Re: [PATCH] printk-formats.txt documentation update

Joe Perches
2011-02-07T19:33:27Z

On Mon, 2011-02-07 at 18:12 +0000, Andrew Murray wrote:
> On 7 February 2011 09:29, Wolfram Sang <w.sang@pengutronix.de> wrote:
> > On Sun, Feb 06, 2011 at 04:23:09PM +0000, Andrew Murray wrote:
> >> +
> >> + For printing kernel pointers which should be hidden from unprivileged
> >> + users. The behaviour of %pK depends on the kptr_resrict sysctl - see
> >
> > Typo: Should be kptr_restrict.
> Updated patch:

trivia:

> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
[]
> +Kernel Pointers:
> +
> + %pK 0x0

Bad example, leading zeros are emitted.

%pK 0x01234567 or 0x01234567890abcdef

depending on 32/64 bit. For 2.6.38, output should be 0x00000000
for a 0 if kptr_restrict is set, "(null)" or value otherwise.

> + For printing kernel pointers which should be hidden from unprivileged
> + users. The behaviour of %pK depends on the kptr_restrict sysctl - see
> + Documentation/sysctl/kernel.txt for more details.
> +
> +Struct Resources:
> +
> + %pr [mem 0x60000000-0x6fffffff flags 0x2200]
> + %pR [mem 0x60000000-0x6fffffff pref]
> +
> + For printing struct resources. The 'R' and 'r' specifiers result in a
> + printed resource with ('R') or without ('r') a decoded flags member.

Same issue, mem resources are printed using sizeof(resource_size_t) * 2

> +IPv6 addresses:
> +
> + %pI6 0001:0002:0003:0004:0005:0006:0007:0008
> + %pi6 00010002000300040005000600070008
> + %pI6c 1:2:3:4:5:6:7:8
> +
> + For printing IPv6 network-order 16 bit hex addresses. The 'I6' and 'i6'
> + specifiers result in a printed address with ('I6') or without ('i6')
> + colon-separators. Leading zeros are always used.
> +
> + The additional 'c' specifier can be used with the 'I' specifier to
> + print a compressed IPv6 address as described by
> + http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-00.

It's probably better to use:

http://tools.ietf.org/html/rfc5952

> +
> +UUID/GUID addresses:
> +
> + %pU 00010203-0506-0708-090a-0b0c0d0e0fff

What happened to 04?

It's probably easier/simpler to just show all possible
output styles. Assuming an in memory incrementing
16 byte array, output is:

%pU 00010203-0405-0607-08090a0b0c0d0e0f

> + %pU[bBlL]

%pUb 00010203-0405-0607-08090a0b0c0d0e0f
%pUB 00010203-0405-0607-08090A0B0C0D0E0F
%pUl 03020100-0504-0706-08090a0b0c0d0e0f
%pUL 03020100-0504-0706-08090A0B0E0D0E0F

> + For printing 16 byte UUID/GUIDs addresses. The additional 'l', 'L',
> + 'b' and 'B' specifiers are used to specify a little endian order in
> + lower ('l') or upper case ('L') hex characters - and big endian order
> + in lower ('b') or upper case ('B') hex characters.
> +
> + Where no additional specifiers are used the default little endian
> + order with lower case hex characters will be printed.
> +
> +struct va_format:
> +
> + %pV
> +
> + For printing struct va_format structures. These contain a format string
> + and va_list as follows:
> +
> + struct va_format {
> + const char *fmt;
> + va_lost *va;

va_list