1 files changed, 548 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/hw_breakpoint.c b/arch/loongarch/kernel/hw_breakpoint.c
new file mode 100644
index 000000000000..2406c95b34cc
--- /dev/null
+++ b/arch/loongarch/kernel/hw_breakpoint.c
@@ -0,0 +1,548 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022-2023 Loongson Technology Corporation Limited
+ */
+#define pr_fmt(fmt) "hw-breakpoint: " fmt
+
+#include <linux/hw_breakpoint.h>
+#include <linux/kprobes.h>
+#include <linux/perf_event.h>
+
+#include <asm/hw_breakpoint.h>
+
+/* Breakpoint currently in use for each BRP. */
+static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[LOONGARCH_MAX_BRP]);
+
+/* Watchpoint currently in use for each WRP. */
+static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[LOONGARCH_MAX_WRP]);
+
+int hw_breakpoint_slots(int type)
+{
+	/*
+	 * We can be called early, so don't rely on
+	 * our static variables being initialised.
+	 */
+	switch (type) {
+	case TYPE_INST:
+		return get_num_brps();
+	case TYPE_DATA:
+		return get_num_wrps();
+	default:
+		pr_warn("unknown slot type: %d\n", type);
+		return 0;
+	}
+}
+
+#define READ_WB_REG_CASE(OFF, N, REG, T, VAL)		\
+	case (OFF + N):					\
+		LOONGARCH_CSR_WATCH_READ(N, REG, T, VAL);	\
+		break
+
+#define WRITE_WB_REG_CASE(OFF, N, REG, T, VAL)		\
+	case (OFF + N):					\
+		LOONGARCH_CSR_WATCH_WRITE(N, REG, T, VAL);	\
+		break
+
+#define GEN_READ_WB_REG_CASES(OFF, REG, T, VAL)		\
+	READ_WB_REG_CASE(OFF, 0, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 1, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 2, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 3, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 4, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 5, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 6, REG, T, VAL);		\
+	READ_WB_REG_CASE(OFF, 7, REG, T, VAL);
+
+#define GEN_WRITE_WB_REG_CASES(OFF, REG, T, VAL)	\
+	WRITE_WB_REG_CASE(OFF, 0, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 1, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 2, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 3, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 4, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 5, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 6, REG, T, VAL);		\
+	WRITE_WB_REG_CASE(OFF, 7, REG, T, VAL);
+
+static u64 read_wb_reg(int reg, int n, int t)
+{
+	u64 val = 0;
+
+	switch (reg + n) {
+	GEN_READ_WB_REG_CASES(CSR_CFG_ADDR, ADDR, t, val);
+	GEN_READ_WB_REG_CASES(CSR_CFG_MASK, MASK, t, val);
+	GEN_READ_WB_REG_CASES(CSR_CFG_CTRL, CTRL, t, val);
+	GEN_READ_WB_REG_CASES(CSR_CFG_ASID, ASID, t, val);
+	default:
+		pr_warn("Attempt to read from unknown breakpoint register %d\n", n);
+	}
+
+	return val;
+}
+NOKPROBE_SYMBOL(read_wb_reg);
+
+static void write_wb_reg(int reg, int n, int t, u64 val)
+{
+	switch (reg + n) {
+	GEN_WRITE_WB_REG_CASES(CSR_CFG_ADDR, ADDR, t, val);
+	GEN_WRITE_WB_REG_CASES(CSR_CFG_MASK, MASK, t, val);
+	GEN_WRITE_WB_REG_CASES(CSR_CFG_CTRL, CTRL, t, val);
+	GEN_WRITE_WB_REG_CASES(CSR_CFG_ASID, ASID, t, val);
+	default:
+		pr_warn("Attempt to write to unknown breakpoint register %d\n", n);
+	}
+}
+NOKPROBE_SYMBOL(write_wb_reg);
+
+enum hw_breakpoint_ops {
+	HW_BREAKPOINT_INSTALL,
+	HW_BREAKPOINT_UNINSTALL,
+};
+
+/*
+ * hw_breakpoint_slot_setup - Find and setup a perf slot according to operations
+ *
+ * @slots: pointer to array of slots
+ * @max_slots: max number of slots
+ * @bp: perf_event to setup
+ * @ops: operation to be carried out on the slot
+ *
+ * Return:
+ *	slot index on success
+ *	-ENOSPC if no slot is available/matches
+ *	-EINVAL on wrong operations parameter
+ */
+
+static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots,
+				    struct perf_event *bp, enum hw_breakpoint_ops ops)
+{
+	int i;
+	struct perf_event **slot;
+
+	for (i = 0; i < max_slots; ++i) {
+		slot = &slots[i];
+		switch (ops) {
+		case HW_BREAKPOINT_INSTALL:
+			if (!*slot) {
+				*slot = bp;
+				return i;
+			}
+			break;
+		case HW_BREAKPOINT_UNINSTALL:
+			if (*slot == bp) {
+				*slot = NULL;
+				return i;
+			}
+			break;
+		default:
+			pr_warn_once("Unhandled hw breakpoint ops %d\n", ops);
+			return -EINVAL;
+		}
+	}
+
+	return -ENOSPC;
+}
+
+void ptrace_hw_copy_thread(struct task_struct *tsk)
+{
+	memset(tsk->thread.hbp_break, 0, sizeof(tsk->thread.hbp_break));
+	memset(tsk->thread.hbp_watch, 0, sizeof(tsk->thread.hbp_watch));
+}
+
+/*
+ * Unregister breakpoints from this task and reset the pointers in the thread_struct.
