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- /*
- * 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(¤t->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 */
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