/* * Kernel Probes (KProbes) * arch/ia64/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 * Copyright (C) Intel Corporation, 2005 * * 2005-Apr Rusty Lynch and Anil S Keshavamurthy * adapted from i386 */ #include #include #include #include #include #include #include #include #include #include extern void jprobe_inst_return(void); DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); enum instruction_type {A, I, M, F, B, L, X, u}; static enum instruction_type bundle_encoding[32][3] = { { M, I, I }, /* 00 */ { M, I, I }, /* 01 */ { M, I, I }, /* 02 */ { M, I, I }, /* 03 */ { M, L, X }, /* 04 */ { M, L, X }, /* 05 */ { u, u, u }, /* 06 */ { u, u, u }, /* 07 */ { M, M, I }, /* 08 */ { M, M, I }, /* 09 */ { M, M, I }, /* 0A */ { M, M, I }, /* 0B */ { M, F, I }, /* 0C */ { M, F, I }, /* 0D */ { M, M, F }, /* 0E */ { M, M, F }, /* 0F */ { M, I, B }, /* 10 */ { M, I, B }, /* 11 */ { M, B, B }, /* 12 */ { M, B, B }, /* 13 */ { u, u, u }, /* 14 */ { u, u, u }, /* 15 */ { B, B, B }, /* 16 */ { B, B, B }, /* 17 */ { M, M, B }, /* 18 */ { M, M, B }, /* 19 */ { u, u, u }, /* 1A */ { u, u, u }, /* 1B */ { M, F, B }, /* 1C */ { M, F, B }, /* 1D */ { u, u, u }, /* 1E */ { u, u, u }, /* 1F */ }; /* * In this function we check to see if the instruction * is IP relative instruction and update the kprobe * inst flag accordingly */ static void __kprobes update_kprobe_inst_flag(uint template, uint slot, uint major_opcode, unsigned long kprobe_inst, struct kprobe *p) { p->ainsn.inst_flag = 0; p->ainsn.target_br_reg = 0; /* Check for Break instruction * Bits 37:40 Major opcode to be zero * Bits 27:32 X6 to be zero * Bits 32:35 X3 to be zero */ if ((!major_opcode) && (!((kprobe_inst >> 27) & 0x1FF)) ) { /* is a break instruction */ p->ainsn.inst_flag |= INST_FLAG_BREAK_INST; return; } if (bundle_encoding[template][slot] == B) { switch (major_opcode) { case INDIRECT_CALL_OPCODE: p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG; p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7); break; case IP_RELATIVE_PREDICT_OPCODE: case IP_RELATIVE_BRANCH_OPCODE: p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR; break; case IP_RELATIVE_CALL_OPCODE: p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR; p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG; p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7); break; } } else if (bundle_encoding[template][slot] == X) { switch (major_opcode) { case LONG_CALL_OPCODE: p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG; p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7); break; } } return; } /* * In this function we check to see if the instruction * on which we are inserting kprobe is supported. * Returns 0 if supported * Returns -EINVAL if unsupported */ static int __kprobes unsupported_inst(uint template, uint slot, uint major_opcode, unsigned long kprobe_inst, struct kprobe *p) { unsigned long addr = (unsigned long)p->addr; if (bundle_encoding[template][slot] == I) { switch (major_opcode) { case 0x0: //I_UNIT_MISC_OPCODE: /* * Check for Integer speculation instruction * - Bit 33-35 to be equal to 0x1 */ if (((kprobe_inst >> 33) & 0x7) == 1) { printk(KERN_WARNING "Kprobes on speculation inst at <0x%lx> not supported\n", addr); return -EINVAL; } /* * IP relative mov instruction * - Bit 27-35 to be equal to 0x30 */ if (((kprobe_inst >> 27) & 0x1FF) == 0x30) { printk(KERN_WARNING "Kprobes on \"mov r1=ip\" at <0x%lx> not supported\n", addr); return -EINVAL; } } } return 0; } /* * In this function we check to see if the instruction * (qp) cmpx.crel.ctype p1,p2=r2,r3 * on which we are inserting kprobe is cmp instruction * with ctype as unc. */ static uint __kprobes is_cmp_ctype_unc_inst(uint template, uint slot, uint major_opcode, unsigned long kprobe_inst) { cmp_inst_t cmp_inst; uint ctype_unc = 0; if (!