/arch/i386/kernel/kprobes.c
https://bitbucket.org/evzijst/gittest · C · 385 lines · 250 code · 36 blank · 99 comment · 44 complexity · 5d4ede5411518fed95daf136aedb8394 MD5 · raw file
- /*
- * Kernel Probes (KProbes)
- * arch/i386/kernel/kprobes.c
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- *
- * Copyright (C) IBM Corporation, 2002, 2004
- *
- * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
- * Probes initial implementation ( includes contributions from
- * Rusty Russell).
- * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
- * interface to access function arguments.
- */
- #include <linux/config.h>
- #include <linux/kprobes.h>
- #include <linux/ptrace.h>
- #include <linux/spinlock.h>
- #include <linux/preempt.h>
- #include <asm/kdebug.h>
- #include <asm/desc.h>
- /* kprobe_status settings */
- #define KPROBE_HIT_ACTIVE 0x00000001
- #define KPROBE_HIT_SS 0x00000002
- static struct kprobe *current_kprobe;
- static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
- static struct pt_regs jprobe_saved_regs;
- static long *jprobe_saved_esp;
- /* copy of the kernel stack at the probe fire time */
- static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
- void jprobe_return_end(void);
- /*
- * returns non-zero if opcode modifies the interrupt flag.
- */
- static inline int is_IF_modifier(kprobe_opcode_t opcode)
- {
- switch (opcode) {
- case 0xfa: /* cli */
- case 0xfb: /* sti */
- case 0xcf: /* iret/iretd */
- case 0x9d: /* popf/popfd */
- return 1;
- }
- return 0;
- }
- int arch_prepare_kprobe(struct kprobe *p)
- {
- return 0;
- }
- void arch_copy_kprobe(struct kprobe *p)
- {
- memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
- }
- void arch_remove_kprobe(struct kprobe *p)
- {
- }
- static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
- {
- *p->addr = p->opcode;
- regs->eip = (unsigned long)p->addr;
- }
- static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
- {
- regs->eflags |= TF_MASK;
- regs->eflags &= ~IF_MASK;
- /*single step inline if the instruction is an int3*/
- if (p->opcode == BREAKPOINT_INSTRUCTION)
- regs->eip = (unsigned long)p->addr;
- else
- regs->eip = (unsigned long)&p->ainsn.insn;
- }
- /*
- * Interrupts are disabled on entry as trap3 is an interrupt gate and they
- * remain disabled thorough out this function.
- */
- static int kprobe_handler(struct pt_regs *regs)
- {
- struct kprobe *p;
- int ret = 0;
- kprobe_opcode_t *addr = NULL;
- unsigned long *lp;
- /* We're in an interrupt, but this is clear and BUG()-safe. */
- preempt_disable();
- /* 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()) {
- /* We *are* holding lock here, so this is safe.
- Disarm the probe we just hit, and ignore it. */
- p = get_kprobe(addr);
- if (p) {
- if (kprobe_status == KPROBE_HIT_SS) {
- regs->eflags &= ~TF_MASK;
- regs->eflags |= kprobe_saved_eflags;
- unlock_kprobes();
- goto no_kprobe;
- }
- disarm_kprobe(p, regs);
- ret = 1;
- } else {
- p = current_kprobe;
- if (p->break_handler && p->break_handler(p, regs)) {
- goto ss_probe;
- }
- }
- /* If it's not ours, can't be delete race, (we hold lock). */
- goto no_kprobe;
- }
- lock_kprobes();
- p = get_kprobe(addr);
- if (!p) {
- unlock_kprobes();
- if (regs->eflags & VM_MASK) {
- /* We are in virtual-8086 mode. Return 0 */
- goto no_kprobe;
- }
- if (*addr != BREAKPOINT_INSTRUCTION) {
- /*
- * The breakpoint instruction was removed right
- * after we hit it. Another cpu has removed
- * either a probepoint or a debugger breakpoint
- * at this address. In either case, no further
- * handling of this interrupt is appropriate.
- */
- ret = 1;
- }
- /* Not one of ours: let kernel handle it */
- goto no_kprobe;
- }
- kprobe_status = KPROBE_HIT_ACTIVE;
- current_kprobe = p;
- kprobe_saved_eflags = kprobe_old_eflags
- = (regs->eflags & (TF_MASK | IF_MASK));
- if (is_IF_modifier(p->opcode))
- kprobe_saved_eflags &= ~IF_MASK;
- if (p->pre_handler && p->pre_handler(p, regs))
- /* handler has already set things up, so skip ss setup */
- return 1;
- ss_probe:
- prepare_singlestep(p, regs);
- kprobe_status = KPROBE_HIT_SS;
- return 1;
- no_kprobe:
- preempt_enable_no_resched();
- return ret;
- }
- /*
- * Called after single-stepping. p->addr is the address of the
- * instruction whose first byte has been replaced by the "int 3"
- * instruction. To avoid the SMP problems that can occur when we
- * temporarily put back the original opcode to single-step, we
- * single-stepped a copy of the instruction. The address of this
- * copy is p->ainsn.insn.
