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 #ifndef CONFIG_ARM64
   6 #include <asm/asm-offsets.h>
   7 #endif
   8
   9 extern void my_direct_func1(unsigned long ip);
  10 extern void my_direct_func2(unsigned long ip);
  11
  12 void my_direct_func1(unsigned long ip)
  13 {
  14         trace_printk("my direct func1 ip %lx\n", ip);
  15 }
  16
  17 void my_direct_func2(unsigned long ip)
  18 {
  19         trace_printk("my direct func2 ip %lx\n", ip);
  20 }
  21
  22 extern void my_tramp1(void *);
  23 extern void my_tramp2(void *);
  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 "       pushq %rdi\n"
  40 "       movq 8(%rbp), %rdi\n"
  41 "       call my_direct_func1\n"
  42 "       popq %rdi\n"
  43 "       leave\n"
  44         ASM_RET
  45 "       .size           my_tramp1, .-my_tramp1\n"
  46
  47 "       .type           my_tramp2, @function\n"
  48 "       .globl          my_tramp2\n"
  49 "   my_tramp2:"
  50         ASM_ENDBR
  51 "       pushq %rbp\n"
  52 "       movq %rsp, %rbp\n"
  53         CALL_DEPTH_ACCOUNT
  54 "       pushq %rdi\n"
  55 "       movq 8(%rbp), %rdi\n"
  56 "       call my_direct_func2\n"
  57 "       popq %rdi\n"
  58 "       leave\n"
  59         ASM_RET
  60 "       .size           my_tramp2, .-my_tramp2\n"
  61 "       .popsection\n"
  62 );
  63
  64 #endif /* CONFIG_X86_64 */
  65
  66 #ifdef CONFIG_S390
  67
  68 asm (
  69 "       .pushsection    .text, \"ax\", @progbits\n"
  70 "       .type           my_tramp1, @function\n"
  71 "       .globl          my_tramp1\n"
  72 "   my_tramp1:"
  73 "       lgr             %r1,%r15\n"
  74 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  75 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  76 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  77 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  78 "       lgr             %r2,%r0\n"
  79 "       brasl           %r14,my_direct_func1\n"
  80 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  81 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  82 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  83 "       lgr             %r1,%r0\n"
  84 "       br              %r1\n"
  85 "       .size           my_tramp1, .-my_tramp1\n"
  86 "\n"
  87 "       .type           my_tramp2, @function\n"
  88 "       .globl          my_tramp2\n"
  89 "   my_tramp2:"
  90 "       lgr             %r1,%r15\n"
  91 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  92 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  93 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  94 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  95 "       lgr             %r2,%r0\n"
  96 "       brasl           %r14,my_direct_func2\n"
  97 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  98 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  99 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 100 "       lgr             %r1,%r0\n"
 101 "       br              %r1\n"
 102 "       .size           my_tramp2, .-my_tramp2\n"
 103 "       .popsection\n"
 104 );
 105
 106 #endif /* CONFIG_S390 */
 107
 108 #ifdef CONFIG_ARM64
 109
 110 asm (
 111 "       .pushsection    .text, \"ax\", @progbits\n"
 112 "       .type           my_tramp1, @function\n"
 113 "       .globl          my_tramp1\n"
 114 "   my_tramp1:"
 115 "       hint    34\n" // bti    c
 116 "       sub     sp, sp, #32\n"
 117 "       stp     x9, x30, [sp]\n"
 118 "       str     x0, [sp, #16]\n"
 119 "       mov     x0, x30\n"
 120 "       bl      my_direct_func1\n"
 121 "       ldp     x30, x9, [sp]\n"
 122 "       ldr     x0, [sp, #16]\n"
 123 "       add     sp, sp, #32\n"
 124 "       ret     x9\n"
