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Subject[PATCH 4/4] 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 | 50 +++++++++++++++++++++++++++++++++++++-----
2 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 82975853c400..d9e407e59059 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -485,6 +485,9 @@ enum {
#define HEXDUMP_SUPPRESS_0XFF (1 << 2)
#define HEXDUMP_SUPPRESS_FIRST (1 << 3)
#define HEXDUMP_SUPPRESS_LAST (1 << 4)
+#define HEXDUMP_2_GRP_LINES (1 << 5)
+#define HEXDUMP_4_GRP_LINES (1 << 6)
+#define HEXDUMP_8_GRP_LINES (1 << 7)

#define HEXDUMP_QUIET (HEXDUMP_SUPPRESS_0X00 | \
HEXDUMP_SUPPRESS_0XFF | \
diff --git a/lib/hexdump.c b/lib/hexdump.c
index 79db784577e7..d42f34b93b2c 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -76,6 +76,20 @@ char *bin2hex(char *dst, const void *src, size_t count)
}
EXPORT_SYMBOL(bin2hex);

+static const char *group_separator(int group, u64 flags)
+{
+ if ((flags & HEXDUMP_8_GRP_LINES) && ((group - 1) % 8))
+ return "|";
+
+ if ((flags & HEXDUMP_4_GRP_LINES) && ((group - 1) % 4))
+ return "|";
+
+ if ((flags & HEXDUMP_2_GRP_LINES) && ((group - 1) % 2))
+ return "|";
+
+ return " ";
+}
+
/**
* hex_dump_to_buffer - convert a blob of data to "hex ASCII" in memory
* @buf: data blob to dump
@@ -86,6 +100,9 @@ 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, i.e.,
* 16, 32 or 64 bytes of input data converted to hex + ASCII output.
@@ -116,6 +133,7 @@ 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 (rowsize != 16 && rowsize != 32 && rowsize != 64)
rowsize = 16;
@@ -141,7 +159,8 @@ 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;
@@ -152,7 +171,8 @@ 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;
@@ -163,7 +183,8 @@ 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;
@@ -193,11 +214,26 @@ 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';
@@ -205,7 +241,8 @@ 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);
@@ -246,6 +283,9 @@ static bool buf_is_all(const u8 *buf, size_t len, u8 val)
* HEXDUMP_SUPPRESS_LAST: allows the last line to be suppressed
* If the first and last line may be suppressed,
* an empty buffer will not produce any 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
*
* 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
@@ -271,7 +311,7 @@ void print_hex_dump_ext(const char *level, const char *prefix_str,
{
const u8 *ptr = buf;
int i, remaining = len;
- unsigned char linebuf[64 * 3 + 2 + 64 + 1];
+ unsigned char linebuf[64 * 3 + 2 + 64 + 31 + 1];
bool first_line = true;

if (rowsize != 16 && rowsize != 32 && rowsize != 64)
--
2.20.1
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