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>

2 files changed, 84 insertions, 0 deletions

diff --git a/lib/et/ChangeLog b/lib/et/ChangeLog
index a43245cf..8940dd7c 100644
--- 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 90d63c41..469ea964 100644
--- 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"
@@ -93,6 +101,60 @@ oops:
 }
 
 /*
+ * 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
  */
 errcode_t add_error_table(const struct error_table * et)
@@ -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;
 }