diff options
Diffstat (limited to 'arch/x86/kernel/kprobes_64.c')
| -rw-r--r-- | arch/x86/kernel/kprobes_64.c | 749 |
1 files changed, 749 insertions, 0 deletions
diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c new file mode 100644 index 00000000000..a30e004682e --- /dev/null +++ b/arch/x86/kernel/kprobes_64.c @@ -0,0 +1,749 @@ +/* + * 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. + * 2005-May Rusty Lynch <rusty.lynch@intel.com> + * Added function return probes functionality + */ + +#include <linux/kprobes.h> +#include <linux/ptrace.h> +#include <linux/string.h> +#include <linux/slab.h> +#include <linux/preempt.h> +#include <linux/module.h> +#include <linux/kdebug.h> + +#include <asm/pgtable.h> +#include <asm/uaccess.h> +#include <asm/alternative.h> + +void jprobe_return_end(void); +static void __kprobes arch_copy_kprobe(struct kprobe *p); + +DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); + +/* + * returns non-zero if opcode modifies the interrupt flag. + */ +static __always_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 __kprobes arch_prepare_kprobe(struct kprobe *p) +{ + /* insn: must be on special executable page on x86_64. */ + p->ainsn.insn = get_insn_slot(); + if (!p->ainsn.insn) { + return -ENOMEM; + } + arch_copy_kprobe(p); + 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 s32 __kprobes *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; +} + +static void __kprobes 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; + } + p->opcode = *p->addr; +} + +void __kprobes arch_arm_kprobe(struct kprobe *p) +{ + text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1); +} + +void __kprobes arch_disarm_kprobe(struct kprobe *p) +{ + text_poke(p->addr, &p->opcode, 1); +} + +void __kprobes arch_remove_kprobe(struct kprobe *p) +{ + mutex_lock(&kprobe_mutex); + free_insn_slot(p->ainsn.insn, 0); + mutex_unlock(&kprobe_mutex); +} + +static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + kcb->prev_kprobe.kp = kprobe_running(); + kcb->prev_kprobe.status = kcb->kprobe_status; + kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags; + kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags; +} + +static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; + kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags; + kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags; +} + +static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + __get_cpu_var(current_kprobe) = p; + kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags + = (regs->eflags & (TF_MASK | IF_MASK)); + if (is_IF_modifier(p->ainsn.insn)) + kcb->kprobe_saved_rflags &= ~IF_MASK; +} + +static void __kprobes 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; +} + +/* Called with kretprobe_lock held */ +void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, + struct pt_regs *regs) +{ + unsigned long *sara = (unsigned long *)regs->rsp; + + ri->ret_addr = (kprobe_opcode_t *) *sara; + /* Replace the return addr with trampoline addr */ + *sara = (unsigned long) &kretprobe_trampoline; +} + +int __kprobes 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)); + struct kprobe_ctlblk *kcb; + + /* + * We don't want to be preempted for the entire + * duration of kprobe processing + */ + preempt_disable(); + kcb = get_kprobe_ctlblk(); + + /* Check we're not actually recursing */ + if (kprobe_running()) { + p = get_kprobe(addr); + if (p) { + if (kcb->kprobe_status == KPROBE_HIT_SS && + *p->ainsn.insn == BREAKPOINT_INSTRUCTION) { + regs->eflags &= ~TF_MASK; + regs->eflags |= kcb->kprobe_saved_rflags; + goto no_kprobe; + } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) { + /* TODO: Provide re-entrancy from + * post_kprobes_handler() and avoid exception + * stack corruption while single-stepping on + * the instruction of the new probe. + */ + arch_disarm_kprobe(p); + regs->rip = (unsigned long)p->addr; + reset_current_kprobe(); + ret = 1; + } else { + /* We have reentered the kprobe_handler(), since + * another probe was hit while within the + * handler. We here save the original kprobe + * variables and just single step on instruction + * of the new probe without calling any user + * handlers. + */ + save_previous_kprobe(kcb); + set_current_kprobe(p, regs, kcb); + kprobes_inc_nmissed_count(p); + prepare_singlestep(p, regs); + kcb->kprobe_status = KPROBE_REENTER; + return 1; + } + } else { + if (*addr != BREAKPOINT_INSTRUCTION) { + /* The breakpoint instruction was removed by + * another cpu right after we hit, no further + * handling of this interrupt is appropriate + */ + regs->rip = (unsigned long)addr; + ret = 1; + goto no_kprobe; + } + p = __get_cpu_var(current_kprobe); + if (p->break_handler && p->break_handler(p, regs)) { + goto ss_probe; + } + } + goto no_kprobe; + } + + p = get_kprobe(addr); + if (!p) { + 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. + * Back up over the (now missing) int3 and run + * the original instruction. + */ + regs->rip = (unsigned long)addr; + ret = 1; + } + /* Not one of ours: let kernel handle it */ + goto no_kprobe; + } + + set_current_kprobe(p, regs, kcb); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + + 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); + kcb->kprobe_status = KPROBE_HIT_SS; + return 1; + +no_kprobe: + preempt_enable_no_resched(); + return ret; +} + +/* + * For function-return probes, init_kprobes() establishes a probepoint + * 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) + { + asm volatile ( ".global kretprobe_trampoline\n" + "kretprobe_trampoline: \n" + "nop\n"); + } + +/* + * Called when we hit the probe point at kretprobe_trampoline + */ +int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct kretprobe_instance *ri = NULL; + struct hlist_head *head, empty_rp; + struct hlist_node *node, *tmp; + unsigned long flags, orig_ret_address = 0; + unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; + + INIT_HLIST_HEAD(&empty_rp); + spin_lock_irqsave(&kretprobe_lock, flags); + head = kretprobe_inst_table_head(current); + + /* + * It is possible to have multiple instances associated with a given + * task either because an multiple functions in the call path + * have a return probe installed on them, and/or more then one return + * return probe was registered for a target function. + * + * We can handle this because: + * - instances are always inserted at the head of the list + * - when multiple return probes are registered for the same + * function, the first instance's ret_addr will point to the + * real return address, and all the rest will point to + * kretprobe_trampoline + */ + hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { + if (ri->task != current) + /* another task is sharing our hash bucket */ + continue; + + if (ri->rp && ri->rp->handler) + ri->rp->handler(ri, regs); + + orig_ret_address = (unsigned long)ri->ret_addr; + recycle_rp_inst(ri, &empty_rp); + + if (orig_ret_address != trampoline_address) + /* + * This is the real return address. Any other + * instances associated with this task are for + * other calls deeper on the call stack + */ + break; + } + + kretprobe_assert(ri, orig_ret_address, trampoline_address); + regs->rip = orig_ret_address; + + reset_current_kprobe(); + spin_unlock_irqrestore(&kretprobe_lock, flags); + preempt_enable_no_resched(); + + hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { + hlist_del(&ri->hlist); + kfree(ri); + } + /* + * 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; +} + +/* + * 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 __kprobes resume_execution(struct kprobe *p, + struct pt_regs *regs, struct kprobe_ctlblk *kcb) +{ + 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 |= kcb->kprobe_old_rflags; + break; + case 0xc3: /* ret/lret */ + case 0xcb: + case 0xc2: + case 0xca: + regs->eflags &= ~TF_MASK; + /* rip is already adjusted, no more changes required*/ + return; + case 0xe8: /* call relative - Fix return addr */ + *tos = orig_rip + (*tos - copy_rip); + break; + case 0xff: + if ((insn[1] & 0x30) == 0x10) { + /* call absolute, indirect */ + /* Fix return addr; rip is correct. */ + next_rip = regs->rip; + *tos = orig_rip + (*tos - copy_rip); + } else if (((insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */ + ((insn[1] & 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); + } +} + +int __kprobes post_kprobe_handler(struct pt_regs *regs) +{ + struct kprobe *cur = kprobe_running(); + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + if (!cur) + return 0; + + if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + cur->post_handler(cur, regs, 0); + } + + resume_execution(cur, regs, kcb); + regs->eflags |= kcb->kprobe_saved_rflags; + + /* Restore the original saved kprobes variables and continue. */ + if (kcb->kprobe_status == KPROBE_REENTER) { + restore_previous_kprobe(kcb); + goto out; + } + reset_current_kprobe(); +out: + 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; +} + +int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) +{ + struct kprobe *cur = kprobe_running(); + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + const struct exception_table_entry *fixup; + + 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 rip points back to the probe address + * and allow the page fault handler to continue as a + * normal page fault. + */ + regs->rip = (unsigned long)cur->addr; + regs->eflags |= kcb->kprobe_old_rflags; + 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. + */ + fixup = search_exception_tables(regs->rip); + if (fixup) { + regs->rip = fixup->fixup; + return 1; + } + + /* + * fixup() could not handle it, + * Let do_page_fault() fix it. + */ + break; + default: + break; + } + return 0; +} + +/* + * Wrapper routine for handling exceptions. + */ +int __kprobes kprobe_exceptions_notify(struct notifier_block *self, + unsigned long val, void *data) +{ + 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)) + ret = NOTIFY_STOP; + break; + case DIE_DEBUG: + if (post_kprobe_handler(args->regs)) + ret = NOTIFY_STOP; + break; + case DIE_GPF: + case DIE_PAGE_FAULT: + /* kprobe_running() needs smp_processor_id() */ + preempt_disable(); + if (kprobe_running() && + kprobe_fault_handler(args->regs, args->trapnr)) + ret = NOTIFY_STOP; + preempt_enable(); + break; + default: + break; + } + return ret; +} + +int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct jprobe *jp = container_of(p, struct jprobe, kp); + unsigned long addr; + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + kcb->jprobe_saved_regs = *regs; + kcb->jprobe_saved_rsp = (long *) regs->rsp; + addr = (unsigned long)(kcb->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(kcb->jprobes_stack, (kprobe_opcode_t *)addr, + MIN_STACK_SIZE(addr)); + regs->eflags &= ~IF_MASK; + regs->rip = (unsigned long)(jp->entry); + return 1; +} + +void __kprobes jprobe_return(void) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + asm volatile (" xchg %%rbx,%%rsp \n" + " int3 \n" + " .globl jprobe_return_end \n" + " jprobe_return_end: \n" + " nop \n"::"b" + (kcb->jprobe_saved_rsp):"memory"); +} + +int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + u8 *addr = (u8 *) (regs->rip - 1); + unsigned long stack_addr = (unsigned long)(kcb->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 != kcb->jprobe_saved_rsp) { + struct pt_regs *saved_regs = + container_of(kcb->jprobe_saved_rsp, + struct pt_regs, rsp); + printk("current rsp %p does not match saved rsp %p\n", + (long *)regs->rsp, kcb->jprobe_saved_rsp); + printk("Saved registers for jprobe %p\n", jp); + show_registers(saved_regs); + printk("Current registers\n"); + show_registers(regs); + BUG(); + } + *regs = kcb->jprobe_saved_regs; + memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack, + MIN_STACK_SIZE(stack_addr)); + preempt_enable_no_resched(); + return 1; + } + 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); +} + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) + return 1; + + return 0; +} |