1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/module.h> 3 #include <linux/kthread.h> 4 #include <linux/ftrace.h> 5 #if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32) 6 #include <asm/asm-offsets.h> 7 #endif 8 9 extern void my_direct_func1(void); 10 extern void my_direct_func2(void); 11 12 void my_direct_func1(void) 13 { 14 trace_printk("my direct func1\n"); 15 } 16 17 void my_direct_func2(void) 18 { 19 trace_printk("my direct func2\n"); 20 } 21 22 extern void my_tramp1(void *); 23 extern void my_tramp2(void *); 24 25 static unsigned long my_ip = (unsigned long)schedule; 26 27 #ifdef CONFIG_RISCV 28 #include <asm/asm.h> 29 30 asm ( 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 67 asm ( 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 99 asm ( 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 137 138 asm ( 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 169 170 asm ( 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 */ 201 202 #ifdef CONFIG_PPC 203 #include <asm/ppc_asm.h> 204 205 #ifdef CONFIG_PPC64 206 #define STACK_FRAME_SIZE 48 207 #else 208 #define STACK_FRAME_SIZE 24 209 #endif 210 211 #if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL) 212 #define PPC64_TOC_SAVE_AND_UPDATE \ 213 " std 2, 24(1)\n" \ 214 " bcl 20, 31, 1f\n" \ 215 " 1: mflr 12\n" \ 216 " ld 2, (99f - 1b)(12)\n" 217 #define PPC64_TOC_RESTORE \ 218 " ld 2, 24(1)\n" 219 #define PPC64_TOC \ 220 " 99: .quad .TOC.@tocbase\n" 221 #else 222 #define PPC64_TOC_SAVE_AND_UPDATE "" 223 #define PPC64_TOC_RESTORE "" 224 #define PPC64_TOC "" 225 #endif 226 227 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE 228 #define PPC_FTRACE_RESTORE_LR \ 229 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \ 230 " mtlr 0\n" 231 #define PPC_FTRACE_RET \ 232 " blr\n" 233 #else 234 #define PPC_FTRACE_RESTORE_LR \ 235 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \ 236 " mtctr 0\n" 237 #define PPC_FTRACE_RET \ 238 " mtlr 0\n" \ 239 " bctr\n" 240 #endif 241 242 asm ( 243 " .pushsection .text, \"ax\", @progbits\n" 244 " .type my_tramp1, @function\n" 245 " .globl my_tramp1\n" 246 " my_tramp1:\n" 247 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 248 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n" 249 " mflr 0\n" 250 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 251 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n" 252 PPC64_TOC_SAVE_AND_UPDATE 253 " bl my_direct_func1\n" 254 PPC64_TOC_RESTORE 255 " addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n" 256 PPC_FTRACE_RESTORE_LR 257 " addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n" 258 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 259 PPC_FTRACE_RET 260 " .size my_tramp1, .-my_tramp1\n" 261 262 " .type my_tramp2, @function\n" 263 " .globl my_tramp2\n" 264 " my_tramp2:\n" 265 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 266 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n" 267 " mflr 0\n" 268 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 269 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n" 270 PPC64_TOC_SAVE_AND_UPDATE 271 " bl my_direct_func2\n" 272 PPC64_TOC_RESTORE 273 " addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n" 274 PPC_FTRACE_RESTORE_LR 275 " addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n" 276 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" 277 PPC_FTRACE_RET 278 PPC64_TOC 279 " .size my_tramp2, .-my_tramp2\n" 280 " .popsection\n" 281 ); 282 283 #endif /* CONFIG_PPC */ 284 285 static struct ftrace_ops direct; 286 287 static unsigned long my_tramp = (unsigned long)my_tramp1; 288 static unsigned long tramps[2] = { 289 (unsigned long)my_tramp1, 290 (unsigned long)my_tramp2, 291 }; 292 293 static int simple_thread(void *arg) 294 { 295 static int t; 296 int ret = 0; 297 298 while (!kthread_should_stop()) { 299 set_current_state(TASK_INTERRUPTIBLE); 300 schedule_timeout(2 * HZ); 301 302 if (ret) 303 continue; 304 t ^= 1; 305 ret = modify_ftrace_direct(&direct, tramps[t]); 306 if (!ret) 307 my_tramp = tramps[t]; 308 WARN_ON_ONCE(ret); 309 } 310 311 return 0; 312 } 313 314 static struct task_struct *simple_tsk; 315 316 static int __init ftrace_direct_init(void) 317 { 318 int ret; 319 320 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0); 321 ret = register_ftrace_direct(&direct, my_tramp); 322 323 if (!ret) 324 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 325 return ret; 326 } 327 328 static void __exit ftrace_direct_exit(void) 329 { 330 kthread_stop(simple_tsk); 331 unregister_ftrace_direct(&direct, my_tramp, true); 332 } 333 334 module_init(ftrace_direct_init); 335 module_exit(ftrace_direct_exit); 336 337 MODULE_AUTHOR("Steven Rostedt"); 338 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); 339 MODULE_LICENSE("GPL"); 340