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![Vasily Gorbik](/assets/img/avatar_default.png)
Use regs->gprs[15] for framepointer verification. This enables additional sanity checks for nested kretprobes. Reviewed-by: Tobias Huschle <huschle@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
556 lines
14 KiB
C
556 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Kernel Probes (KProbes)
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*
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* Copyright IBM Corp. 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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#define pr_fmt(fmt) "kprobes: " fmt
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#include <linux/moduleloader.h>
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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 <linux/uaccess.h>
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#include <linux/extable.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/hardirq.h>
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#include <linux/ftrace.h>
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#include <asm/set_memory.h>
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#include <asm/sections.h>
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#include <asm/dis.h>
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#include "entry.h"
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DEFINE_PER_CPU(struct kprobe *, current_kprobe);
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DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
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struct kretprobe_blackpoint kretprobe_blacklist[] = { };
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DEFINE_INSN_CACHE_OPS(s390_insn);
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static int insn_page_in_use;
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void *alloc_insn_page(void)
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{
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void *page;
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page = module_alloc(PAGE_SIZE);
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if (!page)
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return NULL;
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__set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
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return page;
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}
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static void *alloc_s390_insn_page(void)
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{
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if (xchg(&insn_page_in_use, 1) == 1)
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return NULL;
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return &kprobes_insn_page;
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}
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static void free_s390_insn_page(void *page)
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{
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xchg(&insn_page_in_use, 0);
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}
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struct kprobe_insn_cache kprobe_s390_insn_slots = {
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.mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
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.alloc = alloc_s390_insn_page,
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.free = free_s390_insn_page,
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.pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
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.insn_size = MAX_INSN_SIZE,
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};
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static void copy_instruction(struct kprobe *p)
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{
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kprobe_opcode_t insn[MAX_INSN_SIZE];
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s64 disp, new_disp;
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u64 addr, new_addr;
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unsigned int len;
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len = insn_length(*p->addr >> 8);
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memcpy(&insn, p->addr, len);
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p->opcode = insn[0];
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if (probe_is_insn_relative_long(&insn[0])) {
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/*
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* For pc-relative instructions in RIL-b or RIL-c format patch
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* the RI2 displacement field. We have already made sure that
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* the insn slot for the patched instruction is within the same
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* 2GB area as the original instruction (either kernel image or
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* module area). Therefore the new displacement will always fit.
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*/
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disp = *(s32 *)&insn[1];
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addr = (u64)(unsigned long)p->addr;
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new_addr = (u64)(unsigned long)p->ainsn.insn;
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new_disp = ((addr + (disp * 2)) - new_addr) / 2;
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*(s32 *)&insn[1] = new_disp;
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}
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s390_kernel_write(p->ainsn.insn, &insn, len);
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}
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NOKPROBE_SYMBOL(copy_instruction);
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static int s390_get_insn_slot(struct kprobe *p)
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{
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/*
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* Get an insn slot that is within the same 2GB area like the original
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* instruction. That way instructions with a 32bit signed displacement
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* field can be patched and executed within the insn slot.
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*/
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p->ainsn.insn = NULL;
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if (is_kernel((unsigned long)p->addr))
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p->ainsn.insn = get_s390_insn_slot();
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else if (is_module_addr(p->addr))
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p->ainsn.insn = get_insn_slot();
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return p->ainsn.insn ? 0 : -ENOMEM;
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}
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NOKPROBE_SYMBOL(s390_get_insn_slot);
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static void s390_free_insn_slot(struct kprobe *p)
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{
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if (!p->ainsn.insn)
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return;
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if (is_kernel((unsigned long)p->addr))
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free_s390_insn_slot(p->ainsn.insn, 0);
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else
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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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NOKPROBE_SYMBOL(s390_free_insn_slot);
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/* Check if paddr is at an instruction boundary */
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static bool can_probe(unsigned long paddr)
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{
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unsigned long addr, offset = 0;
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kprobe_opcode_t insn;
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struct kprobe *kp;
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if (paddr & 0x01)
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return false;
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if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
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return false;
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/* Decode instructions */
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addr = paddr - offset;
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while (addr < paddr) {
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if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
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return false;
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if (insn >> 8 == 0) {
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if (insn != BREAKPOINT_INSTRUCTION) {
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/*
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* Note that QEMU inserts opcode 0x0000 to implement
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* software breakpoints for guests. Since the size of
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* the original instruction is unknown, stop following
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* instructions and prevent setting a kprobe.
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*/
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return false;
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}
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/*
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* Check if the instruction has been modified by another
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* kprobe, in which case the original instruction is
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* decoded.
