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BrunoASMauricioBrunoASMauricio
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ARCv3: Implemented ftrace
Implemented both CONFIG_FTRACE (function entry tracing) and CONFIG_FUNCTION_GRAPH_TRACER (function entry and exit tracing) for ARCv33 Signed-off-by: BrunoASMauricio <brunoasmauricio@gmail.com>
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‎arch/arc/Kconfig‎

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@@ -38,6 +38,8 @@ config ARC
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select HAVE_KERNEL_LZMA
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select HAVE_KPROBES
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select HAVE_KRETPROBES
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select HAVE_FUNCTION_TRACER if ISA_ARCV3
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select HAVE_FUNCTION_GRAPH_TRACER if ISA_ARCV3
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select HAVE_MOD_ARCH_SPECIFIC
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select HAVE_PERF_EVENTS
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select HANDLE_DOMAIN_IRQ

‎arch/arc/Makefile‎

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@@ -61,6 +61,10 @@ cflags-$(CONFIG_64BIT) += -mcmodel=large
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cflags-$(CONFIG_ARC_HAS_LL128) += -m128
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endif
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ifdef CONFIG_FTRACE
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cflags-y += -fno-omit-frame-pointer
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endif
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cflags-y += -Wa,-I$(srctree)/arch/arc/include
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ifdef CONFIG_ARC_CURR_IN_REG

‎arch/arc/kernel/Makefile‎

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@@ -13,6 +13,23 @@ else
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obj-y += intc-arcv2.o
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endif
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ifdef CONFIG_FTRACE
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# Currently ftrace only works on arcv3 due to ABI
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ifdef CONFIG_ISA_ARCV3
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# ftrace cant be traced (infinite loop)
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CFLAGS_REMOVE_ftrace.o = -pg
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CFLAGS_REMOVE_mcount.o = -pg
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obj-$(CONFIG_FUNCTION_TRACER) += mcount.o
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obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
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endif
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endif
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obj-$(CONFIG_ISA_ARCOMPACT) += entry-compact.o
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obj-$(CONFIG_ISA_ARCV2) += entry-arcv2.o
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obj-$(CONFIG_ISA_ARCV3) += entry-arcv3.o

‎arch/arc/kernel/ftrace.c‎

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@@ -0,0 +1,31 @@
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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Function tracing support for ARC
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*
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* Copyright (C) 2023 Synopsys, Inc. (www.synopsys.com)
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*/
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#include <linux/ftrace.h>
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/*
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* Setup return hook in traced routine
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* Function copied from riscv
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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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if (unlikely(atomic_read(&current->tracing_graph_pause)))
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return;
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old = *parent;
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if (!function_graph_enter(old, self_addr, frame_pointer, parent))
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*parent = return_hooker;
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}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

‎arch/arc/kernel/mcount.S‎

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Function tracing support for ARC
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*
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* Copyright (C) 2023 Synopsys, Inc. (www.synopsys.com)
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*/
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#include <linux/init.h>
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#include <linux/linkage.h>
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#include <asm-generic/export.h>
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#include <asm/asm-macro-64-bit.h>
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.text
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; ftrace placeholder, just return to caller
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ENTRY(ftrace_stub)
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j_s [blink]
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ENDPROC(ftrace_stub)
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; save ABI necessary registers
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.macro SAVE_ABI
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PUSHR blink
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PUSHR fp
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.endm
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.macro LOAD_ABI
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POPR fp
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POPR blink
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.endm
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.macro SAVE_ABI_RET
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PUSHR r0
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PUSHR r1
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PUSHR blink
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.endm
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.macro LOAD_ABI_RET
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POPR blink
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POPR r1
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POPR r0
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.endm
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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; Return to the actual caller
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ENTRY(return_to_handler)
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; Save return value (if any) from handled routine
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SAVE_ABI_RET
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; Will return true blink on r0
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MOVA r0, @ftrace_return_to_handler
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jl [r0]
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MOVR r2, r0
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LOAD_ABI_RET
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j [r2]
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ENDPROC(return_to_handler)
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#endif
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; r0 has the frompc (targets parent ip)
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; blink has the selfpc (target ip)
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ENTRY(_mcount)
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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; *ftrace_graph_return != ftrace_stub
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MOVA r3, ftrace_graph_return
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LD64 r3, r3
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MOVA r4, @ftrace_stub
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brne r3, r4, @do_ftrace_graph_caller
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; *ftrace_graph_entry != *ftrace_graph_entry_stub
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MOVA r3, @ftrace_graph_entry
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LD64 r3, r3
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MOVA r4, @ftrace_graph_entry_stub
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brne r3, r4, @do_ftrace_graph_caller
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#endif
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; *ftrace_trace_function != ftrace_stub
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MOVA r2, ftrace_trace_function
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LD64 r2, r2
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MOVA r3, @ftrace_stub
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brne r2, r3, @do_trace
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; Return
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j_s [blink]
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ENDPROC(_mcount)
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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do_ftrace_graph_caller:
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SAVE_ABI
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ADDR r0, fp, 8
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MOVR r1, blink
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MOVA r2, @prepare_ftrace_return
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jl [r2]
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LOAD_ABI
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j_s [blink]
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#endif
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do_trace:
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SAVE_ABI
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MOVR r1, r0
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MOVR r0, blink
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jl [r2]
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LOAD_ABI
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j_s [blink]

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