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+	int i;
+	struct thread_struct *t = &tsk->thread;
+
+	for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
+		if (t->hbp_break[i]) {
+			unregister_hw_breakpoint(t->hbp_break[i]);
+			t->hbp_break[i] = NULL;
+		}
+	}
+
+	for (i = 0; i < LOONGARCH_MAX_WRP; i++) {
+		if (t->hbp_watch[i]) {
+			unregister_hw_breakpoint(t->hbp_watch[i]);
+			t->hbp_watch[i] = NULL;
+		}
+	}
+}
+
+static int hw_breakpoint_control(struct perf_event *bp,
+				 enum hw_breakpoint_ops ops)
+{
+	u32 ctrl;
+	int i, max_slots, enable;
+	struct perf_event **slots;
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+	if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
+		/* Breakpoint */
+		slots = this_cpu_ptr(bp_on_reg);
+		max_slots = boot_cpu_data.watch_ireg_count;
+	} else {
+		/* Watchpoint */
+		slots = this_cpu_ptr(wp_on_reg);
+		max_slots = boot_cpu_data.watch_dreg_count;
+	}
+
+	i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops);
+
+	if (WARN_ONCE(i < 0, "Can't find any breakpoint slot"))
+		return i;
+
+	switch (ops) {
+	case HW_BREAKPOINT_INSTALL:
+		/* Set the FWPnCFG/MWPnCFG 1~4 register. */
+		write_wb_reg(CSR_CFG_ADDR, i, 0, info->address);
+		write_wb_reg(CSR_CFG_ADDR, i, 1, info->address);
+		write_wb_reg(CSR_CFG_MASK, i, 0, info->mask);
+		write_wb_reg(CSR_CFG_MASK, i, 1, info->mask);
+		write_wb_reg(CSR_CFG_ASID, i, 0, 0);
+		write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+		if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
+			write_wb_reg(CSR_CFG_CTRL, i, 0, CTRL_PLV_ENABLE);
+		} else {
+			ctrl = encode_ctrl_reg(info->ctrl);
+			write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl | CTRL_PLV_ENABLE |
+				     1 << MWPnCFG3_LoadEn | 1 << MWPnCFG3_StoreEn);
+		}
+		enable = csr_read64(LOONGARCH_CSR_CRMD);
+		csr_write64(CSR_CRMD_WE | enable, LOONGARCH_CSR_CRMD);
+		break;
+	case HW_BREAKPOINT_UNINSTALL:
+		/* Reset the FWPnCFG/MWPnCFG 1~4 register. */
+		write_wb_reg(CSR_CFG_ADDR, i, 0, 0);
+		write_wb_reg(CSR_CFG_ADDR, i, 1, 0);
+		write_wb_reg(CSR_CFG_MASK, i, 0, 0);
+		write_wb_reg(CSR_CFG_MASK, i, 1, 0);
+		write_wb_reg(CSR_CFG_CTRL, i, 0, 0);
+		write_wb_reg(CSR_CFG_CTRL, i, 1, 0);
+		write_wb_reg(CSR_CFG_ASID, i, 0, 0);
+		write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+		break;
+	}
+
+	return 0;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+	return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
+}
+
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+	hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
+}
+
+static int get_hbp_len(u8 hbp_len)
+{
+	unsigned int len_in_bytes = 0;
+
+	switch (hbp_len) {
+	case LOONGARCH_BREAKPOINT_LEN_1:
+		len_in_bytes = 1;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_2:
+		len_in_bytes = 2;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_4:
+		len_in_bytes = 4;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_8:
+		len_in_bytes = 8;
+		break;
+	}
+
+	return len_in_bytes;
+}
+
+/*
+ * Check whether bp virtual address is 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->ctrl.len);
+
+	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+}
+
+/*
+ * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
+ * Hopefully this will disappear when ptrace can bypass the conversion
+ * to generic breakpoint descriptions.
