KDB: Fix dmesg command

index 67b847d..df17c93 100644
@@ -14,6 +14,7 @@
 #include <linux/ctype.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
+#include <linux/kmsg_dump.h>
 #include <linux/reboot.h>
 #include <linux/sched.h>
 #include <linux/sysrq.h>

@@ -2040,8 +2041,15 @@ static int kdb_env(int argc, const char **argv)
  */
 static int kdb_dmesg(int argc, const char **argv)
 {
-	char *syslog_data[4], *start, *end, c = '\0', *p;
-	int diag, logging, logsize, lines = 0, adjust = 0, n;
+	int diag;
+	int logging;
+	int lines = 0;
+	int adjust = 0;
+	int n = 0;
+	int skip = 0;
+	struct kmsg_dumper dumper = { .active = 1 };
+	size_t len;
+	char buf[201];
 
 	if (argc > 2)
 		return KDB_ARGCOUNT;

@@ -2064,22 +2072,10 @@ static int kdb_dmesg(int argc, const char **argv)
 		kdb_set(2, setargs);
 	}
 
-	/* syslog_data[0,1] physical start, end+1.  syslog_data[2,3]
-	 * logical start, end+1. */
-	kdb_syslog_data(syslog_data);
-	if (syslog_data[2] == syslog_data[3])
-		return 0;
-	logsize = syslog_data[1] - syslog_data[0];
-	start = syslog_data[2];
-	end = syslog_data[3];
-#define KDB_WRAP(p) (((p - syslog_data[0]) % logsize) + syslog_data[0])
-	for (n = 0, p = start; p < end; ++p) {
-		c = *KDB_WRAP(p);
-		if (c == '\n')
-			++n;
-	}
-	if (c != '\n')
-		++n;
+	kmsg_dump_rewind(&dumper);
+	while (kmsg_dump_get_line(&dumper, 1, NULL, 0, NULL))
+		n++;
+
 	if (lines < 0) {
 		if (adjust >= n)
 			kdb_printf("buffer only contains %d lines, nothing "

@@ -2087,21 +2083,11 @@ static int kdb_dmesg(int argc, const char **argv)
 		else if (adjust - lines >= n)
 			kdb_printf("buffer only contains %d lines, last %d "
 				   "lines printed\n", n, n - adjust);
-		if (adjust) {
-			for (; start < end && adjust; ++start) {
-				if (*KDB_WRAP(start) == '\n')
-					--adjust;
-			}
-			if (start < end)
-				++start;
-		}
-		for (p = start; p < end && lines; ++p) {
-			if (*KDB_WRAP(p) == '\n')
-				++lines;
-		}
-		end = p;
+		skip = adjust;
+		lines = abs(lines);
 	} else if (lines > 0) {
-		int skip = n - (adjust + lines);
+		skip = n - lines - adjust;
+		lines = abs(lines);
 		if (adjust >= n) {
 			kdb_printf("buffer only contains %d lines, "
 				   "nothing printed\n", n);

@@ -2112,35 +2098,24 @@ static int kdb_dmesg(int argc, const char **argv)
 			kdb_printf("buffer only contains %d lines, first "
 				   "%d lines printed\n", n, lines);
 		}
-		for (; start < end && skip; ++start) {
-			if (*KDB_WRAP(start) == '\n')
-				--skip;
-		}
-		for (p = start; p < end && lines; ++p) {
-			if (*KDB_WRAP(p) == '\n')
-				--lines;
-		}
-		end = p;
+	} else {
+		lines = n;
 	}
-	/* Do a line at a time (max 200 chars) to reduce protocol overhead */
-	c = '\n';
-	while (start != end) {
-		char buf[201];
-		p = buf;
-		if (KDB_FLAG(CMD_INTERRUPT))
-			return 0;
-		while (start < end && (c = *KDB_WRAP(start)) &&
-		       (p - buf) < sizeof(buf)-1) {
-			++start;
-			*p++ = c;
-			if (c == '\n')
-				break;
+
+	if (skip >= n || skip < 0)
+		return 0;
+
+	kmsg_dump_rewind(&dumper);
+	while (kmsg_dump_get_line(&dumper, 1, buf, sizeof(buf), &len)) {
+		if (skip) {
+			skip--;
+			continue;
 		}
-		*p = '\0';
-		kdb_printf("%s", buf);
+		if (!lines--)
+			break;
+
+		kdb_printf("%.*s\n", (int)len - 1, buf);
 	}
-	if (c != '\n')
-		kdb_printf("\n");
 
 	return 0;
 }

index 47c4e56..392ec6a 100644
@@ -205,7 +205,6 @@ extern char kdb_grep_string[];
 extern int kdb_grep_leading;
 extern int kdb_grep_trailing;
 extern char *kdb_cmds[];
-extern void kdb_syslog_data(char *syslog_data[]);
 extern unsigned long kdb_task_state_string(const char *);
 extern char kdb_task_state_char (const struct task_struct *);
 extern unsigned long kdb_task_state(const struct task_struct *p,

index 177fa49..c812967 100644
@@ -1192,21 +1192,6 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 	return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 }
 
-#ifdef	CONFIG_KGDB_KDB
-/* kdb dmesg command needs access to the syslog buffer.  do_syslog()
- * uses locks so it cannot be used during debugging.  Just tell kdb
- * where the start and end of the physical and logical logs are.  This
- * is equivalent to do_syslog(3).
- */
-void kdb_syslog_data(char *syslog_data[4])
-{
-	syslog_data[0] = log_buf;
-	syslog_data[1] = log_buf + log_buf_len;
-	syslog_data[2] = log_buf + log_first_idx;
-	syslog_data[3] = log_buf + log_next_idx;
-}
-#endif	/* CONFIG_KGDB_KDB */
-
 static bool __read_mostly ignore_loglevel;
 
 static int __init ignore_loglevel_setup(char *str)

index d6bd501..2e7a1e0 100644
@@ -55,12 +55,17 @@ struct kmsg_dumper {
 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);
 
+bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+			       char *line, size_t size, size_t *len);
+
 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
 			char *line, size_t size, size_t *len);
 
 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 			  char *buf, size_t size, size_t *len);
 
+void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
+
 void kmsg_dump_rewind(struct kmsg_dumper *dumper);
 
 int kmsg_dump_register(struct kmsg_dumper *dumper);

@@ -71,6 +76,13 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
 }
 
+static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
+					     bool syslog, const char *line,
+					     size_t size, size_t *len)
+{
+	return false;
+}
+
 static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
 				const char *line, size_t size, size_t *len)
 {

@@ -83,6 +95,10 @@ static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
 	return false;
 }
 
+static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+{
+}
+
 static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
 {
 }

118 lines not on this page · raw message

index df17c93..1f91413 100644
@@ -2072,8 +2072,8 @@ static int kdb_dmesg(int argc, const char **argv)
 		kdb_set(2, setargs);
 	}
 
-	kmsg_dump_rewind(&dumper);
-	while (kmsg_dump_get_line(&dumper, 1, NULL, 0, NULL))
+	kmsg_dump_rewind_nolock(&dumper);
+	while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
 		n++;
 
 	if (lines < 0) {

@@ -2105,8 +2105,8 @@ static int kdb_dmesg(int argc, const char **argv)
 	if (skip >= n || skip < 0)
 		return 0;
 
-	kmsg_dump_rewind(&dumper);
-	while (kmsg_dump_get_line(&dumper, 1, buf, sizeof(buf), &len)) {
+	kmsg_dump_rewind_nolock(&dumper);
+	while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
 		if (skip) {
 			skip--;
 			continue;