kmsg - kmsg_dump() use iterator to receive log buffer content

Provide an iterator to receive the log buffer content, and convert all
kmsg_dump() users to it.

The structured data in the kmsg buffer now contains binary data, which
should no longer be copied verbatim to the kmsg_dump() users.

The iterator should provide reliable access to the buffer data, and also
supports proper log line-aware chunking of data while iterating.

Signed-off-by: Kay Sievers <kay@vrfy.org>
Tested-by: Tony Luck <tony.luck@intel.com>
Reported-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Tested-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/platforms/pseries/nvram.c

@@ -68,9 +68,7 @@ static const char *pseries_nvram_os_partitions[] = {
 };
 
 static void oops_to_nvram(struct kmsg_dumper *dumper,
-		enum kmsg_dump_reason reason,
-		const char *old_msgs, unsigned long old_len,
-		const char *new_msgs, unsigned long new_len);
+			  enum kmsg_dump_reason reason);
 
 static struct kmsg_dumper nvram_kmsg_dumper = {
 	.dump = oops_to_nvram
@@ -503,28 +501,6 @@ int __init pSeries_nvram_init(void)
 	return 0;
 }
 
-/*
- * Try to capture the last capture_len bytes of the printk buffer.  Return
- * the amount actually captured.
- */
-static size_t capture_last_msgs(const char *old_msgs, size_t old_len,
-				const char *new_msgs, size_t new_len,
-				char *captured, size_t capture_len)
-{
-	if (new_len >= capture_len) {
-		memcpy(captured, new_msgs + (new_len - capture_len),
-								capture_len);
-		return capture_len;
-	} else {
-		/* Grab the end of old_msgs. */
-		size_t old_tail_len = min(old_len, capture_len - new_len);
-		memcpy(captured, old_msgs + (old_len - old_tail_len),
-								old_tail_len);
-		memcpy(captured + old_tail_len, new_msgs, new_len);
-		return old_tail_len + new_len;
-	}
-}
-
 /*
  * Are we using the ibm,rtas-log for oops/panic reports?  And if so,
  * would logging this oops/panic overwrite an RTAS event that rtas_errd
@@ -541,27 +517,6 @@ static int clobbering_unread_rtas_event(void)
 						NVRAM_RTAS_READ_TIMEOUT);
 }
 
-/* Squeeze out each line's <n> severity prefix. */
-static size_t elide_severities(char *buf, size_t len)
-{
-	char *in, *out, *buf_end = buf + len;
-	/* Assume a <n> at the very beginning marks the start of a line. */
-	int newline = 1;
-
-	in = out = buf;
-	while (in < buf_end) {
-		if (newline && in+3 <= buf_end &&
-				*in == '<' && isdigit(in[1]) && in[2] == '>') {
-			in += 3;
-			newline = 0;
-		} else {
-			newline = (*in == '\n');
-			*out++ = *in++;
-		}
-	}
-	return out - buf;
-}
-
 /* Derived from logfs_compress() */
 static int nvram_compress(const void *in, void *out, size_t inlen,
 							size_t outlen)
@@ -619,9 +574,7 @@ static int zip_oops(size_t text_len)
  * partition.  If that's too much, go back and capture uncompressed text.
  */
 static void oops_to_nvram(struct kmsg_dumper *dumper,
-		enum kmsg_dump_reason reason,
-		const char *old_msgs, unsigned long old_len,
-		const char *new_msgs, unsigned long new_len)
+			  enum kmsg_dump_reason reason)
 {
 	static unsigned int oops_count = 0;
 	static bool panicking = false;
@@ -660,14 +613,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
 		return;
 
 	if (big_oops_buf) {
-		text_len = capture_last_msgs(old_msgs, old_len,
-			new_msgs, new_len, big_oops_buf, big_oops_buf_sz);
-		text_len = elide_severities(big_oops_buf, text_len);
+		kmsg_dump_get_buffer(dumper, false,
+				     big_oops_buf, big_oops_buf_sz, &text_len);
 		rc = zip_oops(text_len);
 	}
 	if (rc != 0) {
-		text_len = capture_last_msgs(old_msgs, old_len,
-				new_msgs, new_len, oops_data, oops_data_sz);
+		kmsg_dump_rewind(dumper);
+		kmsg_dump_get_buffer(dumper, true,
+				     oops_data, oops_data_sz, &text_len);
 		err_type = ERR_TYPE_KERNEL_PANIC;
 		*oops_len = (u16) text_len;
 	}

arch/x86/platform/mrst/early_printk_mrst.c

@@ -110,19 +110,16 @@ static struct kmsg_dumper dw_dumper;
 static int dumper_registered;
 
 static void dw_kmsg_dump(struct kmsg_dumper *dumper,
-			enum kmsg_dump_reason reason,
-			const char *s1, unsigned long l1,
-			const char *s2, unsigned long l2)
+			 enum kmsg_dump_reason reason)
 {
-	int i;
+	static char line[1024];
+	size_t len;
 
 	/* When run to this, we'd better re-init the HW */
 	mrst_early_console_init();
 
-	for (i = 0; i < l1; i++)
-		early_mrst_console.write(&early_mrst_console, s1 + i, 1);
-	for (i = 0; i < l2; i++)
-		early_mrst_console.write(&early_mrst_console, s2 + i, 1);
+	while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len))
+		early_mrst_console.write(&early_mrst_console, line, len);
 }
 
