Merge "ARM: fix user unalignment prefetch abort" (91df1990) · Commits · e / devices / android_kernel_sony_msm8994

arch/arm/mm/Kconfig

+15 −0

Original line number	Diff line number	Diff line
		@@ -675,6 +675,21 @@ config SWP_EMULATE

		If unsure, say Y.

		config FORCE_INSTRUCTION_ALIGNMENT
		bool "Force instructions address alignment"
		depends on CPU_V7 && ALIGNMENT_TRAP
		help
		Branching to an address in ARM state which is not word aligned,
		where this is defined to be UNPREDICTABLE, can cause one of the
		following two behaviours: 1. The unaligned location is forced to
		be aligned. 2. Using the unaligned address generates a Prefetch
		Abort on the first instruction using the unaligned PC value.

		To be consistant for the user space binaries, the unaligned location
		is forced aligned with this config.

		If unsure, say Y.

		config CPU_BIG_ENDIAN
		bool "Build big-endian kernel"
		depends on ARCH_SUPPORTS_BIG_ENDIAN

+35 −0

Original line number	Diff line number	Diff line
		@@ -742,6 +742,36 @@ do_alignment_t32_to_handler(unsigned long pinstr, struct pt_regs regs,
		return NULL;
		}

		#ifdef CONFIG_FORCE_INSTRUCTION_ALIGNMENT
		static int
		do_ialignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
		{
		/*
		* Branching to an address in ARM state which is not word aligned,
		* where this is defined to be UNPREDICTABLE,
		* can cause one of the following two behaviours:
		* 1. The unaligned location is forced to be aligned.
		* 2. Using the unaligned address generates a Prefetch Abort on
		* the first instruction using the unaligned PC value.
		*/
		int isize = 4;

		if (user_mode(regs) && !thumb_mode(regs)) {
		ai_sys += 1;

		/*
		* Force align the instruction in software to be following
		* a single behaviour for the unpredicatable cases.
		*/
		instruction_pointer(regs) &= ~(isize + (-1UL));
		return 0;
		}

		ai_skipped += 1;
		return 1;
		}
		#endif

		static int
		do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
		{
		@@ -973,6 +1003,11 @@ static int __init alignment_init(void)
		hook_fault_code(FAULT_CODE_ALIGNMENT, do_alignment, SIGBUS, BUS_ADRALN,
		"alignment exception");

		#ifdef CONFIG_FORCE_INSTRUCTION_ALIGNMENT
		hook_ifault_code(FAULT_CODE_ALIGNMENT, do_ialignment, SIGBUS,
		BUS_ADRALN, "alignment exception");
		#endif

		/*
		* ARMv6K and ARMv7 use fault status 3 (0b00011) as Access Flag section
		* fault, not as alignment error.