samples/ftrace/ftrace-direct.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/module.h>
   3
   4 #include <linux/sched.h> /* for wake_up_process() */
   5 #include <linux/ftrace.h>
   6 #if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
   7 #include <asm/asm-offsets.h>
   8 #endif
   9
  10 extern void my_direct_func(struct task_struct *p);
  11
  12 void my_direct_func(struct task_struct *p)
  13 {
  14         trace_printk("waking up %s-%d\n", p->comm, p->pid);
  15 }
  16
  17 extern void my_tramp(void *);
  18
  19 #ifdef CONFIG_RISCV
  20 #include <asm/asm.h>
  21
  22 asm (
  23 "       .pushsection    .text, \"ax\", @progbits\n"
  24 "       .type           my_tramp, @function\n"
  25 "       .globl          my_tramp\n"
  26 "   my_tramp:\n"
  27 "       addi    sp,sp,-3*"SZREG"\n"
  28 "       "REG_S" a0,0*"SZREG"(sp)\n"
  29 "       "REG_S" t0,1*"SZREG"(sp)\n"
  30 "       "REG_S" ra,2*"SZREG"(sp)\n"
  31 "       call    my_direct_func\n"
  32 "       "REG_L" a0,0*"SZREG"(sp)\n"
  33 "       "REG_L" t0,1*"SZREG"(sp)\n"
  34 "       "REG_L" ra,2*"SZREG"(sp)\n"
  35 "       addi    sp,sp,3*"SZREG"\n"
  36 "       jr      t0\n"
  37 "       .size           my_tramp, .-my_tramp\n"
  38 "       .popsection\n"
  39 );
  40
  41 #endif /* CONFIG_RISCV */
  42
  43 #ifdef CONFIG_X86_64
  44
  45 #include <asm/ibt.h>
  46 #include <asm/nospec-branch.h>
  47
  48 asm (
  49 "       .pushsection    .text, \"ax\", @progbits\n"
  50 "       .type           my_tramp, @function\n"
  51 "       .globl          my_tramp\n"
  52 "   my_tramp:"
  53         ASM_ENDBR
  54 "       pushq %rbp\n"
  55 "       movq %rsp, %rbp\n"
  56         CALL_DEPTH_ACCOUNT
  57 "       pushq %rdi\n"
  58 "       call my_direct_func\n"
  59 "       popq %rdi\n"
  60 "       leave\n"
  61         ASM_RET
  62 "       .size           my_tramp, .-my_tramp\n"
  63 "       .popsection\n"
  64 );
  65
  66 #endif /* CONFIG_X86_64 */
  67
  68 #ifdef CONFIG_S390
  69
  70 asm (
  71 "       .pushsection    .text, \"ax\", @progbits\n"
  72 "       .type           my_tramp, @function\n"
  73 "       .globl          my_tramp\n"
  74 "   my_tramp:"
  75 "       lgr             %r1,%r15\n"
  76 "       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  77 "       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  78 "       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
  79 "       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
  80 "       brasl           %r14,my_direct_func\n"
  81 "       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
  82 "       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
  83 "       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
  84 "       lgr             %r1,%r0\n"
  85 "       br              %r1\n"
  86 "       .size           my_tramp, .-my_tramp\n"
  87 "       .popsection\n"
  88 );
  89
  90 #endif /* CONFIG_S390 */
  91
  92 #ifdef CONFIG_ARM64
  93
  94 asm (
  95 "       .pushsection    .text, \"ax\", @progbits\n"
  96 "       .type           my_tramp, @function\n"
  97 "       .globl          my_tramp\n"
  98 "   my_tramp:"
  99 "       hint    34\n" // bti    c
 100 "       sub     sp, sp, #32\n"
 101 "       stp     x9, x30, [sp]\n"
 102 "       str     x0, [sp, #16]\n"
 103 "       bl      my_direct_func\n"
 104 "       ldp     x30, x9, [sp]\n"
 105 "       ldr     x0, [sp, #16]\n"
 106 "       add     sp, sp, #32\n"
 107 "       ret     x9\n"
 108 "       .size           my_tramp, .-my_tramp\n"
 109 "       .popsection\n"
 110 );
 111
 112 #endif /* CONFIG_ARM64 */
 113
 114 #ifdef CONFIG_LOONGARCH
 115
 116 asm (
 117 "       .pushsection    .text, \"ax\", @progbits\n"
 118 "       .type           my_tramp, @function\n"
 119 "       .globl          my_tramp\n"
 120 "   my_tramp:\n"
 121 "       addi.d  $sp, $sp, -32\n"
