ftrace/ftrace-direct-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(void);
  10 extern void my_direct_func2(void);
  11
  12 void my_direct_func1(void)
  13 {
  14         trace_printk("my direct func1\n");
  15 }
  16
  17 void my_direct_func2(void)
  18 {
  19         trace_printk("my direct func2\n");
  20 }
  21
  22 extern void my_tramp1(void *);
  23 extern void my_tramp2(void *);
  24
  25 static unsigned long my_ip = (unsigned long)schedule;
  26
  27 #ifdef CONFIG_RISCV
  28 #include <asm/asm.h>
  29
  30 asm (
  31 "       .pushsection    .text, \"ax\", @progbits\n"
  32 "       .type           my_tramp1, @function\n"
  33 "       .globl          my_tramp1\n"
  34 "   my_tramp1:\n"
  35 "       addi    sp,sp,-2*"SZREG"\n"
  36 "       "REG_S" t0,0*"SZREG"(sp)\n"
  37 "       "REG_S" ra,1*"SZREG"(sp)\n"
  38 "       call    my_direct_func1\n"
  39 "       "REG_L" t0,0*"SZREG"(sp)\n"
  40 "       "REG_L" ra,1*"SZREG"(sp)\n"
  41 "       addi    sp,sp,2*"SZREG"\n"
  42 "       jr      t0\n"
  43 "       .size           my_tramp1, .-my_tramp1\n"
  44 "       .type           my_tramp2, @function\n"
  45 "       .globl          my_tramp2\n"
  46
  47 "   my_tramp2:\n"
  48 "       addi    sp,sp,-2*"SZREG"\n"
  49 "       "REG_S" t0,0*"SZREG"(sp)\n"
  50 "       "REG_S" ra,1*"SZREG"(sp)\n"
  51 "       call    my_direct_func2\n"
  52 "       "REG_L" t0,0*"SZREG"(sp)\n"
  53 "       "REG_L" ra,1*"SZREG"(sp)\n"
  54 "       addi    sp,sp,2*"SZREG"\n"
  55 "       jr      t0\n"
  56 "       .size           my_tramp2, .-my_tramp2\n"
  57 "       .popsection\n"
  58 );
  59
  60 #endif /* CONFIG_RISCV */
  61
  62 #ifdef CONFIG_X86_64
  63
  64 #include <asm/ibt.h>
  65 #include <asm/nospec-branch.h>
  66
  67 asm (
  68 "       .pushsection    .text, \"ax\", @progbits\n"
  69 "       .type           my_tramp1, @function\n"
  70 "       .globl          my_tramp1\n"
  71 "   my_tramp1:"
  72         ASM_ENDBR
  73 "       pushq %rbp\n"
  74 "       movq %rsp, %rbp\n"
  75         CALL_DEPTH_ACCOUNT
  76 "       call my_direct_func1\n"
  77 "       leave\n"
  78 "       .size           my_tramp1, .-my_tramp1\n"
  79         ASM_RET
  80
  81 "       .type           my_tramp2, @function\n"
  82 "       .globl          my_tramp2\n"
  83 "   my_tramp2:"
  84         ASM_ENDBR
  85 "       pushq %rbp\n"
  86 "       movq %rsp, %rbp\n"
  87         CALL_DEPTH_ACCOUNT
  88 "       call my_direct_func2\n"
  89 "       leave\n"
  90         ASM_RET
  91 "       .size           my_tramp2, .-my_tramp2\n"
  92 "       .popsection\n"
  93 );
  94
  95 #endif /* CONFIG_X86_64 */
  96
  97 #ifdef CONFIG_S390
  98
  99 asm (
 100 "       .pushsection    .text, \"ax\", @progbits\n"
 101 "       .type           my_tramp1, @function\n"
 102 "       .globl          my_tramp1\n"
 103 "   my_tramp1:"
 104 "       lgr             %r1,%r15\n"
 105 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 106 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 107 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
 108 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
 109 "       brasl           %r14,my_direct_func1\n"
 110 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
 111 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 112 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 113 "       lgr             %r1,%r0\n"
 114 "       br              %r1\n"
 115 "       .size           my_tramp1, .-my_tramp1\n"
 116 "       .type           my_tramp2, @function\n"
 117 "       .globl          my_tramp2\n"
 118 "   my_tramp2:"
 119 "       lgr             %r1,%r15\n"
 120 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 121 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 122 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
 123 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
 124 "       brasl           %r14,my_direct_func2\n"
 125 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
 126 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
