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_X86_64 28 29 #include <asm/ibt.h> 30 #include <asm/nospec-branch.h> 31 32 asm ( 33 " .pushsection .text, \"ax\", @progbits\n" 34 " .type my_tramp1, @function\n" 35 " .globl my_tramp1\n" 36 " my_tramp1:" 37 ASM_ENDBR 38 " pushq %rbp\n" 39 " movq %rsp, %rbp\n" 40 CALL_DEPTH_ACCOUNT 41 " call my_direct_func1\n" 42 " leave\n" 43 " .size my_tramp1, .-my_tramp1\n" 44 ASM_RET 45 46 " .type my_tramp2, @function\n" 47 " .globl my_tramp2\n" 48 " my_tramp2:" 49 ASM_ENDBR 50 " pushq %rbp\n" 51 " movq %rsp, %rbp\n" 52 CALL_DEPTH_ACCOUNT 53 " call my_direct_func2\n" 54 " leave\n" 55 ASM_RET 56 " .size my_tramp2, .-my_tramp2\n" 57 " .popsection\n" 58 ); 59 60 #endif /* CONFIG_X86_64 */ 61 62 #ifdef CONFIG_S390 63 64 asm ( 65 " .pushsection .text, \"ax\", @progbits\n" 66 " .type my_tramp1, @function\n" 67 " .globl my_tramp1\n" 68 " my_tramp1:" 69 " lgr %r1,%r15\n" 70 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 71 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 72 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 73 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 74 " brasl %r14,my_direct_func1\n" 75 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 76 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 77 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 78 " lgr %r1,%r0\n" 79 " br %r1\n" 80 " .size my_tramp1, .-my_tramp1\n" 81 " .type my_tramp2, @function\n" 82 " .globl my_tramp2\n" 83 " my_tramp2:" 84 " lgr %r1,%r15\n" 85 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 86 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 87 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 88 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 89 " brasl %r14,my_direct_func2\n" 90 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 91 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 92 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 93 " lgr %r1,%r0\n" 94 " br %r1\n" 95 " .size my_tramp2, .-my_tramp2\n" 96 " .popsection\n" 97 ); 98 99 #endif /* CONFIG_S390 */ 100 101 #ifdef CONFIG_ARM64 102 103 asm ( 104 " .pushsection .text, \"ax\", @progbits\n" 105 " .type my_tramp1, @function\n" 106 " .globl my_tramp1\n" 107 " my_tramp1:" 108 " hint 34\n" // bti c 109 " sub sp, sp, #16\n" 110 " stp x9, x30, [sp]\n" 111 " bl my_direct_func1\n" 112 " ldp x30, x9, [sp]\n" 113 " add sp, sp, #16\n" 114 " ret x9\n" 115 " .size my_tramp1, .-my_tramp1\n" 116 117 " .type my_tramp2, @function\n" 118 " .globl my_tramp2\n" 119 " my_tramp2:" 120 " hint 34\n" // bti c 121 " sub sp, sp, #16\n" 122 " stp x9, x30, [sp]\n" 123 " bl my_direct_func2\n" 124 " ldp x30, x9, [sp]\n" 125 " add sp, sp, #16\n" 126 " ret x9\n" 127 " .size my_tramp2, .-my_tramp2\n" 128 " .popsection\n" 129 ); 130 131 #endif /* CONFIG_ARM64 */ 132 133 #ifdef CONFIG_LOONGARCH 134 135 asm ( 136 " .pushsection .text, \"ax\", @progbits\n" 137 " .type my_tramp1, @function\n" 138 " .globl my_tramp1\n" 139 " my_tramp1:\n" 140 " addi.d $sp, $sp, -16\n" 141 " st.d $t0, $sp, 0\n" 142 " st.d $ra, $sp, 8\n" 143 " bl my_direct_func1\n" 144 " ld.d $t0, $sp, 0\n" 145 " ld.d $ra, $sp, 8\n" 146 " addi.d $sp, $sp, 16\n" 147 " jr $t0\n" 148 " .size my_tramp1, .-my_tramp1\n" 149 150 " .type my_tramp2, @function\n" 151 " .globl my_tramp2\n" 152 " my_tramp2:\n" 153 " addi.d $sp, $sp, -16\n" 154 " st.d $t0, $sp, 0\n" 155 " st.d $ra, $sp, 8\n" 156 " bl my_direct_func2\n" 157 " ld.d $t0, $sp, 0\n" 158 " ld.d $ra, $sp, 8\n" 159 " addi.d $sp, $sp, 16\n" 160 " jr $t0\n" 161 " .size my_tramp2, .-my_tramp2\n" 162 " .popsection\n" 163 ); 164 165 #endif /* CONFIG_LOONGARCH */ 166 167 static struct ftrace_ops direct; 168 169 static unsigned long my_tramp = (unsigned long)my_tramp1; 170 static unsigned long tramps[2] = { 171 (unsigned long)my_tramp1, 172 (unsigned long)my_tramp2, 173 }; 174 175 static int simple_thread(void *arg) 176 { 177 static int t; 178 int ret = 0; 179 180 while (!kthread_should_stop()) { 181 set_current_state(TASK_INTERRUPTIBLE); 182 schedule_timeout(2 * HZ); 183 184 if (ret) 185 continue; 186 t ^= 1; 187 ret = modify_ftrace_direct(&direct, tramps[t]); 188 if (!ret) 189 my_tramp = tramps[t]; 190 WARN_ON_ONCE(ret); 191 } 192 193 return 0; 194 } 195 196 static struct task_struct *simple_tsk; 197 198 static int __init ftrace_direct_init(void) 199 { 200 int ret; 201 202 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0); 203 ret = register_ftrace_direct(&direct, my_tramp); 204 205 if (!ret) 206 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 207 return ret; 208 } 209 210 static void __exit ftrace_direct_exit(void) 211 { 212 kthread_stop(simple_tsk); 213 unregister_ftrace_direct(&direct, my_tramp, true); 214 } 215 216 module_init(ftrace_direct_init); 217 module_exit(ftrace_direct_exit); 218 219 MODULE_AUTHOR("Steven Rostedt"); 220 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); 221 MODULE_LICENSE("GPL"); 222