blob: 2f08c14a933d05299a15677451d1ed28f81e304d [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0+
#define pr_fmt(fmt) "kprobes: " fmt
#include <linux/kprobes.h>
#include <linux/extable.h>
#include <linux/slab.h>
#include <linux/stop_machine.h>
#include <asm/ptrace.h>
#include <linux/uaccess.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>
#include <asm/bug.h>
#include <asm/patch.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)
{
u32 insn = __BUG_INSN_32;
unsigned long offset = GET_INSN_LENGTH(p->opcode);
p->ainsn.api.restore = (unsigned long)p->addr + offset;
patch_text(p->ainsn.api.insn, &p->opcode, 1);
patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset),
&insn, 1);
}
static void __kprobes arch_prepare_simulate(struct kprobe *p)
{
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,
(unsigned long)p->addr, regs);
post_kprobe_handler(p, kcb, regs);
}
static bool __kprobes arch_check_kprobe(struct kprobe *p)
{
unsigned long tmp = (unsigned long)p->addr - p->offset;
unsigned long addr = (unsigned long)p->addr;
while (tmp <= addr) {
if (tmp == addr)
return true;
tmp += GET_INSN_LENGTH(*(u16 *)tmp);
}
return false;
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
u16 *insn = (u16 *)p->addr;
if ((unsigned long)insn & 0x1)
return -EILSEQ;
if (!arch_check_kprobe(p))
return -EILSEQ;
/* copy instruction */
p->opcode = (kprobe_opcode_t)(*insn++);
if (GET_INSN_LENGTH(p->opcode) == 4)
p->opcode |= (kprobe_opcode_t)(*insn) << 16;
/* decode instruction */
switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
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;
}
#ifdef CONFIG_MMU
void *alloc_insn_page(void)
{
return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
GFP_KERNEL, PAGE_KERNEL_READ_EXEC,
VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
__builtin_return_address(0));
}
#endif
/* install breakpoint in text */
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ?
__BUG_INSN_32 : __BUG_INSN_16;
patch_text(p->addr, &insn, 1);
}
/* remove breakpoint from text */
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
patch_text(p->addr, &p->opcode, 1);
}
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
}
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);
}
/*
* Interrupts need to be disabled before single-step mode is set, and not
* reenabled until after single-step mode ends.
* Without disabling interrupt on local CPU, there is a chance of
* interrupt occurrence in the period of exception return and start of
* out-of-line single-step, that result in wrongly single stepping
* into the interrupt handler.
*/
static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
kcb->saved_status = regs->status;
regs->status &= ~SR_SPIE;
}
static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
regs->status = kcb->saved_status;
}
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;
/* IRQs and single stepping do not mix well. */
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("Failed to recover from reentered kprobes.\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)
regs->epc = 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) {
/* post_handler can hit breakpoint and single step
* again, so we enable D-flag for recursive exception.
*/
cur->post_handler(cur, regs, 0);
}
reset_current_kprobe();
}
int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
switch (kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_REENTER:
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the ip points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
regs->epc = (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:
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
if (fixup_exception(regs))
return 1;
}
return 0;
}
bool __kprobes
kprobe_breakpoint_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 true;
} 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.
*
* pre_handler can hit a breakpoint and can step thru
* before return.
*/
if (!p->pre_handler || !p->pre_handler(p, regs))
setup_singlestep(p, regs, kcb, 0);
else
reset_current_kprobe();
}
return true;
}
/*
* 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.
*/
return false;
}
bool __kprobes
kprobe_single_step_handler(struct pt_regs *regs)
{
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[0] + GET_INSN_LENGTH(cur->opcode) == addr)) {
kprobes_restore_local_irqflag(kcb, regs);
post_kprobe_handler(cur, kcb, regs);
return true;
}
/* not ours, kprobes should ignore it */
return false;
}
/*
* 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)__irqentry_text_start,
(unsigned long)__irqentry_text_end);
return ret;
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
int __init arch_init_kprobes(void)
{
return 0;
}