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Subject[PATCH v4 7/7] lib/hexdump.c: Optionally retain byte ordering
Date
From: Alastair D'Silva <alastair@d-silva.org>

The behaviour of hexdump groups is to print the data out as if
it was a native-endian number.

This patch tweaks the documentation to make this clear, and also
adds the HEXDUMP_RETAIN_BYTE_ORDER flag to allow groups of
multiple bytes to be printed without affecting the ordering
of the printed bytes.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
---
include/linux/printk.h | 1 +
lib/hexdump.c | 30 ++++++++++++++++----
lib/test_hexdump.c | 62 ++++++++++++++++++++++++++++--------------
3 files changed, 68 insertions(+), 25 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 1d082291facf..ed1a79aa9695 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -491,6 +491,7 @@ enum {
#define HEXDUMP_2_GRP_SPACES BIT(5)
#define HEXDUMP_4_GRP_SPACES BIT(6)
#define HEXDUMP_8_GRP_SPACES BIT(7)
+#define HEXDUMP_RETAIN_BYTE_ORDER BIT(8)

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 e09e3cf8e595..29024eccf5da 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -127,7 +127,8 @@ static void separator_parameters(u64 flags, int groupsize, int *sep_chars,
* @buf: data blob to dump
* @len: number of bytes in the @buf
* @rowsize: number of bytes to print per line; must be a multiple of groupsize
- * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
+ * @groupsize: number of bytes to convert to a native endian number and print:
+ * 1, 2, 4, 8; default = 1
* @linebuf: where to put the converted data
* @linebuflen: total size of @linebuf, including space for terminating NUL
* @flags: A bitwise OR of the following flags:
@@ -138,6 +139,9 @@ static void separator_parameters(u64 flags, int groupsize, int *sep_chars,
* HEXDUMP_2_GRP_SPACES: insert a ' ' after every 2 groups
* HEXDUMP_4_GRP_SPACES: insert a ' ' after every 4 groups
* HEXDUMP_8_GRP_SPACES: insert a ' ' after every 8 groups
+ * HEXDUMP_RETAIN_BYTE_ORDER: Retain the byte ordering of groups
+ * instead of treating each group as a
+ * native-endian number
*
* hex_dump_to_buffer() works on one "line" of output at a time, converting
* <groupsize> bytes of input to hexadecimal (and optionally printable ASCII)
@@ -172,6 +176,7 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
int ret;
int sep_chars = 0;
char sep = 0;
+ bool big_endian = (flags & HEXDUMP_RETAIN_BYTE_ORDER) ? 1 : 0;

if (!is_power_of_2(groupsize) || groupsize > 8)
groupsize = 1;
@@ -203,10 +208,13 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
const u64 *ptr8 = buf;

for (j = 0; j < ngroups; j++) {
+ u64 val = big_endian ?
+ be64_to_cpu(get_unaligned(ptr8 + j)) :
+ get_unaligned(ptr8 + j);
ret = snprintf(linebuf + lx, linebuflen - lx,
"%s%16.16llx",
j ? group_separator(j, flags) : "",
- get_unaligned(ptr8 + j));
+ val);
if (ret >= linebuflen - lx)
goto overflow1;
lx += ret;
@@ -215,10 +223,14 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
const u32 *ptr4 = buf;

for (j = 0; j < ngroups; j++) {
+ u32 val = big_endian ?
+ be32_to_cpu(get_unaligned(ptr4 + j)) :
+ get_unaligned(ptr4 + j);
+
ret = snprintf(linebuf + lx, linebuflen - lx,
"%s%8.8x",
j ? group_separator(j, flags) : "",
- get_unaligned(ptr4 + j));
+ val);
if (ret >= linebuflen - lx)
goto overflow1;
lx += ret;
@@ -227,10 +239,14 @@ int hex_dump_to_buffer_ext(const void *buf, size_t len, int rowsize,
const u16 *ptr2 = buf;