 125 "       .size           my_tramp1, .-my_tramp1\n"
 126
 127 "       .type           my_tramp2, @function\n"
 128 "       .globl          my_tramp2\n"
 129 "   my_tramp2:"
 130 "       hint    34\n" // bti    c
 131 "       sub     sp, sp, #32\n"
 132 "       stp     x9, x30, [sp]\n"
 133 "       str     x0, [sp, #16]\n"
 134 "       mov     x0, x30\n"
 135 "       bl      my_direct_func2\n"
 136 "       ldp     x30, x9, [sp]\n"
 137 "       ldr     x0, [sp, #16]\n"
 138 "       add     sp, sp, #32\n"
 139 "       ret     x9\n"
 140 "       .size           my_tramp2, .-my_tramp2\n"
 141 "       .popsection\n"
 142 );
 143
 144 #endif /* CONFIG_ARM64 */
 145
 146 #ifdef CONFIG_LOONGARCH
 147 #include <asm/asm.h>
 148
 149 asm (
 150 "       .pushsection    .text, \"ax\", @progbits\n"
 151 "       .type           my_tramp1, @function\n"
 152 "       .globl          my_tramp1\n"
 153 "   my_tramp1:\n"
 154 "       addi.d  $sp, $sp, -32\n"
 155 "       st.d    $a0, $sp, 0\n"
 156 "       st.d    $t0, $sp, 8\n"
 157 "       st.d    $ra, $sp, 16\n"
 158 "       move    $a0, $t0\n"
 159 "       bl      my_direct_func1\n"
 160 "       ld.d    $a0, $sp, 0\n"
 161 "       ld.d    $t0, $sp, 8\n"
 162 "       ld.d    $ra, $sp, 16\n"
 163 "       addi.d  $sp, $sp, 32\n"
 164 "       jr      $t0\n"
 165 "       .size           my_tramp1, .-my_tramp1\n"
 166
 167 "       .type           my_tramp2, @function\n"
 168 "       .globl          my_tramp2\n"
 169 "   my_tramp2:\n"
 170 "       addi.d  $sp, $sp, -32\n"
 171 "       st.d    $a0, $sp, 0\n"
 172 "       st.d    $t0, $sp, 8\n"
 173 "       st.d    $ra, $sp, 16\n"
 174 "       move    $a0, $t0\n"
 175 "       bl      my_direct_func2\n"
 176 "       ld.d    $a0, $sp, 0\n"
 177 "       ld.d    $t0, $sp, 8\n"
 178 "       ld.d    $ra, $sp, 16\n"
 179 "       addi.d  $sp, $sp, 32\n"
 180 "       jr      $t0\n"
 181 "       .size           my_tramp2, .-my_tramp2\n"
 182 "       .popsection\n"
 183 );
 184
 185 #endif /* CONFIG_LOONGARCH */
 186
 187 static unsigned long my_tramp = (unsigned long)my_tramp1;
 188 static unsigned long tramps[2] = {
 189         (unsigned long)my_tramp1,
 190         (unsigned long)my_tramp2,
 191 };
 192
 193 static struct ftrace_ops direct;
 194
 195 static int simple_thread(void *arg)
 196 {
 197         static int t;
 198         int ret = 0;
 199
 200         while (!kthread_should_stop()) {
 201                 set_current_state(TASK_INTERRUPTIBLE);
 202                 schedule_timeout(2 * HZ);
 203
 204                 if (ret)
 205                         continue;
 206                 t ^= 1;
 207                 ret = modify_ftrace_direct(&direct, tramps[t]);
 208                 if (!ret)
 209                         my_tramp = tramps[t];
 210                 WARN_ON_ONCE(ret);
 211         }
 212
 213         return 0;
 214 }
 215
 216 static struct task_struct *simple_tsk;
 217
 218 static int __init ftrace_direct_multi_init(void)
 219 {
 220         int ret;
 221
 222         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 223         ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
 224
 225         ret = register_ftrace_direct(&direct, my_tramp);
 226
 227         if (!ret)
 228                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 229         return ret;
 230 }
 231
 232 static void __exit ftrace_direct_multi_exit(void)
 233 {
 234         kthread_stop(simple_tsk);
 235         unregister_ftrace_direct(&direct, my_tramp, true);
 236 }
 237
 238 module_init(ftrace_direct_multi_init);
 239 module_exit(ftrace_direct_multi_exit);
 240
 241 MODULE_AUTHOR("Jiri Olsa");
 242 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
 243 MODULE_LICENSE("GPL");