+ */
+int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
+			   int *gen_len, int *gen_type, int *offset)
+{
+	/* Type */
+	switch (ctrl.type) {
+	case LOONGARCH_BREAKPOINT_EXECUTE:
+		*gen_type = HW_BREAKPOINT_X;
+		break;
+	case LOONGARCH_BREAKPOINT_LOAD:
+		*gen_type = HW_BREAKPOINT_R;
+		break;
+	case LOONGARCH_BREAKPOINT_STORE:
+		*gen_type = HW_BREAKPOINT_W;
+		break;
+	case LOONGARCH_BREAKPOINT_LOAD | LOONGARCH_BREAKPOINT_STORE:
+		*gen_type = HW_BREAKPOINT_RW;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (!ctrl.len)
+		return -EINVAL;
+
+	*offset = __ffs(ctrl.len);
+
+	/* Len */
+	switch (ctrl.len) {
+	case LOONGARCH_BREAKPOINT_LEN_1:
+		*gen_len = HW_BREAKPOINT_LEN_1;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_2:
+		*gen_len = HW_BREAKPOINT_LEN_2;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_4:
+		*gen_len = HW_BREAKPOINT_LEN_4;
+		break;
+	case LOONGARCH_BREAKPOINT_LEN_8:
+		*gen_len = HW_BREAKPOINT_LEN_8;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * Construct an arch_hw_breakpoint from a perf_event.
+ */
+static int arch_build_bp_info(struct perf_event *bp,
+			      const struct perf_event_attr *attr,
+			      struct arch_hw_breakpoint *hw)
+{
+	/* Type */
+	switch (attr->bp_type) {
+	case HW_BREAKPOINT_X:
+		hw->ctrl.type = LOONGARCH_BREAKPOINT_EXECUTE;
+		break;
+	case HW_BREAKPOINT_R:
+		hw->ctrl.type = LOONGARCH_BREAKPOINT_LOAD;
+		break;
+	case HW_BREAKPOINT_W:
+		hw->ctrl.type = LOONGARCH_BREAKPOINT_STORE;
+		break;
+	case HW_BREAKPOINT_RW:
+		hw->ctrl.type = LOONGARCH_BREAKPOINT_LOAD | LOONGARCH_BREAKPOINT_STORE;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Len */
+	switch (attr->bp_len) {
+	case HW_BREAKPOINT_LEN_1:
+		hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_1;
+		break;
+	case HW_BREAKPOINT_LEN_2:
+		hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_2;
+		break;
+	case HW_BREAKPOINT_LEN_4:
+		hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_4;
+		break;
+	case HW_BREAKPOINT_LEN_8:
+		hw->ctrl.len = LOONGARCH_BREAKPOINT_LEN_8;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Address */
+	hw->address = attr->bp_addr;
+
+	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)
+{
+	int ret;
+	u64 alignment_mask, offset;
+
+	/* Build the arch_hw_breakpoint. */
+	ret = arch_build_bp_info(bp, attr, hw);
+	if (ret)
+		return ret;
+
+	if (hw->ctrl.type != LOONGARCH_BREAKPOINT_EXECUTE)
+		alignment_mask = 0x7;
+	offset = hw->address & alignment_mask;
+
+	hw->address &= ~alignment_mask;
+	hw->ctrl.len <<= offset;
+
+	return 0;
+}
+
+static void update_bp_registers(struct pt_regs *regs, int enable, int type)
+{
+	u32 ctrl;
+	int i, max_slots;
+	struct perf_event **slots;
+	struct arch_hw_breakpoint *info;
+
+	switch (type) {
+	case 0:
+		slots = this_cpu_ptr(bp_on_reg);
+		max_slots = boot_cpu_data.watch_ireg_count;
+		break;
+	case 1:
+		slots = this_cpu_ptr(wp_on_reg);
+		max_slots = boot_cpu_data.watch_dreg_count;
+		break;
+	default:
+		return;
+	}
+
+	for (i = 0; i < max_slots; ++i) {
+		if (!slots[i])
+			continue;
+
+		info = counter_arch_bp(slots[i]);
+		if (enable) {
