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Subject[PATCH v4] kdb: Simplify kdb commands registration
Date
Simplify kdb commands registration via using linked list instead of
static array for commands storage.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
---

Changes in v4:
- Fix kdb commands memory allocation issue prior to slab being available
with an array of statically allocated commands. Now it works fine with
kgdbwait.
- Fix a misc checkpatch warning.
- I have dropped Doug's review tag as I think this version includes a
major fix that should be reviewed again.

Changes in v3:
- Remove redundant "if" check.
- Pick up review tag from Doug.

Changes in v2:
- Remove redundant NULL check for "cmd_name".
- Incorporate misc. comment.

kernel/debug/kdb/kdb_main.c | 129 ++++++++++++++---------------------------
kernel/debug/kdb/kdb_private.h | 2 +
2 files changed, 47 insertions(+), 84 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 930ac1b..5215e04 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -33,6 +33,7 @@
#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>
@@ -84,15 +85,12 @@ static unsigned int kdb_continue_catastrophic =
static unsigned int kdb_continue_catastrophic;
#endif

-/* kdb_commands describes the available commands. */
-static kdbtab_t *kdb_commands;
-#define KDB_BASE_CMD_MAX 50
-static int kdb_max_commands = KDB_BASE_CMD_MAX;
-static kdbtab_t kdb_base_commands[KDB_BASE_CMD_MAX];
-#define for_each_kdbcmd(cmd, num) \
- for ((cmd) = kdb_base_commands, (num) = 0; \
- num < kdb_max_commands; \
- num++, num == KDB_BASE_CMD_MAX ? cmd = kdb_commands : cmd++)
+/* kdb_cmds_head describes the available commands. */
+static LIST_HEAD(kdb_cmds_head);
+
+#define KDB_CMD_INIT_MAX 50
+static int kdb_cmd_init_idx;
+static kdbtab_t kdb_commands_init[KDB_CMD_INIT_MAX];

typedef struct _kdbmsg {
int km_diag; /* kdb diagnostic */
@@ -921,7 +919,7 @@ int kdb_parse(const char *cmdstr)
char *cp;
char *cpp, quoted;
kdbtab_t *tp;
- int i, escaped, ignore_errors = 0, check_grep = 0;
+ int escaped, ignore_errors = 0, check_grep = 0;

/*
* First tokenize the command string.
@@ -1011,25 +1009,17 @@ int kdb_parse(const char *cmdstr)
++argv[0];
}

- for_each_kdbcmd(tp, i) {
- if (tp->cmd_name) {
- /*
- * If this command is allowed to be abbreviated,
- * check to see if this is it.
- */
-
- if (tp->cmd_minlen
- && (strlen(argv[0]) <= tp->cmd_minlen)) {
- if (strncmp(argv[0],
- tp->cmd_name,
- tp->cmd_minlen) == 0) {
- break;
- }
- }
+ list_for_each_entry(tp, &kdb_cmds_head, list_node) {
+ /*
+ * If this command is allowed to be abbreviated,
+ * check to see if this is it.
+ */
+ if (tp->cmd_minlen && (strlen(argv[0]) <= tp->cmd_minlen) &&
+ (strncmp(argv[0], tp->cmd_name, tp->cmd_minlen) == 0))
+ break;

- if (strcmp(argv[0], tp->cmd_name) == 0)
- break;
- }
+ if (strcmp(argv[0], tp->cmd_name) == 0)
+ break;
}

/*
@@ -1037,19 +1027,15 @@ int kdb_parse(const char *cmdstr)
* few characters of this match any of the known commands.
* e.g., md1c20 should match md.
*/
- if (i == kdb_max_commands) {
- for_each_kdbcmd(tp, i) {
- if (tp->cmd_name) {
- if (strncmp(argv[0],
- tp->cmd_name,
- strlen(tp->cmd_name)) == 0) {
- break;
- }
- }
+ if (list_entry_is_head(tp, &kdb_cmds_head, list_node)) {
+ list_for_each_entry(tp, &kdb_cmds_head, list_node) {
+ if (strncmp(argv[0], tp->cmd_name,
+ strlen(tp->cmd_name)) == 0)
+ break;
}
}

