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ARM: kprobes: Decode 16-bit Thumb IT instruction

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The normal Thumb singlestepping routine updates the IT state after
calling the instruction handler. We don't what this to happen after the
IT instruction simulation sets the IT state, therefore we need to
provide a custom singlestep routine.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
This commit is contained in:
Jon Medhurst 2011-07-02 16:16:05 +01:00 committed by Tixy
parent fd0c8d8a48
commit 5b94faf8d7
1 changed files with 33 additions and 0 deletions
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33
arch/arm/kernel/kprobes-thumb.c
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@ -110,6 +110,37 @@ t16_simulate_cbz(struct kprobe *p, struct pt_regs *regs)
}
}
static void __kprobes
t16_simulate_it(struct kprobe *p, struct pt_regs *regs)
{
/*
* The 8 IT state bits are split into two parts in CPSR:
* ITSTATE<1:0> are in CPSR<26:25>
* ITSTATE<7:2> are in CPSR<15:10>
* The new IT state is in the lower byte of insn.
*/
kprobe_opcode_t insn = p->opcode;
unsigned long cpsr = regs->ARM_cpsr;
cpsr &= ~PSR_IT_MASK;
cpsr |= (insn & 0xfc) << 8;
cpsr |= (insn & 0x03) << 25;
regs->ARM_cpsr = cpsr;
}
static void __kprobes
t16_singlestep_it(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 2;
t16_simulate_it(p, regs);
}
static enum kprobe_insn __kprobes
t16_decode_it(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
asi->insn_singlestep = t16_singlestep_it;
return INSN_GOOD_NO_SLOT;
}
static unsigned long __kprobes
t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs)
{
@ -310,6 +341,8 @@ static const union decode_item t16_table_1011[] = {
DECODE_SIMULATE (0xffcf, 0xbf00, kprobe_simulate_nop),
/* Unassigned hints 1011 1111 xxxx 0000 */
DECODE_REJECT (0xff0f, 0xbf00),
/* IT 1011 1111 xxxx xxxx */
DECODE_CUSTOM (0xff00, 0xbf00, t16_decode_it),
DECODE_END
};