path: root/lib
diff options
authorJim Cromie <jim.cromie@gmail.com>2012-04-27 14:30:35 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-04-30 14:31:46 -0400
commitb48420c1d3019ce8d84fb8e58f4ca86b8e3655b8 (patch)
treefeeeb1008ff2433bba3107c3584ec8b4a403cec5 /lib
parent9fb48c744ba6a4bf58b666f4e6fdac3008ea1bd4 (diff)
dynamic_debug: make dynamic-debug work for module initialization
This introduces a fake module param $module.dyndbg. Its based upon Thomas Renninger's $module.ddebug boot-time debugging patch from https://lkml.org/lkml/2010/9/15/397 The 'fake' module parameter is provided for all modules, whether or not they need it. It is not explicitly added to each module, but is implemented in callbacks invoked from parse_args. For builtin modules, dynamic_debug_init() now directly calls parse_args(..., &ddebug_dyndbg_boot_params_cb), to process the params undeclared in the modules, just after the ddebug tables are processed. While its slightly weird to reprocess the boot params, parse_args() is already called repeatedly by do_initcall_levels(). More importantly, the dyndbg queries (given in ddebug_query or dyndbg params) cannot be activated until after the ddebug tables are ready, and reusing parse_args is cleaner than doing an ad-hoc parse. This reparse would break options like inc_verbosity, but they probably should be params, like verbosity=3. ddebug_dyndbg_boot_params_cb() handles both bare dyndbg (aka: ddebug_query) and module-prefixed dyndbg params, and ignores all other parameters. For example, the following will enable pr_debug()s in 4 builtin modules, in the order given: dyndbg="module params +p; module aio +p" module.dyndbg=+p pci.dyndbg For loadable modules, parse_args() in load_module() calls ddebug_dyndbg_module_params_cb(). This handles bare dyndbg params as passed from modprobe, and errors on other unknown params. Note that modprobe reads /proc/cmdline, so "modprobe foo" grabs all foo.params, strips the "foo.", and passes these to the kernel. ddebug_dyndbg_module_params_cb() is again called for the unknown params; it handles dyndbg, and errors on others. The "doing" arg added previously contains the module name. For non CONFIG_DYNAMIC_DEBUG builds, the stub function accepts and ignores $module.dyndbg params, other unknowns get -ENOENT. If no param value is given (as in pci.dyndbg example above), "+p" is assumed, which enables all pr_debug callsites in the module. The dyndbg fake parameter is not shown in /sys/module/*/parameters, thus it does not use any resources. Changes to it are made via the control file. Also change pr_info in ddebug_exec_queries to vpr_info, no need to see it all the time. Signed-off-by: Jim Cromie <jim.cromie@gmail.com> CC: Thomas Renninger <trenn@suse.de> CC: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
1 files changed, 49 insertions, 0 deletions
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 8675717c0f1..8fba4017930 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -862,6 +862,41 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n,
+/* handle both dyndbg=".." and $module.dyndbg=".." params at boot */
+static int ddebug_dyndbg_boot_param_cb(char *param, char *val,
+ const char *unused)
+ const char *modname = NULL;
+ char *sep;
+ sep = strchr(param, '.');
+ if (sep) {
+ *sep = '\0';
+ modname = param;
+ param = sep + 1;
+ }
+ if (strcmp(param, "dyndbg"))
+ return 0; /* skip all other params w/o error */
+ vpr_info("module: %s %s=\"%s\"\n", modname, param, val);
+ ddebug_exec_queries(val ? val : "+p");
+ return 0; /* query failure shouldnt stop module load */
+/* handle dyndbg args to modprobe */
+int ddebug_dyndbg_module_param_cb(char *param, char *val, const char *doing)
+ if (strcmp(param, "dyndbg"))
+ return -ENOENT;
+ vpr_info("module: %s %s=\"%s\"\n", doing, param, val);
+ ddebug_exec_queries((val ? val : "+p"));
+ return 0; /* query failure shouldnt stop module load */
static void ddebug_table_free(struct ddebug_table *dt)
@@ -929,6 +964,7 @@ static int __init dynamic_debug_init(void)
struct _ddebug *iter, *iter_start;
const char *modname = NULL;
+ char *cmdline;
int ret = 0;
int n = 0;
@@ -967,6 +1003,18 @@ static int __init dynamic_debug_init(void)
/* keep tables even on ddebug_query parse error */
ret = 0;
+ /* now that ddebug tables are loaded, process all boot args
+ * again to find and activate queries given in dyndbg params.
+ * While this has already been done for known boot params, it
+ * ignored the unknown ones (dyndbg in particular). Reusing
+ * parse_args avoids ad-hoc parsing. This will also attempt
+ * to activate queries for not-yet-loaded modules, which is
+ * slightly noisy if verbose, but harmless.
+ */
+ cmdline = kstrdup(saved_command_line, GFP_KERNEL);
+ parse_args("dyndbg params", cmdline, NULL,
+ 0, 0, 0, &ddebug_dyndbg_boot_param_cb);
+ kfree(cmdline);
if (ret)
@@ -977,5 +1025,6 @@ out_free:
/* Allow early initialization for boot messages via boot param */
/* Debugfs setup must be done later */