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d04c02f8aa
Commit22d8b3dec2
("powerpc/kprobes: Emulate instructions on kprobe handler re-entry") enabled emulating instructions on kprobe re-entry, rather than single-stepping always. However, we didn't update the single stepping code to only be run if the emulation fails. Also, we missed re-enabling preemption if the instruction emulation was successful. Fix those issues. Fixes:22d8b3dec2
("powerpc/kprobes: Emulate instructions on kprobe handler re-entry") Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
668 lines
18 KiB
C
668 lines
18 KiB
C
/*
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* Kernel Probes (KProbes)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2002, 2004
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*
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* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
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* Probes initial implementation ( includes contributions from
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* Rusty Russell).
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* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
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* interface to access function arguments.
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* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
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* for PPC64
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*/
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#include <linux/kprobes.h>
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#include <linux/ptrace.h>
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#include <linux/preempt.h>
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#include <linux/extable.h>
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#include <linux/kdebug.h>
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#include <linux/slab.h>
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#include <asm/code-patching.h>
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#include <asm/cacheflush.h>
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#include <asm/sstep.h>
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#include <asm/sections.h>
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#include <linux/uaccess.h>
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DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
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bool arch_within_kprobe_blacklist(unsigned long addr)
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{
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return (addr >= (unsigned long)__kprobes_text_start &&
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addr < (unsigned long)__kprobes_text_end) ||
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(addr >= (unsigned long)_stext &&
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addr < (unsigned long)__head_end);
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}
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kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
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{
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kprobe_opcode_t *addr;
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#ifdef PPC64_ELF_ABI_v2
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/* PPC64 ABIv2 needs local entry point */
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
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if (addr && !offset) {
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#ifdef CONFIG_KPROBES_ON_FTRACE
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unsigned long faddr;
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/*
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* Per livepatch.h, ftrace location is always within the first
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* 16 bytes of a function on powerpc with -mprofile-kernel.
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*/
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faddr = ftrace_location_range((unsigned long)addr,
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(unsigned long)addr + 16);
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if (faddr)
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addr = (kprobe_opcode_t *)faddr;
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else
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#endif
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addr = (kprobe_opcode_t *)ppc_function_entry(addr);
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}
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#elif defined(PPC64_ELF_ABI_v1)
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/*
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* 64bit powerpc ABIv1 uses function descriptors:
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* - Check for the dot variant of the symbol first.
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* - If that fails, try looking up the symbol provided.
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*
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* This ensures we always get to the actual symbol and not
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* the descriptor.
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*
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* Also handle <module:symbol> format.
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*/
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char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
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const char *modsym;
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bool dot_appended = false;
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if ((modsym = strchr(name, ':')) != NULL) {
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modsym++;
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if (*modsym != '\0' && *modsym != '.') {
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/* Convert to <module:.symbol> */
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strncpy(dot_name, name, modsym - name);
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dot_name[modsym - name] = '.';
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dot_name[modsym - name + 1] = '\0';
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strncat(dot_name, modsym,
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sizeof(dot_name) - (modsym - name) - 2);
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dot_appended = true;
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} else {
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dot_name[0] = '\0';
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strncat(dot_name, name, sizeof(dot_name) - 1);
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}
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} else if (name[0] != '.') {
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dot_name[0] = '.';
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dot_name[1] = '\0';
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strncat(dot_name, name, KSYM_NAME_LEN - 2);
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dot_appended = true;
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} else {
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dot_name[0] = '\0';
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strncat(dot_name, name, KSYM_NAME_LEN - 1);
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}
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
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if (!addr && dot_appended) {
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/* Let's try the original non-dot symbol lookup */
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
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}
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#else
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addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
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#endif
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return addr;
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}
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int arch_prepare_kprobe(struct kprobe *p)
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{
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int ret = 0;
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kprobe_opcode_t insn = *p->addr;
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if ((unsigned long)p->addr & 0x03) {
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printk("Attempt to register kprobe at an unaligned address\n");
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ret = -EINVAL;
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} else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
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printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
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ret = -EINVAL;
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}
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/* insn must be on a special executable page on ppc64. This is
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* not explicitly required on ppc32 (right now), but it doesn't hurt */
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if (!ret) {
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p->ainsn.insn = get_insn_slot();
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if (!p->ainsn.insn)
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ret = -ENOMEM;
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}
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if (!ret) {
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memcpy(p->ainsn.insn, p->addr,