((bundle_encoding[template][slot] == I) || (bundle_encoding[template][slot] == M))) goto out; if (!((major_opcode == 0xC) || (major_opcode == 0xD) || (major_opcode == 0xE))) goto out; cmp_inst.l = kprobe_inst; if ((cmp_inst.f.x2 == 0) || (cmp_inst.f.x2 == 1)) { /* Integere compare - Register Register (A6 type)*/ if ((cmp_inst.f.tb == 0) && (cmp_inst.f.ta == 0) &&(cmp_inst.f.c == 1)) ctype_unc = 1; } else if ((cmp_inst.f.x2 == 2)||(cmp_inst.f.x2 == 3)) { /* Integere compare - Immediate Register (A8 type)*/ if ((cmp_inst.f.ta == 0) &&(cmp_inst.f.c == 1)) ctype_unc = 1; } out: return ctype_unc; } /* * In this function we override the bundle with * the break instruction at the given slot. */ static void __kprobes prepare_break_inst(uint template, uint slot, uint major_opcode, unsigned long kprobe_inst, struct kprobe *p) { unsigned long break_inst = BREAK_INST; bundle_t *bundle = &p->ainsn.insn.bundle; /* * Copy the original kprobe_inst qualifying predicate(qp) * to the break instruction iff !is_cmp_ctype_unc_inst * because for cmp instruction with ctype equal to unc, * which is a special instruction always needs to be * executed regradless of qp */ if (!is_cmp_ctype_unc_inst(template, slot, major_opcode, kprobe_inst)) break_inst |= (0x3f & kprobe_inst); switch (slot) { case 0: bundle->quad0.slot0 = break_inst; break; case 1: bundle->quad0.slot1_p0 = break_inst; bundle->quad1.slot1_p1 = break_inst >> (64-46); break; case 2: bundle->quad1.slot2 = break_inst; break; } /* * Update the instruction flag, so that we can * emulate the instruction properly after we * single step on original instruction */ update_kprobe_inst_flag(template, slot, major_opcode, kprobe_inst, p); } static inline void get_kprobe_inst(bundle_t *bundle, uint slot, unsigned long *kprobe_inst, uint *major_opcode) { unsigned long kprobe_inst_p0, kprobe_inst_p1; unsigned int template; template = bundle->quad0.template; switch (slot) { case 0: *major_opcode = (bundle->quad0.slot0 >> SLOT0_OPCODE_SHIFT); *kprobe_inst = bundle->quad0.slot0; break; case 1: *major_opcode = (bundle->quad1.slot1_p1 >> SLOT1_p1_OPCODE_SHIFT); kprobe_inst_p0 = bundle->quad0.slot1_p0; kprobe_inst_p1 = bundle->quad1.slot1_p1; *kprobe_inst = kprobe_inst_p0 | (kprobe_inst_p1 << (64-46)); break; case 2: *major_opcode = (bundle->quad1.slot2 >> SLOT2_OPCODE_SHIFT); *kprobe_inst = bundle->quad1.slot2; break; } } /* Returns non-zero if the addr is in the Interrupt Vector Table */ static inline int in_ivt_functions(unsigned long addr) { return (addr >= (unsigned long)__start_ivt_text && addr < (unsigned long)__end_ivt_text); } static int __kprobes valid_kprobe_addr(int template, int slot, unsigned long addr) { if ((slot > 2) || ((bundle_encoding[template][1] == L) && slot > 1)) { printk(KERN_WARNING "Attempting to insert unaligned kprobe " "at 0x%lx\n", addr); return -EINVAL; } if (in_ivt_functions(addr)) { printk(KERN_WARNING "Kprobes can't be inserted inside " "IVT functions at 0x%lx\n", addr); return -EINVAL; } if (slot == 1 && bundle_encoding[template][1] != L) { printk(KERN_WARNING "Inserting kprobes on slot #1 " "is not supported\n"); return -EINVAL; } return 0; } static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; } static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; kcb->kprobe_status = kcb->prev_kprobe.status; } static inline void set_current_kprobe(struct kprobe *p, struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = p; } static void