Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier

From: Tetsuo Handa
Date: Tue Dec 31 2013 - 01:54:43 EST

Joe Perches wrote:
> I get:
> $ grep-2.5.4 -rP --include=*.[ch] -oh \
> "\b(?:printk|[a-z_]+_(?:printk|emerg|alert|crit|err|warn|notice|info|debug|dbg))[^;]*\bcurrent->[\w_]+" * | \
> grep -P -oh "\bcurrent->[\w_]+"| sort | uniq -c | sort -rn
> 380 current->pid
> 267 current->comm

We also have cases like

struct task_struct *tsk = current;
printk("%s/%d", tsk->comm, tsk->pid);
printk("%d", task_pid_nr(tsk));
snprintf(buf, sizeof(buf), "%d", task_pid_nr(current));

which are not counted with your grep rule.
But anyway, let's start with ->comm and ->pid .

> Also I prefer using ASCII SUB (26 \x1a \032 ^z) or maybe
> PU1 - 145 or PU2 - 146, as an initiator byte as it takes
> up much less of the control word space instead of using
> multiple values like \x80, \x81, \x82, etc. Using an
> initiator byte seems more extensible too.

My format and rules are:

#define EMBED_FORMAT "0x7F"
#define EMBED_CURRENT_COMM "0x80"
#define EMBED_CURRENT_PID "0x81"

We need to use EMBED_FORMAT prefix only when you want to specify one (or
more) of flags, field width and precision options. That is,

pr_info("%s(%d)\n", current->comm, current->pid);

pr_info("[%-6.6s]\n", current->comm);
=> pr_info(EMBED_FORMAT "-6.6" EMBED_CURRENT_COMM "\n");

But I can't imagine what your format and rules are because

#define CURRENT_SUB "\032"
#define CURRENT_SUB_ASCII '\032'

are ' ' character which is also used within the format string.
Also, if you assign one of ('0' to '9', '-', '.') for variable name like


you will need a separating byte in order to distinguish end of
flags, field width and precision options.

Please describe your format and rules (e.g. what byte starts a built-in token;
what bytes are used for representing variable name, what separates flags, field
width and precision options from variable name if these options are specified,
what byte terminates a built-in token) using examples below.

pr_info("%s(%d)\n", current->comm, current->pid);

pr_info("[%-6.6s]\n", current->comm);
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