for (j = 0; j < ngroups; j++) {
+ u16 val = big_endian ?
+ be16_to_cpu(get_unaligned(ptr2 + j)) :
+ get_unaligned(ptr2 + j);
+
ret = snprintf(linebuf + lx, linebuflen - lx,
"%s%4.4x",
j ? group_separator(j, flags) : "",
- get_unaligned(ptr2 + j));
+ val);
if (ret >= linebuflen - lx)
goto overflow1;
lx += ret;
@@ -332,7 +348,8 @@ static void announce_skipped(const char *level, const char *prefix_str,
* @prefix_type: controls whether prefix of an offset, address, or none
* is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
* @rowsize: number of bytes to print per line; must be a multiple of groupsize
- * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
+ * @groupsize: number of bytes to convert to a native endian number and print:
+ * 1, 2, 4, 8; default = 1
* @buf: data blob to dump
* @len: number of bytes in the @buf
* @ascii: include ASCII after the hex output
@@ -343,6 +360,9 @@ static void announce_skipped(const char *level, const char *prefix_str,
* 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
+ * HEXDUMP_RETAIN_BYTE_ORDER: Retain the byte ordering of groups
+ * instead of treating each group as a
+ * native-endian number
*
* 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
diff --git a/lib/test_hexdump.c b/lib/test_hexdump.c
index ad43218437f1..d2cfcb3e2d2b 100644
--- a/lib/test_hexdump.c
+++ b/lib/test_hexdump.c
@@ -98,14 +98,15 @@ static unsigned failed_tests __initdata;

static void __init test_hexdump_prepare_test(size_t len, int rowsize,
int groupsize, char *test,
- size_t testlen, bool ascii)
+ size_t testlen, u64 flags)
{
char *p;
const char * const *result;
size_t l = len;
int gs = groupsize, rs = rowsize;
unsigned int i;
- const bool is_be = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
+ const bool is_be = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) ||
+ (flags & HEXDUMP_RETAIN_BYTE_ORDER);

if (l > rs)
l = rs;
@@ -142,7 +143,7 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
p--;

/* ASCII part */
- if (ascii) {
+ if (flags & HEXDUMP_ASCII) {
do {
*p++ = ' ';
} while (p < test + rs * 2 + rs / gs + 1);
@@ -157,7 +158,7 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
#define TEST_HEXDUMP_BUF_SIZE (64 * 3 + 2 + 64 + 1)

static void __init test_hexdump(size_t len, int rowsize, int groupsize,
- bool ascii)
+ u64 flags)
{
char test[TEST_HEXDUMP_BUF_SIZE];
char real[TEST_HEXDUMP_BUF_SIZE];
@@ -166,12 +167,11 @@ static void __init test_hexdump(size_t len, int rowsize, int groupsize,

memset(real, FILL_CHAR, sizeof(real));
hex_dump_to_buffer_ext(data_b, len, rowsize, groupsize,
- real, sizeof(real),
- ascii ? HEXDUMP_ASCII : 0);
+ real, sizeof(real), flags);

memset(test, FILL_CHAR, sizeof(test));
test_hexdump_prepare_test(len, rowsize, groupsize, test, sizeof(test),
- ascii);
+ flags);

if (memcmp(test, real, TEST_HEXDUMP_BUF_SIZE)) {
pr_err("Len: %zu row: %d group: %d\n", len, rowsize, groupsize);
@@ -194,7 +194,7 @@ static void __init test_hexdump_set(int rowsize, bool ascii)

static void __init test_hexdump_overflow(size_t buflen, size_t len,
int rowsize, int groupsize,
- bool ascii)
+ u64 flags)
{
char test[TEST_HEXDUMP_BUF_SIZE];
char buf[TEST_HEXDUMP_BUF_SIZE];
@@ -206,8 +206,7 @@ static void __init test_hexdump_overflow(size_t buflen, size_t len,
memset(buf, FILL_CHAR, sizeof(buf));

rc = hex_dump_to_buffer_ext(data_b, len, rowsize, groupsize,
- buf, buflen,
- ascii ? HEXDUMP_ASCII : 0);
+ buf, buflen, flags);

/*
* Caller must provide the data length multiple of groupsize. The
@@ -224,12 +223,12 @@ static void __init test_hexdump_overflow(size_t buflen, size_t len,
- 1 /* no trailing space */;
}

- expected_len = (ascii) ? ascii_len : hex_len;
+ expected_len = (flags & HEXDUMP_ASCII) ? ascii_len : hex_len;

fill_point = min_t(int, expected_len + 1, buflen);
if (buflen) {
test_hexdump_prepare_test(len, rowsize, groupsize, test,
- sizeof(test), ascii);
+ sizeof(test), flags);
test[fill_point - 1] = '\0';
}
memset(test + fill_point, FILL_CHAR, sizeof(test) - fill_point);
@@ -239,8 +238,8 @@ static void __init test_hexdump_overflow(size_t buflen, size_t len,
buf[sizeof(buf) - 1] = '\0';

if (!match) {
- pr_err("rowsize: %u groupsize: %u ascii: %d Len: %zu buflen: %zu strlen: %zu\n",
- rowsize, groupsize, ascii, len, buflen,
+ pr_err("rowsize: %u groupsize: %u flags: %llx Len: %zu buflen: %zu strlen: %zu\n",
+ rowsize, groupsize, flags, len, buflen,
strnlen(buf, sizeof(buf)));
pr_err("Result: %d '%-.*s'\n", rc, (int)buflen, buf);
pr_err("Expect: %d '%-.*s'\n", expected_len, (int)buflen, test);
@@ -249,7 +248,7 @@ static void __init test_hexdump_overflow(size_t buflen, size_t len,
}
}

-static void __init test_hexdump_overflow_set(size_t buflen, bool ascii)
+static void __init test_hexdump_overflow_set(size_t buflen, u64 flags)
{
unsigned int i = 0;
int rs = (get_random_int() % 4 + 1) * 16;
@@ -258,7 +257,7 @@ static void __init test_hexdump_overflow_set(size_t buflen, bool ascii)
int gs = 1 << i;
size_t len = get_random_int() % rs + gs;

- test_hexdump_overflow(buflen, rounddown(len, gs), rs, gs, ascii);
+ test_hexdump_overflow(buflen, rounddown(len, gs), rs, gs, flags);
} while (i++ < 3);
}

@@ -266,20 +265,43 @@ static int __init test_hexdump_init(void)
{
unsigned int i;
int rowsize;
+ u64 flags;

+ flags = 0;
rowsize = (get_random_int() % 4 + 1) * 16;
for (i = 0; i < 16; i++)
- test_hexdump_set(rowsize, false);
+ test_hexdump_set(rowsize, flags);

+ flags = HEXDUMP_ASCII;
rowsize = (get_random_int() % 4 + 1) * 16;
for (i = 0; i < 16; i++)
- test_hexdump_set(rowsize, true);
+ test_hexdump_set(rowsize, flags);

+ flags = HEXDUMP_RETAIN_BYTE_ORDER;
+ rowsize = (get_random_int() % 2 + 1) * 16;
+ for (i = 0; i < 16; i++)
+ test_hexdump_set(rowsize, flags);
+
+ flags = HEXDUMP_ASCII | HEXDUMP_RETAIN_BYTE_ORDER;
+ rowsize = (get_random_int() % 2 + 1) * 16;
+ for (i = 0; i < 16; i++)
+ test_hexdump_set(rowsize, flags);
+
+ flags = 0;
+ for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
+ test_hexdump_overflow_set(i, flags);
+
+ flags = HEXDUMP_ASCII;
+ for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
+ test_hexdump_overflow_set(i, flags);
+
+ flags = HEXDUMP_RETAIN_BYTE_ORDER;
for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
- test_hexdump_overflow_set(i, false);
+ test_hexdump_overflow_set(i, flags);

+ flags = HEXDUMP_ASCII | HEXDUMP_RETAIN_BYTE_ORDER;
for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
- test_hexdump_overflow_set(i, true);
+ test_hexdump_overflow_set(i, flags);

if (failed_tests == 0)
pr_info("all %u tests passed\n", total_tests);
--
2.21.0
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