// SPDX-License-Identifier: GPL-2.0
/*
* arch/sh/kernel/hw_breakpoint.c
*
* Unified kernel/user-space hardware breakpoint facility for the on-chip UBC.
*
* Copyright (C) 2009 - 2010 Paul Mundt
*/
#include <linux/init.h>
#include <linux/perf_event.h>
#include <linux/sched/signal.h>
#include <linux/hw_breakpoint.h>
#include <linux/percpu.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <asm/hw_breakpoint.h>
#include <asm/mmu_context.h>
#include <asm/ptrace.h>
#include <asm/traps.h>
/*
* Stores the breakpoints currently in use on each breakpoint address
* register for each cpus
*/
static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
/*
* A dummy placeholder for early accesses until the CPUs get a chance to
* register their UBCs later in the boot process.
*/
static struct sh_ubc ubc_dummy = { .num_events = 0 };
static struct sh_ubc *sh_ubc __read_mostly = &ubc_dummy;
/*
* Install a perf counter breakpoint.
*
* We seek a free UBC channel and use it for this breakpoint.
*
* Atomic: we hold the counter->ctx->lock and we only handle variables
* and registers local to this cpu.
*/
int arch_install_hw_breakpoint(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
int i;
for (i = 0; i < sh_ubc->num_events; i++) {
struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
if (!*slot) {
*slot = bp;
break;
}
}
if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
return -EBUSY;
clk_enable(sh_ubc->clk);
sh_ubc->enable(info, i);
return 0;
}
/*
* Uninstall the breakpoint contained in the given counter.
*
* First we search the debug address register it uses and then we disable
* it.
*
* Atomic: we hold the counter->ctx->lock and we only handle variables
* and registers local to this cpu.
*/
void arch_uninstall_hw_breakpoint(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
int i;
for (i = 0; i < sh_ubc->num_events; i++) {
struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
if (*slot == bp) {
*slot = NULL;
break;
}
}
if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
return;
sh_ubc->disable(info, i);
clk_disable(sh_ubc->clk);
}
static int get_hbp_len(u16 hbp_len)
{
unsigned int len_in_bytes = 0;
switch (hbp_len) {
case SH_BREAKPOINT_LEN_1:
len_in_bytes = 1;
break;
case SH_BREAKPOINT_LEN_2:
len_in_bytes = 2;
break;
case SH_BREAKPOINT_LEN_4:
len_in_bytes = 4;
break;
case SH_BREAKPOINT_LEN_8:
len_in_bytes = 8;
break;
}
return len_in_bytes;
}
/*
* Check for virtual address in kernel space.
*/
int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
{
unsigned int len;
unsigned long va;
va = hw->address;
len = get_hbp_len(hw->len);
return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
}
int arch_bp_generic_fields(int sh_len, int sh_type,
int *gen_len, int *gen_type)
{
/* Len */
switch (sh_len) {
case SH_BREAKPOINT_LEN_1:
*gen_len = HW_BREAKPOINT_LEN_1;
break;
case SH_BREAKPOINT_LEN_2:
*gen_len = HW_BREAKPOINT_LEN_2;
break;
case SH_BREAKPOINT_LEN_4:
*gen_len = HW_BREAKPOINT_LEN_4;
break;
case SH_BREAKPOINT_LEN_8:
*gen_len = HW_BREAKPOINT_LEN_8;
break;
default:
return -EINVAL;
}
/* Type */
switch (sh_type) {
case SH_BREAKPOINT_READ:
*gen_type = HW_BREAKPOINT_R;
break;
case SH_BREAKPOINT_WRITE:
*gen_type = HW_BREAKPOINT_W;
break;
case SH_BREAKPOINT_RW:
*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
break;
default:
return -EINVAL;
}
return 0;
}
static int arch_build_bp_info(struct perf_event *bp,
const struct perf_event_attr *attr,
struct arch_hw_breakpoint *hw)
{
hw->address = attr->bp_addr;
/* Len */
switch (attr->bp_len) {
case HW_BREAKPOINT_LEN_1:
hw->len = SH_BREAKPOINT_LEN_1;
break;
case HW_BREAKPOINT_LEN_2:
hw->len = SH_BREAKPOINT_LEN_2;
break;
case HW_BREAKPOINT_LEN_4:
hw->len = SH_BREAKPOINT_LEN_4;
break;
case HW_BREAKPOINT_LEN_8:
hw->len = SH_BREAKPOINT_LEN_8;
break;
default:
return -EINVAL;
}
/* Type */
switch (attr->bp_type) {
case HW_BREAKPOINT_R:
hw->type = SH_BREAKPOINT_READ;
break;
case HW_BREAKPOINT_W:
hw->type = SH_BREAKPOINT_WRITE;
break;
case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
hw->type = SH_BREAKPOINT_RW;
break;
default:
return -EINVAL;
}
return 0;
}
/*
* Validate the arch-specific HW Breakpoint register settings
*/
int hw_breakpoint_arch_parse(struct perf_event *bp,
const struct perf_event_attr *attr,
struct arch_hw_breakpoint *hw)
{
unsigned int align;
int ret;
ret = arch_build_bp_info(bp, attr, hw);
if (ret)
return ret;
ret = -EINVAL;
switch (hw->len) {
case SH_BREAKPOINT_LEN_1:
align = 0;
break;
case SH_BREAKPOINT_LEN_2:
align = 1;
break;
case SH_BREAKPOINT_LEN_4:
align = 3;
break;
case SH_BREAKPOINT_LEN_8:
align = 7;
break;
default:
return ret;
}
/*
* Check that the low-order bits of the address are appropriate
* for the alignment implied by len.
