Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier
From: Tetsuo Handa
Date: Sat Dec 28 2013 - 19:33:42 EST
Joe Perches wrote:
> On Sat, 2013-12-28 at 12:08 -0800, Andrew Morton wrote:
> > On Sat, 28 Dec 2013 11:53:25 -0800 Joe Perches <joe@xxxxxxxxxxx> wrote:
> > > > > #define PRINTK_PID "\002"
> > > > > #define PRINTK_TASK_ID "\003" /* "comm:pid" */
> > > > >
> > > > > printk(PRINTK_TASK_ID ": hair on fire\n");
> > > > >
> > > > > It's certainly compact. I doubt if there's any existing code which
> > > > > deliberately prints control chars?
What about using bytes from \x7F to \xFF ?
We are not passing multibyte characters like UTF-8 in the format string (are
we?) because the non-first byte of multibyte characters by error matching %
will cause security problem (format string bug) because the format string is
parsed as char array.
Then, we could do something like below.
pr_info("%s", current->comm); => pr_info("\x7F\x80");
pr_info("%d", current->pid); => pr_info("\x7F\x81");
pr_info("%10d", current->pid); => pr_info("\x7F10\x81");
If precision field support is unnecessary, we could use only \x80 to \xFF .
pr_info("%s", current->comm); => pr_info("\x80");
pr_info("%d", current->pid); => pr_info("\x81");
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