Debug extension implementation for NLKD to access the kernel trace
buffer.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>

Index: 2.6.14-nlkd/kernel/printk.c
===================================================================
--- 2.6.14-nlkd.orig/kernel/printk.c	2005-11-09 10:40:17.000000000 +0100
+++ 2.6.14-nlkd/kernel/printk.c	2005-11-04 16:19:34.000000000 +0100
@@ -1032,3 +1032,190 @@ int printk_ratelimit(void)
 				printk_ratelimit_burst);
 }
 EXPORT_SYMBOL(printk_ratelimit);
+
+#if defined(CONFIG_PRINTK) && defined(CONFIG_NLKD)
+# include <linux/ctype.h>
+# include <linux/nlkd.h>
+
+static int match(unsigned long start, unsigned long end, const char *pattern, size_t len)
+{
+	unsigned long stop;
+
+	start &= LOG_BUF_MASK;
+	stop = end &= LOG_BUF_MASK;
+	if (stop < start)
+		stop = log_buf_len;
+	for (;;) {
+		const char *p;
+
+		while (((end - start) & LOG_BUF_MASK) >= len
+		       && (p = memchr(log_buf + start, *pattern, stop - start)) != NULL) {
+			unsigned long where = p - log_buf;
+
+			if (len > stop - where
+			    ? !memcmp(p, pattern, stop - where)
+			      && !memcmp(p + (stop - where),
+			                 pattern + (stop - where),
+			                 len - (stop - where))
+			    : !memcmp(p, pattern, len))
+					return 1;
+			start = where + 1;
+		}
+		if (end >= start)
+			return 0;
+		start = 0;
+		stop = end;
+	}
+}
+
+static void do_mgrep(const char *pattern, long skip, long count)
+{
+	int backward = 1;
+	unsigned long line, cur;
+	size_t len = pattern ? strlen(pattern) : 0;
+
+	if (count == 0)
+		count = 5;
+	else if (count < 0) {
+		count = -count;
+		backward = 0;
+	}
+	if (skip < 0) {
+		skip = -skip;
+		backward = 0;
+	}
+#define LOG_IDX_MATCH(idx1, idx2) (!(((idx1) ^ (idx2)) & LOG_BUF_MASK))
+	if (backward) {
+		/* Search from end.  */
+		int end;
+
+		skip += count - 1;
+		line = log_end;
+		do {
+			for (cur = line - 1; !LOG_IDX_MATCH(cur, log_end) && LOG_BUF(cur) && LOG_BUF(cur) == '\n'; --cur)
+				;
+			for (; !(end = LOG_IDX_MATCH(cur, log_end) || !LOG_BUF(cur)) && LOG_BUF(cur) != '\n'; --cur)
+				;
+			if (len && !match(cur + 1, line, pattern, len))
+				++skip;
+			line = cur + 1;
+		} while (skip-- && !end);
+		if (++skip < count)
+			count -= skip;
+		else
+			count = 0;
+	}
+	else {
+		/* Search from start.  */
+		for (cur = LOG_BUF(log_end) ? log_end : 0; line = cur, skip; --skip) {
+			while (LOG_BUF(cur) != '\n')
+				if (!LOG_BUF(cur) || LOG_IDX_MATCH(++cur, log_end))
+					return;
+			while (LOG_BUF(cur) == '\n')
+				if (!LOG_BUF(cur) || LOG_IDX_MATCH(++cur, log_end))
+					return;
+			if (len && !match(line, cur, pattern, len))
+				++skip;
+		}
+	}
+	while (count) {
+		for (cur = line; LOG_BUF(cur) && LOG_BUF(cur) != '\n'; ++cur)
+			if (LOG_IDX_MATCH(cur + 1, 0)) {
+				for (cur = 0; LOG_BUF(cur) && LOG_BUF(cur) != '\n'; ++cur)
+					if (LOG_IDX_MATCH(cur + 1, line))
+						break;
+				break;
+			}
+		if(!len || match(line, cur, pattern, len)) {
+			if (cur < line) {
+				nlkdExtPrintf("%.*s", log_buf_len - (int)(line & LOG_BUF_MASK), &LOG_BUF(line));
+				nlkdExtPrintf("%.*s\n", (int)cur, log_buf);
+			}
+			else
+				nlkdExtPrintf("%.*s\n", (int)(cur - line), &LOG_BUF(line));
+			--count;
+		}
+		if (LOG_BUF(cur) != '\n')
+			break;
+		for (line = cur + 1; LOG_BUF(line) == '\n'; ++line)
+			;
+	}
+#undef LOG_IDX_MATCH
+}
+
+static char *skipComma(char *s) {
+	while (*s && isspace(*s))
+		++s;
+	if (*s == ';' || *s == ',')
+		++s;
+	while (*s && isspace(*s))
+		++s;
+	return s;
+}
+
+/*
+ * !dmesg [[<# to skip>;]<# of lines>]
+ */
+static void dbgxt_dmesg(void *pattern, const char *command) {
+	long skip = 0, count = 0;
+
+	if (!command)
+		return;
+	if (!pattern && *command == '?') {
+		nlkdExtOutputString("dmesg [[<# to skip>] <# of entries>]");
+		return;
+	}
+	if (*command) {
+		char *tail;
+
+		skip = simple_strtol(command, &tail, 0);
+		if (*(tail = skipComma(tail)))
+			count = simple_strtol(tail, NULL, 0);
+		else {
+			count = skip;
+			skip = 0;
+		}
+	}
+	do_mgrep(pattern, skip, count);
+}
+
+/*
+ * !mgrep <match string> [[<# to skip>];<# of lines>]
+ */
+static void dbgxt_mgrep(void *unused, const char *command) {
+	if (!command)
+		return;
+	if (!strcmp(command, "?")) {
+		nlkdExtOutputString("mgrep <match> [[<# to skip>] <# of entries>]");
+		return;
+	}
+	if (*command) {
+		char pattern[256], *dst;
+		char quote = strchr("\"\'", *command) != NULL ? *command++ : 0;
+
+		for (dst = pattern; *command && (quote ? *command != quote : !isspace(*command)); ++command)
+			if(dst < pattern + ARRAY_SIZE(pattern) - 1)
+				*dst++ = *command;
+		*dst = 0;
+		if (*command)
+			++command;
+		while (*command && isspace(*command))
+			++command;
+		dbgxt_dmesg((void *)pattern, command);
+	}
+}
+
+static THIS_MODULE_ID(printkModuleId);
+NLKD_EXTENSION(dmesg,
+	dbgxt_dmesg,
+	NULL,
+	printkModuleId,
+	"Display trace buffer records",
+	0);
+NLKD_EXTENSION(mgrep,
+	dbgxt_mgrep,
+	NULL,
+	printkModuleId,
+	"Grep trace buffer records",
+	0);
+#endif