diff options
Diffstat (limited to 'arch/i386/kernel/kprobes.c')
| -rw-r--r-- | arch/i386/kernel/kprobes.c | 385 |
1 files changed, 385 insertions, 0 deletions
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c new file mode 100644 index 00000000000..67168165924 --- /dev/null +++ b/arch/i386/kernel/kprobes.c @@ -0,0 +1,385 @@ +/* + * 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; +} |