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MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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p->opcode = *p->addr;
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flush_icache_range((unsigned long)p->ainsn.insn,
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(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
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}
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p->ainsn.boostable = 0;
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return ret;
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}
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NOKPROBE_SYMBOL(arch_prepare_kprobe);
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void arch_arm_kprobe(struct kprobe *p)
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{
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*p->addr = BREAKPOINT_INSTRUCTION;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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NOKPROBE_SYMBOL(arch_arm_kprobe);
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void arch_disarm_kprobe(struct kprobe *p)
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{
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*p->addr = p->opcode;
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flush_icache_range((unsigned long) p->addr,
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(unsigned long) p->addr + sizeof(kprobe_opcode_t));
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}
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NOKPROBE_SYMBOL(arch_disarm_kprobe);
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void arch_remove_kprobe(struct kprobe *p)
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{
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if (p->ainsn.insn) {
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free_insn_slot(p->ainsn.insn, 0);
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p->ainsn.insn = NULL;
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}
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}
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NOKPROBE_SYMBOL(arch_remove_kprobe);
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static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
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{
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enable_single_step(regs);
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/*
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* On powerpc we should single step on the original
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* instruction even if the probed insn is a trap
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* variant as values in regs could play a part in
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* if the trap is taken or not
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*/
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regs->nip = (unsigned long)p->ainsn.insn;
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}
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static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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kcb->prev_kprobe.kp = kprobe_running();
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kcb->prev_kprobe.status = kcb->kprobe_status;
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kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
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}
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static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
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kcb->kprobe_status = kcb->prev_kprobe.status;
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kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
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}
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static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
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struct kprobe_ctlblk *kcb)
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{
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__this_cpu_write(current_kprobe, p);
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kcb->kprobe_saved_msr = regs->msr;
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}
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bool arch_function_offset_within_entry(unsigned long offset)
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{
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#ifdef PPC64_ELF_ABI_v2
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#ifdef CONFIG_KPROBES_ON_FTRACE
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return offset <= 16;
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#else
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return offset <= 8;
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#endif
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#else
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return !offset;
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#endif
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}
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void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
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{
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ri->ret_addr = (kprobe_opcode_t *)regs->link;
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/* Replace the return addr with trampoline addr */
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regs->link = (unsigned long)kretprobe_trampoline;
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}
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NOKPROBE_SYMBOL(arch_prepare_kretprobe);
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int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
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{
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int ret;
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unsigned int insn = *p->ainsn.insn;
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/* regs->nip is also adjusted if emulate_step returns 1 */
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ret = emulate_step(regs, insn);
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if (ret > 0) {
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/*
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* Once this instruction has been boosted
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* successfully, set the boostable flag
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*/
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if (unlikely(p->ainsn.boostable == 0))
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p->ainsn.boostable = 1;
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} else if (ret < 0) {
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/*
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* We don't allow kprobes on mtmsr(d)/rfi(d), etc.
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* So, we should never get here... but, its still
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* good to catch them, just in case...
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*/
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printk("Can't step on instruction %x\n", insn);
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BUG();
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} else if (ret == 0)
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/* This instruction can't be boosted */
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p->ainsn.boostable = -1;
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return ret;
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}
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NOKPROBE_SYMBOL(try_to_emulate);
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int kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe *p;
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int ret = 0;
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unsigned int *addr = (unsigned int *)regs->nip;
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struct kprobe_ctlblk *kcb;
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if (user_mode(regs))
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return 0;
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/*
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* We don't want to be preempted for the entire
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* duration of kprobe processing
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*/
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preempt_disable();
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kcb = get_kprobe_ctlblk();
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/* Check we're not actually recursing */
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if (kprobe_running()) {
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p = get_kprobe(addr);
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if (p) {
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kprobe_opcode_t insn = *p->ainsn.insn;
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if (kcb->kprobe_status == KPROBE_HIT_SS &&
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is_trap(insn)) {
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/* Turn off 'trace' bits */
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regs->msr &= ~MSR_SINGLESTEP;
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regs->msr |= kcb->kprobe_saved_msr;
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goto no_kprobe;
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}
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/* We have reentered the kprobe_handler(), since
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* another probe was hit while within the handler.
