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/*
* arch/arm64/kernel/probes/kprobes.c
*
* Kprobes support for ARM64
*
* Copyright (C) 2013 Linaro Limited.
* Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
*/
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/extable.h>
#include <linux/slab.h>
#include <linux/stop_machine.h>
#include <linux/sched/debug.h>
#include <linux/set_memory.h>
#include <linux/stringify.h>
#include <linux/vmalloc.h>
#include <asm/traps.h>
#include <asm/ptrace.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>
#include <asm/daifflags.h>
#include <asm/system_misc.h>
#include <asm/insn.h>
#include <linux/uaccess.h>
#include <asm/irq.h>
#include <asm/sections.h>
#include "decode-insn.h"
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
static void __kprobes
post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
{
kprobe_opcode_t *addr = p->ainsn.api.insn;
void *addrs[] = {addr, addr + 1};
u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS};
/* prepare insn slot */
aarch64_insn_patch_text(addrs, insns, 2);
flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
/*
* Needs restoring of return address after stepping xol.
*/
p->ainsn.api.restore = (unsigned long) p->addr +
sizeof(kprobe_opcode_t);
}
static void __kprobes arch_prepare_simulate(struct kprobe *p)
{
/* This instructions is not executed xol. No need to adjust the PC */
p->ainsn.api.restore = 0;
}
static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (p->ainsn.api.handler)
p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
/* single step simulated, now go for post processing */
post_kprobe_handler(p, kcb, regs);
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
unsigned long probe_addr = (unsigned long)p->addr;
if (probe_addr & 0x3)
return -EINVAL;
/* copy instruction */
p->opcode = le32_to_cpu(*p->addr);
if (search_exception_tables(probe_addr))
return -EINVAL;
/* decode instruction */
switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
case INSN_REJECTED: /* insn not supported */
return -EINVAL;
case INSN_GOOD_NO_SLOT: /* insn need simulation */
p->ainsn.api.insn = NULL;
break;
case INSN_GOOD: /* instruction uses slot */
p->ainsn.api.insn = get_insn_slot();
if (!p->ainsn.api.insn)
return -ENOMEM;
break;
}
/* prepare the instruction */
if (p->ainsn.api.insn)
arch_prepare_ss_slot(p);
else
arch_prepare_simulate(p);
return 0;
}
void *alloc_insn_page(void)
{
return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
NUMA_NO_NODE, __builtin_return_address(0));
}
/* arm kprobe: install breakpoint in text */
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
void *addr = p->addr;
u32 insn = BRK64_OPCODE_KPROBES;
aarch64_insn_patch_text(&addr, &insn, 1);
}
/* disarm kprobe: remove breakpoint from text */
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
void *addr = p->addr;
aarch64_insn_patch_text(&addr, &p->opcode, 1);
}
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
if (p->ainsn.api.insn) {
free_insn_slot(p->ainsn.api.insn, 0);
p->ainsn.api.insn = NULL;
}
}
static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
}
static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
}
static void __kprobes set_current_kprobe(struct kprobe *p)
{
__this_cpu_write(current_kprobe, p);
}
/*
* Mask all of DAIF while executing the instruction out-of-line, to keep things
* simple and avoid nesting exceptions. Interrupts do have to be disabled since
* the kprobe state is per-CPU and doesn't get migrated.
