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ARM: kprobes: Decode 16-bit Thumb hint instructions

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For hints which may have observable effects, like SEV (send event), we
use kprobe_emulate_none which emulates the hint by executing the
original instruction.

For NOP we simulate the instruction using kprobe_simulate_nop, which
does nothing. As probes execute with interrupts disabled this is also
used for hints which may block for an indefinite time, like WFE (wait
for event).

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 15:36:32 +01:00 • committed by Tixy
parent 0d1a095aa1
commit 3f92dfed6a
3 changed files with 46 additions and 1 deletions
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9
arch/arm/kernel/kprobes-common.c
View file

@ -142,6 +142,15 @@ kprobe_check_cc * const kprobe_condition_checks[16] = {
}; };
void __kprobes kprobe_simulate_nop(struct kprobe *p, struct pt_regs *regs)
{
}
void __kprobes kprobe_emulate_none(struct kprobe *p, struct pt_regs *regs)
{
p->ainsn.insn_fn();
}
/* /*
* Prepare an instruction slot to receive an instruction for emulating. * Prepare an instruction slot to receive an instruction for emulating.
* This is done by placing a subroutine return after the location where the * This is done by placing a subroutine return after the location where the

35
arch/arm/kernel/kprobes-thumb.c
View file

@ -26,6 +26,39 @@
*/ */
#define current_cond(cpsr) ((cpsr >> 12) & 0xf) #define current_cond(cpsr) ((cpsr >> 12) & 0xf)
static const union decode_item t16_table_1011[] = {
/* Miscellaneous 16-bit instructions */
/*
* If-Then, and hints
* 1011 1111 xxxx xxxx
*/
/* YIELD 1011 1111 0001 0000 */
DECODE_OR (0xffff, 0xbf10),
/* SEV 1011 1111 0100 0000 */
DECODE_EMULATE (0xffff, 0xbf40, kprobe_emulate_none),
/* NOP 1011 1111 0000 0000 */
/* WFE 1011 1111 0010 0000 */
/* WFI 1011 1111 0011 0000 */
DECODE_SIMULATE (0xffcf, 0xbf00, kprobe_simulate_nop),
/* Unassigned hints 1011 1111 xxxx 0000 */
DECODE_REJECT (0xff0f, 0xbf00),
DECODE_END
};
const union decode_item kprobe_decode_thumb16_table[] = {
/*
* Miscellaneous 16-bit instructions
* 1011 xxxx xxxx xxxx
*/
DECODE_TABLE (0xf000, 0xb000, t16_table_1011),
DECODE_END
};
static unsigned long __kprobes thumb_check_cc(unsigned long cpsr) static unsigned long __kprobes thumb_check_cc(unsigned long cpsr)
{ {
if (unlikely(in_it_block(cpsr))) if (unlikely(in_it_block(cpsr)))
@ -52,7 +85,7 @@ thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{ {
asi->insn_singlestep = thumb16_singlestep; asi->insn_singlestep = thumb16_singlestep;
asi->insn_check_cc = thumb_check_cc; asi->insn_check_cc = thumb_check_cc;
return INSN_REJECTED; return kprobe_decode_insn(insn, asi, kprobe_decode_thumb16_table, true);
} }
enum kprobe_insn __kprobes enum kprobe_insn __kprobes

3
arch/arm/kernel/kprobes.h
View file

@ -95,6 +95,9 @@ static inline unsigned long it_advance(unsigned long cpsr)
return cpsr; return cpsr;
} }
void __kprobes kprobe_simulate_nop(struct kprobe *p, struct pt_regs *regs);
void __kprobes kprobe_emulate_none(struct kprobe *p, struct pt_regs *regs);
/* /*
* Test if load/store instructions writeback the address register. * Test if load/store instructions writeback the address register.
* if P (bit 24) == 0 or W (bit 21) == 1 * if P (bit 24) == 0 or W (bit 21) == 1