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* We here save the original kprobes variables and
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* just single step on the instruction of the new probe
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* without calling any user handlers.
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*/
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save_previous_kprobe(kcb);
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set_current_kprobe(p, regs, kcb);
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kprobes_inc_nmissed_count(p);
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kcb->kprobe_status = KPROBE_REENTER;
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if (p->ainsn.boostable >= 0) {
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ret = try_to_emulate(p, regs);
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if (ret > 0) {
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restore_previous_kprobe(kcb);
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preempt_enable_no_resched();
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return 1;
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}
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}
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prepare_singlestep(p, regs);
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return 1;
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} else {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/* If trap variant, then it belongs not to us */
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/* The breakpoint instruction was removed by
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* another cpu right after we hit, no further
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* handling of this interrupt is appropriate
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*/
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ret = 1;
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goto no_kprobe;
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}
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p = __this_cpu_read(current_kprobe);
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if (p->break_handler && p->break_handler(p, regs)) {
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if (!skip_singlestep(p, regs, kcb))
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goto ss_probe;
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ret = 1;
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}
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}
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goto no_kprobe;
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}
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p = get_kprobe(addr);
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if (!p) {
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if (*addr != BREAKPOINT_INSTRUCTION) {
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/*
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* PowerPC has multiple variants of the "trap"
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* instruction. If the current instruction is a
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* trap variant, it could belong to someone else
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*/
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kprobe_opcode_t cur_insn = *addr;
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if (is_trap(cur_insn))
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goto no_kprobe;
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/*
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* The breakpoint instruction was removed right
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* after we hit it. Another cpu has removed
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* either a probepoint or a debugger breakpoint
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* at this address. In either case, no further
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* handling of this interrupt is appropriate.
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*/
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ret = 1;
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}
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/* Not one of ours: let kernel handle it */
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goto no_kprobe;
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}
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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set_current_kprobe(p, regs, kcb);
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if (p->pre_handler && p->pre_handler(p, regs))
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/* handler has already set things up, so skip ss setup */
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return 1;
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ss_probe:
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if (p->ainsn.boostable >= 0) {
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ret = try_to_emulate(p, regs);
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if (ret > 0) {
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if (p->post_handler)
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p->post_handler(p, regs, 0);
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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reset_current_kprobe();
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preempt_enable_no_resched();
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return 1;
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}
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}
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_HIT_SS;
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return 1;
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no_kprobe:
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preempt_enable_no_resched();
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return ret;
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}
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NOKPROBE_SYMBOL(kprobe_handler);
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/*
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* Function return probe trampoline:
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* - init_kprobes() establishes a probepoint here
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* - When the probed function returns, this probe
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* causes the handlers to fire
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*/
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asm(".global kretprobe_trampoline\n"
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".type kretprobe_trampoline, @function\n"
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"kretprobe_trampoline:\n"
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"nop\n"
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"blr\n"
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".size kretprobe_trampoline, .-kretprobe_trampoline\n");
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/*
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* Called when the probe at kretprobe trampoline is hit
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*/
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static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
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{
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struct kretprobe_instance *ri = NULL;
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struct hlist_head *head, empty_rp;
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struct hlist_node *tmp;
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unsigned long flags, orig_ret_address = 0;
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unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
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INIT_HLIST_HEAD(&empty_rp);
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kretprobe_hash_lock(current, &head, &flags);
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/*
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* It is possible to have multiple instances associated with a given
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* task either because an multiple functions in the call path
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* have a return probe installed on them, and/or more than one return
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* return probe was registered for a target function.
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*
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* We can handle this because:
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* - instances are always inserted at the head of the list
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* - when multiple return probes are registered for the same
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* function, the first instance's ret_addr will point to the
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* real return address, and all the rest will point to
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* kretprobe_trampoline
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*/
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hlist_for_each_entry_safe(ri, tmp, head, hlist) {
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if (ri->task != current)
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/* another task is sharing our hash bucket */
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continue;
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if (ri->rp && ri->rp->handler)
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ri->rp->handler(ri, regs);
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orig_ret_address = (unsigned long)ri->ret_addr;
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recycle_rp_inst(ri, &empty_rp);
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if (orig_ret_address != trampoline_address)
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/*
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* This is the real return address. Any other
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* instances associated with this task are for
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* other calls deeper on the call stack
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*/
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break;
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}
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kretprobe_assert(ri, orig_ret_address, trampoline_address);
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regs->nip = orig_ret_address;
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/*
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* Make LR point to the orig_ret_address.
