linux/samples/ftrace/ftrace-direct-modify.c

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/ftrace.h>
#ifndef CONFIG_ARM64
#include <asm/asm-offsets.h>
#endif

extern void my_direct_func1(void);
extern void my_direct_func2(void);

void my_direct_func1(void)
{ … }

void my_direct_func2(void)
{ … }

extern void my_tramp1(void *);
extern void my_tramp2(void *);

static unsigned long my_ip = …;

#ifdef CONFIG_RISCV
#include <asm/asm.h>

asm (
"	.pushsection    .text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:\n"
"	addi	sp,sp,-2*"SZREG"\n"
"	"REG_S"	t0,0*"SZREG"(sp)\n"
"	"REG_S"	ra,1*"SZREG"(sp)\n"
"	call	my_direct_func1\n"
"	"REG_L"	t0,0*"SZREG"(sp)\n"
"	"REG_L"	ra,1*"SZREG"(sp)\n"
"	addi	sp,sp,2*"SZREG"\n"
"	jr	t0\n"
"	.size		my_tramp1, .-my_tramp1\n"
"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"

"   my_tramp2:\n"
"	addi	sp,sp,-2*"SZREG"\n"
"	"REG_S"	t0,0*"SZREG"(sp)\n"
"	"REG_S"	ra,1*"SZREG"(sp)\n"
"	call	my_direct_func2\n"
"	"REG_L"	t0,0*"SZREG"(sp)\n"
"	"REG_L"	ra,1*"SZREG"(sp)\n"
"	addi	sp,sp,2*"SZREG"\n"
"	jr	t0\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_RISCV */

#ifdef CONFIG_X86_64

#include <asm/ibt.h>
#include <asm/nospec-branch.h>

asm …;

#endif /* CONFIG_X86_64 */

#ifdef CONFIG_S390

asm (
"	.pushsection	.text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:"
"	lgr		%r1,%r15\n"
"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
"	brasl		%r14,my_direct_func1\n"
"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	lgr		%r1,%r0\n"
"	br		%r1\n"
"	.size		my_tramp1, .-my_tramp1\n"
"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:"
"	lgr		%r1,%r15\n"
"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
"	brasl		%r14,my_direct_func2\n"
"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
"	lgr		%r1,%r0\n"
"	br		%r1\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_S390 */

#ifdef CONFIG_ARM64

asm (
"	.pushsection    .text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:"
"	hint	34\n" // bti	c
"	sub	sp, sp, #16\n"
"	stp	x9, x30, [sp]\n"
"	bl	my_direct_func1\n"
"	ldp	x30, x9, [sp]\n"
"	add	sp, sp, #16\n"
"	ret	x9\n"
"	.size		my_tramp1, .-my_tramp1\n"

"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:"
"	hint	34\n" // bti	c
"	sub	sp, sp, #16\n"
"	stp	x9, x30, [sp]\n"
"	bl	my_direct_func2\n"
"	ldp	x30, x9, [sp]\n"
"	add	sp, sp, #16\n"
"	ret	x9\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_ARM64 */

#ifdef CONFIG_LOONGARCH

asm (
"	.pushsection    .text, \"ax\", @progbits\n"
"	.type		my_tramp1, @function\n"
"	.globl		my_tramp1\n"
"   my_tramp1:\n"
"	addi.d	$sp, $sp, -16\n"
"	st.d	$t0, $sp, 0\n"
"	st.d	$ra, $sp, 8\n"
"	bl	my_direct_func1\n"
"	ld.d	$t0, $sp, 0\n"
"	ld.d	$ra, $sp, 8\n"
"	addi.d	$sp, $sp, 16\n"
"	jr	$t0\n"
"	.size		my_tramp1, .-my_tramp1\n"

"	.type		my_tramp2, @function\n"
"	.globl		my_tramp2\n"
"   my_tramp2:\n"
"	addi.d	$sp, $sp, -16\n"
"	st.d	$t0, $sp, 0\n"
"	st.d	$ra, $sp, 8\n"
"	bl	my_direct_func2\n"
"	ld.d	$t0, $sp, 0\n"
"	ld.d	$ra, $sp, 8\n"
"	addi.d	$sp, $sp, 16\n"
"	jr	$t0\n"
"	.size		my_tramp2, .-my_tramp2\n"
"	.popsection\n"
);

#endif /* CONFIG_LOONGARCH */

static struct ftrace_ops direct;

static unsigned long my_tramp = …;
static unsigned long tramps[2] = …;

static int simple_thread(void *arg)
{ … }

static struct task_struct *simple_tsk;

static int __init ftrace_direct_init(void)
{ … }

static void __exit ftrace_direct_exit(void)
{ … }

module_init(ftrace_direct_init);
module_exit(ftrace_direct_exit);

MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;