[PATCH v2 5/7] lib/hexdump.c: Allow multiple groups to be separated by lines '|'

["Alastair D'Silva" <alastair@au1.ibm.com>]

From: Alastair D'Silva <alastair@d-silva.org>

With the wider display format, it can become hard to identify how many
bytes into the line you are looking at.

The patch adds new flags to hex_dump_to_buffer() and print_hex_dump() to
print vertical lines to separate every N groups of bytes.

eg.
buf:00000000: 454d414e 43415053|4e495f45 00584544  NAMESPAC|E_INDEX.
buf:00000010: 00000000 00000002|00000000 00000000  ........|........

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
---
 include/linux/printk.h |  3 +++
 lib/hexdump.c          | 59 ++++++++++++++++++++++++++++++++++++------
 2 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 00a82e468643..dc693aec394c 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -482,6 +482,9 @@ enum {
 
 #define HEXDUMP_ASCII			(1 << 0)
 #define HEXDUMP_SUPPRESS_REPEATED	(1 << 1)
+#define HEXDUMP_2_GRP_LINES		(1 << 2)
+#define HEXDUMP_4_GRP_LINES		(1 << 3)
+#define HEXDUMP_8_GRP_LINES		(1 << 4)
 
 extern int hex_dump_to_buffer(const void *buf, size_t len, int rowsize,
 			      int groupsize, char *linebuf, size_t linebuflen,
diff --git a/lib/hexdump.c b/lib/hexdump.c
index ddd1697e5f9b..6f4d1176c332 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -77,6 +77,23 @@ char *bin2hex(char *dst, const void *src, size_t count)
 }
 EXPORT_SYMBOL(bin2hex);
 
+static const char *group_separator(int group, u64 flags)
+{
+	if (group == 0)
+		return " ";
+
+	if ((flags & HEXDUMP_8_GRP_LINES) && !((group) % 8))
+		return "|";
+
+	if ((flags & HEXDUMP_4_GRP_LINES) && !((group) % 4))
+		return "|";
+
+	if ((flags & HEXDUMP_2_GRP_LINES) && !((group) % 2))
+		return "|";
+
+	return " ";
+}
+
 /**
  * hex_dump_to_buffer - convert a blob of data to "hex ASCII" in memory
  * @buf: data blob to dump
@@ -87,6 +104,9 @@ EXPORT_SYMBOL(bin2hex);
  * @linebuflen: total size of @linebuf, including space for terminating NUL
  * @flags: A bitwise OR of the following flags:
  *	HEXDUMP_ASCII:			include ASCII after the hex output
+ *	HEXDUMP_2_GRP_LINES:		insert a '|' after every 2 groups
+ *	HEXDUMP_4_GRP_LINES:		insert a '|' after every 4 groups
+ *	HEXDUMP_8_GRP_LINES:		insert a '|' after every 8 groups
  *
  * hex_dump_to_buffer() works on one "line" of output at a time, converting
  * <groupsize> bytes of input to hexadecimal (and optionally printable ASCII)
@@ -118,6 +138,7 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 	int j, lx = 0;
 	int ascii_column;
 	int ret;
+	int line_chars = 0;
 
 	if (!is_power_of_2(groupsize) || groupsize > 8)
 		groupsize = 1;
@@ -144,7 +165,8 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
-				       "%s%16.16llx", j ? " " : "",
+				       "%s%16.16llx",
+				       j ? group_separator(j, flags) : "",
 				       get_unaligned(ptr8 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
@@ -155,7 +177,8 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
-				       "%s%8.8x", j ? " " : "",
+				       "%s%8.8x",
+				       j ? group_separator(j, flags) : "",
 				       get_unaligned(ptr4 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
@@ -166,7 +189,8 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
-				       "%s%4.4x", j ? " " : "",
+				       "%s%4.4x",
+				       j ? group_separator(j, flags) : "",
 				       get_unaligned(ptr2 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
@@ -196,11 +220,26 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 			goto overflow2;
 		linebuf[lx++] = ' ';
 	}
+
+	if (flags & HEXDUMP_2_GRP_LINES)
+		line_chars = groupsize * 2;
+	if (flags & HEXDUMP_4_GRP_LINES)
+		line_chars = groupsize * 4;
+	if (flags & HEXDUMP_8_GRP_LINES)
+		line_chars = groupsize * 8;
+
 	for (j = 0; j < len; j++) {
 		if (linebuflen < lx + 2)
 			goto overflow2;
 		ch = ptr[j];
 		linebuf[lx++] = (isascii(ch) && isprint(ch)) ? ch : '.';
+
+		if (line_chars && ((j + 1) < len) &&
+				((j + 1) % line_chars == 0)) {
+			if (linebuflen < lx + 2)
+				goto overflow2;
+			linebuf[lx++] = '|';
+		}
 	}
 nil:
 	linebuf[lx] = '\0';
@@ -208,7 +247,8 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 overflow2:
 	linebuf[lx++] = '\0';
 overflow1:
-	return (flags & HEXDUMP_ASCII) ? ascii_column + len :
+	return (flags & HEXDUMP_ASCII) ? ascii_column + len +
+					(len - 1) / line_chars :
 					 (groupsize * 2 + 1) * ngroups - 1;
 }
 EXPORT_SYMBOL(hex_dump_to_buffer);
@@ -246,7 +286,7 @@ static void announce_skipped(const char *level, const char *prefix_str,
 	if (count == 0)
 		return;
 
-	printk("%s%s ** Skipped %lu bytes of value 0x%x **\n",
+	printk("%s%s ** Skipped %lu bytes of value 0x%02x **\n",
 	       level, prefix_str, count, val);
 }
 
@@ -266,6 +306,9 @@ static void announce_skipped(const char *level, const char *prefix_str,
  *	HEXDUMP_ASCII:			include ASCII after the hex output
  *	HEXDUMP_SUPPRESS_REPEATED:	suppress repeated lines of identical
  *					bytes
+ *	HEXDUMP_2_GRP_LINES:		insert a '|' after every 2 groups
+ *	HEXDUMP_4_GRP_LINES:		insert a '|' after every 4 groups
+ *	HEXDUMP_8_GRP_LINES:		insert a '|' after every 8 groups
  *
  * Given a buffer of u8 data, print_hex_dump() prints a hex + ASCII dump
  * to the kernel log at the specified kernel log level, with an optional
@@ -295,14 +338,14 @@ void print_hex_dump_ext(const char *level, const char *prefix_str,
 	u8 skipped_val = 0;
 	size_t skipped = 0;
 
-
 	if (rowsize % groupsize)
 		rowsize -= rowsize % groupsize;
 
 	/* Worst case line length:
-	 * 2 hex chars + space per byte in, 2 spaces, 1 char per byte in, NULL
+	 * 2 hex chars + space per byte in, 2 spaces, 1 char per byte in,
+	 * 1 char per N groups, NULL
 	 */
-	linebuf_len = rowsize * 3 + 2 + rowsize + 1;
+	linebuf_len = rowsize * 3 + 2 + rowsize + rowsize / groupsize + 1;
 	linebuf = kzalloc(linebuf_len, GFP_KERNEL);
 	if (!linebuf) {
 		printk("%s%shexdump: Could not alloc %u bytes for buffer\n",
-- 
2.21.0