1 files changed, 408 insertions, 0 deletions
diff --git a/arch/sh/kernel/hw_breakpoint.c b/arch/sh/kernel/hw_breakpoint.c
new file mode 100644
index 000000000..f10d64311
--- /dev/null
+++ b/arch/sh/kernel/hw_breakpoint.c
@@ -0,0 +1,408 @@
+// 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;
+}