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 #include <asm/nospec-branch.h>
   7
   8 extern void my_direct_func1(unsigned long ip);
   9 extern void my_direct_func2(unsigned long ip);
  10
  11 void my_direct_func1(unsigned long ip)
  12 {
  13         trace_printk("my direct func1 ip %lx\n", ip);
  14 }
  15
  16 void my_direct_func2(unsigned long ip)
  17 {
  18         trace_printk("my direct func2 ip %lx\n", ip);
  19 }
  20
  21 extern void my_tramp1(void *);
  22 extern void my_tramp2(void *);
  23
  24 #ifdef CONFIG_X86_64
  25
  26 #include <asm/ibt.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 static unsigned long my_tramp = (unsigned long)my_tramp1;
 107 static unsigned long tramps[2] = {
 108         (unsigned long)my_tramp1,
 109         (unsigned long)my_tramp2,
 110 };
 111
 112 static struct ftrace_ops direct;
 113
 114 static int simple_thread(void *arg)
 115 {
 116         static int t;
 117         int ret = 0;
 118
 119         while (!kthread_should_stop()) {
 120                 set_current_state(TASK_INTERRUPTIBLE);
 121                 schedule_timeout(2 * HZ);
 122
 123                 if (ret)
 124                         continue;
 125                 t ^= 1;
 126                 ret = modify_ftrace_direct_multi(&direct, tramps[t]);
 127                 if (!ret)
 128                         my_tramp = tramps[t];
 129                 WARN_ON_ONCE(ret);
 130         }
 131
 132         return 0;
 133 }
 134
 135 static struct task_struct *simple_tsk;
 136
 137 static int __init ftrace_direct_multi_init(void)
 138 {
 139         int ret;
 140
 141         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 142         ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
 143
 144         ret = register_ftrace_direct_multi(&direct, my_tramp);
 145
 146         if (!ret)
 147                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 148         return ret;
 149 }
 150
 151 static void __exit ftrace_direct_multi_exit(void)
 152 {
 153         kthread_stop(simple_tsk);
 154         unregister_ftrace_direct_multi(&direct, my_tramp);
 155         ftrace_free_filter(&direct);
 156 }
 157
 158 module_init(ftrace_direct_multi_init);
 159 module_exit(ftrace_direct_multi_exit);
 160
 161 MODULE_AUTHOR("Jiri Olsa");
 162 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
 163 MODULE_LICENSE("GPL");