[PATCH v5 2/4] kdb: Get rid of redundant kdb_register_flags()

From: Sumit Garg
Date: Mon Jul 12 2021 - 09:46:51 EST

Commit e4f291b3f7bb ("kdb: Simplify kdb commands registration")
allowed registration of pre-allocated kdb commands with pointer to
struct kdbtab_t. Lets switch other users as well to register pre-
allocated kdb commands via:
- Changing prototype for kdb_register() to pass a pointer to struct
kdbtab_t instead.
- Embed kdbtab_t structure in kdb_macro_t rather than individual params.

With these changes kdb_register_flags() becomes redundant and hence
removed. Also, since we have switched all users to register
pre-allocated commands, "is_dynamic" flag in struct kdbtab_t becomes
redundant and hence removed as well.

Suggested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
include/linux/kdb.h | 27 ++++--
kernel/debug/kdb/kdb_main.c | 167 +++++++++++----------------------
kernel/debug/kdb/kdb_private.h | 13 ---
kernel/trace/trace_kdb.c | 12 ++-
samples/kdb/kdb_hello.c | 20 ++--
5 files changed, 88 insertions(+), 151 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h
index 0125a677b67f..de858edfb3b8 100644
--- a/include/linux/kdb.h
+++ b/include/linux/kdb.h
@@ -13,6 +13,8 @@
* Copyright (C) 2009 Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
*/

+#include <linux/list.h>
+
/* Shifted versions of the command enable bits are be used if the command
* has no arguments (see kdb_check_flags). This allows commands, such as
* go, to have different permissions depending upon whether it is called
@@ -64,6 +66,17 @@ typedef enum {

typedef int (*kdb_func_t)(int, const char **);

+/* The KDB shell command table */
+typedef struct _kdbtab {
+ char *cmd_name; /* Command name */
+ kdb_func_t cmd_func; /* Function to execute command */
+ char *cmd_usage; /* Usage String for this command */
+ char *cmd_help; /* Help message for this command */
+ short cmd_minlen; /* Minimum legal # cmd chars required */
+ kdb_cmdflags_t cmd_flags; /* Command behaviour flags */
+ struct list_head list_node; /* Command list */
+} kdbtab_t;
+
#ifdef CONFIG_KGDB_KDB
#include <linux/init.h>
#include <linux/sched.h>
@@ -193,19 +206,13 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos)
#endif /* ! CONFIG_KALLSYMS */

