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