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Commit 592201a9 authored by Jon Medhurst's avatar Jon Medhurst Committed by Tixy
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ARM: Thumb-2: Support Thumb-2 in undefined instruction handler 



This patch allows undef_hook's to be specified for 32-bit Thumb
instructions and also to be used for thumb kernel-side code.

32-bit Thumb instructions are specified in the form:
	((first_half << 16 ) | second_half)
which matches the layout used by the ARM ARM.

ptrace was handling 32-bit Thumb instructions by hooking the first
halfword and manually checking the second half. This method would be
broken by this patch so it is migrated to make use of the new Thumb-2
support.

Signed-off-by: default avatarJon Medhurst <tixy@yxit.co.uk>
Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
parent 59481062

arch/arm/include/asm/ptrace.h

+8 −0
Original line number Diff line number Diff line
@@ -199,6 +199,14 @@ extern unsigned long profile_pc(struct pt_regs *regs); 
#define predicate(x)		((x) & 0xf0000000)

#define PREDICATE_ALWAYS	0xe0000000



/*

 * True if instr is a 32-bit thumb instruction. This works if instr

 * is the first or only half-word of a thumb instruction. It also works

 * when instr holds all 32-bits of a wide thumb instruction if stored

 * in the form (first_half<<16)|(second_half)

 */

#define is_wide_instruction(instr)	((unsigned)(instr) >= 0xe800)



/*

 * kprobe-based event tracer support

 */

arch/arm/kernel/ptrace.c

+3 −25
Original line number Diff line number Diff line
@@ -228,34 +228,12 @@ static struct undef_hook thumb_break_hook = { 
	.fn		= break_trap,

};



static int thumb2_break_trap(struct pt_regs *regs, unsigned int instr)

{

	unsigned int instr2;

	void __user *pc;



	/* Check the second half of the instruction.  */

	pc = (void __user *)(instruction_pointer(regs) + 2);



	if (processor_mode(regs) == SVC_MODE) {

		instr2 = *(u16 *) pc;

	} else {

		get_user(instr2, (u16 __user *)pc);

	}



	if (instr2 == 0xa000) {

		ptrace_break(current, regs);

		return 0;

	} else {

		return 1;

	}

}



static struct undef_hook thumb2_break_hook = {

	.instr_mask	= 0xffff,

	.instr_val	= 0xf7f0,

	.instr_mask	= 0xffffffff,

	.instr_val	= 0xf7f0a000,

	.cpsr_mask	= PSR_T_BIT,

	.cpsr_val	= PSR_T_BIT,

	.fn		= thumb2_break_trap,

	.fn		= break_trap,

};



static int __init ptrace_break_init(void)

arch/arm/kernel/traps.c

+16 −1
Original line number Diff line number Diff line
@@ -355,9 +355,24 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs) 
	pc = (void __user *)instruction_pointer(regs);



	if (processor_mode(regs) == SVC_MODE) {

#ifdef CONFIG_THUMB2_KERNEL

		if (thumb_mode(regs)) {

			instr = ((u16 *)pc)[0];

			if (is_wide_instruction(instr)) {

				instr <<= 16;

				instr |= ((u16 *)pc)[1];

			}

		} else

#endif

			instr = *(u32 *) pc;

	} else if (thumb_mode(regs)) {

		get_user(instr, (u16 __user *)pc);

		if (is_wide_instruction(instr)) {

			unsigned int instr2;

			get_user(instr2, (u16 __user *)pc+1);

			instr <<= 16;

			instr |= instr2;

		}

	} else {

		get_user(instr, (u32 __user *)pc);

	}