CoCalc -- ftrace-direct-modify.c

GitHub Repository: torvalds/linux
Path: blob/master/samples/ftrace/ftrace-direct-modify.c
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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/module.h>
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#include <linux/kthread.h>
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#include <linux/ftrace.h>
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#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
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#include <asm/asm-offsets.h>
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#endif
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extern void my_direct_func1(void);
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extern void my_direct_func2(void);
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void my_direct_func1(void)
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{
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	trace_printk("my direct func1\n");
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}
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void my_direct_func2(void)
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{
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	trace_printk("my direct func2\n");
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}
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extern void my_tramp1(void *);
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extern void my_tramp2(void *);
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static unsigned long my_ip = (unsigned long)schedule;
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#ifdef CONFIG_RISCV
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#include <asm/asm.h>
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asm (
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"	.pushsection    .text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:\n"
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"	addi	sp,sp,-2*"SZREG"\n"
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"	"REG_S"	t0,0*"SZREG"(sp)\n"
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"	"REG_S"	ra,1*"SZREG"(sp)\n"
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"	call	my_direct_func1\n"
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"	"REG_L"	t0,0*"SZREG"(sp)\n"
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"	"REG_L"	ra,1*"SZREG"(sp)\n"
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"	addi	sp,sp,2*"SZREG"\n"
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"	jr	t0\n"
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"	.size		my_tramp1, .-my_tramp1\n"
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:\n"
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"	addi	sp,sp,-2*"SZREG"\n"
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"	"REG_S"	t0,0*"SZREG"(sp)\n"
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"	"REG_S"	ra,1*"SZREG"(sp)\n"
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"	call	my_direct_func2\n"
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"	"REG_L"	t0,0*"SZREG"(sp)\n"
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"	"REG_L"	ra,1*"SZREG"(sp)\n"
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"	addi	sp,sp,2*"SZREG"\n"
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"	jr	t0\n"
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_RISCV */
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#ifdef CONFIG_X86_64
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#include <asm/ibt.h>
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#include <asm/nospec-branch.h>
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asm (
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"	.pushsection    .text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:"
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	ASM_ENDBR
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"	pushq %rbp\n"
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"	movq %rsp, %rbp\n"
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	CALL_DEPTH_ACCOUNT
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"	call my_direct_func1\n"
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"	leave\n"
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"	.size		my_tramp1, .-my_tramp1\n"
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	ASM_RET
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:"
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	ASM_ENDBR
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"	pushq %rbp\n"
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"	movq %rsp, %rbp\n"
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	CALL_DEPTH_ACCOUNT
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"	call my_direct_func2\n"
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"	leave\n"
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	ASM_RET
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_X86_64 */
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#ifdef CONFIG_S390
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asm (
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"	.pushsection	.text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:"
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"	lgr		%r1,%r15\n"
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"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
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"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
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"	brasl		%r14,my_direct_func1\n"
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"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
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"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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"	lgr		%r1,%r0\n"
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"	br		%r1\n"
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"	.size		my_tramp1, .-my_tramp1\n"
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:"
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"	lgr		%r1,%r15\n"
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"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
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"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
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"	brasl		%r14,my_direct_func2\n"
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"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
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"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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"	lgr		%r1,%r0\n"
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"	br		%r1\n"
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_S390 */
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#ifdef CONFIG_ARM64
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asm (
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"	.pushsection    .text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:"
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"	hint	34\n" // bti	c
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"	sub	sp, sp, #16\n"
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"	stp	x9, x30, [sp]\n"
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"	bl	my_direct_func1\n"
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"	ldp	x30, x9, [sp]\n"
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"	add	sp, sp, #16\n"
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"	ret	x9\n"
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"	.size		my_tramp1, .-my_tramp1\n"
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:"
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"	hint	34\n" // bti	c
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"	sub	sp, sp, #16\n"
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"	stp	x9, x30, [sp]\n"
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"	bl	my_direct_func2\n"
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"	ldp	x30, x9, [sp]\n"
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"	add	sp, sp, #16\n"
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"	ret	x9\n"
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_ARM64 */
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#ifdef CONFIG_LOONGARCH
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asm (
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"	.pushsection    .text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:\n"
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"	addi.d	$sp, $sp, -16\n"
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"	st.d	$t0, $sp, 0\n"
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"	st.d	$ra, $sp, 8\n"
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"	bl	my_direct_func1\n"
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"	ld.d	$t0, $sp, 0\n"
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"	ld.d	$ra, $sp, 8\n"
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"	addi.d	$sp, $sp, 16\n"
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"	jr	$t0\n"
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"	.size		my_tramp1, .-my_tramp1\n"
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:\n"
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"	addi.d	$sp, $sp, -16\n"
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"	st.d	$t0, $sp, 0\n"
