1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/module.h> 3 #include <linux/kthread.h> 4 #include <linux/ftrace.h> 5 #include <asm/asm-offsets.h> 6 7 extern void my_direct_func1(unsigned long ip); 8 extern void my_direct_func2(unsigned long ip); 9 10 void my_direct_func1(unsigned long ip) 11 { 12 trace_printk("my direct func1 ip %lx\n", ip); 13 } 14 15 void my_direct_func2(unsigned long ip) 16 { 17 trace_printk("my direct func2 ip %lx\n", ip); 18 } 19 20 extern void my_tramp1(void *); 21 extern void my_tramp2(void *); 22 23 #ifdef CONFIG_X86_64 24 25 #include <asm/ibt.h> 26 #include <asm/nospec-branch.h> 27 28 asm ( 29 " .pushsection .text, \"ax\", @progbits\n" 30 " .type my_tramp1, @function\n" 31 " .globl my_tramp1\n" 32 " my_tramp1:" 33 ASM_ENDBR 34 " pushq %rbp\n" 35 " movq %rsp, %rbp\n" 36 CALL_DEPTH_ACCOUNT 37 " pushq %rdi\n" 38 " movq 8(%rbp), %rdi\n" 39 " call my_direct_func1\n" 40 " popq %rdi\n" 41 " leave\n" 42 ASM_RET 43 " .size my_tramp1, .-my_tramp1\n" 44 45 " .type my_tramp2, @function\n" 46 " .globl my_tramp2\n" 47 " my_tramp2:" 48 ASM_ENDBR 49 " pushq %rbp\n" 50 " movq %rsp, %rbp\n" 51 CALL_DEPTH_ACCOUNT 52 " pushq %rdi\n" 53 " movq 8(%rbp), %rdi\n" 54 " call my_direct_func2\n" 55 " popq %rdi\n" 56 " leave\n" 57 ASM_RET 58 " .size my_tramp2, .-my_tramp2\n" 59 " .popsection\n" 60 ); 61 62 #endif /* CONFIG_X86_64 */ 63 64 #ifdef CONFIG_S390 65 66 asm ( 67 " .pushsection .text, \"ax\", @progbits\n" 68 " .type my_tramp1, @function\n" 69 " .globl my_tramp1\n" 70 " my_tramp1:" 71 " lgr %r1,%r15\n" 72 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 73 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 74 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 75 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 76 " lgr %r2,%r0\n" 77 " brasl %r14,my_direct_func1\n" 78 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 79 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 80 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 81 " lgr %r1,%r0\n" 82 " br %r1\n" 83 " .size my_tramp1, .-my_tramp1\n" 84 "\n" 85 " .type my_tramp2, @function\n" 86 " .globl my_tramp2\n" 87 " my_tramp2:" 88 " lgr %r1,%r15\n" 89 " stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 90 " stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 91 " aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n" 92 " stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n" 93 " lgr %r2,%r0\n" 94 " brasl %r14,my_direct_func2\n" 95 " aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n" 96 " lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n" 97 " lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n" 98 " lgr %r1,%r0\n" 99 " br %r1\n" 100 " .size my_tramp2, .-my_tramp2\n" 101 " .popsection\n" 102 ); 103 104 #endif /* CONFIG_S390 */ 105 106 #ifdef CONFIG_LOONGARCH 107 #include <asm/asm.h> 108 109 asm ( 110 " .pushsection .text, \"ax\", @progbits\n" 111 " .type my_tramp1, @function\n" 112 " .globl my_tramp1\n" 113 " my_tramp1:\n" 114 " addi.d $sp, $sp, -32\n" 115 " st.d $a0, $sp, 0\n" 116 " st.d $t0, $sp, 8\n" 117 " st.d $ra, $sp, 16\n" 118 " move $a0, $t0\n" 119 " bl my_direct_func1\n" 120 " ld.d $a0, $sp, 0\n" 121 " ld.d $t0, $sp, 8\n" 122 " ld.d $ra, $sp, 16\n" 123 " addi.d $sp, $sp, 32\n" 124 " jr $t0\n" 125 " .size my_tramp1, .-my_tramp1\n" 126 127 " .type my_tramp2, @function\n" 128 " .globl my_tramp2\n" 129 " my_tramp2:\n" 130 " addi.d $sp, $sp, -32\n" 131 " st.d $a0, $sp, 0\n" 132 " st.d $t0, $sp, 8\n" 133 " st.d $ra, $sp, 16\n" 134 " move $a0, $t0\n" 135 " bl my_direct_func2\n" 136 " ld.d $a0, $sp, 0\n" 137 " ld.d $t0, $sp, 8\n" 138 " ld.d $ra, $sp, 16\n" 139 " addi.d $sp, $sp, 32\n" 140 " jr $t0\n" 141 " .size my_tramp2, .-my_tramp2\n" 142 " .popsection\n" 143 ); 144 145 #endif /* CONFIG_LOONGARCH */ 146 147 static unsigned long my_tramp = (unsigned long)my_tramp1; 148 static unsigned long tramps[2] = { 149 (unsigned long)my_tramp1, 150 (unsigned long)my_tramp2, 151 }; 152 153 static struct ftrace_ops direct; 154 155 static int simple_thread(void *arg) 156 { 157 static int t; 158 int ret = 0; 159 160 while (!kthread_should_stop()) { 161 set_current_state(TASK_INTERRUPTIBLE); 162 schedule_timeout(2 * HZ); 163 164 if (ret) 165 continue; 166 t ^= 1; 167 ret = modify_ftrace_direct(&direct, tramps[t]); 168 if (!ret) 169 my_tramp = tramps[t]; 170 WARN_ON_ONCE(ret); 171 } 172 173 return 0; 174 } 175 176 static struct task_struct *simple_tsk; 177 178 static int __init ftrace_direct_multi_init(void) 179 { 180 int ret; 181 182 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); 183 ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0); 184 185 ret = register_ftrace_direct(&direct, my_tramp); 186 187 if (!ret) 188 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); 189 return ret; 190 } 191 192 static void __exit ftrace_direct_multi_exit(void) 193 { 194 kthread_stop(simple_tsk); 195 unregister_ftrace_direct(&direct, my_tramp, true); 196 } 197 198 module_init(ftrace_direct_multi_init); 199 module_exit(ftrace_direct_multi_exit); 200 201 MODULE_AUTHOR("Jiri Olsa"); 202 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); 203 MODULE_LICENSE("GPL"); 204