Re: [PATCH] lib: Documentation: Synchronize %p formatting documentation

From: Martin Kletzander
Date: Mon Sep 21 2015 - 09:04:43 EST

On Mon, Sep 21, 2015 at 12:18:07PM +0300, Andy Shevchenko wrote:
On Mon, 2015-09-21 at 11:13 +0200, Martin Kletzander wrote:
Move all pointer-formatting documentation to one place instead of
keeping it in three places with different level of completeness.


I think we still need at least one in the code. I, for example, often
read it from the actual c-file, not from documentation.

So, good change for printk-formats.txt, but not okay for me for the
vsprintf.c.


OK, I agree with that. Since pointer() is the function handling
exactly this and the documentation there is rather full, I'll go with
that as a place where to also leave it.

I'll add synchronization reminders to all three places in order to
hopefully keep it as clean as possible. Should I also add one to
Documentation/SubmitChecklist or is that too excessive?

Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
---
Documentation/printk-formats.txt | 27 +++++++++
lib/vsprintf.c | 123 ++---------------------------
----------
2 files changed, 32 insertions(+), 118 deletions(-)

diff --git a/Documentation/printk-formats.txt b/Documentation/printk
-formats.txt
index 2ec6d84f391c..c85e27264a2b 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -119,6 +119,7 @@ Raw buffer as an escaped string:
If field width is omitted the 1 byte only will be escaped.

Raw buffer as a hex string:
+
%*ph 00 01 02 ... 3f
%*phC 00:01:02: ... :3f
%*phD 00-01-02- ... -3f
@@ -234,6 +235,7 @@ UUID/GUID addresses:
Passed by reference.

dentry names:
+
%pd{,2,3,4}
%pD{,2,3,4}

@@ -264,6 +266,8 @@ struct va_format:
va_list *va;
};

+ Implements a "recursive vsnprintf".
+
Do not use this feature without some mechanism to verify the
correctness of the format string and va_list arguments.

@@ -292,6 +296,29 @@ bitmap and its derivatives such as cpumask and
nodemask:

Passed by reference.

+Network device features:
+
+ %pNF 0x000000000000c000
+
+ For printing netdev_features_t.
+
+ Passed by reference.
+
+Command from struct task_struct
+
+ %pT ls
+
+ For printing executable name excluding path from struct
+ task_struct.
+
+ Passed by reference.
+
+Ignored argument:
+
+ %pn
+
+ The argument passed will be ignored.
+
Thank you for your cooperation and attention.


diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index becd87facf48..6e358dc81ef0 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1383,91 +1383,9 @@ int kptr_restrict __read_mostly;
* by an extra set of alphanumeric characters that are extended
format
* specifiers.
*
- * Right now we handle:
+ * All format specifiers are documented in Documentation/printk
-formats.txt.
*
- * - 'F' For symbolic function descriptor pointers with offset
- * - 'f' For simple symbolic function names without offset
- * - 'S' For symbolic direct pointers with offset
- * - 's' For symbolic direct pointers without offset
- * - '[FfSs]R' as above with __builtin_extract_return_addr()
translation
- * - 'B' For backtraced symbolic direct pointers with offset
- * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit
pref]
- * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
- * - 'b[l]' For a bitmap, the number of bits is determined by the
field
- * width which must be explicitly specified either as part of
the
- * format string '%32b[l]' or through '%*b[l]', [l] selects
- * range-list format instead of hex format
- * - 'M' For a 6-byte MAC address, it prints the address in the
- * usual colon-separated hex notation
- * - 'm' For a 6-byte MAC address, it prints the hex address without
colons
- * - 'MF' For a 6-byte MAC FDDI address, it prints the address
- * with a dash-separated hex notation
- * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
- * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
- * IPv4 uses dot-separated decimal without leading 0's
(1.2.3.4)
- * IPv6 uses colon separated network-order 16 bit hex with
leading 0's
- * [S][pfs]
- * Generic IPv4/IPv6 address (struct sockaddr *) that falls
back to
- * [4] or [6] and is able to print port [p], flowinfo [f],
scope [s]
- * - 'i' [46] for 'raw' IPv4/IPv6 addresses
- * IPv6 omits the colons (01020304...0f)
- * IPv4 uses dot-separated decimal with leading 0's
(010.123.045.006)
- * [S][pfs]
- * Generic IPv4/IPv6 address (struct sockaddr *) that falls
back to
- * [4] or [6] and is able to print port [p], flowinfo [f],
scope [s]
- * - '[Ii][4S][hnbl]' IPv4 addresses in host, network, big or little
endian order
- * - 'I[6S]c' for IPv6 addresses printed as specified by
- * http://tools.ietf.org/html/rfc5952
- * - 'E[achnops]' For an escaped buffer, where rules are defined by
combination
- * of the following flags (see string_escape_mem()
for the
- * details):
- * a - ESCAPE_ANY
- * c - ESCAPE_SPECIAL
- * h - ESCAPE_HEX
- * n - ESCAPE_NULL
- * o - ESCAPE_OCTAL
- * p - ESCAPE_NP
- * s - ESCAPE_SPACE
- * By default ESCAPE_ANY_NP is used.
- * - 'U' For a 16 byte UUID/GUID, it prints the UUID/GUID in the
form
- * "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
- * Options for %pU are:
- * b big endian lower case hex (default)
- * B big endian UPPER case hex
- * l little endian lower case hex
- * L little endian UPPER case hex
- * big endian output byte order is:
- * [0][1][2][3]-[4][5]-[6][7]-[8][9]
-[10][11][12][13][14][15]
- * little endian output byte order is:
- * [3][2][1][0]-[5][4]-[7][6]-[8][9]
-[10][11][12][13][14][15]
- * - 'V' For a struct va_format which contains a format string * and
va_list *,
- * call vsnprintf(->format, *->va_list).
- * Implements a "recursive vsnprintf".
- * Do not use this feature without some mechanism to verify
the
- * 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.
- * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and
derivatives
- * (default assumed to be phys_addr_t, passed by
reference)
- * - 'd[234]' For a dentry name (optionally 2-4 last components)
- * - 'D[234]' Same as 'd' but for a struct file
- * - 'C' For a clock, it prints the name (Common Clock Framework) or
address
- * (legacy clock framework) of the clock
- * - 'Cn' For a clock, it prints the name (Common Clock Framework)
or address
- * (legacy clock framework) of the clock
- * - 'Cr' For a clock, it prints the current rate of the clock
- * - 'T' task_struct->comm
- *
- * Note: The difference between 'S' and 'F' is that on ia64 and
ppc64
- * function pointers are really function descriptors, which contain
a
- * pointer to the real address.
+ * ** Please update the documentation when making changes **
*/
static noinline_for_stack
char *pointer(const char *fmt, char *buf, char *end, void *ptr,
@@ -1829,41 +1747,10 @@ qualifier:
* @fmt: The format string to use
* @args: Arguments for the format string
*
- * This function follows C99 vsnprintf, but has some extensions:
- * %pS output the name of a text symbol with offset
- * %ps output the name of a text symbol without offset
- * %pF output the name of a function pointer with its offset
- * %pf output the name of a function pointer without its offset
- * %pB output the name of a backtrace symbol with its offset
- * %pR output the address range in a struct resource with decoded
flags
- * %pr output the address range in a struct resource with raw flags
- * %pb output the bitmap with field width as the number of bits
- * %pbl output the bitmap as range list with field width as the
number of bits
- * %pM output a 6-byte MAC address with colons
- * %pMR output a 6-byte MAC address with colons in reversed order
- * %pMF output a 6-byte MAC address with dashes
- * %pm output a 6-byte MAC address without colons
- * %pmR output a 6-byte MAC address without colons in reversed order
- * %pI4 print an IPv4 address without leading zeros
- * %pi4 print an IPv4 address with leading zeros
- * %pI6 print an IPv6 address with colons
- * %pi6 print an IPv6 address without colons
- * %pI6c print an IPv6 address as specified by RFC 5952
- * %pIS depending on sa_family of 'struct sockaddr *' print
IPv4/IPv6 address
- * %piS depending on sa_family of 'struct sockaddr *' print
IPv4/IPv6 address
- * %pU[bBlL] print a UUID/GUID in big or little endian using lower
or upper
- * case.
- * %*pE[achnops] print an escaped buffer
- * %*ph[CDN] a variable-length hex string with a separator (supports
up to 64
- * bytes of the input)
- * %pC output the name (Common Clock Framework) or address (legacy
clock
- * framework) of a clock
- * %pCn output the name (Common Clock Framework) or address (legacy
clock
- * framework) of a clock
- * %pCr output the current rate of a clock
- * %n is ignored
+ * This function follows C99 vsnprintf, but has some extensions.
+ * All format specifiers are documented in Documentation/printk
-formats.txt.
*
- * ** Please update Documentation/printk-formats.txt when making
changes **
+ * ** Please update the documentation when making changes **
*
* The return value is the number of characters which would
* be generated for the given input, excluding the trailing

--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy

Attachment: signature.asc
Description: PGP signature