litmus-rt.git - The LITMUS^RT kernel.

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Diffstat (limited to 'fs/buffer.c')

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/* * Kernel Probes (KProbes) * * 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 <jkenisto@us.ibm.com> and Prasanna S Panchamukhi * <prasanna@in.ibm.com> adapted for x86_64 from i386. * 2005-Mar Roland McGrath <roland@redhat.com> * Fixed to handle %rip-relative addressing mode correctly. * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi * <prasanna@in.ibm.com> added function-return probes. * 2005-May Rusty Lynch <rusty.lynch@intel.com> * Added function return probes functionality * 2006-Feb Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added * kprobe-booster and kretprobe-booster for i386. * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster * and kretprobe-booster for x86-64 * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven * <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com> * unified x86 kprobes code. */ #include <linux/kprobes.h> #include <linux/ptrace.h> #include <linux/string.h> #include <linux/slab.h> #include <linux/hardirq.h> #include <linux/preempt.h> #include <linux/module.h> #include <linux/kdebug.h> #include <linux/kallsyms.h> #include <asm/cacheflush.h> #include <asm/desc.h> #include <asm/pgtable.h> #include <asm/uaccess.h> #include <asm/alternative.h> #include <asm/insn.h> #include <asm/debugreg.h> void jprobe_return_end(void); DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs)) #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 % 32)) /* * Undefined/reserved opcodes, conditional jump, Opcode Extension * Groups, and some special opcodes can not boost. */ static const u32 twobyte_is_boostable[256 / 32] = { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* ---------------------------------------------- */ W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */ W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */ W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */ W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */ W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */ W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */ W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */ W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */ W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */ W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */ W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */ W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */ W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */ /* ----------------------------------------------- */ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ }; #undef W struct kretprobe_blackpoint kretprobe_blacklist[] = { {"__switch_to", }, /* This function switches only current task, but doesn't switch kernel stack.*/ {NULL, NULL} /* Terminator */ }; const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist); /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/ static void __kprobes set_jmp_op(void *from, void *to) { struct __arch_jmp_op { char op; s32 raddr; } __attribute__((packed)) * jop; jop = (struct __arch_jmp_op *)from; jop->raddr = (s32)((long)(to) - ((long)(from) + 5)); jop->op = RELATIVEJUMP_INSTRUCTION; } /* * Check for the REX prefix which can only exist on X86_64 * X86_32 always returns 0 */ static int __kprobes is_REX_prefix(kprobe_opcode_t *insn) { #ifdef CONFIG_X86_64 if ((*insn & 0xf0) == 0x40) return 1; #endif return 0; } /* * Returns non-zero if opcode is boostable. * RIP relative instructions are adjusted at copying time in 64 bits mode */ static int __kprobes can_boost(kprobe_opcode_t *opcodes) { kprobe_opcode_t opcode; kprobe_opcode_t *orig_opcodes = opcodes; if (search_exception_tables((unsigned long)opcodes)) return 0; /* Page fault may occur on this address. */ retry: if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1) return 0; opcode = *(opcodes++); /* 2nd-byte opcode */ if (opcode == 0x0f) { if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1) return 0; return test_bit(*opcodes, (unsigned long *)twobyte_is_boostable); } switch (opcode & 0xf0) { #ifdef CONFIG_X86_64 case 0x40: goto retry; /* REX prefix is boostable */ #endif case 0x60: if (0x63 < opcode && opcode < 0x67) goto retry; /* prefixes */ /* can't boost Address-size override and bound */ return (opcode != 0x62 && opcode != 0x67); case 0x70: return 0; /* can't boost conditional jump */ case 0xc0: /* can't boost software-interruptions */ return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf; case 0xd0: /* can boost AA* and XLAT */ return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7); case 0xe0: /* can boost in/out and absolute jmps */ return ((opcode & 0x04) || opcode == 0xea); case 0xf0: if ((opcode & 0x0c) == 0 && opcode != 0xf1) goto retry; /* lock/rep(ne) prefix */ /* clear and set flags are boostable */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: /* segment override prefixes are boostable */ if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e) goto retry; /* prefixes */ /* CS override prefix and call are not boostable */ return (opcode != 0x2e && opcode != 0x9a); } } /* Recover the probed instruction at addr for further analysis. */ static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) { struct kprobe *kp; kp = get_kprobe((void *)addr); if (!kp) return -EINVAL; /* * Basically, kp->ainsn.insn has an original instruction. * However, RIP-relative instruction can not do single-stepping * at different place, fix_riprel() tweaks