1 files changed, 271 insertions, 0 deletions
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
new file mode 100644
index 000000000000..8d18d6727f0f
--- /dev/null
+++ b/arch/riscv/kernel/ftrace.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2013 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
+ * Copyright (C) 2017 Andes Technology Corporation
+ */
+
+#include <linux/ftrace.h>
+#include <linux/uaccess.h>
+#include <linux/memory.h>
+#include <linux/irqflags.h>
+#include <linux/stop_machine.h>
+#include <asm/cacheflush.h>
+#include <asm/text-patching.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+void ftrace_arch_code_modify_prepare(void)
+	__acquires(&text_mutex)
+{
+	mutex_lock(&text_mutex);
+}
+
+void ftrace_arch_code_modify_post_process(void)
+	__releases(&text_mutex)
+{
+	mutex_unlock(&text_mutex);
+}
+
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return addr + 8 + MCOUNT_AUIPC_SIZE;
+
+	return addr + MCOUNT_AUIPC_SIZE;
+}
+
+unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
+{
+	return fentry_ip - MCOUNT_AUIPC_SIZE;
+}
+
+void arch_ftrace_update_code(int command)
+{
+	command |= FTRACE_MAY_SLEEP;
+	ftrace_modify_all_code(command);
+	flush_icache_all();
+}
+
+static int __ftrace_modify_call(unsigned long source, unsigned long target, bool validate)
+{
+	unsigned int call[2], offset;
+	unsigned int replaced[2];
+
+	offset = target - source;
+	call[1] = to_jalr_t0(offset);
+
+	if (validate) {
+		call[0] = to_auipc_t0(offset);
+		/*
+		 * Read the text we want to modify;
+		 * return must be -EFAULT on read error
+		 */
+		if (copy_from_kernel_nofault(replaced, (void *)source, 2 * MCOUNT_INSN_SIZE))
+			return -EFAULT;
+
+		if (replaced[0] != call[0]) {
+			pr_err("%p: expected (%08x) but got (%08x)\n",
+			       (void *)source, call[0], replaced[0]);
+			return -EINVAL;
+		}
+	}
+
+	/* Replace the jalr at once. Return -EPERM on write error. */
+	if (patch_insn_write((void *)(source + MCOUNT_AUIPC_SIZE), call + 1, MCOUNT_JALR_SIZE))
+		return -EPERM;
+
+	return 0;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+static const struct ftrace_ops *riscv64_rec_get_ops(struct dyn_ftrace *rec)
+{
+	const struct ftrace_ops *ops = NULL;
+
+	if (rec->flags & FTRACE_FL_CALL_OPS_EN) {
+		ops = ftrace_find_unique_ops(rec);
+		WARN_ON_ONCE(!ops);
+	}
+
+	if (!ops)
+		ops = &ftrace_list_ops;
+
+	return ops;
+}
+
+static int ftrace_rec_set_ops(const struct dyn_ftrace *rec, const struct ftrace_ops *ops)
+{
+	unsigned long literal = ALIGN_DOWN(rec->ip - 12, 8);
+
+	return patch_text_nosync((void *)literal, &ops, sizeof(ops));
+}
+
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, &ftrace_nop_ops);
+}
+
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, riscv64_rec_get_ops(rec));
+}
+#else
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec) { return 0; }
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec) { return 0; }
+#endif
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long distance, orig_addr, pc = rec->ip - MCOUNT_AUIPC_SIZE;
+	int ret;
+
+	ret = ftrace_rec_update_ops(rec);
+	if (ret)
+		return ret;
+
+	orig_addr = (unsigned long)&ftrace_caller;
+	distance = addr > orig_addr ? addr - orig_addr : orig_addr - addr;
+	if (distance > JALR_RANGE)
+		addr = FTRACE_ADDR;
+
+	return __ftrace_modify_call(pc, addr, false);
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
+{
+	u32 nop4 = RISCV_INSN_NOP4;
+	int ret;
+
+	ret = ftrace_rec_set_nop_ops(rec);
+	if (ret)
+		return ret;
+
+	if (patch_insn_write((void *)rec->ip, &nop4, MCOUNT_NOP4_SIZE))
+		return -EPERM;
+
+	return 0;
+}
+
+/*
+ * This is called early on, and isn't wrapped by
+ * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
+ * text_mutex, which triggers a lockdep failure.  SMP isn't running so we could
+ * just directly poke the text, but it's simpler to just take the lock
+ * ourselves.
+ */
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+	unsigned long pc = rec->ip - MCOUNT_AUIPC_SIZE;
+	unsigned int nops[2], offset;
+	int ret;
+
+	guard(mutex)(&text_mutex);
+
+	ret = ftrace_rec_set_nop_ops(rec);
+	if (ret)
+		return ret;
+
+	offset = (unsigned long) &ftrace_caller - pc;
+	nops[0] = to_auipc_t0(offset);
+	nops[1] = RISCV_INSN_NOP4;
+
+	ret = patch_insn_write((void *)pc, nops, 2 * MCOUNT_INSN_SIZE);
+
+	return ret;
+}
+
+ftrace_func_t ftrace_call_dest = ftrace_stub;
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	/*
+	 * When using CALL_OPS, the function to call is associated with the
+	 * call site, and we don't have a global function pointer to update.
+	 */
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return 0;
+
+	WRITE_ONCE(ftrace_call_dest, func);
+	/*
+	 * The data fence ensure that the update to ftrace_call_dest happens
+	 * before the write to function_trace_op later in the generic ftrace.
+	 * If the sequence is not enforced, then an old ftrace_call_dest may
+	 * race loading a new function_trace_op set in ftrace_modify_all_code
+	 */
+	smp_wmb();
+	/*
+	 * Updating ftrace dpes not take stop_machine path, so irqs should not
+	 * be disabled.
+	 */
+	WARN_ON(irqs_disabled());
+	smp_call_function(ftrace_sync_ipi, NULL, 1);
+	return 0;
+}
+
+#else /* CONFIG_DYNAMIC_FTRACE */
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+	return addr;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+		       unsigned long addr)
+{
+	unsigned long caller = rec->ip - MCOUNT_AUIPC_SIZE;
+	int ret;
+
+	ret = ftrace_rec_update_ops(rec);
+	if (ret)
+		return ret;
+
+	return __ftrace_modify_call(caller, FTRACE_ADDR, true);
+}
+#endif
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Most of this function is copied from arm64.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+			   unsigned long frame_pointer)
+{
+	unsigned long return_hooker = (unsigned long)&return_to_handler;
+	unsigned long old;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	/*
+	 * We don't suffer access faults, so no extra fault-recovery assembly
+	 * is needed here.
+	 */
+	old = *parent;
+
+	if (!function_graph_enter(old, self_addr, frame_pointer, parent))
+		*parent = return_hooker;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	unsigned long return_hooker = (unsigned long)&return_to_handler;
+	unsigned long frame_pointer = arch_ftrace_regs(fregs)->s0;
+	unsigned long *parent = &arch_ftrace_regs(fregs)->ra;
+	unsigned long old;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	/*
+	 * We don't suffer access faults, so no extra fault-recovery assembly
+	 * is needed here.
+	 */
+	old = *parent;
+
+	if (!function_graph_enter_regs(old, ip, frame_pointer, parent, fregs))
+		*parent = return_hooker;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */