forked from Minki/linux
3d1e220d08
Reduce the number of executed instructions within the mcount block if function tracing is enabled. We achieve that by using a non-standard C function call ABI. Since the called function is also written in assembler this is not a problem. This also allows to replace the unconditional store at the beginning of the mcount block with a larl instruction, which doesn't touch memory. In theory we could also patch the first instruction of the mcount block to enable and disable function tracing. However this would break kprobes. This could be fixed with implementing the "kprobes_on_ftrace" feature; however keeping the odd jprobes working seems not to be possible without a lot of code churn. Therefore keep the code easy and simply accept one wasted 1-cycle "larl" instruction per function prologue. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
32 lines
509 B
C
32 lines
509 B
C
#ifndef _ASM_S390_FTRACE_H
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#define _ASM_S390_FTRACE_H
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#ifndef __ASSEMBLY__
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extern void _mcount(void);
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extern char ftrace_graph_caller_end;
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struct dyn_arch_ftrace { };
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#define MCOUNT_ADDR ((long)_mcount)
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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return addr;
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}
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#endif /* __ASSEMBLY__ */
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#ifdef CONFIG_64BIT
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#define MCOUNT_INSN_SIZE 18
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#else
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#define MCOUNT_INSN_SIZE 22
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#endif
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#ifdef CONFIG_64BIT
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#define ARCH_SUPPORTS_FTRACE_OPS 1
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#endif
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#endif /* _ASM_S390_FTRACE_H */
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