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Commit d0484193 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds
Browse files

lib/vsprintf.c: expand field_width to 24 bits 

Maurizio Lombardi reported a problem [1] with the %pb extension: It
doesn't work for sufficiently large bitmaps, since the size is stashed
in the field_width field of the struct printf_spec, which is currently
an s16.  Concretely, this manifested itself in
/sys/bus/pseudo/drivers/scsi_debug/map being empty, since the bitmap
printer got a size of 0, which is the 16 bit truncation of the actual
bitmap size.

We do want to keep struct printf_spec at 8 bytes so that it can cheaply
be passed by value.  The qualifier field is only used for internal
bookkeeping in format_decode, so we might as well use a local variable
for that.  This gives us an additional 8 bits, which we can then use for
the field width.

To stay in 8 bytes, we need to do a little rearranging and make the type
member a bitfield as well.  For consistency, change all the members to
bit fields.  gcc doesn't generate much worse code with these changes (in
fact, bloat-o-meter says we save 300 bytes - which I think is a little
surprising).

I didn't find a BUILD_BUG/compiletime_assertion/... which would work
outside function context, so for now I just open-coded it.

[1] http://thread.gmane.org/gmane.linux.kernel/2034835



[akpm@linux-foundation.org: avoid open-coded BUILD_BUG_ON]
Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Reported-by: default avatarMaurizio Lombardi <mlombard@redhat.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 34fc8b90

lib/vsprintf.c

+22 −20
Original line number Diff line number Diff line
@@ -383,13 +383,12 @@ enum format_type { 
};



struct printf_spec {

	u8	type;		/* format_type enum */

	u8	flags;		/* flags to number() */

	u8	base;		/* number base, 8, 10 or 16 only */

	u8	qualifier;	/* number qualifier, one of 'hHlLtzZ' */

	s16	field_width;	/* width of output field */

	s16	precision;	/* # of digits/chars */

};

	unsigned int	type:8;		/* format_type enum */

	signed int	field_width:24;	/* width of output field */

	unsigned int	flags:8;	/* flags to number() */

	unsigned int	base:8;		/* number base, 8, 10 or 16 only */

	signed int	precision:16;	/* # of digits/chars */

} __packed;



static noinline_for_stack

char *number(char *buf, char *end, unsigned long long num,
@@ -403,6 +402,8 @@ char *number(char *buf, char *end, unsigned long long num, 
	int i;

	bool is_zero = num == 0LL;



	BUILD_BUG_ON(sizeof(struct printf_spec) != 8);



	/* locase = 0 or 0x20. ORing digits or letters with 'locase'

	 * produces same digits or (maybe lowercased) letters */

	locase = (spec.flags & SMALL);
@@ -1670,6 +1671,7 @@ static noinline_for_stack 
int format_decode(const char *fmt, struct printf_spec *spec)

{

	const char *start = fmt;

	char qualifier;



	/* we finished early by reading the field width */

	if (spec->type == FORMAT_TYPE_WIDTH) {
@@ -1752,16 +1754,16 @@ int format_decode(const char *fmt, struct printf_spec *spec) 


qualifier:

	/* get the conversion qualifier */

	spec->qualifier = -1;

	qualifier = 0;

	if (*fmt == 'h' || _tolower(*fmt) == 'l' ||

	    _tolower(*fmt) == 'z' || *fmt == 't') {

		spec->qualifier = *fmt++;

		if (unlikely(spec->qualifier == *fmt)) {

			if (spec->qualifier == 'l') {

				spec->qualifier = 'L';

		qualifier = *fmt++;

		if (unlikely(qualifier == *fmt)) {

			if (qualifier == 'l') {

				qualifier = 'L';

				++fmt;

			} else if (spec->qualifier == 'h') {

				spec->qualifier = 'H';

			} else if (qualifier == 'h') {

				qualifier = 'H';

				++fmt;

			}

		}
@@ -1818,19 +1820,19 @@ int format_decode(const char *fmt, struct printf_spec *spec) 
		return fmt - start;

	}



	if (spec->qualifier == 'L')

	if (qualifier == 'L')

		spec->type = FORMAT_TYPE_LONG_LONG;

	else if (spec->qualifier == 'l') {

	else if (qualifier == 'l') {

		BUILD_BUG_ON(FORMAT_TYPE_ULONG + SIGN != FORMAT_TYPE_LONG);

		spec->type = FORMAT_TYPE_ULONG + (spec->flags & SIGN);

	} else if (_tolower(spec->qualifier) == 'z') {

	} else if (_tolower(qualifier) == 'z') {

		spec->type = FORMAT_TYPE_SIZE_T;

	} else if (spec->qualifier == 't') {

	} else if (qualifier == 't') {

		spec->type = FORMAT_TYPE_PTRDIFF;

	} else if (spec->qualifier == 'H') {

	} else if (qualifier == 'H') {

		BUILD_BUG_ON(FORMAT_TYPE_UBYTE + SIGN != FORMAT_TYPE_BYTE);

		spec->type = FORMAT_TYPE_UBYTE + (spec->flags & SIGN);

	} else if (spec->qualifier == 'h') {

	} else if (qualifier == 'h') {

		BUILD_BUG_ON(FORMAT_TYPE_USHORT + SIGN != FORMAT_TYPE_SHORT);

		spec->type = FORMAT_TYPE_USHORT + (spec->flags & SIGN);

	} else {