From: Alastair D'Silva <alast...@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 <alast...@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 97dd29a2bd77..c6b748f66a82 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -484,6 +484,9 @@ enum {
 
 #define HEXDUMP_ASCII                  BIT(0)
 #define HEXDUMP_SUPPRESS_REPEATED      BIT(1)
+#define HEXDUMP_2_GRP_LINES            BIT(2)
+#define HEXDUMP_4_GRP_LINES            BIT(3)
+#define HEXDUMP_8_GRP_LINES            BIT(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 08c6084d7daa..4da7d24826fb 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

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