 /* Set the ratio rate to 115200, 8n1, IRQ disabled */

drivers/mtd/mtdoops.c

@@ -304,32 +304,17 @@ static void find_next_position(struct mtdoops_context *cxt)
 }
 
 static void mtdoops_do_dump(struct kmsg_dumper *dumper,
-		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
-		const char *s2, unsigned long l2)
+			    enum kmsg_dump_reason reason)
 {
 	struct mtdoops_context *cxt = container_of(dumper,
 			struct mtdoops_context, dump);
-	unsigned long s1_start, s2_start;
-	unsigned long l1_cpy, l2_cpy;
-	char *dst;
-
-	if (reason != KMSG_DUMP_OOPS &&
-	    reason != KMSG_DUMP_PANIC)
-		return;
 
 	/* Only dump oopses if dump_oops is set */
 	if (reason == KMSG_DUMP_OOPS && !dump_oops)
 		return;
 
-	dst = cxt->oops_buf + MTDOOPS_HEADER_SIZE; /* Skip the header */
-	l2_cpy = min(l2, record_size - MTDOOPS_HEADER_SIZE);
-	l1_cpy = min(l1, record_size - MTDOOPS_HEADER_SIZE - l2_cpy);
-
-	s2_start = l2 - l2_cpy;
-	s1_start = l1 - l1_cpy;
-
-	memcpy(dst, s1 + s1_start, l1_cpy);
-	memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
+	kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
+			     record_size - MTDOOPS_HEADER_SIZE, NULL);
 
 	/* Panics must be written immediately */
 	if (reason != KMSG_DUMP_OOPS)
@@ -375,6 +360,7 @@ static void mtdoops_notify_add(struct mtd_info *mtd)
 		return;
 	}
 
+	cxt->dump.max_reason = KMSG_DUMP_OOPS;
 	cxt->dump.dump = mtdoops_do_dump;
 	err = kmsg_dump_register(&cxt->dump);
 	if (err) {

fs/pstore/platform.c

@@ -94,20 +94,15 @@ static const char *get_reason_str(enum kmsg_dump_reason reason)
  * as we can from the end of the buffer.
  */
 static void pstore_dump(struct kmsg_dumper *dumper,
-	    enum kmsg_dump_reason reason,
-	    const char *s1, unsigned long l1,
-	    const char *s2, unsigned long l2)
+			enum kmsg_dump_reason reason)
 {
-	unsigned long	s1_start, s2_start;
-	unsigned long	l1_cpy, l2_cpy;
-	unsigned long	size, total = 0;
-	char		*dst;
+	unsigned long	total = 0;
 	const char	*why;
 	u64		id;
-	int		hsize, ret;
 	unsigned int	part = 1;
 	unsigned long	flags = 0;
 	int		is_locked = 0;
+	int		ret;
 
 	why = get_reason_str(reason);
 
@@ -119,30 +114,25 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		spin_lock_irqsave(&psinfo->buf_lock, flags);
 	oopscount++;
 	while (total < kmsg_bytes) {
+		char *dst;
+		unsigned long size;
+		int hsize;
+		size_t len;
+
 		dst = psinfo->buf;
 		hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount, part);
 		size = psinfo->bufsize - hsize;
 		dst += hsize;
 
-		l2_cpy = min(l2, size);
-		l1_cpy = min(l1, size - l2_cpy);
-
-		if (l1_cpy + l2_cpy == 0)
+		if (!kmsg_dump_get_buffer(dumper, true, dst, size, &len))
 			break;
 
-		s2_start = l2 - l2_cpy;
-		s1_start = l1 - l1_cpy;
-
-		memcpy(dst, s1 + s1_start, l1_cpy);
-		memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
-
 		ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
-				   hsize + l1_cpy + l2_cpy, psinfo);
+				    hsize + len, psinfo);
 		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
 			pstore_new_entry = 1;
-		l1 -= l1_cpy;
-		l2 -= l2_cpy;
-		total += l1_cpy + l2_cpy;
+
+		total += hsize + len;
 		part++;
 	}
 	if (in_nmi()) {

include/linux/kmsg_dump.h

@@ -21,6 +21,7 @@
  * is passed to the kernel.
  */
 enum kmsg_dump_reason {
+	KMSG_DUMP_UNDEF,
 	KMSG_DUMP_PANIC,
 	KMSG_DUMP_OOPS,
 	KMSG_DUMP_EMERG,
@@ -31,23 +32,37 @@ enum kmsg_dump_reason {
 
 /**
  * struct kmsg_dumper - kernel crash message dumper structure
- * @dump:	The callback which gets called on crashes. The buffer is passed
- * 		as two sections, where s1 (length l1) contains the older
- * 		messages and s2 (length l2) contains the newer.
  * @list:	Entry in the dumper list (private)
+ * @dump:	Call into dumping code which will retrieve the data with
+ * 		through the record iterator
+ * @max_reason:	filter for highest reason number that should be dumped
  * @registered:	Flag that specifies if this is already registered
  */
 struct kmsg_dumper {
-	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason,
-			const char *s1, unsigned long l1,
-			const char *s2, unsigned long l2);
 	struct list_head list;
-	int registered;
+	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
+	enum kmsg_dump_reason max_reason;
+	bool active;
+	bool registered;
+
+	/* private state of the kmsg iterator */
+	u32 cur_idx;
+	u32 next_idx;
+	u64 cur_seq;
+	u64 next_seq;
 };
 
 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);
 
+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(struct kmsg_dumper *dumper);
+
 int kmsg_dump_register(struct kmsg_dumper *dumper);
 
 int kmsg_dump_unregister(struct kmsg_dumper *dumper);
@@ -56,6 +71,22 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
 }
 
+bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+			  const char *line, size_t size, size_t *len)
+{
+	return false;
+}
+
+bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+			    char *buf, size_t size, size_t *len)
+{
+	return false;
+}
+
+void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+{
+}
+
 static inline int kmsg_dump_register(struct kmsg_dumper *dumper)
 {
 	return -EINVAL;