Messages in this thread Patch in this message |  | | | From | Thomas Renninger <> | | Subject | [PATCH 1/4] Dynamic Debug: Introduce global fake module param module.ddebug - V3 | | Date | Thu, 16 Sep 2010 00:11:45 +0200 |
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Dynamic Debug allows enabling of pr_debug and dev_dbg messages at runtime. This is controlled via /sys/kernel/debug/dynamic_debug/control. One major drawback is that the whole initialization of a module cannot be tracked, because ddebug is only aware of debug strings of loaded modules. But this is the most interesting part...
This patch introduces a fake module parameter module.ddebug(not shown in /sys/module/*/parameters, thus it does not use any resources/memory). If a module passes ddebug as a module parameter (e.g. via module.ddebug kernel boot param or via "modprobe module ddebug"), all debug strings of this module get activated by issuing "module module_name +p" internally (not via sysfs) when the module gets loaded.
Possible enhancements for the future if ddebug might get extended with further flags: module.ddebug=flags Then module.ddebug="p" would be the same as module.ddebug, but if there is a "x" ddebug flag added, one could pass: module.ddebug="xp" which would result in such a dynamic debug query: module module_name +xp
Modules must not use "ddebug" as module parameter or it will get ignored. If it's tried, a warning will show up at module load time that it will get ignored (only works for not built-in modules).
Tested with (additional added pr_debug messages): options hp-wmi ddebug in modprobe.conf -> works and pr_debug messages issued at module initialization time show up. Also "p" flag gets set for the whole hp-wmi module: grep hp-wmi /sys/../dynamic_debug/control also tested with compiled-in modules, e.g. pnp.ddebug and an additional patch later in the patch series which instruments pnp code to work with ddebug.
Signed-off-by: Thomas Renninger <trenn@suse.de> CC: Bjorn Helgaas <bjorn.helgaas@hp.com> CC: Jason Baron <jbaron@redhat.com> CC: Greg KH <gregkh@suse.de> CC: lkml <linux-kernel@vger.kernel.org> --- Documentation/dynamic-debug-howto.txt | 28 ++++++++++- include/linux/dynamic_debug.h | 15 ++++++ include/linux/moduleparam.h | 3 + kernel/module.c | 1 + kernel/params.c | 13 +++++- lib/dynamic_debug.c | 86 +++++++++++++++++++++++++++++++- 6 files changed, 141 insertions(+), 5 deletions(-) diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt index 58ea64a..ebbbbdd 100644 --- a/Documentation/dynamic-debug-howto.txt +++ b/Documentation/dynamic-debug-howto.txt @@ -213,7 +213,7 @@ Note also that there is no convenient syntax to remove all the flags at once, you need to use "-psc". -Debug messages during boot process +Debug Messages during Boot Process ================================== To be able to activate debug messages during the boot process, @@ -232,6 +232,32 @@ PCI (or other devices) initialization also is a hot candidate for using this boot parameter for debugging purposes. +Debug Messages at Module Initialization Time +============================================ + +Enabling debug messages inside a module is only possible if the module itself +is loaded already. If you unload a module, the dynamic debug flags associated +to its debug messages are lost. +Therefore, enabling debug messages that get processed at module initialization +time through the <debugfs>/dynamic_debug/control interface is not possible. +Instead, a "ddebug" module paramter can be passed: + + - via kernel boot parameter: + module.ddebug + + - as an ordinary module parameter via modprobe + modprobe module ddebug + + - or the parameter can be used permanently via modprobe.conf(.local) + options module ddebug + +The ddebug option is not implemented