the displacement of * that instruction. In that case, we can't recover the instruction * from the kp->ainsn.insn. * * On the other hand, kp->opcode has a copy of the first byte of * the probed instruction, which is overwritten by int3. And * the instruction at kp->addr is not modified by kprobes except * for the first byte, we can recover the original instruction * from it and kp->opcode. */ memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); buf[0] = kp->opcode; return 0; } /* Dummy buffers for kallsyms_lookup */ static char __dummy_buf[KSYM_NAME_LEN]; /* Check if paddr is at an instruction boundary */ static int __kprobes can_probe(unsigned long paddr) { int ret; unsigned long addr, offset = 0; struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; if (!kallsyms_lookup(paddr, NULL, &offset, NULL, __dummy_buf)) return 0; /* Decode instructions */ addr = paddr - offset; while (addr < paddr) { kernel_insn_init(&insn, (void *)addr); insn_get_opcode(&insn); /* * Check if the instruction has been modified by another * kprobe, in which case we replace the breakpoint by the * original instruction in our buffer. */ if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) { ret = recover_probed_instruction(buf, addr); if (ret) /* * Another debugging subsystem might insert * this breakpoint. In that case, we can't * recover it. */ return 0; kernel_insn_init(&insn, buf); } insn_get_length(&insn); addr += insn.length; } return (addr == paddr); } /* * Returns non-zero if opcode modifies the interrupt flag. */ static int __kprobes 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; } /* * on X86_64, 0x40-0x4f are REX prefixes so we need to look * at the next byte instead.. but of course not recurse infinitely */ if (is_REX_prefix(insn)) return is_IF_modifier(++insn); return 0; } /* * Adjust the displacement 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. * Only applicable to 64-bit x86. */ static void __kprobes fix_riprel(struct kprobe *p) { #ifdef CONFIG_X86_64 struct insn insn; kernel_insn_init(&insn, p->ainsn.insn); if (insn_rip_relative(&insn)) { s64 newdisp; u8 *disp; insn_get_displacement(&insn); /* * 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. */ newdisp = (u8 *) p->addr + (s64) insn.displacement.value - (u8 *) p->ainsn.insn; BUG_ON((s64) (s32) newdisp != newdisp); /* Sanity check. */ disp = (u8 *) p->ainsn.insn + insn_offset_displacement(&insn); *(s32 *) disp = (s32) newdisp; } #endif } static void __kprobes arch_copy_kprobe(struct kprobe *p) { memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); fix_riprel(p); if (can_boost(p->addr)) p->ainsn.boostable = 0; else p->ainsn.boostable = -1; p->opcode = *p->addr; } int __kprobes arch_prepare_kprobe(struct kprobe *p) { if (!can_probe((unsigned long)p->addr)) return -EILSEQ; /* insn: must be on special executable page on x86. */ p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn) return -ENOMEM; arch_copy_kprobe(p); return 0; } 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) { if (p->ainsn.insn) { free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1)); p->ainsn.insn = NULL; } } 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_flags = kcb->kprobe_old_flags; kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags; } 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_flags = kcb->prev_kprobe.old_flags; kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags; } 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_flags = kcb->kprobe_old_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); if (is_IF_modifier(p->ainsn.insn)) kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF; } static void __kprobes clear_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) update_debugctlmsr(0); } static void __kprobes restore_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) update_debugctlmsr(current->thread.debugctlmsr); } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) { clear_btf(); regs->flags |= X86_EFLAGS_TF; regs->flags &= ~X86_EFLAGS_IF; /* single step inline if the instruction is an int3 */ if (p->opcode == BREAKPOINT_INSTRUCTION) regs->ip = (unsigned long)p->addr; else regs->ip = (unsigned long)p->ainsn.insn; } void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { unsigned long *sara = stack_addr(regs); ri->ret_addr = (kprobe_opcode_t *) *sara; /* Replace the return addr with trampoline addr */ *sara = (unsigned long) &kretprobe_trampoline; } static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { #if !defined(CONFIG_PREEMPT) || defined(CONFIG_FREEZER) if (p->ainsn.boostable == 1 && !p->post_handler) { /* Boost up -- we can execute copied instructions directly */ reset_current_kprobe(); regs->ip = (unsigned long)p->ainsn.insn; preempt_enable_no_resched(); return; } #endif prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; } /* * We have reentered the kprobe_handler(), since another probe was hit while * within the handler. We save the original kprobes variables and just single * step on the instruction of the new probe without calling any user handlers. */ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { switch (kcb->kprobe_status) { case KPROBE_HIT_SSDONE: case KPROBE_HIT_ACTIVE: save_previous_kprobe(kcb); set_current_kprobe(p, regs, kcb); kprobes_inc_nmissed_count(p); prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_REENTER; break; case KPROBE_HIT_SS: /* A probe has been hit in the codepath leading up to, or just * after, single-stepping of a probed instruction. This entire * codepath should strictly reside in .kprobes.text