/* Dynamic kdb shell command registration */
-extern int kdb_register(char *, kdb_func_t, char *, char *, short);
-extern int kdb_register_flags(char *, kdb_func_t, char *, char *,
- short, kdb_cmdflags_t);
-extern int kdb_unregister(char *);
+extern int kdb_register(kdbtab_t *cmd);
+extern void kdb_unregister(kdbtab_t *cmd);
#else /* ! CONFIG_KGDB_KDB */
static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; }
static inline void kdb_init(int level) {}
-static inline int kdb_register(char *cmd, kdb_func_t func, char *usage,
- char *help, short minlen) { return 0; }
-static inline int kdb_register_flags(char *cmd, kdb_func_t func, char *usage,
- char *help, short minlen,
- kdb_cmdflags_t flags) { return 0; }
-static inline int kdb_unregister(char *cmd) { return 0; }
+static inline int kdb_register(kdbtab_t *cmd) { return 0; }
+static inline void kdb_unregister(kdbtab_t *cmd) {}
#endif /* CONFIG_KGDB_KDB */
enum {
KDB_NOT_INITIALIZED,
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 5cf9867fa118..b2880fad26d4 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -33,7 +33,6 @@
#include <linux/kallsyms.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
-#include <linux/list.h>
#include <linux/notifier.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
@@ -657,9 +656,7 @@ static void kdb_cmderror(int diag)
struct kdb_macro {
int count;
bool usable;
- char *name;
- char *usage;
- char *help;
+ kdbtab_t cmd;
char **command;
};
static struct kdb_macro *kdb_macro;
@@ -678,13 +675,7 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0)
if (!s->count)
s->usable = false;
if (s->usable)
- /* macros are always safe because when executed each
- * internal command re-enters kdb_parse() and is
- * safety checked individually.
- */
- kdb_register_flags(s->name, kdb_exec_defcmd, s->usage,
- s->help, 0,
- KDB_ENABLE_ALWAYS_SAFE);
+ kdb_register(&s->cmd);
return 0;
}
if (!s->usable)
@@ -705,6 +696,8 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0)
static int kdb_defcmd(int argc, const char **argv)
{
struct kdb_macro *save_kdb_macro = kdb_macro, *s;
+ kdbtab_t *mp;
+
if (defcmd_in_progress) {
kdb_printf("kdb: nested defcmd detected, assuming missing "
"endefcmd\n");
@@ -713,8 +706,8 @@ static int kdb_defcmd(int argc, const char **argv)
if (argc == 0) {
int i;
for (s = kdb_macro; s < kdb_macro + kdb_macro_count; ++s) {
- kdb_printf("defcmd %s \"%s\" \"%s\"\n", s->name,
- s->usage, s->help);
+ kdb_printf("defcmd %s \"%s\" \"%s\"\n", s->cmd.cmd_name,
+ s->cmd.cmd_usage, s->cmd.cmd_help);
for (i = 0; i < s->count; ++i)
kdb_printf("%s", s->command[i]);
kdb_printf("endefcmd\n");
@@ -736,31 +729,36 @@ static int kdb_defcmd(int argc, const char **argv)
s = kdb_macro + kdb_macro_count;
memset(s, 0, sizeof(*s));
s->usable = true;
- s->name = kdb_strdup(argv[1], GFP_KDB);
- if (!s->name)
+
+ mp = &s->cmd;
+ mp->cmd_func = kdb_exec_defcmd;
+ mp->cmd_minlen = 0;
+ mp->cmd_flags = KDB_ENABLE_ALWAYS_SAFE;
+ mp->cmd_name = kdb_strdup(argv[1], GFP_KDB);
+ if (!mp->cmd_name)
goto fail_name;
- s->usage = kdb_strdup(argv[2], GFP_KDB);
- if (!s->usage)
+ mp->cmd_usage = kdb_strdup(argv[2], GFP_KDB);
+ if (!mp->cmd_usage)
goto fail_usage;
- s->help = kdb_strdup(argv[3], GFP_KDB);
- if (!s->help)
+ mp->cmd_help = kdb_strdup(argv[3], GFP_KDB);
+ if (!mp->cmd_help)
goto fail_help;
- if (s->usage[0] == '"') {
- strcpy(s->usage, argv[2]+1);
- s->usage[strlen(s->usage)-1] = '\0';
+ if (mp->cmd_usage[0] == '"') {
+ strcpy(mp->cmd_usage, argv[2]+1);
+ mp->cmd_usage[strlen(mp->cmd_usage)-1] = '\0';
}
- if (s->help[0] == '"') {
- strcpy(s->help, argv[3]+1);
- s->help[strlen(s->help)-1] = '\0';
+ if (mp->cmd_help[0] == '"') {
+ strcpy(mp->cmd_help, argv[3]+1);
+ mp->cmd_help[strlen(mp->cmd_help)-1] = '\0';
}
++kdb_macro_count;
defcmd_in_progress = true;
kfree(save_kdb_macro);
return 0;
fail_help:
- kfree(s->usage);
+ kfree(mp->cmd_usage);
fail_usage:
- kfree(s->name);
+ kfree(mp->cmd_name);
fail_name:
kfree(kdb_macro);
fail_defcmd:
@@ -785,7 +783,7 @@ static int kdb_exec_defcmd(int argc, const char **argv)
if (argc != 0)
return KDB_ARGCOUNT;
for (s = kdb_macro, i = 0; i < kdb_macro_count; ++i, ++s) {
- if (strcmp(s->name, argv[0]) == 0)
+ if (strcmp(s->cmd.cmd_name, argv[0]) == 0)
break;
}
if (i == kdb_macro_count) {
@@ -797,7 +795,7 @@ static int kdb_exec_defcmd(int argc, const char **argv)
/* Recursive use of kdb_parse, do not use argv after
* this point */
argv = NULL;
- kdb_printf("[%s]kdb> %s\n", s->name, s->command[i]);
+ kdb_printf("[%s]kdb> %s\n", s->cmd.cmd_name, s->command[i]);
ret = kdb_parse(s->command[i]);
if (ret)
return ret;
@@ -2613,56 +2611,32 @@ static int kdb_grep_help(int argc, const char **argv)
return 0;
}

