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