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* When the 'nop' inside the kretprobe_trampoline
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* is optimized, we can do a 'blr' after executing the
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* detour buffer code.
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*/
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regs->link = orig_ret_address;
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reset_current_kprobe();
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kretprobe_hash_unlock(current, &flags);
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preempt_enable_no_resched();
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hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
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hlist_del(&ri->hlist);
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kfree(ri);
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}
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/*
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* By returning a non-zero value, we are telling
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* kprobe_handler() that we don't want the post_handler
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* to run (and have re-enabled preemption)
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*/
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return 1;
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}
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NOKPROBE_SYMBOL(trampoline_probe_handler);
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/*
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* Called after single-stepping. p->addr is the address of the
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* instruction whose first byte has been replaced by the "breakpoint"
|
|
* 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.
|
|
*/
|
|
int kprobe_post_handler(struct pt_regs *regs)
|
|
{
|
|
struct kprobe *cur = kprobe_running();
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
if (!cur || user_mode(regs))
|
|
return 0;
|
|
|
|
/* make sure we got here for instruction we have a kprobe on */
|
|
if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
|
|
return 0;
|
|
|
|
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
|
|
kcb->kprobe_status = KPROBE_HIT_SSDONE;
|
|
cur->post_handler(cur, regs, 0);
|
|
}
|
|
|
|
/* Adjust nip to after the single-stepped instruction */
|
|
regs->nip = (unsigned long)cur->addr + 4;
|
|
regs->msr |= kcb->kprobe_saved_msr;
|
|
|
|
/*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, msr
|
|
* will have DE/SE set, in which case, continue the remaining processing
|
|
* of do_debug, as if this is not a probe hit.
|
|
*/
|
|
if (regs->msr & MSR_SINGLESTEP)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_post_handler);
|
|
|
|
int 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 *entry;
|
|
|
|
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 nip points back to the probe address
|
|
* and allow the page fault handler to continue as a
|
|
* normal page fault.
|
|
*/
|
|
regs->nip = (unsigned long)cur->addr;
|
|
regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
|
|
regs->msr |= kcb->kprobe_saved_msr;
|
|
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 ((entry = search_exception_tables(regs->nip)) != NULL) {
|
|
regs->nip = extable_fixup(entry);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* fixup_exception() could not handle it,
|
|
* Let do_page_fault() fix it.
|
|
*/
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_fault_handler);
|
|
|
|
unsigned long arch_deref_entry_point(void *entry)
|
|
{
|
|
return ppc_global_function_entry(entry);
|
|
}
|
|
NOKPROBE_SYMBOL(arch_deref_entry_point);
|
|
|
|
int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
struct jprobe *jp = container_of(p, struct jprobe, kp);
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
|
|
|
|
/* setup return addr to the jprobe handler routine */
|
|
regs->nip = arch_deref_entry_point(jp->entry);
|
|
#ifdef PPC64_ELF_ABI_v2
|
|
regs->gpr[12] = (unsigned long)jp->entry;
|
|
#elif defined(PPC64_ELF_ABI_v1)
|
|
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
|
|
#endif
|
|
|
|
return 1;
|
|
}
|
|
NOKPROBE_SYMBOL(setjmp_pre_handler);
|
|
|
|
void __used jprobe_return(void)
|
|
{
|
|
asm volatile("trap" ::: "memory");
|
|
}
|
|
NOKPROBE_SYMBOL(jprobe_return);
|
|
|
|
static void __used jprobe_return_end(void)
|
|
{
|
|
}
|
|
NOKPROBE_SYMBOL(jprobe_return_end);
|
|
|
|
int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
/*
|
|
* FIXME - we should ideally be validating that we got here 'cos
|
|
* of the "trap" in jprobe_return() above, before restoring the
|
|
* saved regs...
|
|
*/
|
|
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
|
|
preempt_enable_no_resched();
|
|
return 1;
|
|
}
|
|
NOKPROBE_SYMBOL(longjmp_break_handler);
|
|
|
|
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 arch_trampoline_kprobe(struct kprobe *p)
|
|
{
|
|
if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
|