samples/ftrace/ftrace-direct-multi-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(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 asm (
  26 "       .pushsection    .text, \"ax\", @progbits\n"
  27 "       .type           my_tramp1, @function\n"
  28 "       .globl          my_tramp1\n"
  29 "   my_tramp1:"
  30 "       pushq %rbp\n"
  31 "       movq %rsp, %rbp\n"
  32 "       pushq %rdi\n"
  33 "       movq 8(%rbp), %rdi\n"
  34 "       call my_direct_func1\n"
  35 "       popq %rdi\n"
  36 "       leave\n"
  37 "       ret\n"
  38 "       .size           my_tramp1, .-my_tramp1\n"
  39 "       .type           my_tramp2, @function\n"
  40 "\n"
  41 "       .globl          my_tramp2\n"
  42 "   my_tramp2:"
  43 "       pushq %rbp\n"
  44 "       movq %rsp, %rbp\n"
  45 "       pushq %rdi\n"
  46 "       movq 8(%rbp), %rdi\n"
  47 "       call my_direct_func2\n"
  48 "       popq %rdi\n"
  49 "       leave\n"
  50 "       ret\n"
  51 "       .size           my_tramp2, .-my_tramp2\n"
  52 "       .popsection\n"
  53 );
  54
  55 #endif /* CONFIG_X86_64 */
  56
  57 #ifdef CONFIG_S390
  58
  59 asm (
  60 "       .pushsection    .text, \"ax\", @progbits\n"
  61 "       .type           my_tramp1, @function\n"
  62 "       .globl          my_tramp1\n"
  63 "   my_tramp1:"
  64 "       lgr             %r1,%r15\n"
  65 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  66 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  67 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  68 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  69 "       lgr             %r2,%r0\n"
  70 "       brasl           %r14,my_direct_func1\n"
  71 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  72 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  73 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  74 "       lgr             %r1,%r0\n"
  75 "       br              %r1\n"
  76 "       .size           my_tramp1, .-my_tramp1\n"
  77 "\n"
  78 "       .type           my_tramp2, @function\n"
  79 "       .globl          my_tramp2\n"
  80 "   my_tramp2:"
  81 "       lgr             %r1,%r15\n"
  82 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  83 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  84 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  85 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  86 "       lgr             %r2,%r0\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 static unsigned long my_tramp = (unsigned long)my_tramp1;
 100 static unsigned long tramps[2] = {
 101         (unsigned long)my_tramp1,
 102         (unsigned long)my_tramp2,
 103 };
 104
 105 static struct ftrace_ops direct;
 106
 107 static int simple_thread(void *arg)
 108 {
 109         static int t;
 110         int ret = 0;
 111
 112         while (!kthread_should_stop()) {
 113                 set_current_state(TASK_INTERRUPTIBLE);
 114                 schedule_timeout(2 * HZ);
 115
 116                 if (ret)
 117                         continue;
 118                 t ^= 1;
 119                 ret = modify_ftrace_direct_multi(&direct, tramps[t]);
 120                 if (!ret)
 121                         my_tramp = tramps[t];
 122                 WARN_ON_ONCE(ret);
 123         }
 124
 125         return 0;
 126 }
 127
 128 static struct task_struct *simple_tsk;
 129
 130 static int __init ftrace_direct_multi_init(void)
 131 {
 132         int ret;
 133
 134         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 135         ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
 136
 137         ret = register_ftrace_direct_multi(&direct, my_tramp);
 138
 139         if (!ret)
 140                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 141         return ret;
 142 }
 143
 144 static void __exit ftrace_direct_multi_exit(void)
 145 {
 146         kthread_stop(simple_tsk);
 147         unregister_ftrace_direct_multi(&direct, my_tramp);
 148 }
 149
 150 module_init(ftrace_direct_multi_init);
 151 module_exit(ftrace_direct_multi_exit);
 152
 153 MODULE_AUTHOR("Jiri Olsa");
 154 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
 155 MODULE_LICENSE("GPL");