blob: 42920f25e73c8875a9c58401cb8f922d52f5eb20 [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 "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_ctlblk *, struct pt_regs *);
struct csky_insn_patch {
kprobe_opcode_t *addr;
u32 opcode;
atomic_t cpu_count;
};
static int __kprobes patch_text_cb(void *priv)
{
struct csky_insn_patch *param = priv;
unsigned int addr = (unsigned int)param->addr;
if (atomic_inc_return(&param->cpu_count) == 1) {
*(u16 *) addr = cpu_to_le16(param->opcode);
dcache_wb_range(addr, addr + 2);
atomic_inc(&param->cpu_count);
} else {
while (atomic_read(&param->cpu_count) <= num_online_cpus())
cpu_relax();
}
icache_inv_range(addr, addr + 2);
return 0;
}
static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
{
struct csky_insn_patch param = { addr, opcode, ATOMIC_INIT(0) };
return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
}
static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
{
unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
p->ainsn.api.restore = (unsigned long)p->addr + offset;
patch_text(p->ainsn.api.insn, p->opcode);
}
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, (long)p->addr, regs);
post_kprobe_handler(kcb, regs);
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
unsigned long probe_addr = (unsigned long)p->addr;
if (probe_addr & 0x1)
return -EILSEQ;
/* copy instruction */
p->opcode = le32_to_cpu(*p->addr);
/* decode instruction */
switch (csky_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;
}
/* install breakpoint in text */
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
patch_text(p->addr, USR_BKPT);
}
/* remove breakpoint from text */
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
patch_text(p->addr, p->opcode);
}
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_sr = regs->sr;
regs->sr &= ~BIT(6);
}
static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
regs->sr = kcb->saved_sr;
}
static void __kprobes
set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p)
{
unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
kcb->ss_ctx.ss_pending = true;
kcb->ss_ctx.match_addr = addr + offset;
}
static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
{
kcb->ss_ctx.ss_pending = false;
kcb->ss_ctx.match_addr = 0;
}
#define TRACE_MODE_SI BIT(14)
#define TRACE_MODE_MASK ~(0x3 << 14)
#define TRACE_MODE_RUN 0
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;
set_ss_context(kcb, slot, p); /* mark pending ss */
/* IRQs and single stepping do not mix well. */
kprobes_save_local_irqflag(kcb, regs);
regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_SI;
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_ctlblk *kcb, struct pt_regs *regs)
{
struct kprobe *cur = kprobe_running();
if (!cur)
return;
/* return addr restore if non-branching insn */
if (cur->ainsn.api.restore != 0)
regs->pc = 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->pc = (unsigned long) cur->addr;
BUG_ON(!instruction_pointer(regs));
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
else
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;
}
int __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 1;
} 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 1;
}
/*
* 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 0;
}
int __kprobes
kprobe_single_step_handler(struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if ((kcb->ss_ctx.ss_pending)
&& (kcb->ss_ctx.match_addr == instruction_pointer(regs))) {
clear_ss_context(kcb); /* clear pending ss */
kprobes_restore_local_irqflag(kcb, regs);
regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_RUN;
post_kprobe_handler(kcb, regs);
return 1;
}
return 0;
}
/*
* 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;
}
void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
{
return (void *)kretprobe_trampoline_handler(regs, NULL);
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)regs->lr;
ri->fp = NULL;
regs->lr = (unsigned long) &__kretprobe_trampoline;
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
int __init arch_init_kprobes(void)
{
return 0;
}