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 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 static struct ftrace_ops direct; 203 204 static unsigned long my_tramp = (unsigned long)my_tramp1; 205 static unsigned long tramps[2] = { 206 (unsigned long)my_tramp1, 207 (unsigned long)my_tramp2, 208 }; 209 210 static 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 } 230 231 static struct task_struct *simple_tsk; 232 233 static 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 } 244 245 static void __exit ftrace_direct_exit(void) 246 { 247 kthread_stop(simple_tsk); 248 unregister_ftrace_direct(&direct, my_tramp, true); 249 } 250 251 module_init(ftrace_direct_init); 252 module_exit(ftrace_direct_exit); 253 254 MODULE_AUTHOR("Steven Rostedt"); 255 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); 256 MODULE_LICENSE("GPL"); 257