arch/x86/kernel/ftrace_64.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  *  Copyright (C) 2014  Steven Rostedt, Red Hat Inc
   4  */
   5
   6 #include <linux/linkage.h>
   7 #include <asm/ptrace.h>
   8 #include <asm/ftrace.h>
   9 #include <asm/export.h>
  10
  11
  12         .code64
  13         .section .entry.text, "ax"
  14
  15 #ifdef CC_USING_FENTRY
  16 # define function_hook  __fentry__
  17 EXPORT_SYMBOL(__fentry__)
  18 #else
  19 # define function_hook  mcount
  20 EXPORT_SYMBOL(mcount)
  21 #endif
  22
  23 /* All cases save the original rbp (8 bytes) */
  24 #ifdef CONFIG_FRAME_POINTER
  25 # ifdef CC_USING_FENTRY
  26 /* Save parent and function stack frames (rip and rbp) */
  27 #  define MCOUNT_FRAME_SIZE     (8+16*2)
  28 # else
  29 /* Save just function stack frame (rip and rbp) */
  30 #  define MCOUNT_FRAME_SIZE     (8+16)
  31 # endif
  32 #else
  33 /* No need to save a stack frame */
  34 # define MCOUNT_FRAME_SIZE      8
  35 #endif /* CONFIG_FRAME_POINTER */
  36
  37 /* Size of stack used to save mcount regs in save_mcount_regs */
  38 #define MCOUNT_REG_SIZE         (SS+8 + MCOUNT_FRAME_SIZE)
  39
  40 /*
  41  * gcc -pg option adds a call to 'mcount' in most functions.
  42  * When -mfentry is used, the call is to 'fentry' and not 'mcount'
  43  * and is done before the function's stack frame is set up.
  44  * They both require a set of regs to be saved before calling
  45  * any C code and restored before returning back to the function.
  46  *
  47  * On boot up, all these calls are converted into nops. When tracing
  48  * is enabled, the call can jump to either ftrace_caller or
  49  * ftrace_regs_caller. Callbacks (tracing functions) that require
  50  * ftrace_regs_caller (like kprobes) need to have pt_regs passed to
  51  * it. For this reason, the size of the pt_regs structure will be
  52  * allocated on the stack and the required mcount registers will
  53  * be saved in the locations that pt_regs has them in.
  54  */
  55
  56 /*
  57  * @added: the amount of stack added before calling this
  58  *
  59  * After this is called, the following registers contain:
  60  *
  61  *  %rdi - holds the address that called the trampoline
  62  *  %rsi - holds the parent function (traced function's return address)
  63  *  %rdx - holds the original %rbp
  64  */
  65 .macro save_mcount_regs added=0
  66
  67         /* Always save the original rbp */
  68         pushq %rbp
  69
  70 #ifdef CONFIG_FRAME_POINTER
  71         /*
  72          * Stack traces will stop at the ftrace trampoline if the frame pointer
  73          * is not set up properly. If fentry is used, we need to save a frame
  74          * pointer for the parent as well as the function traced, because the
  75          * fentry is called before the stack frame is set up, where as mcount
  76          * is called afterward.
  77          */
  78 #ifdef CC_USING_FENTRY
  79         /* Save the parent pointer (skip orig rbp and our return address) */
  80         pushq \added+8*2(%rsp)
  81         pushq %rbp
  82         movq %rsp, %rbp
  83         /* Save the return address (now skip orig rbp, rbp and parent) */
  84         pushq \added+8*3(%rsp)
  85 #else
  86         /* Can't assume that rip is before this (unless added was zero) */
  87         pushq \added+8(%rsp)
  88 #endif
  89         pushq %rbp
  90         movq %rsp, %rbp
  91 #endif /* CONFIG_FRAME_POINTER */
  92
  93         /*
  94          * We add enough stack to save all regs.
