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This patch allows "dynamic ftrace" if CONFIG_DYNAMIC_FTRACE is enabled. Here we can turn on and off tracing dynamically per-function base. On arm64, this is done by patching single branch instruction to _mcount() inserted by gcc -pg option. The branch is replaced to NOP initially at kernel start up, and later on, NOP to branch to ftrace_caller() when enabled or branch to NOP when disabled. Please note that ftrace_caller() is a counterpart of _mcount() in case of 'static' ftrace. More details on architecture specific requirements are described in Documentation/trace/ftrace-design.txt. Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
39 lines
915 B
C
39 lines
915 B
C
/*
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* arch/arm64/include/asm/ftrace.h
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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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#ifndef __ASM_FTRACE_H
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#define __ASM_FTRACE_H
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#include <asm/insn.h>
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#define MCOUNT_ADDR ((unsigned long)_mcount)
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#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
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#ifndef __ASSEMBLY__
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extern void _mcount(unsigned long);
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struct dyn_arch_ftrace {
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/* No extra data needed for arm64 */
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};
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extern unsigned long ftrace_graph_call;
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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/*
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* addr is the address of the mcount call instruction.
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* recordmcount does the necessary offset calculation.
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*/
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return addr;
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}
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_FTRACE_H */
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