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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/riscv/kernel/mcount.S
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/* SPDX-License-Identifier: GPL-2.0 */

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/* Copyright (C) 2017 Andes Technology Corporation */

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#include <linux/init.h>

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#include <linux/linkage.h>

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#include <linux/cfi_types.h>

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#include <linux/export.h>

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#include <asm/asm.h>

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#include <asm/csr.h>

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#include <asm/unistd.h>

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#include <asm/thread_info.h>

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#include <asm/asm-offsets.h>

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#include <asm/ftrace.h>

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	.text

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	.macro SAVE_ABI_STATE

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	addi	sp, sp, -16

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	REG_S	s0, 0*SZREG(sp)

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	REG_S	ra, 1*SZREG(sp)

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	addi	s0, sp, 16

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	.endm

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	/*

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	 * The call to ftrace_return_to_handler would overwrite the return

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	 * register if a0 was not saved.

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	 */

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	.macro SAVE_RET_ABI_STATE

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	addi	sp, sp, -FREGS_SIZE_ON_STACK

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	REG_S	ra, FREGS_RA(sp)

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	REG_S	s0, FREGS_S0(sp)

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	REG_S	a0, FREGS_A0(sp)

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	REG_S	a1, FREGS_A1(sp)

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	addi	s0, sp, FREGS_SIZE_ON_STACK

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	.endm

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	.macro RESTORE_ABI_STATE

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	REG_L	ra, 1*SZREG(sp)

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	REG_L	s0, 0*SZREG(sp)

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	addi	sp, sp, 16

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	.endm

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	.macro RESTORE_RET_ABI_STATE

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	REG_L	ra, FREGS_RA(sp)

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	REG_L	s0, FREGS_S0(sp)

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	REG_L	a0, FREGS_A0(sp)

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	REG_L	a1, FREGS_A1(sp)

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	addi	sp, sp, FREGS_SIZE_ON_STACK

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	.endm

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SYM_TYPED_FUNC_START(ftrace_stub)

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#ifdef CONFIG_DYNAMIC_FTRACE

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       .global _mcount

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       .set    _mcount, ftrace_stub

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#endif

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	ret

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SYM_FUNC_END(ftrace_stub)

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#ifdef CONFIG_FUNCTION_GRAPH_TRACER

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SYM_TYPED_FUNC_START(ftrace_stub_graph)

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	ret

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SYM_FUNC_END(ftrace_stub_graph)

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SYM_FUNC_START(return_to_handler)

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/*

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 * On implementing the frame point test, the ideal way is to compare the

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 * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return.

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 * However, the psABI of variable-length-argument functions does not allow this.

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 *

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 * So alternatively we check the *old* frame pointer position, that is, the

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 * value stored in -16(s0) on entry, and the s0 on return.

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 */

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	SAVE_RET_ABI_STATE

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	mv	a0, sp

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	call	ftrace_return_to_handler

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	mv	a2, a0

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	RESTORE_RET_ABI_STATE

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	jalr	a2

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SYM_FUNC_END(return_to_handler)

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#endif

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#ifndef CONFIG_DYNAMIC_FTRACE

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SYM_FUNC_START(_mcount)

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	la	t4, ftrace_stub

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#ifdef CONFIG_FUNCTION_GRAPH_TRACER

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	la	t0, ftrace_graph_return

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	REG_L	t1, 0(t0)

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	bne	t1, t4, .Ldo_ftrace_graph_caller

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	la	t3, ftrace_graph_entry

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	REG_L	t2, 0(t3)

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	la	t6, ftrace_graph_entry_stub

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	bne	t2, t6, .Ldo_ftrace_graph_caller

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#endif

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	la	t3, ftrace_trace_function

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	REG_L	t5, 0(t3)

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	bne	t5, t4, .Ldo_trace

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	ret

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#ifdef CONFIG_FUNCTION_GRAPH_TRACER

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/*

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 * A pseudo representation for the function graph tracer:

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 * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)

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 */

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.Ldo_ftrace_graph_caller:

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	addi	a0, s0, -SZREG

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	mv	a1, ra

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#ifdef HAVE_FUNCTION_GRAPH_FP_TEST

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	REG_L	a2, -2*SZREG(s0)

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#endif

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	SAVE_ABI_STATE

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	call	prepare_ftrace_return

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	RESTORE_ABI_STATE

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	ret

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#endif

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/*

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 * A pseudo representation for the function tracer:

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 * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)

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 */

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.Ldo_trace:

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	REG_L	a1, -SZREG(s0)

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	mv	a0, ra

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	SAVE_ABI_STATE

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	jalr	t5

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	RESTORE_ABI_STATE

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	ret

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SYM_FUNC_END(_mcount)

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#endif

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EXPORT_SYMBOL(_mcount)

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