 127 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
 128 "       lgr             %r1,%r0\n"
 129 "       br              %r1\n"
 130 "       .size           my_tramp2, .-my_tramp2\n"
 131 "       .popsection\n"
 132 );
 133
 134 #endif /* CONFIG_S390 */
 135
 136 #ifdef CONFIG_ARM64
 137
 138 asm (
 139 "       .pushsection    .text, \"ax\", @progbits\n"
 140 "       .type           my_tramp1, @function\n"
 141 "       .globl          my_tramp1\n"
 142 "   my_tramp1:"
 143 "       hint    34\n" // bti    c
 144 "       sub     sp, sp, #16\n"
 145 "       stp     x9, x30, [sp]\n"
 146 "       bl      my_direct_func1\n"
 147 "       ldp     x30, x9, [sp]\n"
 148 "       add     sp, sp, #16\n"
 149 "       ret     x9\n"
 150 "       .size           my_tramp1, .-my_tramp1\n"
 151
 152 "       .type           my_tramp2, @function\n"
 153 "       .globl          my_tramp2\n"
 154 "   my_tramp2:"
 155 "       hint    34\n" // bti    c
 156 "       sub     sp, sp, #16\n"
 157 "       stp     x9, x30, [sp]\n"
 158 "       bl      my_direct_func2\n"
 159 "       ldp     x30, x9, [sp]\n"
 160 "       add     sp, sp, #16\n"
 161 "       ret     x9\n"
 162 "       .size           my_tramp2, .-my_tramp2\n"
 163 "       .popsection\n"
 164 );
 165
 166 #endif /* CONFIG_ARM64 */
 167
 168 #ifdef CONFIG_LOONGARCH
 169
 170 asm (
 171 "       .pushsection    .text, \"ax\", @progbits\n"
 172 "       .type           my_tramp1, @function\n"
 173 "       .globl          my_tramp1\n"
 174 "   my_tramp1:\n"
 175 "       addi.d  $sp, $sp, -16\n"
 176 "       st.d    $t0, $sp, 0\n"
 177 "       st.d    $ra, $sp, 8\n"
 178 "       bl      my_direct_func1\n"
 179 "       ld.d    $t0, $sp, 0\n"
 180 "       ld.d    $ra, $sp, 8\n"
 181 "       addi.d  $sp, $sp, 16\n"
 182 "       jr      $t0\n"
 183 "       .size           my_tramp1, .-my_tramp1\n"
 184
 185 "       .type           my_tramp2, @function\n"
 186 "       .globl          my_tramp2\n"
 187 "   my_tramp2:\n"
 188 "       addi.d  $sp, $sp, -16\n"
 189 "       st.d    $t0, $sp, 0\n"
 190 "       st.d    $ra, $sp, 8\n"
 191 "       bl      my_direct_func2\n"
 192 "       ld.d    $t0, $sp, 0\n"
 193 "       ld.d    $ra, $sp, 8\n"
 194 "       addi.d  $sp, $sp, 16\n"
 195 "       jr      $t0\n"
 196 "       .size           my_tramp2, .-my_tramp2\n"
 197 "       .popsection\n"
 198 );
 199
 200 #endif /* CONFIG_LOONGARCH */
 201
 202 static struct ftrace_ops direct;
 203
 204 static unsigned long my_tramp = (unsigned long)my_tramp1;
 205 static unsigned long tramps[2] = {
 206         (unsigned long)my_tramp1,
 207         (unsigned long)my_tramp2,
 208 };
 209
 210 static int simple_thread(void *arg)
 211 {
 212         static int t;
 213         int ret = 0;
 214
 215         while (!kthread_should_stop()) {
 216                 set_current_state(TASK_INTERRUPTIBLE);
 217                 schedule_timeout(2 * HZ);
 218
 219                 if (ret)
 220                         continue;
 221                 t ^= 1;
 222                 ret = modify_ftrace_direct(&direct, tramps[t]);
 223                 if (!ret)
 224                         my_tramp = tramps[t];
 225                 WARN_ON_ONCE(ret);
 226         }
 227
 228         return 0;
 229 }
 230
 231 static struct task_struct *simple_tsk;
 232
 233 static int __init ftrace_direct_init(void)
 234 {
 235         int ret;
 236
 237         ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
 238         ret = register_ftrace_direct(&direct, my_tramp);
 239
 240         if (!ret)
 241                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 242         return ret;
 243 }
 244
 245 static void __exit ftrace_direct_exit(void)
 246 {
 247         kthread_stop(simple_tsk);
 248         unregister_ftrace_direct(&direct, my_tramp, true);
 249 }
 250
 251 module_init(ftrace_direct_init);
 252 module_exit(ftrace_direct_exit);
 253
 254 MODULE_AUTHOR("Steven Rostedt");
 255 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
 256 MODULE_LICENSE("GPL");