summaryrefslogtreecommitdiff
path: root/include/linux/bits.h
AgeCommit message (Collapse)Author
2020-04-07linux/bits.h: add compile time sanity check of GENMASK inputsRikard Falkeborn
GENMASK() and GENMASK_ULL() are supposed to be called with the high bit as the first argument and the low bit as the second argument. Mixing them will return a mask with zero bits set. Recent commits show getting this wrong is not uncommon, see e.g. commit aa4c0c9091b0 ("net: stmmac: Fix misuses of GENMASK macro") and commit 9bdd7bb3a844 ("clocksource/drivers/npcm: Fix misuse of GENMASK macro"). To prevent such mistakes from appearing again, add compile time sanity checking to the arguments of GENMASK() and GENMASK_ULL(). If both arguments are known at compile time, and the low bit is higher than the high bit, break the build to detect the mistake immediately. Since GENMASK() is used in declarations, BUILD_BUG_ON_ZERO() must be used instead of BUILD_BUG_ON(). __builtin_constant_p does not evaluate is argument, it only checks if it is a constant or not at compile time, and __builtin_choose_expr does not evaluate the expression that is not chosen. Therefore, GENMASK(x++, 0) does only evaluate x++ once. Commit 95b980d62d52 ("linux/bits.h: make BIT(), GENMASK(), and friends available in assembly") made the macros in linux/bits.h available in assembly. Since BUILD_BUG_OR_ZERO() is not asm compatible, disable the checks if the file is included in an asm file. Due to bugs in GCC versions before 4.9 [0], disable the check if building with a too old GCC compiler. [0]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Haren Myneni <haren@us.ibm.com> Cc: Joe Perches <joe@perches.com> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: lkml <linux-kernel@vger.kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20200308193954.2372399-1-rikard.falkeborn@gmail.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-03-21linux/bits.h: Extract common header for vDSOVincenzo Frascino
The vDSO library should only include the necessary headers required for a userspace library (UAPI and a minimal set of kernel headers). To make this possible it is necessary to isolate from the kernel headers the common parts that are strictly necessary to build the library. Split bits.h into linux and common headers to make the latter suitable for inclusion in the vDSO library. Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200320145351.32292-3-vincenzo.frascino@arm.com
2019-07-16linux/bits.h: make BIT(), GENMASK(), and friends available in assemblyMasahiro Yamada
BIT(), GENMASK(), etc. are useful to define register bits of hardware. However, low-level code is often written in assembly, where they are not available due to the hard-coded 1UL, 0UL. In fact, in-kernel headers such as arch/arm64/include/asm/sysreg.h use _BITUL() instead of BIT() so that the register bit macros are available in assembly. Using macros in include/uapi/linux/const.h have two reasons: [1] For use in uapi headers We should use underscore-prefixed variants for user-space. [2] For use in assembly code Since _BITUL() uses UL(1) instead of 1UL, it can be used as an alternative of BIT(). For [2], it is pretty easy to change BIT() etc. for use in assembly. This allows to replace _BUTUL() in kernel-space headers with BIT(). Link: http://lkml.kernel.org/r/20190609153941.17249-1-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-21locking/atomics, asm-generic: Move some macros from <linux/bitops.h> to a ↵Will Deacon
new <linux/bits.h> file In preparation for implementing the asm-generic atomic bitops in terms of atomic_long_*(), we need to prevent <asm/atomic.h> implementations from pulling in <linux/bitops.h>. A common reason for this include is for the BITS_PER_BYTE definition, so move this and some other BIT() and masking macros into a new header file, <linux/bits.h>. Signed-off-by: Will Deacon <will.deacon@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arm-kernel@lists.infradead.org Cc: yamada.masahiro@socionext.com Link: https://lore.kernel.org/lkml/1529412794-17720-4-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>