2 * arch/sh/kernel/hw_breakpoint.c
4 * Unified kernel/user-space hardware breakpoint facility for the on-chip UBC.
6 * Copyright (C) 2009 - 2010 Paul Mundt
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
12 #include <linux/init.h>
13 #include <linux/perf_event.h>
14 #include <linux/hw_breakpoint.h>
15 #include <linux/percpu.h>
16 #include <linux/kallsyms.h>
17 #include <linux/notifier.h>
18 #include <linux/kprobes.h>
19 #include <linux/kdebug.h>
21 #include <linux/clk.h>
22 #include <asm/hw_breakpoint.h>
23 #include <asm/mmu_context.h>
24 #include <asm/ptrace.h>
27 * Stores the breakpoints currently in use on each breakpoint address
28 * register for each cpus
30 static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
33 * A dummy placeholder for early accesses until the CPUs get a chance to
34 * register their UBCs later in the boot process.
36 static struct sh_ubc ubc_dummy = { .num_events = 0 };
38 static struct sh_ubc *sh_ubc __read_mostly = &ubc_dummy;
41 * Install a perf counter breakpoint.
43 * We seek a free UBC channel and use it for this breakpoint.
45 * Atomic: we hold the counter->ctx->lock and we only handle variables
46 * and registers local to this cpu.
48 int arch_install_hw_breakpoint(struct perf_event *bp)
50 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
53 for (i = 0; i < sh_ubc->num_events; i++) {
54 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
62 if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
65 clk_enable(sh_ubc->clk);
66 sh_ubc->enable(info, i);
72 * Uninstall the breakpoint contained in the given counter.
74 * First we search the debug address register it uses and then we disable
77 * Atomic: we hold the counter->ctx->lock and we only handle variables
78 * and registers local to this cpu.
80 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
82 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
85 for (i = 0; i < sh_ubc->num_events; i++) {
86 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
94 if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
97 sh_ubc->disable(info, i);
98 clk_disable(sh_ubc->clk);
101 static int get_hbp_len(u16 hbp_len)
103 unsigned int len_in_bytes = 0;
106 case SH_BREAKPOINT_LEN_1:
109 case SH_BREAKPOINT_LEN_2:
112 case SH_BREAKPOINT_LEN_4:
115 case SH_BREAKPOINT_LEN_8:
123 * Check for virtual address in kernel space.
125 int arch_check_bp_in_kernelspace(struct perf_event *bp)
129 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
132 len = get_hbp_len(info->len);
134 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
137 int arch_bp_generic_fields(int sh_len, int sh_type,
138 int *gen_len, int *gen_type)
142 case SH_BREAKPOINT_LEN_1:
143 *gen_len = HW_BREAKPOINT_LEN_1;
145 case SH_BREAKPOINT_LEN_2:
146 *gen_len = HW_BREAKPOINT_LEN_2;
148 case SH_BREAKPOINT_LEN_4:
149 *gen_len = HW_BREAKPOINT_LEN_4;
151 case SH_BREAKPOINT_LEN_8:
152 *gen_len = HW_BREAKPOINT_LEN_8;
160 case SH_BREAKPOINT_READ:
161 *gen_type = HW_BREAKPOINT_R;
162 case SH_BREAKPOINT_WRITE:
163 *gen_type = HW_BREAKPOINT_W;
165 case SH_BREAKPOINT_RW:
166 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
175 static int arch_build_bp_info(struct perf_event *bp)
177 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
179 info->address = bp->attr.bp_addr;
182 switch (bp->attr.bp_len) {
183 case HW_BREAKPOINT_LEN_1:
184 info->len = SH_BREAKPOINT_LEN_1;
186 case HW_BREAKPOINT_LEN_2:
187 info->len = SH_BREAKPOINT_LEN_2;
189 case HW_BREAKPOINT_LEN_4:
190 info->len = SH_BREAKPOINT_LEN_4;
192 case HW_BREAKPOINT_LEN_8:
193 info->len = SH_BREAKPOINT_LEN_8;
200 switch (bp->attr.bp_type) {
201 case HW_BREAKPOINT_R:
202 info->type = SH_BREAKPOINT_READ;
204 case HW_BREAKPOINT_W:
205 info->type = SH_BREAKPOINT_WRITE;
207 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
208 info->type = SH_BREAKPOINT_RW;
218 * Validate the arch-specific HW Breakpoint register settings
220 int arch_validate_hwbkpt_settings(struct perf_event *bp)
222 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
226 ret = arch_build_bp_info(bp);
233 case SH_BREAKPOINT_LEN_1:
236 case SH_BREAKPOINT_LEN_2:
239 case SH_BREAKPOINT_LEN_4:
242 case SH_BREAKPOINT_LEN_8:
250 * For kernel-addresses, either the address or symbol name can be
254 info->address = (unsigned long)kallsyms_lookup_name(info->name);
257 * Check that the low-order bits of the address are appropriate
258 * for the alignment implied by len.