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*/
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kp = get_kprobe((void *)addr);
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if (!kp) {
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/* not a kprobe */
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return false;
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}
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insn = kp->opcode;
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}
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addr += insn_length(insn >> 8);
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}
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return addr == paddr;
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}
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int arch_prepare_kprobe(struct kprobe *p)
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{
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if (!can_probe((unsigned long)p->addr))
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return -EINVAL;
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/* Make sure the probe isn't going on a difficult instruction */
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if (probe_is_prohibited_opcode(p->addr))
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return -EINVAL;
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if (s390_get_insn_slot(p))
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return -ENOMEM;
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copy_instruction(p);
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return 0;
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}
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NOKPROBE_SYMBOL(arch_prepare_kprobe);
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struct swap_insn_args {
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struct kprobe *p;
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unsigned int arm_kprobe : 1;
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};
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static int swap_instruction(void *data)
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{
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struct swap_insn_args *args = data;
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struct kprobe *p = args->p;
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u16 opc;
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opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
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s390_kernel_write(p->addr, &opc, sizeof(opc));
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return 0;
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}
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NOKPROBE_SYMBOL(swap_instruction);
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void arch_arm_kprobe(struct kprobe *p)
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{
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struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
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stop_machine_cpuslocked(swap_instruction, &args, NULL);
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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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struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
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stop_machine_cpuslocked(swap_instruction, &args, NULL);
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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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s390_free_insn_slot(p);
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}
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NOKPROBE_SYMBOL(arch_remove_kprobe);
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static void enable_singlestep(struct kprobe_ctlblk *kcb,
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struct pt_regs *regs,
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unsigned long ip)
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{
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struct per_regs per_kprobe;
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/* Set up the PER control registers %cr9-%cr11 */
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per_kprobe.control = PER_EVENT_IFETCH;
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per_kprobe.start = ip;
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per_kprobe.end = ip;
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/* Save control regs and psw mask */
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__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
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kcb->kprobe_saved_imask = regs->psw.mask &
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(PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
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/* Set PER control regs, turns on single step for the given address */
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__ctl_load(per_kprobe, 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);
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regs->psw.addr = ip;
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}
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NOKPROBE_SYMBOL(enable_singlestep);
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static void disable_singlestep(struct kprobe_ctlblk *kcb,
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struct pt_regs *regs,
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unsigned long ip)
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{
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/* Restore control regs and psw mask, set new psw address */
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__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
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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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regs->psw.addr = ip;
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}
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NOKPROBE_SYMBOL(disable_singlestep);
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/*
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* Activate a kprobe by storing its pointer to current_kprobe. The
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* previous kprobe is stored in kcb->prev_kprobe. A stack of up to
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* two kprobes can be active, see KPROBE_REENTER.
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*/
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static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
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{
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kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
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kcb->prev_kprobe.status = kcb->kprobe_status;
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__this_cpu_write(current_kprobe, p);
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}
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NOKPROBE_SYMBOL(push_kprobe);
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/*
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* Deactivate a kprobe by backing up to the previous state. If the
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* current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
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* for any other state prev_kprobe.kp will be NULL.
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*/
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static void pop_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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}
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NOKPROBE_SYMBOL(pop_kprobe);
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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->gprs[14];
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ri->fp = (void *)regs->gprs[15];
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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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NOKPROBE_SYMBOL(arch_prepare_kretprobe);
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static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
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{
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switch (kcb->kprobe_status) {
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case KPROBE_HIT_SSDONE:
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case KPROBE_HIT_ACTIVE:
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kprobes_inc_nmissed_count(p);
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break;
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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default:
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/*
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* A kprobe on the code path to single step an instruction
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* is a BUG. The code path resides in the .kprobes.text
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* section and is executed with interrupts disabled.
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*/
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pr_err("Failed to recover from reentered kprobes.\n");
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dump_kprobe(p);
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BUG();
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}
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}
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NOKPROBE_SYMBOL(kprobe_reenter_check);
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static int kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe_ctlblk *kcb;
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struct kprobe *p;
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/*
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* We want to disable preemption for the entire duration of kprobe
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* processing. That includes the calls to the pre/post handlers
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* and single stepping the kprobe instruction.
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*/
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preempt_disable();
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kcb = get_kprobe_ctlblk();
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p = get_kprobe((void *)(regs->psw.addr - 2));
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if (p) {
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if (kprobe_running()) {
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/*
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* We have hit a kprobe while another is still
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* active. This can happen in the pre and post
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* handler. Single step the instruction of the
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* new probe but do not call any handler function
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* of this secondary kprobe.
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* push_kprobe and pop_kprobe saves and restores
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* the currently active kprobe.
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*/
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kprobe_reenter_check(kcb, p);
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push_kprobe(kcb, p);
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kcb->kprobe_status = KPROBE_REENTER;
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} else {
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/*
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* If we have no pre-handler or it returned 0, we
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* continue with single stepping. If we have a
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* pre-handler and it returned non-zero, it prepped
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* for changing execution path, so get out doing
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* nothing more here.
