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1// SPDX-License-Identifier: GPL-2.0-only2#include <linux/module.h>3#include <linux/kthread.h>4#include <linux/ftrace.h>5#ifndef CONFIG_ARM646#include <asm/asm-offsets.h>7#endif8 9extern void my_direct_func1(void);10extern void my_direct_func2(void);11 12void my_direct_func1(void)13{14 trace_printk("my direct func1\n");15}16 17void my_direct_func2(void)18{19 trace_printk("my direct func2\n");20}21 22extern void my_tramp1(void *);23extern void my_tramp2(void *);24 25static unsigned long my_ip = (unsigned long)schedule;26 27#ifdef CONFIG_RISCV28#include <asm/asm.h>29 30asm (31" .pushsection .text, \"ax\", @progbits\n"32" .type my_tramp1, @function\n"33" .globl my_tramp1\n"34" my_tramp1:\n"35" addi sp,sp,-2*"SZREG"\n"36" "REG_S" t0,0*"SZREG"(sp)\n"37" "REG_S" ra,1*"SZREG"(sp)\n"38" call my_direct_func1\n"39" "REG_L" t0,0*"SZREG"(sp)\n"40" "REG_L" ra,1*"SZREG"(sp)\n"41" addi sp,sp,2*"SZREG"\n"42" jr t0\n"43" .size my_tramp1, .-my_tramp1\n"44" .type my_tramp2, @function\n"45" .globl my_tramp2\n"46 47" my_tramp2:\n"48" addi sp,sp,-2*"SZREG"\n"49" "REG_S" t0,0*"SZREG"(sp)\n"50" "REG_S" ra,1*"SZREG"(sp)\n"51" call my_direct_func2\n"52" "REG_L" t0,0*"SZREG"(sp)\n"53" "REG_L" ra,1*"SZREG"(sp)\n"54" addi sp,sp,2*"SZREG"\n"55" jr t0\n"56" .size my_tramp2, .-my_tramp2\n"57" .popsection\n"58);59 60#endif /* CONFIG_RISCV */61 62#ifdef CONFIG_X86_6463 64#include <asm/ibt.h>65#include <asm/nospec-branch.h>66 67asm (68" .pushsection .text, \"ax\", @progbits\n"69" .type my_tramp1, @function\n"70" .globl my_tramp1\n"71" my_tramp1:"72 ASM_ENDBR73" pushq %rbp\n"74" movq %rsp, %rbp\n"75 CALL_DEPTH_ACCOUNT76" call my_direct_func1\n"77" leave\n"78" .size my_tramp1, .-my_tramp1\n"79 ASM_RET80 81" .type my_tramp2, @function\n"82" .globl my_tramp2\n"83" my_tramp2:"84 ASM_ENDBR85" pushq %rbp\n"86" movq %rsp, %rbp\n"87 CALL_DEPTH_ACCOUNT88" call my_direct_func2\n"89" leave\n"90 ASM_RET91" .size my_tramp2, .-my_tramp2\n"92" .popsection\n"93);94 95#endif /* CONFIG_X86_64 */96 97#ifdef CONFIG_S39098 99asm (100" .pushsection .text, \"ax\", @progbits\n"101" .type my_tramp1, @function\n"102" .globl my_tramp1\n"103" my_tramp1:"104" lgr %r1,%r15\n"105" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"106" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"107" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"108" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"109" brasl %r14,my_direct_func1\n"110" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"111" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"112" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"113" lgr %r1,%r0\n"114" br %r1\n"115" .size my_tramp1, .-my_tramp1\n"116" .type my_tramp2, @function\n"117" .globl my_tramp2\n"118" my_tramp2:"119" lgr %r1,%r15\n"120" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"121" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"122" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"123" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"124" brasl %r14,my_direct_func2\n"125" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"126" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"127" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"128" lgr %r1,%r0\n"129" br %r1\n"130" .size my_tramp2, .-my_tramp2\n"131" .popsection\n"132);133 134#endif /* CONFIG_S390 */135 136#ifdef CONFIG_ARM64137 138asm (139" .pushsection .text, \"ax\", @progbits\n"140" .type my_tramp1, @function\n"141" .globl my_tramp1\n"142" my_tramp1:"143" hint 34\n" // bti c144" sub sp, sp, #16\n"145" stp x9, x30, [sp]\n"146" bl my_direct_func1\n"147" ldp x30, x9, [sp]\n"148" add sp, sp, #16\n"149" ret x9\n"150" .size my_tramp1, .-my_tramp1\n"151 152" .type my_tramp2, @function\n"153" .globl my_tramp2\n"154" my_tramp2:"155" hint 34\n" // bti c156" sub sp, sp, #16\n"157" stp x9, x30, [sp]\n"158" bl my_direct_func2\n"159" ldp x30, x9, [sp]\n"160" add sp, sp, #16\n"161" ret x9\n"162" .size my_tramp2, .-my_tramp2\n"163" .popsection\n"164);165 166#endif /* CONFIG_ARM64 */167 168#ifdef CONFIG_LOONGARCH169 170asm (171" .pushsection .text, \"ax\", @progbits\n"172" .type my_tramp1, @function\n"173" .globl my_tramp1\n"174" my_tramp1:\n"175" addi.d $sp, $sp, -16\n"176" st.d $t0, $sp, 0\n"177" st.d $ra, $sp, 8\n"178" bl my_direct_func1\n"179" ld.d $t0, $sp, 0\n"180" ld.d $ra, $sp, 8\n"181" addi.d $sp, $sp, 16\n"182" jr $t0\n"183" .size my_tramp1, .-my_tramp1\n"184 185" .type my_tramp2, @function\n"186" .globl my_tramp2\n"187" my_tramp2:\n"188" addi.d $sp, $sp, -16\n"189" st.d $t0, $sp, 0\n"190" st.d $ra, $sp, 8\n"191" bl my_direct_func2\n"192" ld.d $t0, $sp, 0\n"193" ld.d $ra, $sp, 8\n"194" addi.d $sp, $sp, 16\n"195" jr $t0\n"196" .size my_tramp2, .-my_tramp2\n"197" .popsection\n"198);199 200#endif /* CONFIG_LOONGARCH */201 202static struct ftrace_ops direct;203 204static unsigned long my_tramp = (unsigned long)my_tramp1;205static unsigned long tramps[2] = {206 (unsigned long)my_tramp1,207 (unsigned long)my_tramp2,208};209 210static int simple_thread(void *arg)211{212 static int t;213 int ret = 0;214 215 while (!kthread_should_stop()) {216 set_current_state(TASK_INTERRUPTIBLE);217 schedule_timeout(2 * HZ);218 219 if (ret)220 continue;221 t ^= 1;222 ret = modify_ftrace_direct(&direct, tramps[t]);223 if (!ret)224 my_tramp = tramps[t];225 WARN_ON_ONCE(ret);226 }227 228 return 0;229}230 231static struct task_struct *simple_tsk;232 233static int __init ftrace_direct_init(void)234{235 int ret;236 237 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);238 ret = register_ftrace_direct(&direct, my_tramp);239 240 if (!ret)241 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");242 return ret;243}244 245static void __exit ftrace_direct_exit(void)246{247 kthread_stop(simple_tsk);248 unregister_ftrace_direct(&direct, my_tramp, true);249}250 251module_init(ftrace_direct_init);252module_exit(ftrace_direct_exit);253 254MODULE_AUTHOR("Steven Rostedt");255MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");256MODULE_LICENSE("GPL");257