Re: [PATCH v7 07/10] vsprintf: Consolidate handling of unknown pointer specifiers

From: Geert Uytterhoeven
Date: Tue Jun 25 2019 - 07:00:12 EST

Hi Petr,

On Wed, Apr 17, 2019 at 1:56 PM Petr Mladek <pmladek@xxxxxxxx> wrote:
> There are few printk formats that make sense only with two or more
> specifiers. Also some specifiers make sense only when a kernel feature
> is enabled.
> The handling of unknown specifiers is inconsistent and not helpful.
> Using WARN() looks like an overkill for this type of error. pr_warn()
> is not good either. It would by handled via printk_safe buffer and
> it might be hard to match it with the problematic string.
> A reasonable compromise seems to be writing the unknown format specifier
> into the original string with a question mark, for example (%pC?).
> It should be self-explaining enough. Note that it is in brackets
> to follow the (null) style.
> Note that it introduces a warning about that test_hashed() function
> is unused. It is going to be used again by a later patch.
> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>

> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1697,7 +1700,10 @@ static noinline_for_stack
> char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
> const char *fmt)
> {
> - if (!IS_ENABLED(CONFIG_HAVE_CLK) || !clk)
> + return string_nocheck(buf, end, "(%pC?)", spec);

This one is OK, as there is no clock support compiled in.

> +
> + if (!clk)
> return string(buf, end, NULL, spec);
> switch (fmt[1]) {
> @@ -1706,7 +1712,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
> return string(buf, end, __clk_get_name(clk), spec);
> #else
> - return ptr_to_id(buf, end, clk, spec);
> + return string_nocheck(buf, end, "(%pC?)", spec);

What's the reason behind this change? This is not an error case,
but for printing the clock pointer as a distinguishable ID when using
the legacy clock framework, which does not store names with clocks.




Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds