![David Wilder](/assets/img/avatar_default.png)
Placing a kprobe on "bc" instruction (s390/s390x) can cause an oops. The instruction length is encoded into the first two bits of the s390 instruction. Kprobe is incorrectly computing the instruction length. The instruction length is used for determining what type of "fix-up" is needed for conditional branch instruction. The problem can bee seen by placing a kprobe on a "bc" instruction that will not branch. The results is that Kprobe incorrectly computes the new instruction pointer (psw.addr) after single stepping the instruction. The problem is corrected with this patch. Signed-off-by: David Wilder <dwilder@us.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
671 lines
18 KiB
C
671 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, 2006
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*
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* s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
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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/stop_machine.h>
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#include <linux/kdebug.h>
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#include <asm/cacheflush.h>
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#include <asm/sections.h>
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#include <asm/uaccess.h>
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#include <linux/module.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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int __kprobes arch_prepare_kprobe(struct kprobe *p)
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{
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/* Make sure the probe isn't going on a difficult instruction */
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if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
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return -EINVAL;
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if ((unsigned long)p->addr & 0x01) {
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printk("Attempt to register kprobe at an unaligned address\n");
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return -EINVAL;
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}
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/* Use the get_insn_slot() facility for correctness */
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if (!(p->ainsn.insn = get_insn_slot()))
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return -ENOMEM;
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memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
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get_instruction_type(&p->ainsn);
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p->opcode = *p->addr;
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return 0;
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}
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int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
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{
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switch (*(__u8 *) instruction) {
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case 0x0c: /* bassm */
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case 0x0b: /* bsm */
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case 0x83: /* diag */
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case 0x44: /* ex */
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return -EINVAL;
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}
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switch (*(__u16 *) instruction) {
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case 0x0101: /* pr */
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case 0xb25a: /* bsa */
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case 0xb240: /* bakr */
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case 0xb258: /* bsg */
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case 0xb218: /* pc */
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case 0xb228: /* pt */
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return -EINVAL;
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}
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return 0;
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}
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void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
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{
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/* default fixup method */
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ainsn->fixup = FIXUP_PSW_NORMAL;
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/* save r1 operand */
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ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
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/* save the instruction length (pop 5-5) in bytes */
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switch (*(__u8 *) (ainsn->insn) >> 6) {
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case 0:
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ainsn->ilen = 2;
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break;
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case 1:
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case 2:
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ainsn->ilen = 4;
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break;
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case 3:
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ainsn->ilen = 6;
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break;
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}
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switch (*(__u8 *) ainsn->insn) {
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case 0x05: /* balr */
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case 0x0d: /* basr */
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ainsn->fixup = FIXUP_RETURN_REGISTER;
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/* if r2 = 0, no branch will be taken */
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if ((*ainsn->insn & 0x0f) == 0)
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ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
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break;
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case 0x06: /* bctr */
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case 0x07: /* bcr */
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ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
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break;
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case 0x45: /* bal */
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case 0x4d: /* bas */
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ainsn->fixup = FIXUP_RETURN_REGISTER;
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break;
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case 0x47: /* bc */
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case 0x46: /* bct */
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case 0x86: /* bxh */
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case 0x87: /* bxle */
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ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
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break;
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case 0x82: /* lpsw */
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ainsn->fixup = FIXUP_NOT_REQUIRED;
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break;
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case 0xb2: /* lpswe */
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if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
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ainsn->fixup = FIXUP_NOT_REQUIRED;
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}
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break;
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case 0xa7: /* bras */
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if ((*ainsn->insn & 0x0f) == 0x05) {
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ainsn->fixup |= FIXUP_RETURN_REGISTER;
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}
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break;
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case 0xc0:
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if ((*ainsn->insn & 0x0f) == 0x00 /* larl */
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|| (*ainsn->insn & 0x0f) == 0x05) /* brasl */
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ainsn->fixup |= FIXUP_RETURN_REGISTER;
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break;
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case 0xeb:
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if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 || /* bxhg */
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*(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
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ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
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}
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break;
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case 0xe3: /* bctg */
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if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
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ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
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}
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break;
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}
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}
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static int __kprobes swap_instruction(void *aref)
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{
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struct ins_replace_args *args = aref;
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u32 *addr;
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u32 instr;
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int err = -EFAULT;
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/*
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* Text segment is read-only, hence we use stura to bypass dynamic
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* address translation to exchange the instruction. Since stura
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* always operates on four bytes, but we only want to exchange two
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* bytes do some calculations to get things right. In addition we
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* shall not cross any page boundaries (vmalloc area!) when writing
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* the new instruction.
