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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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e6d60b368b
Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
85 lines
1.6 KiB
C
85 lines
1.6 KiB
C
#ifndef _ASM_S390_FTRACE_H
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#define _ASM_S390_FTRACE_H
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#define ARCH_SUPPORTS_FTRACE_OPS 1
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#ifdef CC_USING_HOTPATCH
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#define MCOUNT_INSN_SIZE 6
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#else
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#define MCOUNT_INSN_SIZE 24
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#define MCOUNT_RETURN_FIXUP 18
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#endif
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#ifndef __ASSEMBLY__
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#define ftrace_return_address(n) __builtin_return_address(n)
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void _mcount(void);
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void ftrace_caller(void);
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extern char ftrace_graph_caller_end;
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extern unsigned long ftrace_plt;
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struct dyn_arch_ftrace { };
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#define MCOUNT_ADDR ((unsigned long)_mcount)
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#define FTRACE_ADDR ((unsigned long)ftrace_caller)
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#define KPROBE_ON_FTRACE_NOP 0
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#define KPROBE_ON_FTRACE_CALL 1
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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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struct ftrace_insn {
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u16 opc;
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s32 disp;
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} __packed;
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static inline void ftrace_generate_nop_insn(struct ftrace_insn *insn)
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{
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#ifdef CONFIG_FUNCTION_TRACER
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#ifdef CC_USING_HOTPATCH
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/* brcl 0,0 */
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insn->opc = 0xc004;
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insn->disp = 0;
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#else
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/* jg .+24 */
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insn->opc = 0xc0f4;
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insn->disp = MCOUNT_INSN_SIZE / 2;
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#endif
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#endif
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}
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static inline int is_ftrace_nop(struct ftrace_insn *insn)
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{
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#ifdef CONFIG_FUNCTION_TRACER
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#ifdef CC_USING_HOTPATCH
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if (insn->disp == 0)
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return 1;
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#else
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if (insn->disp == MCOUNT_INSN_SIZE / 2)
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return 1;
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#endif
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#endif
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return 0;
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}
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static inline void ftrace_generate_call_insn(struct ftrace_insn *insn,
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unsigned long ip)
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{
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#ifdef CONFIG_FUNCTION_TRACER
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unsigned long target;
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/* brasl r0,ftrace_caller */
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target = is_module_addr((void *) ip) ? ftrace_plt : FTRACE_ADDR;
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insn->opc = 0xc005;
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insn->disp = (target - ip) / 2;
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#endif
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}
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_S390_FTRACE_H */
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