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"	st.d	$ra, $sp, 8\n"
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"	bl	my_direct_func2\n"
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"	ld.d	$t0, $sp, 0\n"
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"	ld.d	$ra, $sp, 8\n"
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"	addi.d	$sp, $sp, 16\n"
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"	jr	$t0\n"
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_LOONGARCH */
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#ifdef CONFIG_PPC
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#include <asm/ppc_asm.h>
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#ifdef CONFIG_PPC64
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#define STACK_FRAME_SIZE 48
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#else
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#define STACK_FRAME_SIZE 24
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#endif
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#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
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#define PPC64_TOC_SAVE_AND_UPDATE			\
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"	std		2, 24(1)\n"			\
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"	bcl		20, 31, 1f\n"			\
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"   1:	mflr		12\n"				\
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"	ld		2, (99f - 1b)(12)\n"
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#define PPC64_TOC_RESTORE				\
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"	ld		2, 24(1)\n"
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#define PPC64_TOC					\
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"   99:	.quad		.TOC.@tocbase\n"
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#else
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#define PPC64_TOC_SAVE_AND_UPDATE ""
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#define PPC64_TOC_RESTORE ""
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#define PPC64_TOC ""
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#endif
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#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
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#define PPC_FTRACE_RESTORE_LR				\
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	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
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"	mtlr		0\n"
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#define PPC_FTRACE_RET					\
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"	blr\n"
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#else
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#define PPC_FTRACE_RESTORE_LR				\
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	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
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"	mtctr		0\n"
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#define PPC_FTRACE_RET					\
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"	mtlr		0\n"				\
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"	bctr\n"
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#endif
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asm (
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"	.pushsection	.text, \"ax\", @progbits\n"
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"	.type		my_tramp1, @function\n"
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"	.globl		my_tramp1\n"
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"   my_tramp1:\n"
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	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
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"	mflr		0\n"
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	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
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	PPC64_TOC_SAVE_AND_UPDATE
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"	bl		my_direct_func1\n"
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	PPC64_TOC_RESTORE
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"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
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	PPC_FTRACE_RESTORE_LR
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"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
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	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_FTRACE_RET
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"	.size		my_tramp1, .-my_tramp1\n"
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"	.type		my_tramp2, @function\n"
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"	.globl		my_tramp2\n"
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"   my_tramp2:\n"
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	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
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"	mflr		0\n"
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	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
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	PPC64_TOC_SAVE_AND_UPDATE
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"	bl		my_direct_func2\n"
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	PPC64_TOC_RESTORE
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"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
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	PPC_FTRACE_RESTORE_LR
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"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
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	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
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	PPC_FTRACE_RET
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	PPC64_TOC
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"	.size		my_tramp2, .-my_tramp2\n"
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"	.popsection\n"
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);
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#endif /* CONFIG_PPC */
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static struct ftrace_ops direct;
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static unsigned long my_tramp = (unsigned long)my_tramp1;
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static unsigned long tramps[2] = {
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	(unsigned long)my_tramp1,
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	(unsigned long)my_tramp2,
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};
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static int simple_thread(void *arg)
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{
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	static int t;
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	int ret = 0;
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	while (!kthread_should_stop()) {
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		set_current_state(TASK_INTERRUPTIBLE);
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		schedule_timeout(2 * HZ);
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		if (ret)
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			continue;
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		t ^= 1;
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		ret = modify_ftrace_direct(&direct, tramps[t]);
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		if (!ret)
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			my_tramp = tramps[t];
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		WARN_ON_ONCE(ret);
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	}
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	return 0;
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}
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static struct task_struct *simple_tsk;
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static int __init ftrace_direct_init(void)
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{
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	int ret;
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	ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
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	ret = register_ftrace_direct(&direct, my_tramp);
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	if (!ret)
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		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
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	return ret;
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}
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static void __exit ftrace_direct_exit(void)
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{
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	kthread_stop(simple_tsk);
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	unregister_ftrace_direct(&direct, my_tramp, true);
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}
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module_init(ftrace_direct_init);
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module_exit(ftrace_direct_exit);
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MODULE_AUTHOR("Steven Rostedt");
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MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
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MODULE_LICENSE("GPL");
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