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-rw-r--r--arch/riscv/kernel/ftrace.c209
1 files changed, 209 insertions, 0 deletions
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
new file mode 100644
index 0000000000..03a6434a8c
--- /dev/null
+++ b/arch/riscv/kernel/ftrace.c
@@ -0,0 +1,209 @@
+// 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 <asm/cacheflush.h>
+#include <asm/patch.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
+{
+ mutex_lock(&text_mutex);
+
+ /*
+ * The code sequences we use for ftrace can't be patched while the
+ * kernel is running, so we need to use stop_machine() to modify them
+ * for now. This doesn't play nice with text_mutex, we use this flag
+ * to elide the check.
+ */
+ riscv_patch_in_stop_machine = true;
+}
+
+void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
+{
+ riscv_patch_in_stop_machine = false;
+ mutex_unlock(&text_mutex);
+}
+
+static int ftrace_check_current_call(unsigned long hook_pos,
+ unsigned int *expected)
+{
+ unsigned int replaced[2];
+ unsigned int nops[2] = {NOP4, NOP4};
+
+ /* we expect nops at the hook position */
+ if (!expected)
+ expected = nops;
+
+ /*
+ * Read the text we want to modify;
+ * return must be -EFAULT on read error
+ */
+ if (copy_from_kernel_nofault(replaced, (void *)hook_pos,
+ MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ /*
+ * Make sure it is what we expect it to be;
+ * return must be -EINVAL on failed comparison
+ */
+ if (memcmp(expected, replaced, sizeof(replaced))) {
+ pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
+ (void *)hook_pos, expected[0], expected[1], replaced[0],
+ replaced[1]);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
+ bool enable, bool ra)
+{
+ unsigned int call[2];
+ unsigned int nops[2] = {NOP4, NOP4};
+
+ if (ra)
+ make_call_ra(hook_pos, target, call);
+ else
+ make_call_t0(hook_pos, target, call);
+
+ /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
+ if (patch_text_nosync
+ ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
+ return -EPERM;
+
+ return 0;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned int call[2];
+
+ make_call_t0(rec->ip, addr, call);
+
+ if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE))
+ return -EPERM;
+
+ return 0;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+{
+ unsigned int nops[2] = {NOP4, NOP4};
+
+ if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_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)
+{
+ int out;
+
+ mutex_lock(&text_mutex);
+ out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+ mutex_unlock(&text_mutex);
+
+ return out;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
+ (unsigned long)func, true, true);
+ if (!ret) {
+ ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
+ (unsigned long)func, true, true);
+ }
+
+ return ret;
+}
+#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned int call[2];
+ unsigned long caller = rec->ip;
+ int ret;
+
+ make_call_t0(caller, old_addr, call);
+ ret = ftrace_check_current_call(caller, call);
+
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call(caller, addr, true, false);
+}
+#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
+extern void ftrace_graph_call(void);
+extern void ftrace_graph_regs_call(void);
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ int ret;
+
+ ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+ (unsigned long)&prepare_ftrace_return, true, true);
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
+ (unsigned long)&prepare_ftrace_return, true, true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ int ret;
+
+ ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+ (unsigned long)&prepare_ftrace_return, false, true);
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
+ (unsigned long)&prepare_ftrace_return, false, true);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */