From ec6931b281797b69e6cf109f9cc94d5a2bf994e0 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Wed, 23 Apr 2014 17:52:52 +0100 Subject: word-at-a-time: avoid undefined behaviour in zero_bytemask macro The asm-generic, big-endian version of zero_bytemask creates a mask of bytes preceding the first zero-byte by left shifting ~0ul based on the position of the first zero byte. Unfortunately, if the first (top) byte is zero, the output of prep_zero_mask has only the top bit set, resulting in undefined C behaviour as we shift left by an amount equal to the width of the type. As it happens, GCC doesn't manage to spot this through the call to fls(), but the issue remains if architectures choose to implement their shift instructions differently. An example would be arch/arm/ (AArch32), where LSL Rd, Rn, #32 results in Rd == 0x0, whilst on arch/arm64 (AArch64) LSL Xd, Xn, #64 results in Xd == Xn. Rather than check explicitly for the problematic shift, this patch adds an extra shift by 1, replacing fls with __fls. Since zero_bytemask is never called with a zero argument (has_zero() is used to check the data first), we don't need to worry about calling __fls(0), which is undefined. Cc: Cc: Victor Kamensky Signed-off-by: Will Deacon Signed-off-by: Linus Torvalds --- include/asm-generic/word-at-a-time.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h index d3909effd725..d96deb443f18 100644 --- a/include/asm-generic/word-at-a-time.h +++ b/include/asm-generic/word-at-a-time.h @@ -50,11 +50,7 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct } #ifndef zero_bytemask -#ifdef CONFIG_64BIT -#define zero_bytemask(mask) (~0ul << fls64(mask)) -#else -#define zero_bytemask(mask) (~0ul << fls(mask)) -#endif /* CONFIG_64BIT */ -#endif /* zero_bytemask */ +#define zero_bytemask(mask) (~0ul << __fls(mask) << 1) +#endif #endif /* _ASM_WORD_AT_A_TIME_H */ -- cgit v1.2.2 From 789ce9dca8007ab5d7c72b9a174a29243817ac32 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Wed, 30 Apr 2014 14:22:19 -0700 Subject: word-at-a-time: simplify big-endian zero_bytemask macro This is simpler and cleaner. Depending on architecture, a smart compiler may or may not generate the same code. Acked-by: Will Deacon Signed-off-by: Linus Torvalds --- include/asm-generic/word-at-a-time.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h index d96deb443f18..94f9ea8abcae 100644 --- a/include/asm-generic/word-at-a-time.h +++ b/include/asm-generic/word-at-a-time.h @@ -50,7 +50,7 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct } #ifndef zero_bytemask -#define zero_bytemask(mask) (~0ul << __fls(mask) << 1) +#define zero_bytemask(mask) (~1ul << __fls(mask)) #endif #endif /* _ASM_WORD_AT_A_TIME_H */ -- cgit v1.2.2 From f774b7d10e2155e52b92dfce2f8cb099a6d6d0e6 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 28 Apr 2014 19:50:06 +0100 Subject: arm64: fixmap: fix missing sub-page offset for earlyprintk Commit d57c33c5daa4 (add generic fixmap.h) added (among other similar things) set_fixmap_io to deal with early ioremap of devices. More recently, commit bf4b558eba92 (arm64: add early_ioremap support) converted the arm64 earlyprintk to use set_fixmap_io. A side effect of this conversion is that my virtual machines have stopped booting when I pass "earlyprintk=uart8250-8bit,0x3f8" to the guest kernel. Turns out that the new earlyprintk code doesn't care at all about sub-page offsets, and just assumes that the earlyprintk device will be page-aligned. Obviously, that doesn't play well with the above example. Further investigation shows that set_fixmap_io uses __set_fixmap instead of __set_fixmap_offset. A fix is to introduce a set_fixmap_offset_io that uses the latter, and to remove the superflous call to fix_to_virt (which only returns the value that set_fixmap_io has already given us). With this applied, my VMs are back in business. Tested on a Cortex-A57 platform with kvmtool as platform emulation. Cc: Will Deacon Acked-by: Mark Salter Acked-by: Arnd Bergmann Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas --- include/asm-generic/fixmap.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/asm-generic') diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h index 5a64ca4621f3..f23174fb9ec4 100644 --- a/include/asm-generic/fixmap.h +++ b/include/asm-generic/fixmap.h @@ -93,5 +93,8 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr) #define set_fixmap_io(idx, phys) \ __set_fixmap(idx, phys, FIXMAP_PAGE_IO) +#define set_fixmap_offset_io(idx, phys) \ + __set_fixmap_offset(idx, phys, FIXMAP_PAGE_IO) + #endif /* __ASSEMBLY__ */ #endif /* __ASM_GENERIC_FIXMAP_H */ -- cgit v1.2.2