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Subject[PATCH v4 5/7] lib/hexdump.c: Allow multiple groups to be separated by lines '|'
Date
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 f0761b3a2d5d..ae80d7af82ab 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -485,6 +485,9 @@ 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_ext(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 1bf838c1a568..4dcf759fe048 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)
@@ -119,6 +139,7 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
int j, lx = 0;
int ascii_column;
int ret;
+ int line_chars = 0;

if (!is_power_of_2(groupsize) || groupsize > 8)
groupsize = 1;
@@ -145,7 +166,8 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,

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;
@@ -156,7 +178,8 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,

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;
@@ -167,7 +190,8 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,

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;
@@ -197,11 +221,26 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
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';
@@ -209,7 +248,8 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
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_ext);
@@ -247,7 +287,7 @@ 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);
}

@@ -267,6 +307,9 @@ 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
@@ -296,15 +339,15 @@ 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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