- *
- * This function prepares to return from the post-single-step
- * interrupt. We have to fix up the stack as follows:
- *
- * 0) Except in the case of absolute or indirect jump or call instructions,
- * the new eip is relative to the copied instruction. We need to make
- * it relative to the original instruction.
- *
- * 1) If the single-stepped instruction was pushfl, then the TF and IF
- * flags are set in the just-pushed eflags, and may need to be cleared.
- *
- * 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.
- */
- static void resume_execution(struct kprobe *p, struct pt_regs *regs)
- {
- 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;
- switch (p->ainsn.insn[0]) {
- case 0x9c: /* pushfl */
- *tos &= ~(TF_MASK | IF_MASK);
- *tos |= kprobe_old_eflags;
- break;
- 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;
- *tos = orig_eip + (*tos - copy_eip);
- } 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;
- }
- 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);
- }
- }
- /*
- * Interrupts are disabled on entry as trap1 is an interrupt gate and they
- * remain disabled thoroughout this function. And we hold kprobe lock.
- */
- static inline int post_kprobe_handler(struct pt_regs *regs)
- {
- if (!kprobe_running())
- return 0;
- if (current_kprobe->post_handler)
- current_kprobe->post_handler(current_kprobe, regs, 0);
- resume_execution(current_kprobe, regs);
- regs->eflags |= kprobe_saved_eflags;
- unlock_kprobes();
- preempt_enable_no_resched();
- /*
- * if somebody else is singlestepping across a probe point, eflags
- * will have TF set, in which case, continue the remaining processing
- * of do_debug, as if this is not a probe hit.
- */
- if (regs->eflags & TF_MASK)
- return 0;
- return 1;
- }
- /* Interrupts disabled, kprobe_lock held. */
- static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
- {
- if (current_kprobe->fault_handler
- && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
- return 1;
- if (kprobe_status & KPROBE_HIT_SS) {
- resume_execution(current_kprobe, regs);
- regs->eflags |= kprobe_old_eflags;
- unlock_kprobes();
- preempt_enable_no_resched();
- }
- return 0;
- }
- /*
- * Wrapper routine to for handling exceptions.
- */
- int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
- void *data)
- {
- struct die_args *args = (struct die_args *)data;
- switch (val) {
- case DIE_INT3:
- if (kprobe_handler(args->regs))
- return NOTIFY_STOP;
- break;
- case DIE_DEBUG:
- if (post_kprobe_handler(args->regs))
- return NOTIFY_STOP;
- break;
- case DIE_GPF:
- if (kprobe_running() &&
- kprobe_fault_handler(args->regs, args->trapnr))
- return NOTIFY_STOP;
- break;
- case DIE_PAGE_FAULT:
- if (kprobe_running() &&
- kprobe_fault_handler(args->regs, args->trapnr))
- return NOTIFY_STOP;
- break;
- default:
- break;
- }
- return NOTIFY_DONE;
- }
- int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
- {
- struct jprobe *jp = container_of(p, struct jprobe, kp);
- unsigned long addr;
- jprobe_saved_regs = *regs;
- jprobe_saved_esp = ®s->esp;
- addr = (unsigned long)jprobe_saved_esp;
- /*
- * TBD: As Linus pointed out, gcc assumes that the callee
- * owns the argument space and could overwrite it, e.g.
- * tailcall optimization. So, to be absolutely safe
- * we also save and restore enough stack bytes to cover
- * the argument area.
- */
- memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));
- regs->eflags &= ~IF_MASK;
- regs->eip = (unsigned long)(jp->entry);
- return 1;
- }
- void jprobe_return(void)
- {
- preempt_enable_no_resched();
- asm volatile (" xchgl %%ebx,%%esp \n"
- " int3 \n"
- " .globl jprobe_return_end \n"
- " jprobe_return_end: \n"
- " nop \n"::"b"
- (jprobe_saved_esp):"memory");
- }
- int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
- {
- u8 *addr = (u8 *) (regs->eip - 1);
- unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
- struct jprobe *jp = container_of(p, struct jprobe, kp);
- if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
- if (®s->esp != jprobe_saved_esp) {
- struct pt_regs *saved_regs =
- container_of(jprobe_saved_esp, struct pt_regs, esp);
- printk("current esp %p does not match saved esp %p\n",
- ®s->esp, jprobe_saved_esp);
- printk("Saved registers for jprobe %p\n", jp);
- show_registers(saved_regs);
- printk("Current registers\n");
- show_registers(regs);
- BUG();
- }
- *regs = jprobe_saved_regs;
- memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
- MIN_STACK_SIZE(stack_addr));
- return 1;
- }
- return 0;
- }