 122 "       st.d    $a0, $sp, 0\n"
 123 "       st.d    $t0, $sp, 8\n"
 124 "       st.d    $ra, $sp, 16\n"
 125 "       bl      my_direct_func\n"
 126 "       ld.d    $a0, $sp, 0\n"
 127 "       ld.d    $t0, $sp, 8\n"
 128 "       ld.d    $ra, $sp, 16\n"
 129 "       addi.d  $sp, $sp, 32\n"
 130 "       jr      $t0\n"
 131 "       .size           my_tramp, .-my_tramp\n"
 132 "       .popsection\n"
 133 );
 134
 135 #endif /* CONFIG_LOONGARCH */
 136
 137 #ifdef CONFIG_PPC
 138 #include <asm/ppc_asm.h>
 139
 140 #ifdef CONFIG_PPC64
 141 #define STACK_FRAME_SIZE 48
 142 #else
 143 #define STACK_FRAME_SIZE 24
 144 #endif
 145
 146 #if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
 147 #define PPC64_TOC_SAVE_AND_UPDATE                       \
 148 "       std             2, 24(1)\n"                     \
 149 "       bcl             20, 31, 1f\n"                   \
 150 "   1:  mflr            12\n"                           \
 151 "       ld              2, (99f - 1b)(12)\n"
 152 #define PPC64_TOC_RESTORE                               \
 153 "       ld              2, 24(1)\n"
 154 #define PPC64_TOC                                       \
 155 "   99: .quad           .TOC.@tocbase\n"
 156 #else
 157 #define PPC64_TOC_SAVE_AND_UPDATE ""
 158 #define PPC64_TOC_RESTORE ""
 159 #define PPC64_TOC ""
 160 #endif
 161
 162 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 163 #define PPC_FTRACE_RESTORE_LR                           \
 164         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"   \
 165 "       mtlr            0\n"
 166 #define PPC_FTRACE_RET                                  \
 167 "       blr\n"
 168 #else
 169 #define PPC_FTRACE_RESTORE_LR                           \
 170         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"   \
 171 "       mtctr           0\n"
 172 #define PPC_FTRACE_RET                                  \
 173 "       mtlr            0\n"                            \
 174 "       bctr\n"
 175 #endif
 176
 177 asm (
 178 "       .pushsection    .text, \"ax\", @progbits\n"
 179 "       .type           my_tramp, @function\n"
 180 "       .globl          my_tramp\n"
 181 "   my_tramp:\n"
 182         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 183         PPC_STLU"       1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 184 "       mflr            0\n"
 185         PPC_STL"        0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 186         PPC_STLU"       1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
 187         PPC64_TOC_SAVE_AND_UPDATE
 188         PPC_STL"        3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 189 "       bl              my_direct_func\n"
 190         PPC_LL"         3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 191         PPC64_TOC_RESTORE
 192 "       addi            1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
 193         PPC_FTRACE_RESTORE_LR
 194 "       addi            1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
 195         PPC_LL"         0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 196         PPC_FTRACE_RET
 197         PPC64_TOC
 198 "       .size           my_tramp, .-my_tramp\n"
 199 "       .popsection\n"
 200 );
 201
 202 #endif /* CONFIG_PPC */
 203
 204 static struct ftrace_ops direct;
 205
 206 static int __init ftrace_direct_init(void)
 207 {
 208         ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
 209
 210         return register_ftrace_direct(&direct, (unsigned long) my_tramp);
 211 }
 212
 213 static void __exit ftrace_direct_exit(void)
 214 {
 215         unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
 216 }
 217
 218 module_init(ftrace_direct_init);
 219 module_exit(ftrace_direct_exit);
 220
 221 MODULE_AUTHOR("Steven Rostedt");
 222 MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
 223 MODULE_LICENSE("GPL");