-/*
- * kdb_register_flags - This function is used to register a kernel
- * debugger command.
- * Inputs:
- * cmd Command name
- * func Function to execute the command
- * usage A simple usage string showing arguments
- * help A simple help string describing command
- * repeat Does the command auto repeat on enter?
- * Returns:
- * zero for success, one if a duplicate command.
+/**
+ * kdb_register() - This function is used to register a kernel debugger
+ * command.
+ * @cmd: pointer to kdb command
+ *
+ * Note that it's the job of the caller to keep the memory for the cmd
+ * allocated until unregister is called.
*/
-int kdb_register_flags(char *cmd,
- kdb_func_t func,
- char *usage,
- char *help,
- short minlen,
- kdb_cmdflags_t flags)
+int kdb_register(kdbtab_t *cmd)
{
kdbtab_t *kp;

list_for_each_entry(kp, &kdb_cmds_head, list_node) {
- if (strcmp(kp->cmd_name, cmd) == 0) {
- kdb_printf("Duplicate kdb command registered: "
- "%s, func %px help %s\n", cmd, func, help);
+ if (strcmp(kp->cmd_name, cmd->cmd_name) == 0) {
+ kdb_printf("Duplicate kdb cmd: %s, func %p help %s\n",
+ cmd->cmd_name, cmd->cmd_func, cmd->cmd_help);
return 1;
}
}

- kp = kmalloc(sizeof(*kp), GFP_KDB);
- if (!kp) {
- kdb_printf("Could not allocate new kdb_command table\n");
- return 1;
- }
-
- kp->cmd_name = cmd;
- kp->cmd_func = func;
- kp->cmd_usage = usage;
- kp->cmd_help = help;
- kp->cmd_minlen = minlen;
- kp->cmd_flags = flags;
- kp->is_dynamic = true;
-
- list_add_tail(&kp->list_node, &kdb_cmds_head);
-
+ list_add_tail(&cmd->list_node, &kdb_cmds_head);
return 0;
}
-EXPORT_SYMBOL_GPL(kdb_register_flags);
+EXPORT_SYMBOL_GPL(kdb_register);

-/*
+/**
* kdb_register_table() - This function is used to register a kdb command
* table.
* @kp: pointer to kdb command table
@@ -2676,55 +2650,15 @@ void kdb_register_table(kdbtab_t *kp, size_t len)
}
}

-/*
- * kdb_register - Compatibility register function for commands that do
- * not need to specify a repeat state. Equivalent to
- * kdb_register_flags with flags set to 0.
- * Inputs:
- * cmd Command name
- * func Function to execute the command
- * usage A simple usage string showing arguments
- * help A simple help string describing command
- * Returns:
- * zero for success, one if a duplicate command.
- */
-int kdb_register(char *cmd,
- kdb_func_t func,
- char *usage,
- char *help,
- short minlen)
-{
- return kdb_register_flags(cmd, func, usage, help, minlen, 0);
-}
-EXPORT_SYMBOL_GPL(kdb_register);
-
-/*
- * kdb_unregister - This function is used to unregister a kernel
- * debugger command. It is generally called when a module which
- * implements kdb commands is unloaded.
- * Inputs:
- * cmd Command name
- * Returns:
- * zero for success, one command not registered.
+/**
+ * kdb_unregister() - This function is used to unregister a kernel debugger
+ * command. It is generally called when a module which
+ * implements kdb command is unloaded.
+ * @cmd: pointer to kdb command
*/
-int kdb_unregister(char *cmd)
+void kdb_unregister(kdbtab_t *cmd)
{
- kdbtab_t *kp;
-
- /*
- * find the command.
- */
- list_for_each_entry(kp, &kdb_cmds_head, list_node) {
- if (strcmp(kp->cmd_name, cmd) == 0) {
- list_del(&kp->list_node);
- if (kp->is_dynamic)
- kfree(kp);
- return 0;
- }
- }
-
- /* Couldn't find it. */
- return 1;
+ list_del(&cmd->list_node);
}
EXPORT_SYMBOL_GPL(kdb_unregister);

