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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/arm64/kernel/ftrace.c
Initial import
Diffstat (limited to 'arch/arm64/kernel/ftrace.c')
-rw-r--r--arch/arm64/kernel/ftrace.c178
1 files changed, 178 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
new file mode 100644
index 000000000..c851be795
--- /dev/null
+++ b/arch/arm64/kernel/ftrace.c
@@ -0,0 +1,178 @@
+/*
+ * arch/arm64/kernel/ftrace.c
+ *
+ * Copyright (C) 2013 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/ftrace.h>
+#include <linux/swab.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+#include <asm/ftrace.h>
+#include <asm/insn.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+/*
+ * Replace a single instruction, which may be a branch or NOP.
+ * If @validate == true, a replaced instruction is checked against 'old'.
+ */
+static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
+ bool validate)
+{
+ u32 replaced;
+
+ /*
+ * Note:
+ * Due to modules and __init, code can disappear and change,
+ * we need to protect against faulting as well as code changing.
+ * We do this by aarch64_insn_*() which use the probe_kernel_*().
+ *
+ * No lock is held here because all the modifications are run
+ * through stop_machine().
+ */
+ if (validate) {
+ if (aarch64_insn_read((void *)pc, &replaced))
+ return -EFAULT;
+
+ if (replaced != old)
+ return -EINVAL;
+ }
+ if (aarch64_insn_patch_text_nosync((void *)pc, new))
+ return -EPERM;
+
+ return 0;
+}
+
+/*
+ * Replace tracer function in ftrace_caller()
+ */
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ unsigned long pc;
+ u32 new;
+
+ pc = (unsigned long)&ftrace_call;
+ new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
+ AARCH64_INSN_BRANCH_LINK);
+
+ return ftrace_modify_code(pc, 0, new, false);
+}
+
+/*
+ * Turn on the call to ftrace_caller() in instrumented function
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long pc = rec->ip;
+ u32 old, new;
+
+ old = aarch64_insn_gen_nop();
+ new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
+
+ return ftrace_modify_code(pc, old, new, true);
+}
+
+/*
+ * Turn off the call to ftrace_caller() in instrumented function
+ */
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+{
+ unsigned long pc = rec->ip;
+ u32 old, new;
+
+ old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
+ new = aarch64_insn_gen_nop();
+
+ return ftrace_modify_code(pc, old, new, true);
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+ return 0;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * function_graph tracer expects ftrace_return_to_handler() to be called
+ * on the way back to parent. For this purpose, this function is called
+ * in _mcount() or ftrace_caller() to replace return address (*parent) on
+ * the call stack to return_to_handler.
+ *
+ * Note that @frame_pointer is used only for sanity check later.
+ */
+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;
+ struct ftrace_graph_ent trace;
+ int err;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ /*
+ * Note:
+ * No protection against faulting at *parent, which may be seen
+ * on other archs. It's unlikely on AArch64.
+ */
+ old = *parent;
+ *parent = return_hooker;
+
+ trace.func = self_addr;
+ trace.depth = current->curr_ret_stack + 1;
+
+ /* Only trace if the calling function expects to */
+ if (!ftrace_graph_entry(&trace)) {
+ *parent = old;
+ return;
+ }
+
+ err = ftrace_push_return_trace(old, self_addr, &trace.depth,
+ frame_pointer);
+ if (err == -EBUSY) {
+ *parent = old;
+ return;
+ }
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+/*
+ * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
+ * depending on @enable.
+ */
+static int ftrace_modify_graph_caller(bool enable)
+{
+ unsigned long pc = (unsigned long)&ftrace_graph_call;
+ u32 branch, nop;
+
+ branch = aarch64_insn_gen_branch_imm(pc,
+ (unsigned long)ftrace_graph_caller,
+ AARCH64_INSN_BRANCH_NOLINK);
+ nop = aarch64_insn_gen_nop();
+
+ if (enable)
+ return ftrace_modify_code(pc, nop, branch, true);
+ else
+ return ftrace_modify_code(pc, branch, nop, true);
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_graph_caller(true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_graph_caller(false);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */