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Commit 2e651ea1 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARC: Unaligned access emulation 



ARC700 doesn't natively support unaligned access, but can be emulated
-Unaligned Access Exception
-Disassembly at the Fault address to find the exact insn (long/short)

Also per Arnd's comment, we runtime control it using 2 sysctl knobs:
* SYSCTL_ARCH_UNALIGN_ALLOW: Runtime enable/disble
* SYSCTL_ARCH_UNALIGN_NO_WARN: Warn on each emulation attempt

Originally contributed by Tim Yao <tim.yao@amlogic.com>

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
Cc: Tim Yao <tim.yao@amlogic.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
parent bf14e3b9

arch/arc/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -336,6 +336,17 @@ config ARC_CURR_IN_REG 
	  This reserved Register R25 to point to Current Task in

	  kernel mode. This saves memory access for each such access





config ARC_MISALIGN_ACCESS

	bool "Emulate unaligned memory access (userspace only)"

	default N

	select SYSCTL_ARCH_UNALIGN_NO_WARN

	select SYSCTL_ARCH_UNALIGN_ALLOW

	help

	  This enables misaligned 16 & 32 bit memory access from user space.

	  Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide

	  potential bugs in code



config ARC_STACK_NONEXEC

	bool "Make stack non-executable"

	default n

arch/arc/include/asm/Kbuild

+0 −1
Original line number Diff line number Diff line
@@ -52,7 +52,6 @@ generic-y += topology.h 
generic-y += trace_clock.h

generic-y += types.h

generic-y += ucontext.h

generic-y += unaligned.h

generic-y += user.h

generic-y += vga.h

generic-y += xor.h

arch/arc/include/asm/ptrace.h

+3 −0
Original line number Diff line number Diff line
@@ -97,6 +97,9 @@ struct callee_regs { 
	sp;			\

})



/* return 1 if PC in delay slot */

#define delay_mode(regs) ((regs->status32 & STATUS_DE_MASK) == STATUS_DE_MASK)



#define in_syscall(regs)    (regs->event & orig_r8_IS_SCALL)

#define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT)

arch/arc/include/asm/unaligned.h

0 → 100644
+29 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#ifndef _ASM_ARC_UNALIGNED_H

#define _ASM_ARC_UNALIGNED_H



/* ARC700 can't handle unaligned Data accesses. */



#include <asm-generic/unaligned.h>

#include <asm/ptrace.h>



#ifdef CONFIG_ARC_MISALIGN_ACCESS

int misaligned_fixup(unsigned long address, struct pt_regs *regs,

		     unsigned long cause, struct callee_regs *cregs);

#else

static inline int

misaligned_fixup(unsigned long address, struct pt_regs *regs,

		 unsigned long cause, struct callee_regs *cregs)

{

	return 0;

}

#endif



#endif /* _ASM_ARC_UNALIGNED_H */

arch/arc/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ obj-$(CONFIG_MODULES) += arcksyms.o module.o 
obj-$(CONFIG_SMP) 			+= smp.o

obj-$(CONFIG_ARC_DW2_UNWIND)		+= unwind.o

obj-$(CONFIG_KPROBES)      		+= kprobes.o

obj-$(CONFIG_ARC_MISALIGN_ACCESS) 	+= unaligned.o



obj-$(CONFIG_ARC_FPU_SAVE_RESTORE)	+= fpu.o

CFLAGS_fpu.o   += -mdpfp