_message.c
+++ b/lib/et/error_message.c
@@ -20,6 +20,14 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#else
+#define PR_GET_DUMPABLE 3
+#endif
+#if (!defined(HAVE_PRCTL) && defined(linux))
+#include <sys/syscall.h>
+#endif
 #include "com_err.h"
 #include "error_table.h"
 #include "internal.h"
@@ -92,6 +100,60 @@ oops:
     return(buffer);
 }
 
+/*
+ * This routine will only return a value if the we are not running as
+ * a privileged process.
+ */
+static char *safe_getenv(const char *arg)
+{
+       if ((getuid() != geteuid()) || (getgid() != getegid()))
+               return NULL;
+#if HAVE_PRCTL
+       if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+               return NULL;
+#else
+#if (defined(linux) && defined(SYS_prctl))
+       if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+               return NULL;
+#endif
+#endif
+
+#ifdef HAVE___SECURE_GETENV
+       return __secure_getenv(arg);
+#else
+       return getenv(arg);
+#endif
+}
+
+#define DEBUG_INIT     0x8000
+#define DEBUG_ADDREMOVE 0x0001
+
+static int debug_mask = 0;
+static FILE *debug_f = 0;
+
+static void init_debug(void)
+{
+       char *dstr;
+       char *fn;
+
+       if (debug_mask & DEBUG_INIT)
+               return;
+
+       dstr = getenv("COMERR_DEBUG");
+       if (dstr)
+               debug_mask = strtoul(dstr, 0, 0);
+
+       fn = safe_getenv("COMERR_DEBUG_FILE");
+       if (fn)
+               debug_f = fopen(fn, "a");
+       if (!debug_f)
+               debug_f = fopen("/dev/tty", "a");
+       if (!debug_f)
+               debug_mask = 0;
+
+       debug_mask |= DEBUG_INIT;
+}
+
 /*
  * New interface provided by krb5's com_err library
  */
@@ -106,6 +168,12 @@ errcode_t add_error_table(const struct error_table * et)
        el->next = _et_dynamic_list;
        _et_dynamic_list = el;
 
+       init_debug();
+       if (debug_mask & DEBUG_ADDREMOVE)
+               fprintf(debug_f, "add_error_table: %s (0x%p)\n",
+                       error_table_name(et->base),
+                       (const void *) et);
+
        return 0;
 }
 
@@ -117,6 +185,7 @@ errcode_t remove_error_table(const struct error_table * et)
        struct et_list *el = _et_dynamic_list;
        struct et_list *el2 = 0;
 
+       init_debug();
        while (el) {
                if (el->table->base == et->base) {
                        if (el2)        /* Not the beginning of the list */
@@ -124,11 +193,20 @@ errcode_t remove_error_table(const struct error_table * et)
                        else
                                _et_dynamic_list = el->next;
                        (void) free(el);
+                       if (debug_mask & DEBUG_ADDREMOVE)
+                               fprintf(debug_f,
+                                       "remove_error_table: %s (0x%p)\n",
+                                       error_table_name(et->base),
+                                       (const void *) et);
                        return 0;
                }
                el2 = el;
                el = el->next;
        }
+       if (debug_mask & DEBUG_ADDREMOVE)
+               fprintf(debug_f, "remove_error_table FAILED: %s (0x%p)\n",
+                       error_table_name(et->base),
+                       (const void *) et);
        return ENOENT;
 }