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*/
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addr = (u32 *)((unsigned long)args->ptr & -4UL);
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if ((unsigned long)args->ptr & 2)
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instr = ((*addr) & 0xffff0000) | args->new;
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else
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instr = ((*addr) & 0x0000ffff) | args->new << 16;
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asm volatile(
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" lra %1,0(%1)\n"
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"0: stura %2,%1\n"
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"1: la %0,0\n"
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"2:\n"
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EX_TABLE(0b,2b)
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: "+d" (err)
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: "a" (addr), "d" (instr)
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: "memory", "cc");
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return err;
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}
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void __kprobes arch_arm_kprobe(struct kprobe *p)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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unsigned long status = kcb->kprobe_status;
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struct ins_replace_args args;
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args.ptr = p->addr;
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args.old = p->opcode;
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args.new = BREAKPOINT_INSTRUCTION;
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kcb->kprobe_status = KPROBE_SWAP_INST;
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stop_machine_run(swap_instruction, &args, NR_CPUS);
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kcb->kprobe_status = status;
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}
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void __kprobes arch_disarm_kprobe(struct kprobe *p)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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unsigned long status = kcb->kprobe_status;
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struct ins_replace_args args;
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args.ptr = p->addr;
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args.old = BREAKPOINT_INSTRUCTION;
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args.new = p->opcode;
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kcb->kprobe_status = KPROBE_SWAP_INST;
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stop_machine_run(swap_instruction, &args, NR_CPUS);
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kcb->kprobe_status = status;
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}
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void __kprobes arch_remove_kprobe(struct kprobe *p)
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{
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mutex_lock(&kprobe_mutex);
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free_insn_slot(p->ainsn.insn, 0);
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mutex_unlock(&kprobe_mutex);
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}
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static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
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{
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per_cr_bits kprobe_per_regs[1];
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memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
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regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
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/* Set up the per control reg info, will pass to lctl */
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kprobe_per_regs[0].em_instruction_fetch = 1;
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kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
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kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
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/* Set the PER control regs, turns on single step for this address */
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__ctl_load(kprobe_per_regs, 9, 11);
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regs->psw.mask |= PSW_MASK_PER;
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regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
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}
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static void __kprobes 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.kprobe_saved_imask = kcb->kprobe_saved_imask;
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memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
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sizeof(kcb->kprobe_saved_ctl));
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}
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static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
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{
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__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
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kcb->kprobe_status = kcb->prev_kprobe.status;
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kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
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memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
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sizeof(kcb->kprobe_saved_ctl));
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}
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static void __kprobes 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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__get_cpu_var(current_kprobe) = p;
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/* Save the interrupt and per flags */
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kcb->kprobe_saved_imask = regs->psw.mask &
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(PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
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/* Save the control regs that govern PER */
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__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
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}
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/* Called with kretprobe_lock held */
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void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
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struct pt_regs *regs)
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{
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ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
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/* Replace the return addr with trampoline addr */
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regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
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}
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static int __kprobes 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 long *addr = (unsigned long *)
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((regs->psw.addr & PSW_ADDR_INSN) - 2);
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struct kprobe_ctlblk *kcb;
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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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if (kcb->kprobe_status == KPROBE_HIT_SS &&
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*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
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regs->psw.mask &= ~PSW_MASK_PER;
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regs->psw.mask |= kcb->kprobe_saved_imask;
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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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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_REENTER;
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return 1;
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} else {
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p = __get_cpu_var(current_kprobe);
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if (p->break_handler && p->break_handler(p, regs)) {
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goto ss_probe;
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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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/*
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* No kprobe at this address. The fault has not been
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* caused by a kprobe breakpoint. The race of breakpoint
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* vs. kprobe remove does not exist because on s390 we
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* use stop_machine_run to arm/disarm the breakpoints.
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*/
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goto no_kprobe;
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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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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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/*
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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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void kretprobe_trampoline_holder(void)
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{
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asm volatile(".global kretprobe_trampoline\n"
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"kretprobe_trampoline: bcr 0,0\n");
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}
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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 __kprobes trampoline_probe_handler(struct kprobe *p,
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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 *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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spin_lock_irqsave(&kretprobe_lock, flags);
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head = kretprobe_inst_table_head(current);
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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 then 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, node, 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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}
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kretprobe_assert(ri, orig_ret_address, trampoline_address);
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regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
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reset_current_kprobe();
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spin_unlock_irqrestore(&kretprobe_lock, flags);
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preempt_enable_no_resched();
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hlist_for_each_entry_safe(ri, node, 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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/*
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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"
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* instruction. To avoid the SMP problems that can occur when we
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* temporarily put back the original opcode to single-step, we
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* single-stepped a copy of the instruction. The address of this
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* copy is p->ainsn.insn.
