From 3b26945597d5eff5d428a268c9d109338fce801e Mon Sep 17 00:00:00 2001 From: Jon Medhurst Date: Thu, 16 Jun 2011 17:22:37 +0100 Subject: [PATCH] ARM: kprobes: Use conditional breakpoints for ARM probes Now we no longer trigger probes on conditional instructions when the condition is false, we can make use of conditional instructions as breakpoints in ARM code to avoid taking unnecessary exceptions. Note, we can't rely on not getting an exception when the condition check fails, as that is Implementation Defined on newer ARM architectures. We therefore still need to perform manual condition checks as well. Signed-off-by: Jon Medhurst Acked-by: Nicolas Pitre --- arch/arm/kernel/kprobes.c | 10 ++++++++-- arch/arm/kernel/kprobes.h | 2 +- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c index b6e9a1c..0003dfd 100644 --- a/arch/arm/kernel/kprobes.c +++ b/arch/arm/kernel/kprobes.c @@ -138,7 +138,13 @@ void __kprobes arch_arm_kprobe(struct kprobe *p) void __kprobes arch_arm_kprobe(struct kprobe *p) { - *p->addr = KPROBE_ARM_BREAKPOINT_INSTRUCTION; + kprobe_opcode_t insn = p->opcode; + kprobe_opcode_t brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION; + if (insn >= 0xe0000000) + brkp |= 0xe0000000; /* Unconditional instruction */ + else + brkp |= insn & 0xf0000000; /* Copy condition from insn */ + *p->addr = brkp; flush_insns(p->addr, sizeof(p->addr[0])); } @@ -625,7 +631,7 @@ static struct undef_hook kprobes_thumb32_break_hook = { #else /* !CONFIG_THUMB2_KERNEL */ static struct undef_hook kprobes_arm_break_hook = { - .instr_mask = 0xffffffff, + .instr_mask = 0x0fffffff, .instr_val = KPROBE_ARM_BREAKPOINT_INSTRUCTION, .cpsr_mask = MODE_MASK, .cpsr_val = SVC_MODE, diff --git a/arch/arm/kernel/kprobes.h b/arch/arm/kernel/kprobes.h index 5e2485c..e3803c6 100644 --- a/arch/arm/kernel/kprobes.h +++ b/arch/arm/kernel/kprobes.h @@ -21,7 +21,7 @@ * These undefined instructions must be unique and * reserved solely for kprobes' use. */ -#define KPROBE_ARM_BREAKPOINT_INSTRUCTION 0xe7f001f8 +#define KPROBE_ARM_BREAKPOINT_INSTRUCTION 0x07f001f8 #define KPROBE_THUMB16_BREAKPOINT_INSTRUCTION 0xde18 #define KPROBE_THUMB32_BREAKPOINT_INSTRUCTION 0xf7f0a018 -- 2.7.4