diff options
Diffstat (limited to 'arch/arm/probes/kprobes/opt-arm.c')
| -rw-r--r-- | arch/arm/probes/kprobes/opt-arm.c | 52 |
1 files changed, 50 insertions, 2 deletions
diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c index 13d5232118df..bcdecc25461b 100644 --- a/arch/arm/probes/kprobes/opt-arm.c +++ b/arch/arm/probes/kprobes/opt-arm.c @@ -32,6 +32,14 @@ #include "core.h" /* + * See register_usage_flags. If the probed instruction doesn't use PC, + * we can copy it into template and have it executed directly without + * simulation or emulation. + */ +#define ARM_REG_PC 15 +#define can_kprobe_direct_exec(m) (!test_bit(ARM_REG_PC, &(m))) + +/* * NOTE: the first sub and add instruction will be modified according * to the stack cost of the instruction. */ @@ -71,7 +79,15 @@ asm ( " orrne r2, #1\n" " strne r2, [sp, #60] @ set bit0 of PC for thumb\n" " msr cpsr_cxsf, r1\n" + ".global optprobe_template_restore_begin\n" + "optprobe_template_restore_begin:\n" " ldmia sp, {r0 - r15}\n" + ".global optprobe_template_restore_orig_insn\n" + "optprobe_template_restore_orig_insn:\n" + " nop\n" + ".global optprobe_template_restore_end\n" + "optprobe_template_restore_end:\n" + " nop\n" ".global optprobe_template_val\n" "optprobe_template_val:\n" "1: .long 0\n" @@ -91,6 +107,12 @@ asm ( ((unsigned long *)&optprobe_template_add_sp - (unsigned long *)&optprobe_template_entry) #define TMPL_SUB_SP \ ((unsigned long *)&optprobe_template_sub_sp - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_BEGIN \ + ((unsigned long *)&optprobe_template_restore_begin - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_ORIGN_INSN \ + ((unsigned long *)&optprobe_template_restore_orig_insn - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_END \ + ((unsigned long *)&optprobe_template_restore_end - (unsigned long *)&optprobe_template_entry) /* * ARM can always optimize an instruction when using ARM ISA, except @@ -160,8 +182,12 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) __this_cpu_write(current_kprobe, NULL); } - /* In each case, we must singlestep the replaced instruction. */ - op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); + /* + * We singlestep the replaced instruction only when it can't be + * executed directly during restore. + */ + if (!p->ainsn.kprobe_direct_exec) + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); local_irq_restore(flags); } @@ -243,6 +269,28 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *or val = (unsigned long)optimized_callback; code[TMPL_CALL_IDX] = val; + /* If possible, copy insn and have it executed during restore */ + orig->ainsn.kprobe_direct_exec = false; + if (can_kprobe_direct_exec(orig->ainsn.register_usage_flags)) { + kprobe_opcode_t final_branch = arm_gen_branch( + (unsigned long)(&code[TMPL_RESTORE_END]), + (unsigned long)(op->kp.addr) + 4); + if (final_branch != 0) { + /* + * Replace original 'ldmia sp, {r0 - r15}' with + * 'ldmia {r0 - r14}', restore all registers except pc. + */ + code[TMPL_RESTORE_BEGIN] = __opcode_to_mem_arm(0xe89d7fff); + + /* The original probed instruction */ + code[TMPL_RESTORE_ORIGN_INSN] = __opcode_to_mem_arm(orig->opcode); + + /* Jump back to next instruction */ + code[TMPL_RESTORE_END] = __opcode_to_mem_arm(final_branch); + orig->ainsn.kprobe_direct_exec = true; + } + } + flush_icache_range((unsigned long)code, (unsigned long)(&code[TMPL_END_IDX])); |