diff options
Diffstat (limited to 'arch/i386/kernel/kprobes.c')
-rw-r--r-- | arch/i386/kernel/kprobes.c | 257 |
1 files changed, 196 insertions, 61 deletions
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c index 694a1399763..f19768789e8 100644 --- a/arch/i386/kernel/kprobes.c +++ b/arch/i386/kernel/kprobes.c @@ -35,12 +35,56 @@ #include <asm/cacheflush.h> #include <asm/kdebug.h> #include <asm/desc.h> +#include <asm/uaccess.h> void jprobe_return_end(void); DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); +/* insert a jmp code */ +static inline void set_jmp_op(void *from, void *to) +{ + struct __arch_jmp_op { + char op; + long raddr; + } __attribute__((packed)) *jop; + jop = (struct __arch_jmp_op *)from; + jop->raddr = (long)(to) - ((long)(from) + 5); + jop->op = RELATIVEJUMP_INSTRUCTION; +} + +/* + * returns non-zero if opcodes can be boosted. + */ +static inline int can_boost(kprobe_opcode_t opcode) +{ + switch (opcode & 0xf0 ) { + case 0x70: + return 0; /* can't boost conditional jump */ + case 0x90: + /* can't boost call and pushf */ + return opcode != 0x9a && opcode != 0x9c; + case 0xc0: + /* can't boost undefined opcodes and soft-interruptions */ + return (0xc1 < opcode && opcode < 0xc6) || + (0xc7 < opcode && opcode < 0xcc) || opcode == 0xcf; + case 0xd0: + /* can boost AA* and XLAT */ + return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7); + case 0xe0: + /* can boost in/out and (may be) jmps */ + return (0xe3 < opcode && opcode != 0xe8); + case 0xf0: + /* clear and set flags can be boost */ + return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); + default: + /* currently, can't boost 2 bytes opcodes */ + return opcode != 0x0f; + } +} + + /* * returns non-zero if opcode modifies the interrupt flag. */ @@ -65,6 +109,11 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); p->opcode = *p->addr; + if (can_boost(p->opcode)) { + p->ainsn.boostable = 0; + } else { + p->ainsn.boostable = -1; + } return 0; } @@ -84,9 +133,9 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { - down(&kprobe_mutex); + mutex_lock(&kprobe_mutex); free_insn_slot(p->ainsn.insn); - up(&kprobe_mutex); + mutex_unlock(&kprobe_mutex); } static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb) @@ -155,9 +204,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; int ret = 0; - kprobe_opcode_t *addr = NULL; - unsigned long *lp; + kprobe_opcode_t *addr; struct kprobe_ctlblk *kcb; +#ifdef CONFIG_PREEMPT + unsigned pre_preempt_count = preempt_count(); +#endif /* CONFIG_PREEMPT */ + + addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t)); /* * We don't want to be preempted for the entire @@ -166,17 +219,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) preempt_disable(); kcb = get_kprobe_ctlblk(); - /* Check if the application is using LDT entry for its code segment and - * calculate the address by reading the base address from the LDT entry. - */ - if ((regs->xcs & 4) && (current->mm)) { - lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8) - + (char *) current->mm->context.ldt); - addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip - - sizeof(kprobe_opcode_t)); - } else { - addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t)); - } /* Check we're not actually recursing */ if (kprobe_running()) { p = get_kprobe(addr); @@ -252,6 +294,21 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) /* handler has already set things up, so skip ss setup */ return 1; + if (p->ainsn.boostable == 1 && +#ifdef CONFIG_PREEMPT + !(pre_preempt_count) && /* + * This enables booster when the direct + * execution path aren't preempted. + */ +#endif /* CONFIG_PREEMPT */ + !p->post_handler && !p->break_handler ) { + /* Boost up -- we can execute copied instructions directly */ + reset_current_kprobe(); + regs->eip = (unsigned long)p->ainsn.insn; + preempt_enable_no_resched(); + return 1; + } + ss_probe: prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; @@ -267,17 +324,44 @@ no_kprobe: * here. When a retprobed function returns, this probe is hit and * trampoline_probe_handler() runs, calling the kretprobe's handler. */ - void kretprobe_trampoline_holder(void) + void __kprobes kretprobe_trampoline_holder(void) { - asm volatile ( ".global kretprobe_trampoline\n" + asm volatile ( ".global kretprobe_trampoline\n" "kretprobe_trampoline: \n" - "nop\n"); - } + " pushf\n" + /* skip cs, eip, orig_eax, es, ds */ + " subl $20, %esp\n" + " pushl %eax\n" + " pushl %ebp\n" + " pushl %edi\n" + " pushl %esi\n" + " pushl %edx\n" + " pushl %ecx\n" + " pushl %ebx\n" + " movl %esp, %eax\n" + " call trampoline_handler\n" + /* move eflags to cs */ + " movl 48(%esp), %edx\n" + " movl %edx, 44(%esp)\n" + /* save true return address on eflags */ + " movl %eax, 48(%esp)\n" + " popl %ebx\n" + " popl %ecx\n" + " popl %edx\n" + " popl %esi\n" + " popl %edi\n" + " popl %ebp\n" + " popl %eax\n" + /* skip eip, orig_eax, es, ds */ + " addl $16, %esp\n" + " popf\n" + " ret\n"); +} /* - * Called when we hit the probe point at kretprobe_trampoline + * Called from kretprobe_trampoline */ -int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) +fastcall void *__kprobes trampoline_handler(struct pt_regs *regs) { struct kretprobe_instance *ri = NULL; struct hlist_head *head; @@ -306,8 +390,11 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) /* another