From: Michael Walle <mwa...@kernel.org>
Sent: Tuesday, April 1, 2025 10:56 AM
>
> Hi,
>
>> The issue is that disabling TINY_PRINTF may not be possible (size
>> constraints) and some code is compiled for different stages and people
>> typically don't check whether the format used in printf is valid with
>> tiny_printf. I've had this issue already in the past, I vaguely recall
>> "complaining" about it on IRC.
>
> Yes, I've stumbled on "%pa" with tiny printf (i.e. in
> drivers/pinctrl/pinctrl-single.c) which is printing the very wrong
> value, actually :) So printing anything unknown as '?' would really
> help here.
Something like that would help:
diff --git a/lib/tiny-printf.c b/lib/tiny-printf.c
index 48db7b1f78f..b918d6d7386 100644
--- a/lib/tiny-printf.c
+++ b/lib/tiny-printf.c
@@ -280,6 +280,12 @@ static int _vprintf(struct printf_info *info, const char
*fmt, va_list va)
while (isalnum(fmt[0]))
fmt++;
break;
+ } else {
+ if (fmt[0] != '\0' && (fmt[0] == 'a' ||
fmt[0] == 'm' ||
+ fmt[0] == 'M' ||
fmt[0] == 'I')) {
+ fmt++;
+ goto unsupported;
+ }
}
islong = true;
/* no break */
@@ -308,6 +314,8 @@ static int _vprintf(struct printf_info *info, const char
*fmt, va_list va)
case '%':
out(info, '%');
default:
+unsupported:
+ out(info, '?');
break;
}
But maybe it is too much for tiny printf, because tiny means
tiny. It's a question of either gain or small code size.
Regards
Christoph