@@ -2900,6 +2834,11 @@ static kdbtab_t maintab[] = {
.cmd_func = kdb_defcmd,
.cmd_usage = "name \"usage\" \"help\"",
.cmd_help = "Define a set of commands, down to endefcmd",
+ /*
+ * Macros are always safe because when executed each
+ * internal command re-enters kdb_parse() and is safety
+ * checked individually.
+ */
.cmd_flags = KDB_ENABLE_ALWAYS_SAFE,
},
{ .cmd_name = "kill",
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 8dbc840113c9..629590084a0d 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -164,19 +164,6 @@ typedef struct _kdb_bp {
#ifdef CONFIG_KGDB_KDB
extern kdb_bp_t kdb_breakpoints[/* KDB_MAXBPT */];

-/* The KDB shell command table */
-typedef struct _kdbtab {
- char *cmd_name; /* Command name */
- kdb_func_t cmd_func; /* Function to execute command */
- char *cmd_usage; /* Usage String for this command */
- char *cmd_help; /* Help message for this command */
- short cmd_minlen; /* Minimum legal # command
- * chars required */
- kdb_cmdflags_t cmd_flags; /* Command behaviour flags */
- struct list_head list_node; /* Command list */
- bool is_dynamic; /* Command table allocation type */
-} kdbtab_t;
-
extern void kdb_register_table(kdbtab_t *kp, size_t len);
extern int kdb_bt(int, const char **); /* KDB display back trace */

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 9da76104f7a2..6c4f92c79e43 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -147,11 +147,17 @@ static int kdb_ftdump(int argc, const char **argv)
return 0;
}

+static kdbtab_t ftdump_cmd = {
+ .cmd_name = "ftdump",
+ .cmd_func = kdb_ftdump,
+ .cmd_usage = "[skip_#entries] [cpu]",
+ .cmd_help = "Dump ftrace log; -skip dumps last #entries",
+ .cmd_flags = KDB_ENABLE_ALWAYS_SAFE,
+};
+
static __init int kdb_ftrace_register(void)
{
- kdb_register_flags("ftdump", kdb_ftdump, "[skip_#entries] [cpu]",
- "Dump ftrace log; -skip dumps last #entries", 0,
- KDB_ENABLE_ALWAYS_SAFE);
+ kdb_register(&ftdump_cmd);
return 0;
}

diff --git a/samples/kdb/kdb_hello.c b/samples/kdb/kdb_hello.c
index c1c2fa0f62c2..9ad514a6648b 100644
--- a/samples/kdb/kdb_hello.c
+++ b/samples/kdb/kdb_hello.c
@@ -28,28 +28,26 @@ static int kdb_hello_cmd(int argc, const char **argv)
return 0;
}

+static kdbtab_t hello_cmd = {
+ .cmd_name = "hello",
+ .cmd_func = kdb_hello_cmd,
+ .cmd_usage = "[string]",
+ .cmd_help = "Say Hello World or Hello [string]",
+};

static int __init kdb_hello_cmd_init(void)
{
/*
* Registration of a dynamically added kdb command is done with
- * kdb_register() with the arguments being:
- * 1: The name of the shell command
- * 2: The function that processes the command
- * 3: Description of the usage of any arguments
- * 4: Descriptive text when you run help
- * 5: Number of characters to complete the command
- * 0 == type the whole command
- * 1 == match both "g" and "go" for example
+ * kdb_register().
*/
- kdb_register("hello", kdb_hello_cmd, "[string]",
- "Say Hello World or Hello [string]", 0);
+ kdb_register(&hello_cmd);
return 0;
}

static void __exit kdb_hello_cmd_exit(void)
{
- kdb_unregister("hello");
+ kdb_unregister(&hello_cmd);
}

module_init(kdb_hello_cmd_init);
--
2.25.1