Commit 995ddc58 authored by David Laight's avatar David Laight Committed by Kees Cook
Browse files

fortify: Use C arithmetic not FIELD_xxx() in FORTIFY_REASON defines 



FIELD_GET() and FIELD_PREP() are mainly useful for hardware register
accesses, but here they are being used for some very simple oprations.

This wouldn't matter much, but they contain a lot of compile-time
checks (that really aren't needed here) that bloat the expansion
of FIELD_GET(GENMASK(7, 1), func) to over 18KB.
Even with the 'bloat reduced' FIELD_GET/PREP they are still hundreds of
characters.

Replace FIELD_GET(BIT(0), r) with ((r) & 1), FIELD_GET(GENMASK(7, 1), r) with
(r) >> 1), and (FIELD_PREP(BIT(0), write) | FIELD_PREP(GENMASK(7, 1), func))
with ((func) << 1 | (write)).

The generated code is the same, but it makes the .c file less obfuctaced,
the .i file much easier to read, and should marginally decrease compilation
time.

Signed-off-by: default avatarDavid Laight <david.laight.linux@gmail.com>
Link: https://patch.msgid.link/20251214125857.3308-1-david.laight.linux@gmail.com


Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent cc34c669

include/linux/fortify-string.h

+3 −5
Original line number Diff line number Diff line
@@ -2,7 +2,6 @@ 
#ifndef _LINUX_FORTIFY_STRING_H_

#define _LINUX_FORTIFY_STRING_H_



#include <linux/bitfield.h>

#include <linux/bug.h>

#include <linux/const.h>

#include <linux/limits.h>
@@ -10,10 +9,9 @@ 
#define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable

#define __RENAME(x) __asm__(#x)



#define FORTIFY_REASON_DIR(r)		FIELD_GET(BIT(0), r)

#define FORTIFY_REASON_FUNC(r)		FIELD_GET(GENMASK(7, 1), r)

#define FORTIFY_REASON(func, write)	(FIELD_PREP(BIT(0), write) | \

					 FIELD_PREP(GENMASK(7, 1), func))

#define FORTIFY_REASON_DIR(r)		((r) & 1)

#define FORTIFY_REASON_FUNC(r)		((r) >> 1)

#define FORTIFY_REASON(func, write)	((func) << 1 | (write))



/* Overridden by KUnit tests. */

#ifndef fortify_panic