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 #include <asm/ibt.h>
  26
  27 asm (
  28 "       .pushsection    .text, \"ax\", @progbits\n"
  29 "       .type           my_tramp1, @function\n"
  30 "       .globl          my_tramp1\n"
  31 "   my_tramp1:"
  32         ASM_ENDBR
  33 "       pushq %rbp\n"
  34 "       movq %rsp, %rbp\n"
  35 "       pushq %rdi\n"
  36 "       movq 8(%rbp), %rdi\n"
  37 "       call my_direct_func1\n"
  38 "       popq %rdi\n"
  39 "       leave\n"
  40         ASM_RET
  41 "       .size           my_tramp1, .-my_tramp1\n"
  42
  43 "       .type           my_tramp2, @function\n"
  44 "       .globl          my_tramp2\n"
  45 "   my_tramp2:"
  46         ASM_ENDBR
  47 "       pushq %rbp\n"
  48 "       movq %rsp, %rbp\n"
  49 "       pushq %rdi\n"
  50 "       movq 8(%rbp), %rdi\n"
  51 "       call my_direct_func2\n"
  52 "       popq %rdi\n"
  53 "       leave\n"
  54         ASM_RET
  55 "       .size           my_tramp2, .-my_tramp2\n"
  56 "       .popsection\n"
  57 );
  58
  59 #endif /* CONFIG_X86_64 */
  60
  61 #ifdef CONFIG_S390
  62
  63 asm (
  64 "       .pushsection    .text, \"ax\", @progbits\n"
  65 "       .type           my_tramp1, @function\n"
  66 "       .globl          my_tramp1\n"
  67 "   my_tramp1:"
  68 "       lgr             %r1,%r15\n"
  69 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  70 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  71 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  72 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  73 "       lgr             %r2,%r0\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 "\n"
  82 "       .type           my_tramp2, @function\n"
  83 "       .globl          my_tramp2\n"
  84 "   my_tramp2:"
  85 "       lgr             %r1,%r15\n"
  86 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  87 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  88 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  89 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  90 "       lgr             %r2,%r0\n"
  91 "       brasl           %r14,my_direct_func2\n"
  92 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  93 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  94 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  95 "       lgr             %r1,%r0\n"
  96 "       br              %r1\n"
  97 "       .size           my_tramp2, .-my_tramp2\n"
  98 "       .popsection\n"
  99 );
 100
 101 #endif /* CONFIG_S390 */
 102
 103 static unsigned long my_tramp = (unsigned long)my_tramp1;
 104 static unsigned long tramps[2] = {
 105         (unsigned long)my_tramp1,
 106         (unsigned long)my_tramp2,
 107 };
 108
 109 static struct ftrace_ops direct;
 110
 111 static int simple_thread(void *arg)
 112 {
 113         static int t;
 114         int ret = 0;
 115
 116         while (!kthread_should_stop()) {
 117                 set_current_state(TASK_INTERRUPTIBLE);
 118                 schedule_timeout(2 * HZ);
 119
 120                 if (ret)
 121                         continue;
 122                 t ^= 1;
 123                 ret = modify_ftrace_direct_multi(&direct, tramps[t]);
 124                 if (!ret)
 125                         my_tramp = tramps[t];
 126                 WARN_ON_ONCE(ret);
 127         }
 128
 129         return 0;
 130 }
 131
 132 static struct task_struct *simple_tsk;
 133
 134 static int __init ftrace_direct_multi_init(void)
 135 {
 136         int ret;
 137
 138         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 139         ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
 140
 141         ret = register_ftrace_direct_multi(&direct, my_tramp);
 142
 143         if (!ret)
 144                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 145         return ret;
 146 }
 147
 148 static void __exit ftrace_direct_multi_exit(void)
 149 {
 150         kthread_stop(simple_tsk);
 151         unregister_ftrace_direct_multi(&direct, my_tramp);
 152 }
 153
 154 module_init(ftrace_direct_multi_init);
 155 module_exit(ftrace_direct_multi_exit);
 156
 157 MODULE_AUTHOR("Jiri Olsa");
 158 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
 159 MODULE_LICENSE("GPL");