as an ordinary module parameter and thus +will not show up in /sys/module/module_name/parameters/ddebug +The settings can get reverted through the sysfs interface again when the +module got loaded as soon as debug messages are not needed anymore: +echo "module module_name -p" > <debugfs>/dynamic_debug/control +as described in the "Command Language Reference" chapter above. + Examples ======== diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h index 52c0da4..56c0c3a 100644 --- a/include/linux/dynamic_debug.h +++ b/include/linux/dynamic_debug.h @@ -39,8 +39,13 @@ struct _ddebug { int ddebug_add_module(struct _ddebug *tab, unsigned int n, const char *modname); +struct kernel_param; + #if defined(CONFIG_DYNAMIC_DEBUG) extern int ddebug_remove_module(const char *mod_name); +extern int ddebug_exec_query(char *query_string); +extern void ddebug_module_parse_args(const char *name, char* args, + struct kernel_param *params, unsigned num); #define __dynamic_dbg_enabled(dd) ({ \ int __ret = 0; \ @@ -77,6 +82,16 @@ static inline int ddebug_remove_module(const char *mod) { return 0; } +static inline int ddebug_exec_query(char *query_string) +{ + return 0; +} +static incline void ddebug_module_parse_args(const char *name, char* args, + struct kernel_param *params, + unsigned num) +{ + return 0; +} #define dynamic_pr_debug(fmt, ...) \ do { if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); } while (0) diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h index 82a9124..ab0c88c 100644 --- a/include/linux/moduleparam.h +++ b/include/linux/moduleparam.h @@ -251,4 +251,7 @@ static inline void module_param_sysfs_remove(struct module *mod) { } #endif +/* For being able to parse parameters the same way params.c does */ +extern char *next_arg(char *args, char **param, char **val); + #endif /* _LINUX_MODULE_PARAMS_H */ diff --git a/kernel/module.c b/kernel/module.c index d0b5f8d..3912e12 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2628,6 +2628,7 @@ static struct module *load_module(void __user *umod, list_add_rcu(&mod->list, &modules); mutex_unlock(&module_mutex); + ddebug_module_parse_args(mod->name, mod->args, mod->kp, mod->num_kp); /* Module is ready to execute: parsing args may do that. */ err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL); if (err < 0) diff --git a/kernel/params.c b/kernel/params.c index 0b30ecd..df06dc0 100644 --- a/kernel/params.c +++ b/kernel/params.c @@ -54,6 +54,7 @@ static int parse_one(char *param, int (*handle_unknown)(char *param, char *val)) { unsigned int i; + char *tmp; /* Find parameter */ for (i = 0; i < num_params; i++) { @@ -64,6 +65,16 @@ static int parse_one(char *param, } } + /* + * Ignore ddebug module params and module.ddebug boot params: + * Documentation/dynamic-debug-howto.txt + */ + tmp = strstr(param, ".ddebug"); + if (parameq(param, "ddebug") || (tmp && strlen(tmp) == 7)) { + DEBUGP("Ignoring ddebug parameter %s\n", param); + return 0; + } + if (handle_unknown) { DEBUGP("Unknown argument: calling %p\n", handle_unknown); return handle_unknown(param, val); @@ -75,7 +86,7 @@ static int parse_one(char *param, /* You can use " around spaces, but can't escape ". */ /* Hyphens and underscores equivalent in parameter names. */ -static char *next_arg(char *args, char **param, char **val) +char *next_arg(char *args, char **param, char **val) { unsigned int i, equals = 0; int in_quote = 0, quoted = 0; diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index a687d90..826ea2e 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -10,6 +10,7 @@ */ #include <linux/kernel.h> +#include <linux/init.h> #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/kallsyms.h> @@ -27,9 +28,13 @@ #include <linux/debugfs.h> #include <linux/slab.h> +#include <asm/setup.h> + extern