  95          */
  96         subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
  97         movq %rax, RAX(%rsp)
  98         movq %rcx, RCX(%rsp)
  99         movq %rdx, RDX(%rsp)
 100         movq %rsi, RSI(%rsp)
 101         movq %rdi, RDI(%rsp)
 102         movq %r8, R8(%rsp)
 103         movq %r9, R9(%rsp)
 104         /*
 105          * Save the original RBP. Even though the mcount ABI does not
 106          * require this, it helps out callers.
 107          */
 108         movq MCOUNT_REG_SIZE-8(%rsp), %rdx
 109         movq %rdx, RBP(%rsp)
 110
 111         /* Copy the parent address into %rsi (second parameter) */
 112 #ifdef CC_USING_FENTRY
 113         movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi
 114 #else
 115         /* %rdx contains original %rbp */
 116         movq 8(%rdx), %rsi
 117 #endif
 118
 119          /* Move RIP to its proper location */
 120         movq MCOUNT_REG_SIZE+\added(%rsp), %rdi
 121         movq %rdi, RIP(%rsp)
 122
 123         /*
 124          * Now %rdi (the first parameter) has the return address of
 125          * where ftrace_call returns. But the callbacks expect the
 126          * address of the call itself.
 127          */
 128         subq $MCOUNT_INSN_SIZE, %rdi
 129         .endm
 130
 131 .macro restore_mcount_regs
 132         movq R9(%rsp), %r9
 133         movq R8(%rsp), %r8
 134         movq RDI(%rsp), %rdi
 135         movq RSI(%rsp), %rsi
 136         movq RDX(%rsp), %rdx
 137         movq RCX(%rsp), %rcx
 138         movq RAX(%rsp), %rax
 139
 140         /* ftrace_regs_caller can modify %rbp */
 141         movq RBP(%rsp), %rbp
 142
 143         addq $MCOUNT_REG_SIZE, %rsp
 144
 145         .endm
 146
 147 #ifdef CONFIG_DYNAMIC_FTRACE
 148
 149 ENTRY(function_hook)
 150         retq
 151 END(function_hook)
 152
 153 ENTRY(ftrace_caller)
 154         /* save_mcount_regs fills in first two parameters */
 155         save_mcount_regs
 156
 157 GLOBAL(ftrace_caller_op_ptr)
 158         /* Load the ftrace_ops into the 3rd parameter */
 159         movq function_trace_op(%rip), %rdx
 160
 161         /* regs go into 4th parameter (but make it NULL) */
 162         movq $0, %rcx
 163
 164 GLOBAL(ftrace_call)
 165         call ftrace_stub
 166
 167         restore_mcount_regs
 168
 169         /*
 170          * The copied trampoline must call ftrace_epilogue as it
 171          * still may need to call the function graph tracer.
 172          *
 173          * The code up to this label is copied into trampolines so
 174          * think twice before adding any new code or changing the
 175          * layout here.
 176          */
 177 GLOBAL(ftrace_epilogue)
 178
 179 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 180 GLOBAL(ftrace_graph_call)
 181         jmp ftrace_stub
 182 #endif
 183
 184 /* This is weak to keep gas from relaxing the jumps */
 185 WEAK(ftrace_stub)
 186         retq
 187 END(ftrace_caller)
 188
 189 ENTRY(ftrace_regs_caller)
 190         /* Save the current flags before any operations that can change them */
 191         pushfq
 192
 193         /* added 8 bytes to save flags */
 194         save_mcount_regs 8
 195         /* save_mcount_regs fills in first two parameters */
 196
 197 GLOBAL(ftrace_regs_caller_op_ptr)
 198         /* Load the ftrace_ops into the 3rd parameter */
 199         movq function_trace_op(%rip), %rdx
 200
 201         /* Save the rest of pt_regs */
 202         movq %r15, R15(%rsp)
 203         movq %r14, R14(%rsp)
 204         movq %r13, R13(%rsp)
 205         movq %r12, R12(%rsp)
 206         movq %r11, R11(%rsp)
 207         movq %r10, R10(%rsp)
 208         movq %rbx, RBX(%rsp)
 209         /* Copy saved flags */
 210         movq MCOUNT_REG_SIZE(%rsp), %rcx