task is sharing our hash bucket */ continue; - if (ri->rp && ri->rp->handler) + if (ri->rp && ri->rp->handler){ + __get_cpu_var(current_kprobe) = &ri->rp->kp; ri->rp->handler(ri, regs); + __get_cpu_var(current_kprobe) = NULL; + } orig_ret_address = (unsigned long)ri->ret_addr; recycle_rp_inst(ri); @@ -322,18 +409,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) } BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); - regs->eip = orig_ret_address; - reset_current_kprobe(); spin_unlock_irqrestore(&kretprobe_lock, flags); - preempt_enable_no_resched(); - /* - * By returning a non-zero value, we are telling - * kprobe_handler() that we don't want the post_handler - * to run (and have re-enabled preemption) - */ - return 1; + return (void*)orig_ret_address; } /* @@ -357,15 +436,17 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) * 2) If the single-stepped instruction was a call, the return address * that is atop the stack is the address following the copied instruction. * We need to make it the address following the original instruction. + * + * This function also checks instruction size for preparing direct execution. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { unsigned long *tos = (unsigned long *)®s->esp; - unsigned long next_eip = 0; unsigned long copy_eip = (unsigned long)p->ainsn.insn; unsigned long orig_eip = (unsigned long)p->addr; + regs->eflags &= ~TF_MASK; switch (p->ainsn.insn[0]) { case 0x9c: /* pushfl */ *tos &= ~(TF_MASK | IF_MASK); @@ -375,37 +456,51 @@ static void __kprobes resume_execution(struct kprobe *p, case 0xcb: case 0xc2: case 0xca: - regs->eflags &= ~TF_MASK; - /* eip is already adjusted, no more changes required*/ - return; + case 0xea: /* jmp absolute -- eip is correct */ + /* eip is already adjusted, no more changes required */ + p->ainsn.boostable = 1; + goto no_change; case 0xe8: /* call relative - Fix return addr */ *tos = orig_eip + (*tos - copy_eip); break; case 0xff: if ((p->ainsn.insn[1] & 0x30) == 0x10) { /* call absolute, indirect */ - /* Fix return addr; eip is correct. */ - next_eip = regs->eip; + /* + * Fix return addr; eip is correct. + * But this is not boostable + */ *tos = orig_eip + (*tos - copy_eip); + goto no_change; } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */ ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */ - /* eip is correct. */ - next_eip = regs->eip; + /* eip is correct. And this is boostable */ + p->ainsn.boostable = 1; + goto no_change; } - break; - case 0xea: /* jmp absolute -- eip is correct */ - next_eip = regs->eip; - break; default: break; } - regs->eflags &= ~TF_MASK; - if (next_eip) { - regs->eip = next_eip; - } else { - regs->eip = orig_eip + (regs->eip - copy_eip); + if (p->ainsn.boostable == 0) { + if ((regs->eip > copy_eip) && + (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) { + /* + * These instructions can be executed directly if it + * jumps back to correct address. + */ + set_jmp_op((void *)regs->eip, + (void *)orig_eip + (regs->eip - copy_eip)); + p->ainsn.boostable = 1; + } else { + p->ainsn.boostable = -1; + } } + + regs->eip = orig_eip + (regs->eip - copy_eip); + +no_change: + return; } /* @@ -453,15 +548,57 @@ static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - if (kcb->kprobe_status & KPROBE_HIT_SS) { - resume_execution(cur, regs, kcb); + switch(kcb->kprobe_status) { + case KPROBE_HIT_SS: + case KPROBE_REENTER: + /* + * We are here because the instruction being single + * stepped caused a page fault. We reset the current + * kprobe and the eip points back to the probe address + * and allow the page fault handler to continue as a + * normal page fault. + */ + regs->eip = (unsigned long)cur->addr; regs->eflags |= kcb->kprobe_old_eflags; - - reset_current_kprobe(); + if (kcb->kprobe_status == KPROBE_REENTER) + restore_previous_kprobe(kcb); + else + reset_current_kprobe(); preempt_enable_no_resched(); + break; + case KPROBE_HIT_ACTIVE: + case KPROBE_HIT_SSDONE: + /* + * We increment the nmissed count for accounting, + * we can also use npre/npostfault count for accouting + * these specific fault cases. + */ + kprobes_inc_nmissed_count(cur); + + /* + * We come here because instructions in the pre/post + * handler caused the page_fault, this could happen + * if handler tries to access user space by + * copy_from_user(), get_user() etc. Let the + * user-specified handler try to fix it first. + */ + if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) + return 1; + + /* + * In case the user-specified fault handler returned + * zero, try to fix up. + */ + if (fixup_exception(regs)) + return 1; + + /* + * fixup_exception() could not handle it, + * Let do_page_fault() fix it. + */ + break; + default: + break; } return 0; } @@ -475,6 +612,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, struct die_args *args = (struct die_args *)data; int ret = NOTIFY_DONE; + if (args->regs && user_mode(args->regs)) + return ret; + switch (val) { case DIE_INT3: if (kprobe_handler(args->regs)) @@ -564,12 +704,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) return 0; } -static struct kprobe trampoline_p = { - .addr = (kprobe_opcode_t *) &kretprobe_trampoline, - .pre_handler = trampoline_probe_handler -}; - int __init arch_init_kprobes(void) { - return register_kprobe(&trampoline_p); + return 0; } |