samples/ftrace/ftrace-direct-modify.c

   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");