kretprobe_trampoline(void) { } /* * At this point the target function has been tricked into * returning into our trampoline. Lookup the associated instance * and then: * - call the handler function * - cleanup by marking the instance as unused * - long jump back to the original return address */ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) { struct kretprobe_instance *ri = NULL; struct hlist_head *head; struct hlist_node *node, *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = ((struct fnptr *)kretprobe_trampoline)->ip; 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); 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; } BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); regs->cr_iip = 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; } /* Called with kretprobe_lock held */ void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs) { struct kretprobe_instance *ri; if ((ri = get_free_rp_inst(rp)) != NULL) { ri->rp = rp; ri->task = current; ri->ret_addr = (kprobe_opcode_t *)regs->b0; /* Replace the return addr with trampoline addr */ regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip; add_rp_inst(ri); } else { rp->nmissed++; } } int __kprobes arch_prepare_kprobe(struct kprobe *p) { unsigned long addr = (unsigned long) p->addr; unsigned long *kprobe_addr = (unsigned long *)(addr & ~0xFULL); unsigned long kprobe_inst=0; unsigned int slot = addr & 0xf, template, major_opcode = 0; bundle_t *bundle = &p->ainsn.insn.bundle; memcpy(&p->opcode.bundle, kprobe_addr, sizeof(bundle_t)); memcpy(&p->ainsn.insn.bundle, kprobe_addr, sizeof(bundle_t)); template = bundle->quad0.template; if(valid_kprobe_addr(template, slot, addr)) return -EINVAL; /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */ if (slot == 1 && bundle_encoding[template][1] == L) slot++; /* Get kprobe_inst and major_opcode from the bundle */ get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode); if (unsupported_inst(template, slot, major_opcode, kprobe_inst, p)) return -EINVAL; prepare_break_inst(template, slot, major_opcode, kprobe_inst, p); return 0; } void __kprobes arch_arm_kprobe(struct kprobe *p) { unsigned long addr = (unsigned long)p->addr; unsigned long arm_addr = addr & ~0xFULL; memcpy((char *)arm_addr, &p->ainsn.insn.bundle, sizeof(bundle_t)); flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t)); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { unsigned long addr = (unsigned long)p->addr; unsigned long arm_addr = addr & ~0xFULL; /* p->opcode contains the original unaltered bundle */ memcpy((char *) arm_addr, (char *) &p->opcode.bundle, sizeof(bundle_t)); flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t)); } /* * We are resuming execution after a single step fault, so the pt_regs * structure reflects the register state after we executed the instruction * located in the kprobe (p->ainsn.insn.bundle). We still need to adjust * the ip to point back to the original stack address. To set the IP address * to original stack address, handle the case where we need to fixup the * relative IP address and/or fixup branch register. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs) { unsigned long bundle_addr = ((unsigned long) (&p->opcode.bundle)) & ~0xFULL; unsigned long resume_addr = (unsigned long)p->addr & ~0xFULL; unsigned long template; int slot = ((unsigned long)p->addr & 0xf); template = p->opcode.bundle.quad0.template; if (slot == 1 && bundle_encoding[template][1] == L) slot = 2; if (p->ainsn.inst_flag) { if (p->ainsn.inst_flag & INST_FLAG_FIX_RELATIVE_IP_ADDR) { /* Fix relative IP address */ regs->cr_iip = (regs->cr_iip - bundle_addr) + resume_addr; } if (p->ainsn.inst_flag & INST_FLAG_FIX_BRANCH_REG) { /* * Fix target branch register, software convention is * to use either b0 or b6 or b7, so just checking * only those registers */ switch (p->ainsn.target_br_reg) { case 0: if ((regs->b0 == bundle_addr) || (regs->b0 == bundle_addr + 0x10)) { regs->b0 = (regs->b0 - bundle_addr) + resume_addr; } break; case 6: if ((regs->b6 == bundle_addr) || (regs->b6 == bundle_addr + 0x10)) { regs->b6 = (regs->b6 - bundle_addr) + resume_addr; } break; case 7: if ((regs->b7 == bundle_addr) || (regs->b7 == bundle_addr + 0x10)) { regs->b7 = (regs->b7 - bundle_addr) + resume_addr; } break; } /* end switch */ } goto turn_ss_off; } if (slot == 2) { if (regs->cr_iip == bundle_addr + 0x10) { regs->cr_iip = resume_addr + 0x10; } } else { if (regs->cr_iip == bundle_addr) { regs->cr_iip = resume_addr; } } turn_ss_off: /* Turn off Single Step bit */ ia64_psr(regs)->ss = 0; } static void __kprobes prepare_ss(struct kprobe *p, struct pt_regs *regs) { unsigned long bundle_addr = (unsigned long) &p->opcode.bundle; unsigned long slot = (unsigned long)p->addr & 0xf; /* single step inline if break instruction */ if (p->ainsn.inst_flag == INST_FLAG_BREAK_INST) regs->cr_iip = (unsigned long)p->addr & ~0xFULL; else regs->cr_iip = bundle_addr & ~0xFULL; if (slot > 2) slot = 0; ia64_psr(regs)->ri = slot; /* turn on single stepping */ ia64_psr(regs)->ss = 1; } static int __kprobes is_ia64_break_inst(struct pt_regs *regs) { unsigned int slot = ia64_psr(regs)->ri; unsigned int template, major_opcode; unsigned long kprobe_inst; unsigned long *kprobe_addr = (unsigned long *)regs->cr_iip; bundle_t bundle; memcpy(&bundle, kprobe_addr, sizeof(bundle_t)); template = bundle.quad0.template; /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */ if (slot == 1 && bundle_encoding[template][1] == L) slot++; /* Get Kprobe probe instruction at given slot*/ get_kprobe_inst(&bundle, slot, &kprobe_inst, &major_opcode); /* For break instruction, * Bits 37:40 Major opcode to be zero * Bits 27:32 X6 to be zero * Bits 32:35 X3 to be zero */ if (major_opcode || ((kprobe_inst >> 27) & 0x1FF) ) { /* Not a break instruction */ return 0; } /* Is a break instruction */ return 1; } static int __kprobes pre_kprobes_handler(struct die_args *args) { struct kprobe *p; int ret = 0; struct pt_regs *regs = args->regs; kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs); struct kprobe_ctlblk *kcb; /* * We don't want to be preempted for the entire * duration of kprobe processing */ preempt_disable(); kcb = get_kprobe_ctlblk(); /* Handle recursion cases */ if (kprobe_running()) { p = get_kprobe(addr); if (p) { if ((kcb->kprobe_status == KPROBE_HIT_SS) && (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) { ia64_psr(regs)->ss = 0; goto no_kprobe; } /* We have reentered the pre_kprobe_handler(), since * another probe was hit while within the handler. * We here save the original kprobes variables and * just single step on the instruction of the new probe * without calling any user handlers. */ save_previous_kprobe(kcb); set_current_kprobe(p, kcb); kprobes_inc_nmissed_count(p); prepare_ss(p, regs); kcb->kprobe_status = KPROBE_REENTER; return 1; } else if (args->err == __IA64_BREAK_JPROBE) { /* * jprobe instrumented function just completed */ p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; } } else if (!is_ia64_break_inst(regs)) { /* The breakpoint instruction was removed by * another cpu right after we hit, no further * handling of this interrupt is appropriate */ ret = 1; goto no_kprobe; } else { /* Not our break */ goto no_kprobe; } } p = get_kprobe(addr); if (!p) { if (!is_ia64_break_inst(regs)) { /* * 