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*/
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static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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regs->psw.addr &= PSW_ADDR_INSN;
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if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
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regs->psw.addr = (unsigned long)p->addr +
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((unsigned long)regs->psw.addr -
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(unsigned long)p->ainsn.insn);
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if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
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if ((unsigned long)regs->psw.addr -
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(unsigned long)p->ainsn.insn == p->ainsn.ilen)
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regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
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if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
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regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
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(regs->gprs[p->ainsn.reg] -
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(unsigned long)p->ainsn.insn))
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| PSW_ADDR_AMODE;
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regs->psw.addr |= PSW_ADDR_AMODE;
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/* turn off PER mode */
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regs->psw.mask &= ~PSW_MASK_PER;
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/* Restore the original per control regs */
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__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
|
|
regs->psw.mask |= kcb->kprobe_saved_imask;
|
|
}
|
|
|
|
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;
|
|
|
|
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
|
|
kcb->kprobe_status = KPROBE_HIT_SSDONE;
|
|
cur->post_handler(cur, regs, 0);
|
|
}
|
|
|
|
resume_execution(cur, regs);
|
|
|
|
/*Restore back the original saved kprobes variables and continue. */
|
|
if (kcb->kprobe_status == KPROBE_REENTER) {
|
|
restore_previous_kprobe(kcb);
|
|
goto out;
|
|
}
|
|
reset_current_kprobe();
|
|
out:
|
|
preempt_enable_no_resched();
|
|
|
|
/*
|
|
* if somebody else is singlestepping across a probe point, psw mask
|
|
* will have PER set, in which case, continue the remaining processing
|
|
* of do_single_step, as if this is not a probe hit.
|
|
*/
|
|
if (regs->psw.mask & PSW_MASK_PER) {
|
|
return 0;
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
|
|
{
|
|
struct kprobe *cur = kprobe_running();
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
const struct exception_table_entry *entry;
|
|
|
|
switch(kcb->kprobe_status) {
|
|
case KPROBE_SWAP_INST:
|
|
/* We are here because the instruction replacement failed */
|
|
return 0;
|
|
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->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
|
|
regs->psw.mask &= ~PSW_MASK_PER;
|
|
regs->psw.mask |= kcb->kprobe_saved_imask;
|
|
if (kcb->kprobe_status == KPROBE_REENTER)
|
|
restore_previous_kprobe(kcb);
|
|
else
|
|
reset_current_kprobe();
|
|
preempt_enable_no_resched();
|
|
break;
|
|
case KPROBE_HIT_ACTIVE:
|
|
case KPROBE_HIT_SSDONE:
|
|
/*
|
|
* We increment the nmissed count for accounting,
|
|
* we can also use npre/npostfault count for accouting
|
|
* these specific fault cases.
|
|
*/
|
|
kprobes_inc_nmissed_count(cur);
|
|
|
|
/*
|
|
* We come here because instructions in the pre/post
|
|
* handler caused the page_fault, this could happen
|
|
* if handler tries to access user space by
|
|
* copy_from_user(), get_user() etc. Let the
|
|
* user-specified handler try to fix it first.
|
|
*/
|
|
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
|
|
return 1;
|
|
|
|
/*
|
|
* In case the user-specified fault handler returned
|
|
* zero, try to fix up.
|
|
*/
|
|
entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
|
|
if (entry) {
|
|
regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* fixup_exception() could not handle it,
|
|
* Let do_page_fault() fix it.
|
|
*/
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Wrapper routine to for handling exceptions.
|
|
*/
|
|
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
|
|
unsigned long val, void *data)
|
|
{
|
|
struct die_args *args = (struct die_args *)data;
|
|
int ret = NOTIFY_DONE;
|
|
|
|
switch (val) {
|
|
case DIE_BPT:
|
|
if (kprobe_handler(args->regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
case DIE_SSTEP:
|
|
if (post_kprobe_handler(args->regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
case DIE_TRAP:
|
|
/* kprobe_running() needs smp_processor_id() */
|
|
preempt_disable();
|
|
if (kprobe_running() &&
|
|
kprobe_fault_handler(args->regs, args->trapnr))
|
|
ret = NOTIFY_STOP;
|
|
preempt_enable();
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
struct jprobe *jp = container_of(p, struct jprobe, kp);
|
|
unsigned long addr;
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
|
|
memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
|
|
|
|
/* setup return addr to the jprobe handler routine */
|
|
regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
|
|
|
|
/* r14 is the function return address */
|
|
kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
|
|
/* r15 is the stack pointer */
|
|
kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
|
|
addr = (unsigned long)kcb->jprobe_saved_r15;
|
|
|
|
memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
|
|
MIN_STACK_SIZE(addr));
|
|
return 1;
|
|
}
|
|
|
|
void __kprobes jprobe_return(void)
|
|
{
|
|
asm volatile(".word 0x0002");
|
|
}
|
|
|
|
void __kprobes jprobe_return_end(void)
|
|
{
|
|
asm volatile("bcr 0,0");
|
|
}
|
|
|
|
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
|
|
{
|
|
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
|
|
unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
|
|
|
|
/* Put the regs back */
|
|
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
|
|
/* put the stack back */
|
|
memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
|
|
MIN_STACK_SIZE(stack_addr));
|
|
preempt_enable_no_resched();
|
|
return 1;
|
|
}
|
|
|
|
static struct kprobe trampoline_p = {
|
|
.addr = (kprobe_opcode_t *) & kretprobe_trampoline,
|
|
.pre_handler = trampoline_probe_handler
|
|
};
|
|
|
|
int __init arch_init_kprobes(void)
|
|
{
|
|
return register_kprobe(&trampoline_p);
|
|
}
|
|
|
|
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
|
|
{
|
|
if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
|
|
return 1;
|
|
return 0;
|
|
}
|