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ARM: kprobes: Add hooks to override singlestep() 

When a probe fires we must single-step the instruction which was
replaced by a breakpoint. As the steps to do this vary between ARM and
Thumb instructions we need a way to customise single-stepping.

This is done by adding a new hook called insn_singlestep to
arch_specific_insn which is initialised by the instruction decoding
functions.

These single-step hooks must update PC and call the instruction handler.
For Thumb instructions an additional step of updating ITSTATE is needed.
We do this after calling the handler because some handlers will need to
test if they are running in an IT block.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
This commit is contained in:
Jon Medhurst 2011-06-09 12:11:27 +01:00 committed by Tixy
parent 3b26945597
commit c6a7d97d57
4 changed files with 31 additions and 9 deletions
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9
arch/arm/include/asm/kprobes.h
View File

@ -32,14 +32,15 @@ typedef u32 kprobe_opcode_t;
struct kprobe; struct kprobe;
typedef void (kprobe_insn_handler_t)(struct kprobe *, struct pt_regs *); typedef void (kprobe_insn_handler_t)(struct kprobe *, struct pt_regs *);
typedef unsigned long (kprobe_check_cc)(unsigned long); typedef unsigned long (kprobe_check_cc)(unsigned long);
typedef void (kprobe_insn_singlestep_t)(struct kprobe *, struct pt_regs *);
/* Architecture specific copy of original instruction. */ /* Architecture specific copy of original instruction. */
struct arch_specific_insn { struct arch_specific_insn {
kprobe_opcode_t *insn; kprobe_opcode_t *insn;
kprobe_insn_handler_t *insn_handler; kprobe_insn_handler_t *insn_handler;
kprobe_check_cc *insn_check_cc; kprobe_check_cc *insn_check_cc;
kprobe_insn_singlestep_t *insn_singlestep;
}; };
struct prev_kprobe { struct prev_kprobe {

7
arch/arm/kernel/kprobes-arm.c
View File

@ -1494,6 +1494,12 @@ space_cccc_11xx(kprobe_opcode_t insn, struct arch_specific_insn *asi)
return INSN_REJECTED; return INSN_REJECTED;
} }
static void __kprobes arm_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 4;
p->ainsn.insn_handler(p, regs);
}
/* Return: /* Return:
* INSN_REJECTED If instruction is one not allowed to kprobe, * INSN_REJECTED If instruction is one not allowed to kprobe,
* INSN_GOOD If instruction is supported and uses instruction slot, * INSN_GOOD If instruction is supported and uses instruction slot,
@ -1509,6 +1515,7 @@ space_cccc_11xx(kprobe_opcode_t insn, struct arch_specific_insn *asi)
enum kprobe_insn __kprobes enum kprobe_insn __kprobes
arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi) arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{ {
asi->insn_singlestep = arm_singlestep;
asi->insn_check_cc = kprobe_condition_checks[insn>>28]; asi->insn_check_cc = kprobe_condition_checks[insn>>28];
asi->insn[1] = KPROBE_RETURN_INSTRUCTION; asi->insn[1] = KPROBE_RETURN_INSTRUCTION;

16
arch/arm/kernel/kprobes-thumb.c
View File

@ -33,9 +33,24 @@ static unsigned long __kprobes thumb_check_cc(unsigned long cpsr)
return true; return true;
} }
static void __kprobes thumb16_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 2;
p->ainsn.insn_handler(p, regs);
regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}
static void __kprobes thumb32_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 4;
p->ainsn.insn_handler(p, regs);
regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}
enum kprobe_insn __kprobes enum kprobe_insn __kprobes
thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi) thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{ {
asi->insn_singlestep = thumb16_singlestep;
asi->insn_check_cc = thumb_check_cc; asi->insn_check_cc = thumb_check_cc;
return INSN_REJECTED; return INSN_REJECTED;
} }
@ -43,6 +58,7 @@ thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
enum kprobe_insn __kprobes enum kprobe_insn __kprobes
thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi) thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{ {
asi->insn_singlestep = thumb32_singlestep;
asi->insn_check_cc = thumb_check_cc; asi->insn_check_cc = thumb_check_cc;
return INSN_REJECTED; return INSN_REJECTED;
} }

8
arch/arm/kernel/kprobes.c
View File

@ -227,12 +227,10 @@ singlestep_skip(struct kprobe *p, struct pt_regs *regs)
#endif #endif
} }
static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs, static inline void __kprobes
struct kprobe_ctlblk *kcb) singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
{ {
regs->ARM_pc += 4; p->ainsn.insn_singlestep(p, regs);
if (p->ainsn.insn_check_cc(regs->ARM_cpsr))
p->ainsn.insn_handler(p, regs);
} }
/* /*