Kernel/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2024-12-28 00:33:16 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

vsprintf: don't make the 'binary' version pack small integer arguments

Browse Source 
The strange vbin_printf / bstr_printf interface used to save one- and
two-byte printf numerical arguments into their packed format.

That's more than a bit strange since the argument buffer is supposed to
be an array of 'u32' words, and it's also very different from how the
source of the data (varargs) work - which always do the normal integer
type conversions, so 'char' and 'short' are always passed as int-sized
anyway.

This odd packing causes extra code complexity, and it really isn't worth
it, since the space savings are simply not there: it only happens for
formats like '%hd' (short) and '%hhd' (char), which are very rare
indeed.

In fact, the only other user of this interface seems to be the bpf
helper code (bpf_bprintf_prepare()), and Alexei points out that that
case doesn't support those truncated integer formatting options at all
in the first place.

As a result, bpf_bprintf_prepare() doesn't need any changes for this,
and TRACE_BPRINT uses 'vbin_printf()' -> 'bstr_printf()' for the
formatting and hopefully doesn't expose the odd packing any other way
(knock wood).

Link: https://lore.kernel.org/all/CAADnVQJy65oOubjxM-378O3wDfhuwg8TGa9hc-cTv6NmmUSykQ@mail.gmail.com/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2024-12-23 11:34:32 -08:00
parent 8d4826cc8a
commit 4c538044ee
1 changed files with 6 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
lib/vsprintf.c
View File

@ -3137,17 +3137,9 @@ int vbin_printf(u32 *bin_buf, size_t size, const char *fmt_str, va_list args)
break;
case FORMAT_STATE_NUM:
switch (fmt.size) {
case 8:
if (fmt.size > sizeof(int)) {
save_arg(long long);
break;
case 1:
save_arg(char);
break;
case 2:
save_arg(short);
break;
default:
} else {
save_arg(int);
}
}
@ -3318,23 +3310,14 @@ int bstr_printf(char *buf, size_t size, const char *fmt_str, const u32 *bin_buf)
goto out;
case FORMAT_STATE_NUM:
switch (fmt.size) {
case 8:
if (fmt.size > sizeof(int)) {
num = get_arg(long long);
break;
case 1:
num = convert_num_spec(get_arg(char), fmt.size, spec);
break;
case 2:
num = convert_num_spec(get_arg(short), fmt.size, spec);
break;
default:
} else {
num = convert_num_spec(get_arg(int), fmt.size, spec);
break;
}
str = number(str, end, num, spec);
continue;
}
str = number(str, end, num, spec);
} /* while(*fmt.str) */
out: