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Subject[PATCHv3.6] lib: printf: append support of '%*ph[CDN]'
Date
There are many places in the kernel where the drivers print small buffers as a
hex string. This patch adds a support of the variable width buffer to print it
as a hex string with a delimiter. The idea came from Pavel Roskin here:
http://www.digipedia.pl/usenet/thread/18835/17449/

Sample output of
pr_info("buf[%d:%d] %*phC\n", from, len, len, &buf[from]);
could be look like this:
[ 0.726130] buf[51:8] e8:16:b6:ef:e3:74:45:6e
[ 0.750736] buf[59:15] 31:81:b8:3f:35:49:06:ae:df:32:06:05:4a:af:55
[ 0.757602] buf[17:5] ac:16:d5:2c:ef

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
Documentation/printk-formats.txt | 10 +++++++
lib/vsprintf.c | 55 ++++++++++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+)

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 90ff4d7..8ffb274 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -53,6 +53,16 @@ Struct Resources:
For printing struct resources. The 'R' and 'r' specifiers result in a
printed resource with ('R') or without ('r') a decoded flags member.

+Raw buffer as a hex string:
+ %*ph 00 01 02 ... 3f
+ %*phC 00:01:02: ... :3f
+ %*phD 00-01-02- ... -3f
+ %*phN 000102 ... 3f
+
+ For printing a small buffers (up to 64 bytes long) as a hex string with
+ certain separator. For the larger buffers consider to use
+ print_hex_dump().
+
MAC/FDDI addresses:

%pM 00:01:02:03:04:05
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index e500158..8afa954 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -655,6 +655,50 @@ char *resource_string(char *buf, char *end, struct resource *res,
}

static noinline_for_stack
+char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
+ const char *fmt)
+{
+ int i, len = 1; /* if we pass '%ph[CDN]', field witdh remains
+ negative value, fallback to the default */
+ char separator;
+
+ if (spec.field_width == 0)
+ /* nothing to print */
+ return buf;
+
+ if (ZERO_OR_NULL_PTR(addr))
+ /* NULL pointer */
+ return string(buf, end, NULL, spec);
+
+ switch (fmt[1]) {
+ case 'C':
+ separator = ':';
+ break;
+ case 'D':
+ separator = '-';
+ break;
+ case 'N':
+ separator = 0;
+ break;
+ default:
+ separator = ' ';
+ break;
+ }
+
+ if (spec.field_width > 0)
+ len = min_t(int, spec.field_width, 64);
+
+ for (i = 0; i < len && buf < end - 1; i++) {
+ buf = hex_byte_pack(buf, addr[i]);
+
+ if (buf < end && separator && i != len - 1)
+ *buf++ = separator;
+ }
+
+ return buf;
+}
+
+static noinline_for_stack
char *mac_address_string(char *buf, char *end, u8 *addr,
struct printf_spec spec, const char *fmt)
{
@@ -974,6 +1018,13 @@ int kptr_restrict __read_mostly;
* correctness of the format string and va_list arguments.
* - 'K' For a kernel pointer that should be hidden from unprivileged users
* - 'NF' For a netdev_features_t
+ * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
+ * a certain separator (' ' by default):
+ * C colon
+ * D dash
+ * N no separator
+ * The maximum supported length is 64 bytes of the input. Consider
+ * to use print_hex_dump() for the larger input.
*
* Note: The difference between 'S' and 'F' is that on ia64 and ppc64
* function pointers are really function descriptors, which contain a
@@ -1007,6 +1058,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
case 'R':
case 'r':
return resource_string(buf, end, ptr, spec, fmt);
+ case 'h':
+ return hex_string(buf, end, ptr, spec, fmt);
case 'M': /* Colon separated: 00:01:02:03:04:05 */
case 'm': /* Contiguous: 000102030405 */
/* [mM]F (FDDI) */
@@ -1298,6 +1351,8 @@ qualifier:
* %pI6c print an IPv6 address as specified by RFC 5952
* %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
* case.
+ * %*ph[CDN] a variable-length hex string with a separator (supports up to 64
+ * bytes of the input)
* %n is ignored
*
* ** Please update Documentation/printk-formats.txt when making changes **
--
1.7.10


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