*/
static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
kcb->saved_irqflag = regs->pstate & DAIF_MASK;
regs->pstate |= DAIF_MASK;
}
static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
regs->pstate &= ~DAIF_MASK;
regs->pstate |= kcb->saved_irqflag;
}
static void __kprobes setup_singlestep(struct kprobe *p,
struct pt_regs *regs,
struct kprobe_ctlblk *kcb, int reenter)
{
unsigned long slot;
if (reenter) {
save_previous_kprobe(kcb);
set_current_kprobe(p);
kcb->kprobe_status = KPROBE_REENTER;
} else {
kcb->kprobe_status = KPROBE_HIT_SS;
}
if (p->ainsn.api.insn) {
/* prepare for single stepping */
slot = (unsigned long)p->ainsn.api.insn;
kprobes_save_local_irqflag(kcb, regs);
instruction_pointer_set(regs, slot);
} else {
/* insn simulation */
arch_simulate_insn(p, regs);
}
}
static int __kprobes reenter_kprobe(struct kprobe *p,
struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
switch (kcb->kprobe_status) {
case KPROBE_HIT_SSDONE:
case KPROBE_HIT_ACTIVE:
kprobes_inc_nmissed_count(p);
setup_singlestep(p, regs, kcb, 1);
break;
case KPROBE_HIT_SS:
case KPROBE_REENTER:
pr_warn("Unrecoverable kprobe detected.\n");
dump_kprobe(p);
BUG();
break;
default:
WARN_ON(1);
return 0;
}
return 1;
}
static void __kprobes
post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
{
/* return addr restore if non-branching insn */
if (cur->ainsn.api.restore != 0)
instruction_pointer_set(regs, cur->ainsn.api.restore);
/* restore back original saved kprobe variables and continue */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
return;
}
/* call post handler */
kcb->kprobe_status = KPROBE_HIT_SSDONE;
if (cur->post_handler)
cur->post_handler(cur, regs, 0);
reset_current_kprobe();
}
int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
switch (kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_REENTER:
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the ip points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
instruction_pointer_set(regs, (unsigned long) cur->addr);
BUG_ON(!instruction_pointer(regs));
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
} else {
kprobes_restore_local_irqflag(kcb, regs);
reset_current_kprobe();
}
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, fsr))
return 1;
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
if (fixup_exception(regs))
return 1;
}
return 0;
}
static void __kprobes kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p, *cur_kprobe;
struct kprobe_ctlblk *kcb;
unsigned long addr = instruction_pointer(regs);
kcb = get_kprobe_ctlblk();
cur_kprobe = kprobe_running();
p = get_kprobe((kprobe_opcode_t *) addr);
if (p) {
if (cur_kprobe) {
if (reenter_kprobe(p, regs, kcb))
return;
} else {
/* Probe hit */
set_current_kprobe(p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
/*
* If we have no pre-handler or it returned 0, we
* continue with normal processing. If we have a
* pre-handler and it returned non-zero, it will
* modify the execution path and no need to single
* stepping. Let's just reset current kprobe and exit.
*/
if (!p->pre_handler || !p->pre_handler(p, regs)) {
setup_singlestep(p, regs, kcb, 0);
} else
reset_current_kprobe();
}
}
/*
* The breakpoint instruction was removed right
* after we hit it. Another cpu has removed
* either a probepoint or a debugger breakpoint
* at this address. In either case, no further
* handling of this interrupt is appropriate.
* Return back to original instruction, and continue.
*/
}
static int __kprobes
kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
unsigned long addr = instruction_pointer(regs);
struct kprobe *cur = kprobe_running();
if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
((unsigned long)&cur->ainsn.api.insn[1] == addr)) {
kprobes_restore_local_irqflag(kcb, regs);
post_kprobe_handler(cur, kcb, regs);
return DBG_HOOK_HANDLED;
}
/* not ours, kprobes should ignore it */
return DBG_HOOK_ERROR;
}
static struct break_hook kprobes_break_ss_hook = {
.imm = KPROBES_BRK_SS_IMM,
.fn = kprobe_breakpoint_ss_handler,
};
static int __kprobes
kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
{
kprobe_handler(regs);
return DBG_HOOK_HANDLED;
}
static struct break_hook kprobes_break_hook = {
.imm = KPROBES_BRK_IMM,
.fn = kprobe_breakpoint_handler,
};
/*
* Provide a blacklist of symbols identifying ranges which cannot be kprobed.
* This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
*/
int __init arch_populate_kprobe_blacklist(void)
{
int ret;
ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
(unsigned long)__entry_text_end);
if (ret)
return ret;
ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
(unsigned long)__irqentry_text_end);
if (ret)
return ret;
ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start,
(unsigned long)__idmap_text_end);
if (ret)
return ret;
ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
(unsigned long)__hyp_text_end);
if (ret || is_kernel_in_hyp_mode())
return ret;
ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
(unsigned long)__hyp_idmap_text_end);
return ret;
}
void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
{
return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline,
(void *)kernel_stack_pointer(regs));
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
ri->fp = (void *)kernel_stack_pointer(regs);
/* replace return addr (x30) with trampoline */
regs->regs[30] = (long)&kretprobe_trampoline;
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
int __init arch_init_kprobes(void)
{
register_kernel_break_hook(&kprobes_break_hook);
register_kernel_break_hook(&kprobes_break_ss_hook);
return 0;
}
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