*/
if (hw->address & align)
return -EINVAL;
return 0;
}
/*
* Release the user breakpoints used by ptrace
*/
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
int i;
struct thread_struct *t = &tsk->thread;
for (i = 0; i < sh_ubc->num_events; i++) {
unregister_hw_breakpoint(t->ptrace_bps[i]);
t->ptrace_bps[i] = NULL;
}
}
static int __kprobes hw_breakpoint_handler(struct die_args *args)
{
int cpu, i, rc = NOTIFY_STOP;
struct perf_event *bp;
unsigned int cmf, resume_mask;
/*
* Do an early return if none of the channels triggered.
*/
cmf = sh_ubc->triggered_mask();
if (unlikely(!cmf))
return NOTIFY_DONE;
/*
* By default, resume all of the active channels.
*/
resume_mask = sh_ubc->active_mask();
/*
* Disable breakpoints during exception handling.
*/
sh_ubc->disable_all();
cpu = get_cpu();
for (i = 0; i < sh_ubc->num_events; i++) {
unsigned long event_mask = (1 << i);
if (likely(!(cmf & event_mask)))
continue;
/*
* The counter may be concurrently released but that can only
* occur from a call_rcu() path. We can then safely fetch
* the breakpoint, use its callback, touch its counter
* while we are in an rcu_read_lock() path.
*/
rcu_read_lock();
bp = per_cpu(bp_per_reg[i], cpu);
if (bp)
rc = NOTIFY_DONE;
/*
* Reset the condition match flag to denote completion of
* exception handling.
*/
sh_ubc->clear_triggered_mask(event_mask);
/*
* bp can be NULL due to concurrent perf counter
* removing.
*/
if (!bp) {
rcu_read_unlock();
break;
}
/*
* Don't restore the channel if the breakpoint is from
* ptrace, as it always operates in one-shot mode.
*/
if (bp->overflow_handler == ptrace_triggered)
resume_mask &= ~(1 << i);
perf_bp_event(bp, args->regs);
/* Deliver the signal to userspace */
if (!arch_check_bp_in_kernelspace(&bp->hw.info)) {
force_sig_fault(SIGTRAP, TRAP_HWBKPT,
(void __user *)NULL);
}
rcu_read_unlock();
}
if (cmf == 0)
rc = NOTIFY_DONE;
sh_ubc->enable_all(resume_mask);
put_cpu();
return rc;
}
BUILD_TRAP_HANDLER(breakpoint)
{
unsigned long ex = lookup_exception_vector();
TRAP_HANDLER_DECL;
notify_die(DIE_BREAKPOINT, "breakpoint", regs, 0, ex, SIGTRAP);
}
/*
* Handle debug exception notifications.
*/
int __kprobes hw_breakpoint_exceptions_notify(struct notifier_block *unused,
unsigned long val, void *data)
{
struct die_args *args = data;
if (val != DIE_BREAKPOINT)
return NOTIFY_DONE;
/*
* If the breakpoint hasn't been triggered by the UBC, it's
* probably from a debugger, so don't do anything more here.
*
* This also permits the UBC interface clock to remain off for
* non-UBC breakpoints, as we don't need to check the triggered
* or active channel masks.
*/
if (args->trapnr != sh_ubc->trap_nr)
return NOTIFY_DONE;
return hw_breakpoint_handler(data);
}
void hw_breakpoint_pmu_read(struct perf_event *bp)
{
/* TODO */
}
int register_sh_ubc(struct sh_ubc *ubc)
{
/* Bail if it's already assigned */
if (sh_ubc != &ubc_dummy)
return -EBUSY;
sh_ubc = ubc;
pr_info("HW Breakpoints: %s UBC support registered\n", ubc->name);
WARN_ON(ubc->num_events > HBP_NUM);
return 0;
}