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-rw-r--r--arch/loongarch/kernel/ftrace.c73
1 files changed, 73 insertions, 0 deletions
diff --git a/arch/loongarch/kernel/ftrace.c b/arch/loongarch/kernel/ftrace.c
new file mode 100644
index 000000000000..8c3ec1bc7aad
--- /dev/null
+++ b/arch/loongarch/kernel/ftrace.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/init.h>
+#include <linux/ftrace.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include <asm/inst.h>
+#include <asm/loongarch.h>
+#include <asm/syscall.h>
+
+#include <asm-generic/sections.h>
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+/*
+ * As `call _mcount` follows LoongArch psABI, ra-saved operation and
+ * stack operation can be found before this insn.
+ */
+
+static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
+{
+ int limit = 32;
+ union loongarch_instruction *insn;
+
+ insn = (union loongarch_instruction *)insn_addr;
+
+ do {
+ insn--;
+ limit--;
+
+ if (is_ra_save_ins(insn))
+ *ra_off = -((1 << 12) - insn->reg2i12_format.immediate);
+
+ } while (!is_stack_alloc_ins(insn) && limit);
+
+ if (!limit)
+ return -EINVAL;
+
+ return 0;
+}
+
+void prepare_ftrace_return(unsigned long self_addr,
+ unsigned long callsite_sp, unsigned long old)
+{
+ int ra_off;
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+ if (unlikely(ftrace_graph_is_dead()))
+ return;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
+ goto out;
+
+ if (!function_graph_enter(old, self_addr, 0, NULL))
+ *(unsigned long *)(callsite_sp + ra_off) = return_hooker;
+
+ return;
+
+out:
+ ftrace_graph_stop();
+ WARN_ON(1);
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */