samples/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 #if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
   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 #ifdef CONFIG_PPC
 203 #include <asm/ppc_asm.h>
 204
 205 #ifdef CONFIG_PPC64
 206 #define STACK_FRAME_SIZE 48
 207 #else
 208 #define STACK_FRAME_SIZE 24
 209 #endif
 210
 211 #if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
 212 #define PPC64_TOC_SAVE_AND_UPDATE                       \
 213 "       std             2, 24(1)\n"                     \
 214 "       bcl             20, 31, 1f\n"                   \
 215 "   1:  mflr            12\n"                           \
 216 "       ld              2, (99f - 1b)(12)\n"
 217 #define PPC64_TOC_RESTORE                               \
 218 "       ld              2, 24(1)\n"
 219 #define PPC64_TOC                                       \
 220 "   99: .quad           .TOC.@tocbase\n"
 221 #else
 222 #define PPC64_TOC_SAVE_AND_UPDATE ""
 223 #define PPC64_TOC_RESTORE ""
 224 #define PPC64_TOC ""
 225 #endif
 226
 227 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 228 #define PPC_FTRACE_RESTORE_LR                           \
 229         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"   \
 230 "       mtlr            0\n"
 231 #define PPC_FTRACE_RET                                  \
 232 "       blr\n"
 233 #else
 234 #define PPC_FTRACE_RESTORE_LR                           \
 235         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"   \
 236 "       mtctr           0\n"
 237 #define PPC_FTRACE_RET                                  \
 238 "       mtlr            0\n"                            \
 239 "       bctr\n"
 240 #endif
 241
 242 asm (
 243 "       .pushsection    .text, \"ax\", @progbits\n"
 244 "       .type           my_tramp1, @function\n"
 245 "       .globl          my_tramp1\n"
 246 "   my_tramp1:\n"
 247         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 248         PPC_STLU"       1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 249 "       mflr            0\n"
 250         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 251         PPC_STLU"       1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
 252         PPC64_TOC_SAVE_AND_UPDATE
 253 "       bl              my_direct_func1\n"
 254         PPC64_TOC_RESTORE
 255 "       addi            1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
 256         PPC_FTRACE_RESTORE_LR
 257 "       addi            1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
 258         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 259         PPC_FTRACE_RET
 260 "       .size           my_tramp1, .-my_tramp1\n"
 261
 262 "       .type           my_tramp2, @function\n"
 263 "       .globl          my_tramp2\n"
 264 "   my_tramp2:\n"
 265         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 266         PPC_STLU"       1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 267 "       mflr            0\n"
 268         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 269         PPC_STLU"       1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
 270         PPC64_TOC_SAVE_AND_UPDATE
 271 "       bl              my_direct_func2\n"
 272         PPC64_TOC_RESTORE
 273 "       addi            1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
 274         PPC_FTRACE_RESTORE_LR
 275 "       addi            1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
 276         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 277         PPC_FTRACE_RET
 278         PPC64_TOC
 279 "       .size           my_tramp2, .-my_tramp2\n"
 280 "       .popsection\n"
 281 );
 282
 283 #endif /* CONFIG_PPC */
 284
 285 static struct ftrace_ops direct;
 286
 287 static unsigned long my_tramp = (unsigned long)my_tramp1;
 288 static unsigned long tramps[2] = {
 289         (unsigned long)my_tramp1,
 290         (unsigned long)my_tramp2,
 291 };
 292
 293 static int simple_thread(void *arg)
 294 {
 295         static int t;
 296         int ret = 0;
 297
 298         while (!kthread_should_stop()) {
 299                 set_current_state(TASK_INTERRUPTIBLE);
 300                 schedule_timeout(2 * HZ);
 301
 302                 if (ret)
 303                         continue;
 304                 t ^= 1;
 305                 ret = modify_ftrace_direct(&direct, tramps[t]);
 306                 if (!ret)
 307                         my_tramp = tramps[t];
 308                 WARN_ON_ONCE(ret);
 309         }
 310
 311         return 0;
 312 }
 313
 314 static struct task_struct *simple_tsk;
 315
 316 static int __init ftrace_direct_init(void)
 317 {
 318         int ret;
 319
 320         ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
 321         ret = register_ftrace_direct(&direct, my_tramp);
 322
 323         if (!ret)
 324                 simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 325         return ret;
 326 }
 327
 328 static void __exit ftrace_direct_exit(void)
 329 {
 330         kthread_stop(simple_tsk);
 331         unregister_ftrace_direct(&direct, my_tramp, true);
 332 }
 333
 334 module_init(ftrace_direct_init);
 335 module_exit(ftrace_direct_exit);
 336
 337 MODULE_AUTHOR("Steven Rostedt");
 338 MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
 339 MODULE_LICENSE("GPL");