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Diffstat (limited to 'arch/x86/kernel/kprobes/core.c')
-rw-r--r-- | arch/x86/kernel/kprobes/core.c | 1067 |
1 files changed, 1067 insertions, 0 deletions
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c new file mode 100644 index 000000000000..7bfe318d3d8a --- /dev/null +++ b/arch/x86/kernel/kprobes/core.c @@ -0,0 +1,1067 @@ +/* + * 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 <linux/ftrace.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> + +#include "common.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. + * This is non-const and volatile to keep gcc from statically + * optimizing it out, as variable_test_bit makes gcc think only + * *(unsigned long*) is used. + */ +static volatile 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); + +static void __kprobes __synthesize_relative_insn(void *from, void *to, u8 op) +{ + struct __arch_relative_insn { + u8 op; + s32 raddr; + } __packed *insn; + + insn = (struct __arch_relative_insn *)from; + insn->raddr = (s32)((long)(to) - ((long)(from) + 5)); + insn->op = op; +} + +/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/ +void __kprobes synthesize_reljump(void *from, void *to) +{ + __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE); +} + +/* Insert a call instruction at address 'from', which calls address 'to'.*/ +void __kprobes synthesize_relcall(void *from, void *to) +{ + __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE); +} + +/* + * Skip the prefixes of the instruction. + */ +static kprobe_opcode_t *__kprobes skip_prefixes(kprobe_opcode_t *insn) +{ + insn_attr_t attr; + + attr = inat_get_opcode_attribute((insn_byte_t)*insn); + while (inat_is_legacy_prefix(attr)) { + insn++; + attr = inat_get_opcode_attribute((insn_byte_t)*insn); + } +#ifdef CONFIG_X86_64 + if (inat_is_rex_prefix(attr)) + insn++; +#endif + return insn; +} + +/* + * Returns non-zero if opcode is boostable. + * RIP relative instructions are adjusted at copying time in 64 bits mode + */ +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); + } +} + +static unsigned long +__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) +{ + struct kprobe *kp; + + kp = get_kprobe((void *)addr); + /* There is no probe, return original address */ + if (!kp) + return addr; + + /* + * Basically, kp->ainsn.insn has an original instruction. + * However, RIP-relative instruction can not do single-stepping + * at different place, __copy_instruction() 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 (unsigned long)buf; +} + +/* + * Recover the probed instruction at addr for further analysis. + * Caller must lock kprobes by kprobe_mutex, or disable preemption + * for preventing to release referencing kprobes. + */ +unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) +{ + unsigned long __addr; + + __addr = __recover_optprobed_insn(buf, addr); + if (__addr != addr) + return __addr; + + return __recover_probed_insn(buf, addr); +} + +/* Check if paddr is at an instruction boundary */ +static int __kprobes can_probe(unsigned long paddr) +{ + unsigned long addr, __addr, offset = 0; + struct insn insn; + kprobe_opcode_t buf[MAX_INSN_SIZE]; + + if (!kallsyms_lookup_size_offset(paddr, NULL, &offset)) + return 0; + + /* Decode instructions */ + addr = paddr - offset; + while (addr < paddr) { + /* + * Check if the instruction has been modified by another + * kprobe, in which case we replace the breakpoint by the + * original instruction in our buffer. + * Also, jump optimization will change the breakpoint to + * relative-jump. Since the relative-jump itself is + * normally used, we just go through if there is no kprobe. + */ + __addr = recover_probed_instruction(buf, addr); + kernel_insn_init(&insn, (void *)__addr); + insn_get_length(&insn); + + /* + * Another debugging subsystem might insert this breakpoint. + * In that case, we can't recover it. + */ + if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) + return 0; + 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) +{ + /* Skip prefixes */ + insn = skip_prefixes(insn); + + switch (*insn) { + case 0xfa: /* cli */ + case 0xfb: /* sti */ + case 0xcf: /* iret/iretd */ + case 0x9d: /* popf/popfd */ + return 1; + } + + return 0; +} + +/* + * Copy an instruction and 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. + */ +int __kprobes __copy_instruction(u8 *dest, u8 *src) +{ + struct insn insn; + kprobe_opcode_t buf[MAX_INSN_SIZE]; + + kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, (unsigned long)src)); + insn_get_length(&insn); + /* Another subsystem puts a breakpoint, failed to recover */ + if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) + return 0; + memcpy(dest, insn.kaddr, insn.length); + +#ifdef CONFIG_X86_64 + if (insn_rip_relative(&insn)) { + s64 newdisp; + u8 *disp; + kernel_insn_init(&insn, dest); + 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 *) src + (s64) insn.displacement.value - (u8 *) dest; + BUG_ON((s64) (s32) newdisp != newdisp); /* Sanity check. */ + disp = (u8 *) dest + insn_offset_displacement(&insn); + *(s32 *) disp = (s32) newdisp; + } +#endif + return insn.length; +} + +static void __kprobes arch_copy_kprobe(struct kprobe *p) +{ + /* Copy an instruction with recovering if other optprobe modifies it.