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*/
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push_kprobe(kcb, p);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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if (p->pre_handler && p->pre_handler(p, regs)) {
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pop_kprobe(kcb);
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preempt_enable_no_resched();
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return 1;
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}
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kcb->kprobe_status = KPROBE_HIT_SS;
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}
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enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
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return 1;
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} /* else:
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* No kprobe at this address and no active kprobe. The trap has
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* not been caused by a kprobe breakpoint. The race of breakpoint
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* vs. kprobe remove does not exist because on s390 as we use
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* stop_machine to arm/disarm the breakpoints.
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*/
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preempt_enable_no_resched();
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return 0;
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}
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NOKPROBE_SYMBOL(kprobe_handler);
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void arch_kretprobe_fixup_return(struct pt_regs *regs,
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kprobe_opcode_t *correct_ret_addr)
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{
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/* Replace fake return address with real one. */
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regs->gprs[14] = (unsigned long)correct_ret_addr;
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}
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NOKPROBE_SYMBOL(arch_kretprobe_fixup_return);
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/*
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* Called from __kretprobe_trampoline
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*/
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void trampoline_probe_handler(struct pt_regs *regs)
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{
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kretprobe_trampoline_handler(regs, (void *)regs->gprs[15]);
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}
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NOKPROBE_SYMBOL(trampoline_probe_handler);
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/* assembler function that handles the kretprobes must not be probed itself */
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NOKPROBE_SYMBOL(__kretprobe_trampoline);
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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 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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unsigned long ip = regs->psw.addr;
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int fixup = probe_get_fixup_type(p->ainsn.insn);
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if (fixup & FIXUP_PSW_NORMAL)
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ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
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if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
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int ilen = insn_length(p->ainsn.insn[0] >> 8);
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if (ip - (unsigned long) p->ainsn.insn == ilen)
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ip = (unsigned long) p->addr + ilen;
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}
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if (fixup & FIXUP_RETURN_REGISTER) {
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int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
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regs->gprs[reg] += (unsigned long) p->addr -
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(unsigned long) p->ainsn.insn;
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}
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disable_singlestep(kcb, regs, ip);
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}
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NOKPROBE_SYMBOL(resume_execution);
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static int post_kprobe_handler(struct pt_regs *regs)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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struct kprobe *p = kprobe_running();
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if (!p)
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return 0;
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if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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p->post_handler(p, regs, 0);
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}
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resume_execution(p, regs);
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pop_kprobe(kcb);
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preempt_enable_no_resched();
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/*
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* if somebody else is singlestepping across a probe point, psw mask
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* will have PER set, in which case, continue the remaining processing
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* of do_single_step, as if this is not a probe hit.
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*/
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if (regs->psw.mask & PSW_MASK_PER)
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return 0;
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return 1;
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}
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NOKPROBE_SYMBOL(post_kprobe_handler);
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static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
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{
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struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
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struct kprobe *p = kprobe_running();
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switch(kcb->kprobe_status) {
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case KPROBE_HIT_SS:
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case KPROBE_REENTER:
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/*
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* We are here because the instruction being single
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* stepped caused a page fault. We reset the current
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* kprobe and the nip points back to the probe address
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* and allow the page fault handler to continue as a
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* normal page fault.
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*/
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disable_singlestep(kcb, regs, (unsigned long) p->addr);
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pop_kprobe(kcb);
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preempt_enable_no_resched();
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break;
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case KPROBE_HIT_ACTIVE:
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case KPROBE_HIT_SSDONE:
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/*
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* In case the user-specified fault handler returned
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* zero, try to fix up.
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*/
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if (fixup_exception(regs))
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return 1;
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/*
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* fixup_exception() could not handle it,
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* Let do_page_fault() fix it.
|
|
*/
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_trap_handler);
|
|
|
|
int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
|
|
{
|
|
int ret;
|
|
|
|
if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
|
|
local_irq_disable();
|
|
ret = kprobe_trap_handler(regs, trapnr);
|
|
if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
|
|
local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
|
|
return ret;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_fault_handler);
|
|
|
|
/*
|
|
* Wrapper routine to for handling exceptions.
|
|
*/
|
|
int kprobe_exceptions_notify(struct notifier_block *self,
|
|
unsigned long val, void *data)
|
|
{
|
|
struct die_args *args = (struct die_args *) data;
|
|
struct pt_regs *regs = args->regs;
|
|
int ret = NOTIFY_DONE;
|
|
|
|
if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
|
|
local_irq_disable();
|
|
|
|
switch (val) {
|
|
case DIE_BPT:
|
|
if (kprobe_handler(regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
case DIE_SSTEP:
|
|
if (post_kprobe_handler(regs))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
case DIE_TRAP:
|
|
if (!preemptible() && kprobe_running() &&
|
|
kprobe_trap_handler(regs, args->trapnr))
|
|
ret = NOTIFY_STOP;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
|
|
local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
|
|
|
|
return ret;
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_exceptions_notify);
|
|
|
|
int __init arch_init_kprobes(void)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int arch_trampoline_kprobe(struct kprobe *p)
|
|
{
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
|