- if (i < kdb_max_commands) {
+ if (!list_entry_is_head(tp, &kdb_cmds_head, list_node)) {
int result;

if (!kdb_check_flags(tp->cmd_flags, kdb_cmd_enabled, argc <= 1))
@@ -2428,17 +2414,14 @@ static int kdb_kgdb(int argc, const char **argv)
static int kdb_help(int argc, const char **argv)
{
kdbtab_t *kt;
- int i;

kdb_printf("%-15.15s %-20.20s %s\n", "Command", "Usage", "Description");
kdb_printf("-----------------------------"
"-----------------------------\n");
- for_each_kdbcmd(kt, i) {
+ list_for_each_entry(kt, &kdb_cmds_head, list_node) {
char *space = "";
if (KDB_FLAG(CMD_INTERRUPT))
return 0;
- if (!kt->cmd_name)
- continue;
if (!kdb_check_flags(kt->cmd_flags, kdb_cmd_enabled, true))
continue;
if (strlen(kt->cmd_usage) > 20)
@@ -2667,49 +2650,30 @@ int kdb_register_flags(char *cmd,
short minlen,
kdb_cmdflags_t flags)
{
- int i;
kdbtab_t *kp;

- /*
- * Brute force method to determine duplicates
- */
- for_each_kdbcmd(kp, i) {
- if (kp->cmd_name && (strcmp(kp->cmd_name, cmd) == 0)) {
+ 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);
return 1;
}
}

- /*
- * Insert command into first available location in table
- */
- for_each_kdbcmd(kp, i) {
- if (kp->cmd_name == NULL)
- break;
- }
-
- if (i >= kdb_max_commands) {
- kdbtab_t *new = kmalloc_array(kdb_max_commands -
- KDB_BASE_CMD_MAX +
- kdb_command_extend,
- sizeof(*new),
- GFP_KDB);
- if (!new) {
- kdb_printf("Could not allocate new kdb_command "
- "table\n");
+ if (slab_is_available()) {
+ kp = kmalloc(sizeof(*kp), GFP_KDB);
+ if (!kp) {
+ kdb_printf("Could not allocate new kdb_command table\n");
return 1;
}
- if (kdb_commands) {
- memcpy(new, kdb_commands,
- (kdb_max_commands - KDB_BASE_CMD_MAX) * sizeof(*new));
- kfree(kdb_commands);
+ kp->is_dynamic = true;
+ } else {
+ if (kdb_cmd_init_idx >= KDB_CMD_INIT_MAX) {
+ kdb_printf("Could not allocate init kdb_command table\n");
+ return 1;
}
- memset(new + kdb_max_commands - KDB_BASE_CMD_MAX, 0,
- kdb_command_extend * sizeof(*new));
- kdb_commands = new;
- kp = kdb_commands + kdb_max_commands - KDB_BASE_CMD_MAX;
- kdb_max_commands += kdb_command_extend;
+ kp = &kdb_commands_init[kdb_cmd_init_idx];
+ kdb_cmd_init_idx++;
}

kp->cmd_name = cmd;
@@ -2719,6 +2683,8 @@ int kdb_register_flags(char *cmd,
kp->cmd_minlen = minlen;
kp->cmd_flags = flags;

+ list_add_tail(&kp->list_node, &kdb_cmds_head);
+
return 0;
}
EXPORT_SYMBOL_GPL(kdb_register_flags);
@@ -2757,15 +2723,16 @@ EXPORT_SYMBOL_GPL(kdb_register);
*/
int kdb_unregister(char *cmd)
{
- int i;
kdbtab_t *kp;

/*
* find the command.
*/
- for_each_kdbcmd(kp, i) {
- if (kp->cmd_name && (strcmp(kp->cmd_name, cmd) == 0)) {
- kp->cmd_name = NULL;
+ 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;
}
}
@@ -2778,12 +2745,6 @@ EXPORT_SYMBOL_GPL(kdb_unregister);
/* Initialize the kdb command table. */
static void __init kdb_inittab(void)
{
- int i;
- kdbtab_t *kp;
-
- for_each_kdbcmd(kp, i)
- kp->cmd_name = NULL;
-
kdb_register_flags("md", kdb_md, "<vaddr>",
"Display Memory Contents, also mdWcN, e.g. md8c1", 1,
KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS);
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index a4281fb..f969a6a 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -174,6 +174,8 @@ typedef struct _kdbtab {
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 int kdb_bt(int, const char **); /* KDB display back trace */
--
2.7.4
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