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 our break, let kernel handle it */ goto no_kprobe; } set_current_kprobe(p, kcb); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (p->pre_handler && p->pre_handler(p, regs)) /* * Our pre-handler is specifically requesting that we just * do a return. This is used for both the jprobe pre-handler * and the kretprobe trampoline */ return 1; ss_probe: prepare_ss(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; return 1; no_kprobe: preempt_enable_no_resched(); return ret; } static int __kprobes post_kprobes_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); /*Restore back 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(); return 1; } static int __kprobes kprobes_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); reset_current_kprobe(); preempt_enable_no_resched(); } return 0; } 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; switch(val) { case DIE_BREAK: /* err is break number from ia64_bad_break() */ if (args->err == 0x80200 || args->err == 0x80300 || args->err == 0) if (pre_kprobes_handler(args)) ret = NOTIFY_STOP; break; case DIE_FAULT: /* err is vector number from ia64_fault() */ if (args->err == 36) if (post_kprobes_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_PAGE_FAULT: /* kprobe_running() needs smp_processor_id() */ preempt_disable(); if (kprobe_running() && kprobes_fault_handler(args->regs, args->trapnr)) ret = NOTIFY_STOP; preempt_enable(); default: break; } return ret; } struct param_bsp_cfm { unsigned long ip; unsigned long *bsp; unsigned long cfm; }; static void ia64_get_bsp_cfm(struct unw_frame_info *info, void *arg) { unsigned long ip; struct param_bsp_cfm *lp = arg; do { unw_get_ip(info, &ip); if (ip == 0) break; if (ip == lp->ip) { unw_get_bsp(info, (unsigned long*)&lp->bsp); unw_get_cfm(info, (unsigned long*)&lp->cfm); return; } } while (unw_unwind(info) >= 0); lp->bsp = 0; lp->cfm = 0; return; } 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 fnptr *)(jp->entry))->ip; struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); struct param_bsp_cfm pa; int bytes; /* * Callee owns the argument space and could overwrite it, eg * tail call optimization. So to be absolutely safe * we save the argument space before transfering the control * to instrumented jprobe function which runs in * the process context */ pa.ip = regs->cr_iip; unw_init_running(ia64_get_bsp_cfm, &pa); bytes = (char *)ia64_rse_skip_regs(pa.bsp, pa.cfm & 0x3f) - (char *)pa.bsp; memcpy( kcb->jprobes_saved_stacked_regs, pa.bsp, bytes ); kcb->bsp = pa.bsp; kcb->cfm = pa.cfm; /* save architectural state */ kcb->jprobe_saved_regs = *regs; /* after rfi, execute the jprobe instrumented function */ regs->cr_iip = addr & ~0xFULL; ia64_psr(regs)->ri = addr & 0xf; regs->r1 = ((struct fnptr *)(jp->entry))->gp; /* * fix the return address to our jprobe_inst_return() function * in the jprobes.S file */ regs->b0 = ((struct fnptr *)(jprobe_inst_return))->ip; return 1; } int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); int bytes; /* restoring architectural state */ *regs = kcb->jprobe_saved_regs; /* restoring the original argument space */ flush_register_stack(); bytes = (char *)ia64_rse_skip_regs(kcb->bsp, kcb->cfm & 0x3f) - (char *)kcb->bsp; memcpy( kcb->bsp, kcb->jprobes_saved_stacked_regs, bytes ); invalidate_stacked_regs(); preempt_enable_no_resched(); return 1; } static struct kprobe trampoline_p = { .pre_handler = trampoline_probe_handler }; int __init arch_init_kprobes(void) { trampoline_p.addr = (kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip; return register_kprobe(&trampoline_p); }