+			if ((info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) && (type == 0)) {
+				write_wb_reg(CSR_CFG_CTRL, i, 0, CTRL_PLV_ENABLE);
+				write_wb_reg(CSR_CFG_CTRL, i, 0, CTRL_PLV_ENABLE);
+			} else {
+				ctrl = read_wb_reg(CSR_CFG_CTRL, i, 1);
+				if (info->ctrl.type == LOONGARCH_BREAKPOINT_LOAD)
+					ctrl |= 0x1 << MWPnCFG3_LoadEn;
+				if (info->ctrl.type == LOONGARCH_BREAKPOINT_STORE)
+					ctrl |= 0x1 << MWPnCFG3_StoreEn;
+				write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl);
+			}
+			regs->csr_prmd |= CSR_PRMD_PWE;
+		} else {
+			if ((info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) && (type == 0)) {
+				write_wb_reg(CSR_CFG_CTRL, i, 0, 0);
+			} else {
+				ctrl = read_wb_reg(CSR_CFG_CTRL, i, 1);
+				if (info->ctrl.type == LOONGARCH_BREAKPOINT_LOAD)
+					ctrl &= ~0x1 << MWPnCFG3_LoadEn;
+				if (info->ctrl.type == LOONGARCH_BREAKPOINT_STORE)
+					ctrl &= ~0x1 << MWPnCFG3_StoreEn;
+				write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl);
+			}
+			regs->csr_prmd &= ~CSR_PRMD_PWE;
+		}
+	}
+}
+NOKPROBE_SYMBOL(update_bp_registers);
+
+/*
+ * Debug exception handlers.
+ */
+void breakpoint_handler(struct pt_regs *regs)
+{
+	int i;
+	struct perf_event *bp, **slots;
+
+	slots = this_cpu_ptr(bp_on_reg);
+
+	for (i = 0; i < boot_cpu_data.watch_ireg_count; ++i) {
+		bp = slots[i];
+		if (bp == NULL)
+			continue;
+		perf_bp_event(bp, regs);
+	}
+	update_bp_registers(regs, 0, 0);
+}
+NOKPROBE_SYMBOL(breakpoint_handler);
+
+void watchpoint_handler(struct pt_regs *regs)
+{
+	int i;
+	struct perf_event *wp, **slots;
+
+	slots = this_cpu_ptr(wp_on_reg);
+
+	for (i = 0; i < boot_cpu_data.watch_dreg_count; ++i) {
+		wp = slots[i];
+		if (wp == NULL)
+			continue;
+		perf_bp_event(wp, regs);
+	}
+	update_bp_registers(regs, 0, 1);
+}
+NOKPROBE_SYMBOL(watchpoint_handler);
+
+static int __init arch_hw_breakpoint_init(void)
+{
+	int cpu;
+
+	boot_cpu_data.watch_ireg_count = get_num_brps();
+	boot_cpu_data.watch_dreg_count = get_num_wrps();
+
+	pr_info("Found %d breakpoint and %d watchpoint registers.\n",
+		boot_cpu_data.watch_ireg_count, boot_cpu_data.watch_dreg_count);
+
+	for (cpu = 1; cpu < NR_CPUS; cpu++) {
+		cpu_data[cpu].watch_ireg_count = boot_cpu_data.watch_ireg_count;
+		cpu_data[cpu].watch_dreg_count = boot_cpu_data.watch_dreg_count;
+	}
+
+	return 0;
+}
+arch_initcall(arch_hw_breakpoint_init);
+
+void hw_breakpoint_thread_switch(struct task_struct *next)
+{
+	u64 addr, mask;
+	struct pt_regs *regs = task_pt_regs(next);
+
+	if (test_tsk_thread_flag(next, TIF_SINGLESTEP)) {
+		addr = read_wb_reg(CSR_CFG_ADDR, 0, 0);
+		mask = read_wb_reg(CSR_CFG_MASK, 0, 0);
+		if (!((regs->csr_era ^ addr) & ~mask))
+			csr_write32(CSR_FWPC_SKIP, LOONGARCH_CSR_FWPS);
+		regs->csr_prmd |= CSR_PRMD_PWE;
+	} else {
+		/* Update breakpoints */
+		update_bp_registers(regs, 1, 0);
+		/* Update watchpoints */
+		update_bp_registers(regs, 1, 1);
+	}
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+}
+
+/*
+ * Dummy function to register with die_notifier.
+ */
+int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+				    unsigned long val, void *data)
+{
+	return NOTIFY_DONE;
+}