struct _ddebug __start___verbose[]; extern struct _ddebug __stop___verbose[]; +#define DDEBUG_STRING_SIZE 1024 + /* dynamic_debug_enabled, and dynamic_debug_enabled2 are bitmasks in which * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They * use independent hash functions, to reduce the chance of false positives. @@ -429,7 +434,7 @@ static int ddebug_parse_flags(const char *str, unsigned int *flagsp, return 0; } -static int ddebug_exec_query(char *query_string) +int ddebug_exec_query(char *query_string) { unsigned int flags = 0, mask = 0; struct ddebug_query query; @@ -437,6 +442,9 @@ static int ddebug_exec_query(char *query_string) int nwords; char *words[MAXWORDS]; + if (verbose) + printk(KERN_INFO "%s: got query: %s\n", __func__, query_string); + nwords = ddebug_tokenize(query_string, words, MAXWORDS); if (nwords <= 0) return -EINVAL; @@ -450,10 +458,10 @@ static int ddebug_exec_query(char *query_string) return 0; } -static __initdata char ddebug_setup_string[1024]; +static __initdata char ddebug_setup_string[DDEBUG_STRING_SIZE]; static __init int ddebug_setup_query(char *str) { - if (strlen(str) >= 1024) { + if (strlen(str) >= DDEBUG_STRING_SIZE) { pr_warning("ddebug boot param string too large\n"); return 0; } @@ -704,6 +712,76 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n, } EXPORT_SYMBOL_GPL(ddebug_add_module); +/* We search for *ddebug* module params */ +void ddebug_module_parse_args(const char *name, char* args, + struct kernel_param *params, unsigned num) +{ + char ddebug[DDEBUG_STRING_SIZE], *param, *val, *args_it, *arg_dup_ptr; + int i; + + /* + * We must not modify the passed args string and need to store the + * kstrdup pointer to be able to free memory later, TBD: find a way + * to do this nicer + */ + arg_dup_ptr = args_it = kstrdup(args, GFP_KERNEL); + + if (verbose) + printk(KERN_INFO "%s: Parsing ARGS: -%s- of %s\n", + __func__, args_it, name); + + for (i = 0; i < num; i++) { + if (!strcmp("ddebug", params[i].name)) + pr_warning("Module %s uses reserved keyword " + "*ddebug* as parameter\n", name); + } + + /* Chew leading spaces */ + args_it = skip_spaces(args_it); + + while (*args_it) { + args_it = next_arg(args_it, ¶m, &val); + if (verbose) + printk(KERN_INFO "%s: Param: %s, val: %s\n", + __func__, param, val); + if (!strcmp(param, "ddebug")) { + pr_info("Enabling debugging for module %s\n", name); + snprintf(ddebug, DDEBUG_STRING_SIZE, "module %s +p", + name); + ddebug_exec_query(ddebug); + } + } + kfree(arg_dup_ptr); + if (verbose) + printk(KERN_INFO "%s: Finished %s parsing\n", __func__, name); +} +/* We search for module.ddebug kernel boot params */ +static void ddebug_boot_parse_args(void) +{ + char tmp_cmd_arr[COMMAND_LINE_SIZE], *tmp_cmd_ptr, *param, *val, *tmp; + char module[MODULE_NAME_LEN], ddebug[DDEBUG_STRING_SIZE]; + + /* next_arg touches the passed buffer and chops each argument */ + strlcpy(tmp_cmd_arr, saved_command_line, COMMAND_LINE_SIZE); + /* Chew leading spaces */ + tmp_cmd_ptr = skip_spaces(tmp_cmd_arr); + + while (*tmp_cmd_ptr) { + tmp_cmd_ptr = next_arg(tmp_cmd_ptr, ¶m, &val); + if (verbose) + printk(KERN_INFO "%s: Param: %s, val: %s\n", + __func__, param, val); + tmp = strstr(param, ".ddebug"); + if (tmp && strlen(tmp) == 7) { + strlcpy(module, param, tmp - param + 1); + pr_info("Enabling debugging for module %s\n", module); + snprintf(ddebug, DDEBUG_STRING_SIZE, "module %s +p", + module); + ddebug_exec_query(ddebug); + } + } +} + static void ddebug_table_free(struct ddebug_table *dt) { list_del_init(&dt->link); @@ -805,6 +883,8 @@ static int __init dynamic_debug_init(void) ddebug_setup_string); } + ddebug_boot_parse_args(); + out_free: if (ret) ddebug_remove_all_tables(); -- 1.6.0.2
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