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 #include <asm/nospec-branch.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 #ifdef CONFIG_LOONGARCH
 107 #include <asm/asm.h>
 108
 109 asm (
 110 "       .pushsection    .text, \"ax\", @progbits\n"
 111 "       .type           my_tramp1, @function\n"
 112 "       .globl          my_tramp1\n"
 113 "   my_tramp1:\n"
 114 "       addi.d  $sp, $sp, -32\n"
 115 "       st.d    $a0, $sp, 0\n"
 116 "       st.d    $t0, $sp, 8\n"
 117 "       st.d    $ra, $sp, 16\n"
 118 "       move    $a0, $t0\n"
 119 "       bl      my_direct_func1\n"
 120 "       ld.d    $a0, $sp, 0\n"
 121 "       ld.d    $t0, $sp, 8\n"
 122 "       ld.d    $ra, $sp, 16\n"
 123 "       addi.d  $sp, $sp, 32\n"
 124 "       jr      $t0\n"
 125 "       .size           my_tramp1, .-my_tramp1\n"
 126
 127 "       .type           my_tramp2, @function\n"
 128 "       .globl          my_tramp2\n"
 129 "   my_tramp2:\n"
 130 "       addi.d  $sp, $sp, -32\n"
 131 "       st.d    $a0, $sp, 0\n"
 132 "       st.d    $t0, $sp, 8\n"
 133 "       st.d    $ra, $sp, 16\n"
 134 "       move    $a0, $t0\n"
 135 "       bl      my_direct_func2\n"
 136 "       ld.d    $a0, $sp, 0\n"
 137 "       ld.d    $t0, $sp, 8\n"
 138 "       ld.d    $ra, $sp, 16\n"
 139 "       addi.d  $sp, $sp, 32\n"
 140 "       jr      $t0\n"
 141 "       .size           my_tramp2, .-my_tramp2\n"
 142 "       .popsection\n"
 143 );
 144
 145 #endif /* CONFIG_LOONGARCH */
 146
 147 static unsigned long my_tramp = (unsigned long)my_tramp1;
 148 static unsigned long tramps[2] = {
 149         (unsigned long)my_tramp1,
 150         (unsigned long)my_tramp2,
 151 };
 152
 153 static struct ftrace_ops direct;
 154
 155 static int simple_thread(void *arg)
 156 {
 157         static int t;
 158         int ret = 0;
 159
 160         while (!kthread_should_stop()) {
 161                 set_current_state(TASK_INTERRUPTIBLE);
 162                 schedule_timeout(2 * HZ);
 163
 164                 if (ret)
 165                         continue;
 166                 t ^= 1;
 167                 ret = modify_ftrace_direct(&direct, tramps[t]);
 168                 if (!ret)
 169                         my_tramp = tramps[t];
 170                 WARN_ON_ONCE(ret);
 171         }
 172
 173         return 0;
 174 }
 175
 176 static struct task_struct *simple_tsk;
 177
 178 static int __init ftrace_direct_multi_init(void)
 179 {
 180         int ret;
 181
 182         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 183         ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
 184
 185         ret = register_ftrace_direct(&direct, my_tramp);
 186
 187         if (!ret)
 188                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 189         return ret;
 190 }
 191
 192 static void __exit ftrace_direct_multi_exit(void)
 193 {
 194         kthread_stop(simple_tsk);
 195         unregister_ftrace_direct(&direct, my_tramp, true);
 196 }
 197
 198 module_init(ftrace_direct_multi_init);
 199 module_exit(ftrace_direct_multi_exit);
 200
 201 MODULE_AUTHOR("Jiri Olsa");
 202 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
 203 MODULE_LICENSE("GPL");