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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/kdebug.h>
#include <linux/kprobes.h>
#include <linux/preempt.h>
#include <asm/break.h>
static const union loongarch_instruction breakpoint_insn = {
.reg0i15_format = {
.opcode = break_op,
.immediate = BRK_KPROBE_BP,
}
};
static const union loongarch_instruction singlestep_insn = {
.reg0i15_format = {
.opcode = break_op,
.immediate = BRK_KPROBE_SSTEPBP,
}
};
DEFINE_PER_CPU(struct kprobe *, current_kprobe);
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
static bool insns_not_supported(union loongarch_instruction insn)
{
switch (insn.reg2i14_format.opcode) {
case llw_op:
case lld_op:
case scw_op:
case scd_op:
pr_notice("kprobe: ll and sc instructions are not supported\n");
return true;
}
switch (insn.reg1i21_format.opcode) {
case bceqz_op:
pr_notice("kprobe: bceqz and bcnez instructions are not supported\n");
return true;
}
return false;
}
NOKPROBE_SYMBOL(insns_not_supported);
static bool insns_need_simulation(struct kprobe *p)
{
if (is_pc_ins(&p->opcode))
return true;
if (is_branch_ins(&p->opcode))
return true;
return false;
}
NOKPROBE_SYMBOL(insns_need_simulation);
static void arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
{
if (is_pc_ins(&p->opcode))
simu_pc(regs, p->opcode);
else if (is_branch_ins(&p->opcode))
simu_branch(regs, p->opcode);
}
NOKPROBE_SYMBOL(arch_simulate_insn);
static void arch_prepare_ss_slot(struct kprobe *p)
{
p->ainsn.insn[0] = *p->addr;
p->ainsn.insn[1] = singlestep_insn;
p->ainsn.restore = (unsigned long)p->addr + LOONGARCH_INSN_SIZE;
}
NOKPROBE_SYMBOL(arch_prepare_ss_slot);
static void arch_prepare_simulate(struct kprobe *p)
{
p->ainsn.restore = 0;
}
NOKPROBE_SYMBOL(arch_prepare_simulate);
int arch_prepare_kprobe(struct kprobe *p)
{
if ((unsigned long)p->addr & 0x3)
return -EILSEQ;
/* copy instruction */
p->opcode = *p->addr;
/* decode instruction */
if (insns_not_supported(p->opcode))
return -EINVAL;
if (insns_need_simulation(p)) {
p->ainsn.insn = NULL;
} else {
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
return -ENOMEM;
}
/* prepare the instruction */
if (p->ainsn.insn)
arch_prepare_ss_slot(p);
else
arch_prepare_simulate(p);
return 0;
}
NOKPROBE_SYMBOL(arch_prepare_kprobe);
/* Install breakpoint in text */
void arch_arm_kprobe(struct kprobe *p)
{
*p->addr = breakpoint_insn;
flush_insn_slot(p);
}
NOKPROBE_SYMBOL(arch_arm_kprobe);
/* Remove breakpoint from text */
void arch_disarm_kprobe(struct kprobe *p)
{
*p->addr = p->opcode;
flush_insn_slot(p);
}
NOKPROBE_SYMBOL(arch_disarm_kprobe);
void arch_remove_kprobe(struct kprobe *p)
{
if (p->ainsn.insn) {
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
}
NOKPROBE_SYMBOL(arch_remove_kprobe);
static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
}
NOKPROBE_SYMBOL(save_previous_kprobe);
static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
}
NOKPROBE_SYMBOL(restore_previous_kprobe);
static void set_current_kprobe(struct kprobe *p)
{
__this_cpu_write(current_kprobe, p);
}
NOKPROBE_SYMBOL(set_current_kprobe);
/*
* 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 save_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
kcb->saved_status = regs->csr_prmd;
regs->csr_prmd &= ~CSR_PRMD_PIE;
}
NOKPROBE_SYMBOL(save_local_irqflag);
static void restore_local_irqflag(struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
regs->csr_prmd = kcb->saved_status;
}
NOKPROBE_SYMBOL(restore_local_irqflag);
static void post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb,
struct pt_regs *regs)
{
/* return addr restore if non-branching insn */
if (cur->ainsn.restore != 0)
instruction_pointer_set(regs, cur->ainsn.restore);
/* restore back original saved kprobe variables and continue */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
preempt_enable_no_resched();
return;
}
/*
* update the kcb status even if the cur->post_handler is
* not set because reset_curent_kprobe() doesn't update kcb.
*/
kcb->kprobe_status = KPROBE_HIT_SSDONE;
if (cur->post_handler)
cur->post_handler(cur, regs, 0);
reset_current_kprobe();
preempt_enable_no_resched();
}
NOKPROBE_SYMBOL(post_kprobe_handler);
static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb, int reenter)
{
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.insn) {
/* IRQs and single stepping do not mix well */
save_local_irqflag(kcb, regs);
/* set ip register to prepare for single stepping */
regs->csr_era = (unsigned long)p->ainsn.insn;
} else {
/* simulate single steping */
arch_simulate_insn(p, regs);
/* now go for post processing */
post_kprobe_handler(p, kcb, regs);
}
}
NOKPROBE_SYMBOL(setup_singlestep);
static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
switch (kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_HIT_SSDONE:
case KPROBE_HIT_ACTIVE:
kprobes_inc_nmissed_count(p);
setup_singlestep(p, regs, kcb, 1);
break;
case KPROBE_REENTER:
pr_warn("Failed to recover from reentered kprobes.\n");
dump_kprobe(p);
WARN_ON_ONCE(1);
break;
default:
WARN_ON(1);
return false;
}
return true;
}
NOKPROBE_SYMBOL(reenter_kprobe);
bool kprobe_breakpoint_handler(struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb;
struct kprobe *p, *cur_kprobe;
kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->csr_era;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing.
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
cur_kprobe = kprobe_running();
p = get_kprobe(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();
preempt_enable_no_resched();
}
return true;
}
}
if (addr->word != breakpoint_insn.word) {
/*
* 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.
*/
regs->csr_era = (unsigned long)addr;
preempt_enable_no_resched();
return true;
}
preempt_enable_no_resched();
return false;
}
NOKPROBE_SYMBOL(kprobe_breakpoint_handler);
bool kprobe_singlestep_handler(struct pt_regs *regs)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
unsigned long addr = instruction_pointer(regs);
if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
((unsigned long)&cur->ainsn.insn[1] == addr)) {
restore_local_irqflag(kcb, regs);
post_kprobe_handler(cur, kcb, regs);
return true;
}
preempt_enable_no_resched();
return false;
}
NOKPROBE_SYMBOL(kprobe_singlestep_handler);
bool kprobe_fault_handler(struct pt_regs *regs, 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->csr_era = (unsigned long)cur->addr;
WARN_ON_ONCE(!instruction_pointer(regs));
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
} else {
restore_local_irqflag(kcb, regs);
reset_current_kprobe();
}
preempt_enable_no_resched();
break;
}
return false;
}
NOKPROBE_SYMBOL(kprobe_fault_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)
{
return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
(unsigned long)__irqentry_text_end);
}
int __init arch_init_kprobes(void)
{
return 0;
}
int arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
NOKPROBE_SYMBOL(arch_trampoline_kprobe);
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