On Tue, 2016-06-28 at 18:07 -0400, valdis.kletni...@vt.edu wrote:
> On Tue, 28 Jun 2016 14:49:15 -0700, Joe Perches said:
>
> >
> > Another potentially useful plugin, especially for embedded systems,
> > would be to compress any string literal marked with
> >
> > __attribute__((format(printf, string-index,)))
> >
> > and decompress the compressed format on the stack in lib/vsprintf.c
> > vsnprintf just before use.
> Are there enough such strings in the kernel to make it worth the effort?
> I'm assuming that the string literals in printk("some string here") are
> automatically so marked?
Yes, that's the concept.
> Is there a minimum length under which the compression overhead actually
> makes it larger?
No, compression would have to be possible, otherwise it'd
be stored directly. Compression would use a special
"compressed string" header with a 2 byte overhead and
then stored with no trailing \0.
Something like struct compressed_format_header {
u8 flag; /* Must be ASCII STX or "\b" */
u8 length;
}
Depends on the config of course, but it could reduce total
image size ~50k on an x86-32 defconfig