260 if (info->address & align)
267 * Release the user breakpoints used by ptrace
269 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
272 struct thread_struct *t = &tsk->thread;
274 for (i = 0; i < sh_ubc->num_events; i++) {
275 unregister_hw_breakpoint(t->ptrace_bps[i]);
276 t->ptrace_bps[i] = NULL;
280 static int __kprobes hw_breakpoint_handler(struct die_args *args)
282 int cpu, i, rc = NOTIFY_STOP;
283 struct perf_event *bp;
284 unsigned int cmf, resume_mask;
287 * Do an early return if none of the channels triggered.
289 cmf = sh_ubc->triggered_mask();
294 * By default, resume all of the active channels.
296 resume_mask = sh_ubc->active_mask();
299 * Disable breakpoints during exception handling.
301 sh_ubc->disable_all();
304 for (i = 0; i < sh_ubc->num_events; i++) {
305 unsigned long event_mask = (1 << i);
307 if (likely(!(cmf & event_mask)))
311 * The counter may be concurrently released but that can only
312 * occur from a call_rcu() path. We can then safely fetch
313 * the breakpoint, use its callback, touch its counter
314 * while we are in an rcu_read_lock() path.
318 bp = per_cpu(bp_per_reg[i], cpu);
323 * Reset the condition match flag to denote completion of
324 * exception handling.
326 sh_ubc->clear_triggered_mask(event_mask);
329 * bp can be NULL due to concurrent perf counter
338 * Don't restore the channel if the breakpoint is from
339 * ptrace, as it always operates in one-shot mode.
341 if (bp->overflow_handler == ptrace_triggered)
342 resume_mask &= ~(1 << i);
344 perf_bp_event(bp, args->regs);
346 /* Deliver the signal to userspace */
347 if (!arch_check_bp_in_kernelspace(bp)) {
350 info.si_signo = args->signr;
351 info.si_errno = notifier_to_errno(rc);
352 info.si_code = TRAP_HWBKPT;
354 force_sig_info(args->signr, &info, current);
363 sh_ubc->enable_all(resume_mask);
370 BUILD_TRAP_HANDLER(breakpoint)
372 unsigned long ex = lookup_exception_vector();
375 notify_die(DIE_BREAKPOINT, "breakpoint", regs, 0, ex, SIGTRAP);
379 * Handle debug exception notifications.
381 int __kprobes hw_breakpoint_exceptions_notify(struct notifier_block *unused,
382 unsigned long val, void *data)
384 struct die_args *args = data;
386 if (val != DIE_BREAKPOINT)
390 * If the breakpoint hasn't been triggered by the UBC, it's
391 * probably from a debugger, so don't do anything more here.
393 * This also permits the UBC interface clock to remain off for
394 * non-UBC breakpoints, as we don't need to check the triggered
395 * or active channel masks.
397 if (args->trapnr != sh_ubc->trap_nr)
400 return hw_breakpoint_handler(data);
403 void hw_breakpoint_pmu_read(struct perf_event *bp)
408 int register_sh_ubc(struct sh_ubc *ubc)
410 /* Bail if it's already assigned */
411 if (sh_ubc != &ubc_dummy)
415 pr_info("HW Breakpoints: %s UBC support registered\n", ubc->name);
417 WARN_ON(ubc->num_events > HBP_NUM);