1// SPDX-License-Identifier: GPL-2.0-only 2#include <linux/module.h> 3#include <linux/kthread.h> 4#include <linux/ftrace.h> 5#ifndef CONFIG_ARM64 6#include <asm/asm-offsets.h> 7#endif 8 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_RISCV 28#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_64 63 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_ENDBR 73" pushq %rbp\n" 74" movq %rsp, %rbp\n" 75 CALL_DEPTH_ACCOUNT 76" call my_direct_func1\n" 77" leave\n" 78" .size my_tramp1, .-my_tramp1\n" 79 ASM_RET 80 81" .type my_tramp2, @function\n" 82" .globl my_tramp2\n" 83" my_tramp2:" 84 ASM_ENDBR 85" pushq %rbp\n" 86" movq %rsp, %rbp\n" 87 CALL_DEPTH_ACCOUNT 88" call my_direct_func2\n" 89" leave\n" 90 ASM_RET 91" .size my_tramp2, .-my_tramp2\n" 92" .popsection\n" 93); 94 95#endif /* CONFIG_X86_64 */ 96 97#ifdef CONFIG_S390 98 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_ARM64 137 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 c 144" 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 c 156" 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_LOONGARCH 169 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