 211         movq %rcx, EFLAGS(%rsp)
 212         /* Kernel segments */
 213         movq $__KERNEL_DS, %rcx
 214         movq %rcx, SS(%rsp)
 215         movq $__KERNEL_CS, %rcx
 216         movq %rcx, CS(%rsp)
 217         /* Stack - skipping return address and flags */
 218         leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx
 219         movq %rcx, RSP(%rsp)
 220
 221         /* regs go into 4th parameter */
 222         leaq (%rsp), %rcx
 223
 224 GLOBAL(ftrace_regs_call)
 225         call ftrace_stub
 226
 227         /* Copy flags back to SS, to restore them */
 228         movq EFLAGS(%rsp), %rax
 229         movq %rax, MCOUNT_REG_SIZE(%rsp)
 230
 231         /* Handlers can change the RIP */
 232         movq RIP(%rsp), %rax
 233         movq %rax, MCOUNT_REG_SIZE+8(%rsp)
 234
 235         /* restore the rest of pt_regs */
 236         movq R15(%rsp), %r15
 237         movq R14(%rsp), %r14
 238         movq R13(%rsp), %r13
 239         movq R12(%rsp), %r12
 240         movq R10(%rsp), %r10
 241         movq RBX(%rsp), %rbx
 242
 243         restore_mcount_regs
 244
 245         /* Restore flags */
 246         popfq
 247
 248         /*
 249          * As this jmp to ftrace_epilogue can be a short jump
 250          * it must not be copied into the trampoline.
 251          * The trampoline will add the code to jump
 252          * to the return.
 253          */
 254 GLOBAL(ftrace_regs_caller_end)
 255
 256         jmp ftrace_epilogue
 257
 258 END(ftrace_regs_caller)
 259
 260
 261 #else /* ! CONFIG_DYNAMIC_FTRACE */
 262
 263 ENTRY(function_hook)
 264         cmpq $ftrace_stub, ftrace_trace_function
 265         jnz trace
 266
 267 fgraph_trace:
 268 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 269         cmpq $ftrace_stub, ftrace_graph_return
 270         jnz ftrace_graph_caller
 271
 272         cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
 273         jnz ftrace_graph_caller
 274 #endif
 275
 276 GLOBAL(ftrace_stub)
 277         retq
 278
 279 trace:
 280         /* save_mcount_regs fills in first two parameters */
 281         save_mcount_regs
 282
 283         /*
 284          * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not
 285          * set (see include/asm/ftrace.h and include/linux/ftrace.h).  Only the
 286          * ip and parent ip are used and the list function is called when
 287          * function tracing is enabled.
 288          */
 289         call   *ftrace_trace_function
 290
 291         restore_mcount_regs
 292
 293         jmp fgraph_trace
 294 END(function_hook)
 295 #endif /* CONFIG_DYNAMIC_FTRACE */
 296
 297 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 298 ENTRY(ftrace_graph_caller)
 299         /* Saves rbp into %rdx and fills first parameter  */
 300         save_mcount_regs
 301
 302 #ifdef CC_USING_FENTRY
 303         leaq MCOUNT_REG_SIZE+8(%rsp), %rsi
 304         movq $0, %rdx   /* No framepointers needed */
 305 #else
 306         /* Save address of the return address of traced function */
 307         leaq 8(%rdx), %rsi
 308         /* ftrace does sanity checks against frame pointers */
 309         movq (%rdx), %rdx
 310 #endif
 311         call    prepare_ftrace_return
 312
 313         restore_mcount_regs
 314
 315         retq
 316 END(ftrace_graph_caller)
 317
 318 GLOBAL(return_to_handler)
 319         subq  $24, %rsp
 320
 321         /* Save the return values */
 322         movq %rax, (%rsp)
 323         movq %rdx, 8(%rsp)
 324         movq %rbp, %rdi
 325
 326         call ftrace_return_to_handler
 327
 328         movq %rax, %rdi
 329         movq 8(%rsp), %rdx
 330         movq (%rsp), %rax
 331         addq $24, %rsp
 332         jmp *%rdi
 333 #endif