section. * Raise a BUG or we'll continue in an endless reentering loop * and eventually a stack overflow. */ printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n", p->addr); dump_kprobe(p); BUG(); default: /* impossible cases */ WARN_ON(1); return 0; } return 1; } /* * Interrupts are disabled on entry as trap3 is an interrupt gate and they * remain disabled thorough out this function. */ static int __kprobes kprobe_handler(struct pt_regs *regs) { kprobe_opcode_t *addr; struct kprobe *p; struct kprobe_ctlblk *kcb; addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t)); 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->ip = (unsigned long)addr; return 1; } /* * We don't want to be preempted for the entire * duration of kprobe processing. We conditionally * re-enable preemption at the end of this function, * and also in reenter_kprobe() and setup_singlestep(). */ preempt_disable(); kcb = get_kprobe_ctlblk(); p = get_kprobe(addr); if (p) { if (kprobe_running()) { if (reenter_kprobe(p, regs, kcb)) return 1; } else { set_current_kprobe(p, regs, kcb); kcb->kprobe_status = KPROBE_HIT_ACTIVE; /* * If we have no pre-handler or it returned 0, we * continue with normal processing. If we have a * pre-handler and it returned non-zero, it prepped * for calling the break_handler below on re-entry * for jprobe processing, so get out doing nothing * more here. */ if (!p->pre_handler || !p->pre_handler(p, regs)) setup_singlestep(p, regs, kcb); return 1; } } else if (kprobe_running()) { p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { setup_singlestep(p, regs, kcb); return 1; } } /* else: not a kprobe fault; let the kernel handle it */ preempt_enable_no_resched(); return 0; } /* * When a retprobed function returns, this code saves registers and * calls trampoline_handler() runs, which calls the kretprobe's handler. */ static void __used __kprobes kretprobe_trampoline_holder(void) { asm volatile ( ".global kretprobe_trampoline\n" "kretprobe_trampoline: \n" #ifdef CONFIG_X86_64 /* We don't bother saving the ss register */ " pushq %rsp\n" " pushfq\n" /* * Skip cs, ip, orig_ax. * trampoline_handler() will plug in these values */ " subq $24, %rsp\n" " pushq %rdi\n" " pushq %rsi\n" " pushq %rdx\n" " pushq %rcx\n" " pushq %rax\n" " pushq %r8\n" " pushq %r9\n" " pushq %r10\n" " pushq %r11\n" " pushq %rbx\n" " pushq %rbp\n" " pushq %r12\n" " pushq %r13\n" " pushq %r14\n" " pushq %r15\n" " movq %rsp, %rdi\n" " call trampoline_handler\n" /* Replace saved sp with true return address. */ " movq %rax, 152(%rsp)\n" " popq %r15\n" " popq %r14\n" " popq %r13\n" " popq %r12\n" " popq %rbp\n" " popq %rbx\n" " popq %r11\n" " popq %r10\n" " popq %r9\n" " popq %r8\n" " popq %rax\n" " popq %rcx\n" " popq %rdx\n" " popq %rsi\n" " popq %rdi\n" /* Skip orig_ax, ip, cs */ " addq $24, %rsp\n" " popfq\n" #else " pushf\n" /* * Skip cs, ip, orig_ax and gs. * trampoline_handler() will plug in these values */ " subl $16, %esp\n" " pushl %fs\n" " pushl %es\n" " pushl %ds\n" " pushl %eax\n" " pushl %ebp\n" " pushl %edi\n" " pushl %esi\n" " pushl %edx\n" " pushl %ecx\n" " pushl %ebx\n" " movl %esp, %eax\n" " call trampoline_handler\n" /* Move flags to cs */ " movl 56(%esp), %edx\n" " movl %edx, 52(%esp)\n" /* Replace saved flags with true return address. */ " movl %eax, 56(%esp)\n" " popl %ebx\n" " popl %ecx\n" " popl %edx\n" " popl %esi\n" " popl %edi\n" " popl %ebp\n" " popl %eax\n" /* Skip ds, es, fs, gs, orig_ax and ip */ " addl $24, %esp\n" " popf\n" #endif " ret\n"); } /* * Called from kretprobe_trampoline */ static __used __kprobes void *trampoline_handler(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); kretprobe_hash_lock(current, &head, &flags); /* fixup registers */ #ifdef CONFIG_X86_64 regs->cs = __KERNEL_CS; #else regs->cs = __KERNEL_CS | get_kernel_rpl(); regs->gs = 0; #endif regs->ip = trampoline_address; regs->orig_ax = ~0UL; /* * It is possible to have multiple instances associated with a given * task either because multiple functions in the call path have * return probes installed on them, and/or more than one * return probe was registered for a target function. * * We can handle this because: * - instances are always pushed into the head of the list * - when multiple return probes are registered for the same * function, the (chronologically) first instance's ret_addr * will be 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) { __get_cpu_var(current_kprobe) = &ri->rp->kp; get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; ri->rp->handler(ri, regs); __get_cpu_var(current_kprobe) = NULL; } 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); kretprobe_hash_unlock(current, &flags); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } return (void *)orig_ret_address; } /* * 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 ip 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 flags, 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. * * If this is the first time we've single-stepped the instruction at * this probepoint, and the instruction is boostable, boost it: add a * jump instruction after the copied instruction, that jumps to the next * instruction after the probepoint. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { unsigned long *tos = stack_addr(regs); unsigned long copy_ip = (unsigned long)p->ainsn.insn; unsigned long orig_ip = (unsigned long)p->addr; kprobe_opcode_t *insn = p->ainsn.insn; /*skip the REX prefix*/ if (is_REX_prefix(insn)) insn++; regs->flags &= ~X86_EFLAGS_TF; switch (*insn) {


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