diff options
Diffstat (limited to 'arch/x86_64/kernel/kprobes.c')
| -rw-r--r-- | arch/x86_64/kernel/kprobes.c | 631 |
1 files changed, 631 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c new file mode 100644 index 00000000000..4f2a852299b --- /dev/null +++ b/arch/x86_64/kernel/kprobes.c @@ -0,0 +1,631 @@ +/* + * Kernel Probes (KProbes) + * arch/x86_64/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. + * 2004-Oct Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi + * <prasanna@in.ibm.com> adapted for x86_64 + * 2005-Mar Roland McGrath <roland@redhat.com> + * Fixed to handle %rip-relative addressing mode correctly. + */ + +#include <linux/config.h> +#include <linux/kprobes.h> +#include <linux/ptrace.h> +#include <linux/spinlock.h> +#include <linux/string.h> +#include <linux/slab.h> +#include <linux/preempt.h> +#include <linux/moduleloader.h> + +#include <asm/pgtable.h> +#include <asm/kdebug.h> + +static DECLARE_MUTEX(kprobe_mutex); + +/* 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_rflags, kprobe_saved_rflags; +static struct pt_regs jprobe_saved_regs; +static long *jprobe_saved_rsp; +static kprobe_opcode_t *get_insn_slot(void); +static void free_insn_slot(kprobe_opcode_t *slot); +void jprobe_return_end(void); + +/* copy of the kernel stack at the probe fire time */ +static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE]; + +/* + * returns non-zero if opcode modifies the interrupt flag. + */ +static inline int is_IF_modifier(kprobe_opcode_t *insn) +{ + switch (*insn) { + case 0xfa: /* cli */ + case 0xfb: /* sti */ + case 0xcf: /* iret/iretd */ + case 0x9d: /* popf/popfd */ + return 1; + } + + if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf) + return 1; + return 0; +} + +int arch_prepare_kprobe(struct kprobe *p) +{ + /* insn: must be on special executable page on x86_64. */ + up(&kprobe_mutex); + p->ainsn.insn = get_insn_slot(); + down(&kprobe_mutex); + if (!p->ainsn.insn) { + return -ENOMEM; + } + return 0; +} + +/* + * Determine if the instruction uses the %rip-relative addressing mode. + * If it does, return the address of the 32-bit displacement word. + * If not, return null. + */ +static inline s32 *is_riprel(u8 *insn) +{ +#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \ + (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \ + (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \ + (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \ + (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \ + << (row % 64)) + static const u64 onebyte_has_modrm[256 / 64] = { + /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ + /* ------------------------------- */ + W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */ + W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */ + W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */ + W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */ + W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */ + W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */ + W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */ + W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */ + W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */ + W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */ + W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */ + W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */ + W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */ + W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */ + W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */ + W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */ + /* ------------------------------- */ + /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ + }; + static const u64 twobyte_has_modrm[256 / 64] = { + /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ + /* ------------------------------- */ + W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */ + W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */ + W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */ + W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */ + W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */ + W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */ + W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */ + W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */ + W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */ + W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */ + W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */ + W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */ + W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */ + W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */ + W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */ + W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */ + /* ------------------------------- */ + /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ + }; +#undef W + int need_modrm; + + /* Skip legacy instruction prefixes. */ + while (1) { + switch (*insn) { + case 0x66: + case 0x67: + case 0x2e: + case 0x3e: + case 0x26: + case 0x64: + case 0x65: + case 0x36: + case 0xf0: + case 0xf3: + case 0xf2: + ++insn; + continue; + } + break; + } + + /* Skip REX instruction prefix. */ + if ((*insn & 0xf0) == 0x40) + ++insn; + + if (*insn == 0x0f) { /* Two-byte opcode. */ + ++insn; + need_modrm = test_bit(*insn, twobyte_has_modrm); + } else { /* One-byte opcode. */ + need_modrm = test_bit(*insn, onebyte_has_modrm); + } + + if (need_modrm) { + u8 modrm = *++insn; + if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */ + /* Displacement follows ModRM byte. */ + return (s32 *) ++insn; + } + } + + /* No %rip-relative addressing mode here. */ + return NULL; +} + +void arch_copy_kprobe(struct kprobe *p) +{ + s32 *ripdisp; + memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE); + ripdisp = is_riprel(p->ainsn.insn); + if (ripdisp) { + /* + * The copied instruction uses the %rip-relative + * addressing mode. Adjust the displacement for the + * difference between the original location of this + * instruction and the location of the copy that will + * actually be run. The tricky bit here is making sure + * that the sign extension happens correctly in this + * calculation, since we need a signed 32-bit result to + * be sign-extended to 64 bits when it's added to the + * %rip value and yield the same 64-bit result that the + * sign-extension of the original signed 32-bit + * displacement would have given. + */ + s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn; + BUG_ON((s64) (s32) disp != disp); /* Sanity check. */ + *ripdisp = disp; + } +} + +void arch_remove_kprobe(struct kprobe *p) +{ + up(&kprobe_mutex); + free_insn_slot(p->ainsn.insn); + down(&kprobe_mutex); +} + +static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs) +{ + *p->addr = p->opcode; + regs->rip = (unsigned long)p->addr; +} + +static 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->rip = (unsigned long)p->addr; + else + regs->rip = (unsigned long)p->ainsn.insn; +} + +/* + * Interrupts are disabled on entry as trap3 is an interrupt gate and they + * remain disabled thorough out this function. + */ +int kprobe_handler(struct pt_regs *regs) +{ + struct kprobe *p; + int ret = 0; + kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t)); + + /* We're in an interrupt, but this is clear and BUG()-safe. */ + preempt_disable(); + + /* 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_rflags; + 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 (*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_rflags = kprobe_old_rflags + = (regs->eflags & (TF_MASK | IF_MASK)); + if (is_IF_modifier(p->ainsn.insn)) + kprobe_saved_rflags &= ~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 rip 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 *)regs->rsp; + unsigned long next_rip = 0; + unsigned long copy_rip = (unsigned long)p->ainsn.insn; + unsigned long orig_rip = (unsigned long)p->addr; + kprobe_opcode_t *insn = p->ainsn.insn; + + /*skip the REX prefix*/ + if (*insn >= 0x40 && *insn <= 0x4f) + insn++; + + switch (*insn) { + case 0x9c: /* pushfl */ + *tos &= ~(TF_MASK | IF_MASK); + *tos |= kprobe_old_rflags; + break; + case 0xe8: /* call relative - Fix return addr */ + *tos = orig_rip + (*tos - copy_rip); + break; + case 0xff: + if ((*insn & 0x30) == 0x10) { + /* call absolute, indirect */ + /* Fix return addr; rip is correct. */ + next_rip = regs->rip; + *tos = orig_rip + (*tos - copy_rip); + } else if (((*insn & 0x31) == 0x20) || /* jmp near, absolute indirect */ + ((*insn & 0x31) == 0x21)) { /* jmp far, absolute indirect */ + /* rip is correct. */ + next_rip = regs->rip; + } + break; + case 0xea: /* jmp absolute -- rip is correct */ + next_rip = regs->rip; + break; + default: + break; + } + + regs->eflags &= ~TF_MASK; + if (next_rip) { + regs->rip = next_rip; + } else { + regs->rip = orig_rip + (regs->rip - copy_rip); + } +} + +/* + * Interrupts are disabled on entry as trap1 is an interrupt gate and they + * remain disabled thoroughout this function. And we hold kprobe lock. + */ +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_rflags; + + 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. */ +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_rflags; + + unlock_kprobes(); + preempt_enable_no_resched(); + } + return 0; +} + +/* + * Wrapper routine 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_rsp = (long *) regs->rsp; + addr = (unsigned long)jprobe_saved_rsp; + /* + * 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->rip = (unsigned long)(jp->entry); + return 1; +} + +void jprobe_return(void) +{ + preempt_enable_no_resched(); + asm volatile (" xchg %%rbx,%%rsp \n" + " int3 \n" + " .globl jprobe_return_end \n" + " jprobe_return_end: \n" + " nop \n"::"b" + (jprobe_saved_rsp):"memory"); +} + +int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) +{ + u8 *addr = (u8 *) (regs->rip - 1); + unsigned long stack_addr = (unsigned long)jprobe_saved_rsp; + struct jprobe *jp = container_of(p, struct jprobe, kp); + + if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) { + if ((long *)regs->rsp != jprobe_saved_rsp) { + struct pt_regs *saved_regs = + container_of(jprobe_saved_rsp, struct pt_regs, rsp); + printk("current rsp %p does not match saved rsp %p\n", + (long *)regs->rsp, jprobe_saved_rsp); + 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; +} + +/* + * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped. + * By default on x86_64, pages we get from kmalloc or vmalloc are not + * executable. Single-stepping an instruction on such a page yields an + * oops. So instead of storing the instruction copies in their respective + * kprobe objects, we allocate a page, map it executable, and store all the + * instruction copies there. (We can allocate additional pages if somebody + * inserts a huge number of probes.) Each page can hold up to INSNS_PER_PAGE + * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t) + * bytes. + */ +#define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE*sizeof(kprobe_opcode_t))) +struct kprobe_insn_page { + struct hlist_node hlist; + kprobe_opcode_t *insns; /* page of instruction slots */ + char slot_used[INSNS_PER_PAGE]; + int nused; +}; + +static struct hlist_head kprobe_insn_pages; + +/** + * get_insn_slot() - Find a slot on an executable page for an instruction. + * We allocate an executable page if there's no room on existing ones. + */ +static kprobe_opcode_t *get_insn_slot(void) +{ + struct kprobe_insn_page *kip; + struct hlist_node *pos; + + hlist_for_each(pos, &kprobe_insn_pages) { + kip = hlist_entry(pos, struct kprobe_insn_page, hlist); + if (kip->nused < INSNS_PER_PAGE) { + int i; + for (i = 0; i < INSNS_PER_PAGE; i++) { + if (!kip->slot_used[i]) { + kip->slot_used[i] = 1; + kip->nused++; + return kip->insns + (i*MAX_INSN_SIZE); + } + } + /* Surprise! No unused slots. Fix kip->nused. */ + kip->nused = INSNS_PER_PAGE; + } + } + + /* All out of space. Need to allocate a new page. Use slot 0.*/ + kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); + if (!kip) { + return NULL; + } + + /* + * For the %rip-relative displacement fixups to be doable, we + * need our instruction copy to be within +/- 2GB of any data it + * might access via %rip. That is, within 2GB of where the + * kernel image and loaded module images reside. So we allocate + * a page in the module loading area. + */ + kip->insns = module_alloc(PAGE_SIZE); + if (!kip->insns) { + kfree(kip); + return NULL; + } + INIT_HLIST_NODE(&kip->hlist); + hlist_add_head(&kip->hlist, &kprobe_insn_pages); + memset(kip->slot_used, 0, INSNS_PER_PAGE); + kip->slot_used[0] = 1; + kip->nused = 1; + return kip->insns; +} + +/** + * free_insn_slot() - Free instruction slot obtained from get_insn_slot(). + */ +static void free_insn_slot(kprobe_opcode_t *slot) +{ + struct kprobe_insn_page *kip; + struct hlist_node *pos; + + hlist_for_each(pos, &kprobe_insn_pages) { + kip = hlist_entry(pos, struct kprobe_insn_page, hlist); + if (kip->insns <= slot + && slot < kip->insns+(INSNS_PER_PAGE*MAX_INSN_SIZE)) { + int i = (slot - kip->insns) / MAX_INSN_SIZE; + kip->slot_used[i] = 0; + kip->nused--; + if (kip->nused == 0) { + /* + * Page is no longer in use. Free it unless + * it's the last one. We keep the last one + * so as not to have to set it up again the + * next time somebody inserts a probe. + */ + hlist_del(&kip->hlist); + if (hlist_empty(&kprobe_insn_pages)) { + INIT_HLIST_NODE(&kip->hlist); + hlist_add_head(&kip->hlist, + &kprobe_insn_pages); + } else { + module_free(NULL, kip->insns); + kfree(kip); + } + } + return; + } + } +} |