*/ + __copy_instruction(p->ainsn.insn, p->addr); + + /* + * __copy_instruction can modify the displacement of the instruction, + * but it doesn't affect boostable check. + */ + if (can_boost(p->ainsn.insn)) + p->ainsn.boostable = 0; + else + p->ainsn.boostable = -1; + + /* Check whether the instruction modifies Interrupt Flag or not */ + p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn); + + /* Also, displacement change doesn't affect the first byte */ + p->opcode = p->ainsn.insn[0]; +} + +int __kprobes arch_prepare_kprobe(struct kprobe *p) +{ + if (alternatives_text_reserved(p->addr, p->addr)) + return -EINVAL; + + 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) +{ + __this_cpu_write(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) +{ + __this_cpu_write(current_kprobe, p); + kcb->kprobe_saved_flags = kcb->kprobe_old_flags + = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); + if (p->ainsn.if_modifier) + kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF; +} + +static void __kprobes clear_btf(void) +{ + if (test_thread_flag(TIF_BLOCKSTEP)) { + unsigned long debugctl = get_debugctlmsr(); + + debugctl &= ~DEBUGCTLMSR_BTF; + update_debugctlmsr(debugctl); + } +} + +static void __kprobes restore_btf(void) +{ + if (test_thread_flag(TIF_BLOCKSTEP)) { + unsigned long debugctl = get_debugctlmsr(); + + debugctl |= DEBUGCTLMSR_BTF; + update_debugctlmsr(debugctl); + } +} + +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, int reenter) +{ + if (setup_detour_execution(p, regs, reenter)) + return; + +#if !defined(CONFIG_PREEMPT) + if (p->ainsn.boostable == 1 && !p->post_handler) { + /* Boost up -- we can execute copied instructions directly */ + if (!reenter) + reset_current_kprobe(); + /* + * Reentering boosted probe doesn't reset current_kprobe, + * nor set current_kprobe, because it doesn't use single + * stepping. + */ + regs->ip = (unsigned long)p->ainsn.insn; + preempt_enable_no_resched(); + return; + } +#endif + if (reenter) { + save_previous_kprobe(kcb); + set_current_kprobe(p, regs, kcb); + kcb->kprobe_status = KPROBE_REENTER; + } else + kcb->kprobe_status = KPROBE_HIT_SS; + /* Prepare real single stepping */ + 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; +} + +/* + * 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: + kprobes_inc_nmissed_count(p); + setup_singlestep(p, regs, kcb, 1); + 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 throughout 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)); + /* + * 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, 0); + return 1; + } + } else 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; + preempt_enable_no_resched(); + return 1; + } else if (kprobe_running()) { + p = __this_cpu_read(current_kprobe); + if (p->break_handler && p->break_handler(p, regs)) { + if (!skip_singlestep(p, regs, kcb)) + setup_singlestep(p, regs, kcb, 0); + 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" + SAVE_REGS_STRING + " movq %rsp, %rdi\n" + " call trampoline_handler\n" + /* Replace saved sp with true return address. */ + " movq %rax, 152(%rsp)\n" + RESTORE_REGS_STRING + " popfq\n" +#else + " pushf\n" + SAVE_REGS_STRING + " 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" + RESTORE_REGS_STRING + " 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 *tmp; + unsigned long flags, orig_ret_address = 0; + unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; + kprobe_opcode_t *correct_ret_addr = NULL; + + 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, tmp, head, hlist) { + if (ri->task != current) + /* another task is sharing our hash bucket */ + continue; + + orig_ret_address = (unsigned long)ri->ret_addr; + + 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); + + correct_ret_addr = ri->ret_addr; + hlist_for_each_entry_safe(ri, tmp, head, hlist) { + if (ri->task != current) + /* another task is sharing our hash bucket */ + continue; + + orig_ret_address = (unsigned long)ri->ret_addr; + if (ri->rp && ri->rp->handler) { + __this_cpu_write(current_kprobe, &ri->rp->kp); + get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; + ri->ret_addr = correct_ret_addr; + ri->rp->handler(ri, regs); + __this_cpu_write(current_kprobe, NULL); + } + + 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_hash_unlock(current, &flags); + + hlist_for_each_entry_safe(ri, 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 prefixes */ + insn = skip_prefixes(insn); + + regs->flags &= ~X86_EFLAGS_TF; + switch (*insn) { + case 0x9c: /* pushfl */ + *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF); + *tos |= kcb->kprobe_old_flags; + break; + case 0xc2: /* iret/ret/lret */ + case 0xc3: + case 0xca: + case 0xcb: + case 0xcf: + case 0xea: /* jmp absolute -- ip is correct */ + /* ip is already adjusted, no more changes required */ + p->ainsn.boostable = 1; + goto no_change; + case 0xe8: /* call relative - Fix return addr */ + *tos = orig_ip + (*tos - copy_ip); + break; +#ifdef CONFIG_X86_32 + case 0x9a: /* call absolute -- same as call absolute, indirect */ + *tos = orig_ip + (*tos - copy_ip); + goto no_change; +#endif + case 0xff: + if ((insn[1] & 0x30) == 0x10) { + /* + * call absolute, indirect + * Fix return addr; ip is correct. + * But this is not boostable + */ + *tos = orig_ip + (*tos - copy_ip); + goto no_change; + } else if (((insn[1] & 0x31) == 0x20) || + ((insn[1] & 0x31) == 0x21)) { + /* + * jmp near and far, absolute indirect + * ip is correct. And this is boostable + */ + p->ainsn.boostable = 1; + goto no_change; + } + default: + break; + } + + if (p->ainsn.boostable == 0) { + if ((regs->ip > copy_ip) && + (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) { + /* + * These instructions can be executed directly if it + * jumps back to correct address. + */ + synthesize_reljump((void *)regs->ip, + (void *)orig_ip + (regs->ip - copy_ip)); + p->ainsn.boostable = 1; + } else { + p->ainsn.boostable = -1; + } + } + + regs->ip += orig_ip - copy_ip; + +no_change: + restore_btf(); +} + +/* + * Interrupts are disabled on entry as trap1 is an interrupt gate and they + * remain disabled throughout this function. + */ +static 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; + + resume_execution(cur, regs, kcb); + regs->flags |= kcb->kprobe_saved_flags; + + if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + cur->post_handler(cur, regs, 0); + } + + /* 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(); + + /* + * if somebody else is singlestepping across a probe point, flags + * will have TF set, in which case, continue the remaining processing + * of do_debug, as if this is not a probe hit. + */ + if (regs->flags & X86_EFLAGS_TF) + 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(); + + 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 ip points back to the probe address + * and allow the page fault handler to continue as a + * normal page fault. + */ + regs->ip = (unsigned long)cur->addr; + regs->flags |= kcb->kprobe_old_flags; + 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 accounting + * 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. + */ + if (fixup_exception(regs)) + return 1; + + /* + * fixup routine 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 = data; + int ret = NOTIFY_DONE; + + if (args->regs && user_mode_vm(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)) { + /* + * Reset the BS bit in dr6 (pointed by args->err) to + * denote completion of processing + */ + (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; + ret = NOTIFY_STOP; + } + break; + case DIE_GPF: + /* + * To be potentially processing a kprobe fault and to + * trust the result from kprobe_running(), we have + * be non-preemptible. + */ + if (!preemptible() && kprobe_running() && + kprobe_fault_handler(args->regs, args->trapnr)) + ret = NOTIFY_STOP; + 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_sp = stack_addr(regs); + addr = (unsigned long)(kcb->jprobe_saved_sp); + + /* + * 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->flags &= ~X86_EFLAGS_IF; + trace_hardirqs_off(); + regs->ip = (unsigned long)(jp->entry); + return 1; +} + +void __kprobes jprobe_return(void) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + asm volatile ( +#ifdef CONFIG_X86_64 + " xchg %%rbx,%%rsp \n" +#else + " xchgl %%ebx,%%esp \n" +#endif + " int3 \n" + " .globl jprobe_return_end\n" + " jprobe_return_end: \n" + " nop \n"::"b" + (kcb->jprobe_saved_sp):"memory"); +} + +int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) +{ + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + u8 *addr = (u8 *) (regs->ip - 1); + struct jprobe *jp = container_of(p, struct jprobe, kp); + + if ((addr > (u8 *) jprobe_return) && + (addr < (u8 *) jprobe_return_end)) { + if (stack_addr(regs) != kcb->jprobe_saved_sp) { + struct pt_regs *saved_regs = &kcb->jprobe_saved_regs; + printk(KERN_ERR + "current sp %p does not match saved sp %p\n", + stack_addr(regs), kcb->jprobe_saved_sp); + printk(KERN_ERR "Saved registers for jprobe %p\n", jp); + show_regs(saved_regs); + printk(KERN_ERR "Current registers\n"); + show_regs(regs); + BUG(); + } + *regs = kcb->jprobe_saved_regs; + memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp), + kcb->jprobes_stack, + MIN_STACK_SIZE(kcb->jprobe_saved_sp)); + preempt_enable_no_resched(); + return 1; + } + return 0; +} + +int __init arch_init_kprobes(void) +{ + return arch_init_optprobes(); +} + +int __kprobes arch_trampoline_kprobe(struct kprobe *p) +{ + return 0; +} |