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#include <asm/nospec-branch.h> 11#include <asm/unwind_hints.h> 12#include <asm/frame.h> 13 14 .code64 15 .section .text, "ax" 16 17#ifdef CONFIG_FRAME_POINTER 18/* Save parent and function stack frames (rip and rbp) */ 19# define MCOUNT_FRAME_SIZE (8+16*2) 20#else 21/* No need to save a stack frame */ 22# define MCOUNT_FRAME_SIZE 0 23#endif /* CONFIG_FRAME_POINTER */ 24 25/* Size of stack used to save mcount regs in save_mcount_regs */ 26#define MCOUNT_REG_SIZE (FRAME_SIZE + MCOUNT_FRAME_SIZE) 27 28/* 29 * gcc -pg option adds a call to 'mcount' in most functions. 30 * When -mfentry is used, the call is to 'fentry' and not 'mcount' 31 * and is done before the function's stack frame is set up. 32 * They both require a set of regs to be saved before calling 33 * any C code and restored before returning back to the function. 34 * 35 * On boot up, all these calls are converted into nops. When tracing 36 * is enabled, the call can jump to either ftrace_caller or 37 * ftrace_regs_caller. Callbacks (tracing functions) that require 38 * ftrace_regs_caller (like kprobes) need to have pt_regs passed to 39 * it. For this reason, the size of the pt_regs structure will be 40 * allocated on the stack and the required mcount registers will 41 * be saved in the locations that pt_regs has them in. 42 */ 43 44/* 45 * @added: the amount of stack added before calling this 46 * 47 * After this is called, the following registers contain: 48 * 49 * %rdi - holds the address that called the trampoline 50 * %rsi - holds the parent function (traced function's return address) 51 * %rdx - holds the original %rbp 52 */ 53.macro save_mcount_regs added=0 54 55#ifdef CONFIG_FRAME_POINTER 56 /* Save the original rbp */ 57 pushq %rbp 58 59 /* 60 * Stack traces will stop at the ftrace trampoline if the frame pointer 61 * is not set up properly. If fentry is used, we need to save a frame 62 * pointer for the parent as well as the function traced, because the 63 * fentry is called before the stack frame is set up, where as mcount 64 * is called afterward. 65 */ 66 67 /* Save the parent pointer (skip orig rbp and our return address) */ 68 pushq \added+8*2(%rsp) 69 pushq %rbp 70 movq %rsp, %rbp 71 /* Save the return address (now skip orig rbp, rbp and parent) */ 72 pushq \added+8*3(%rsp) 73 pushq %rbp 74 movq %rsp, %rbp 75#endif /* CONFIG_FRAME_POINTER */ 76 77 /* 78 * We add enough stack to save all regs. 79 */ 80 subq $(FRAME_SIZE), %rsp 81 movq %rax, RAX(%rsp) 82 movq %rcx, RCX(%rsp) 83 movq %rdx, RDX(%rsp) 84 movq %rsi, RSI(%rsp) 85 movq %rdi, RDI(%rsp) 86 movq %r8, R8(%rsp) 87 movq %r9, R9(%rsp) 88 movq $0, ORIG_RAX(%rsp) 89 /* 90 * Save the original RBP. Even though the mcount ABI does not 91 * require this, it helps out callers. 92 */ 93#ifdef CONFIG_FRAME_POINTER 94 movq MCOUNT_REG_SIZE-8(%rsp), %rdx 95#else 96 movq %rbp, %rdx 97#endif 98 movq %rdx, RBP(%rsp) 99 100 /* Copy the parent address into %rsi (second parameter) */ 101 movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi 102 103 /* Move RIP to its proper location */ 104 movq MCOUNT_REG_SIZE+\added(%rsp), %rdi 105 movq %rdi, RIP(%rsp) 106 107 /* 108 * Now %rdi (the first parameter) has the return address of 109 * where ftrace_call returns. But the callbacks expect the 110 * address of the call itself. 111 */ 112 subq $MCOUNT_INSN_SIZE, %rdi 113 .endm 114 115.macro restore_mcount_regs save=0 116 117 /* ftrace_regs_caller or frame pointers require this */ 118 movq RBP(%rsp), %rbp 119 120 movq R9(%rsp), %r9 121 movq R8(%rsp), %r8 122 movq RDI(%rsp), %rdi 123 movq RSI(%rsp), %rsi 124 movq RDX(%rsp), %rdx 125 movq RCX(%rsp), %rcx 126 movq RAX(%rsp), %rax 127 128 addq $MCOUNT_REG_SIZE-\save, %rsp 129 130 .endm 131 132#ifdef CONFIG_DYNAMIC_FTRACE 133 134SYM_FUNC_START(__fentry__) 135 retq 136SYM_FUNC_END(__fentry__) 137EXPORT_SYMBOL(__fentry__) 138 139SYM_FUNC_START(ftrace_caller) 140 /* save_mcount_regs fills in first two parameters */ 141 save_mcount_regs 142 143SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) 144 /* Load the ftrace_ops into the 3rd parameter */ 145 movq function_trace_op(%rip), %rdx 146 147 /* regs go into 4th parameter (but make it NULL) */ 148 movq $0, %rcx 149 150SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) 151 call ftrace_stub 152 153 restore_mcount_regs 154 155 /* 156 * The code up to this label is copied into trampolines so 157 * think twice before adding any new code or changing the 158 * layout here. 159 */ 160SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL) 161 162 jmp ftrace_epilogue 163SYM_FUNC_END(ftrace_caller); 164 165SYM_FUNC_START(ftrace_epilogue) 166#ifdef CONFIG_FUNCTION_GRAPH_TRACER 167SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) 168 jmp ftrace_stub 169#endif 170 171/* 172 * This is weak to keep gas from relaxing the jumps. 173 * It is also used to copy the retq for trampolines. 174 */ 175SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK) 176 retq 177SYM_FUNC_END(ftrace_epilogue) 178 179SYM_FUNC_START(ftrace_regs_caller) 180 /* Save the current flags before any operations that can change them */ 181 pushfq 182 183 /* added 8 bytes to save flags */ 184 save_mcount_regs 8 185 /* save_mcount_regs fills in first two parameters */ 186 187SYM_INNER_LABEL(ftrace_regs_caller_op_ptr, SYM_L_GLOBAL) 188 /* Load the ftrace_ops into the 3rd parameter */ 189 movq function_trace_op(%rip), %rdx 190 191 /* Save the rest of pt_regs */ 192 movq %r15, R15(%rsp) 193 movq %r14, R14(%rsp) 194 movq %r13, R13(%rsp) 195 movq %r12, R12(%rsp) 196 movq %r11, R11(%rsp) 197 movq %r10, R10(%rsp) 198 movq %rbx, RBX(%rsp) 199 /* Copy saved flags */ 200 movq MCOUNT_REG_SIZE(%rsp), %rcx 201 movq %rcx, EFLAGS(%rsp) 202 /* Kernel segments */ 203 movq $__KERNEL_DS, %rcx 204 movq %rcx, SS(%rsp) 205 movq $__KERNEL_CS, %rcx 206 movq %rcx, CS(%rsp) 207 /* Stack - skipping return address and flags */ 208 leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx 209 movq %rcx, RSP(%rsp) 210 211 ENCODE_FRAME_POINTER 212 213 /* regs go into 4th parameter */ 214 leaq (%rsp), %rcx 215 216SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL) 217 call ftrace_stub 218 219 /* Copy flags back to SS, to restore them */ 220 movq EFLAGS(%rsp), %rax 221 movq %rax, MCOUNT_REG_SIZE(%rsp) 222 223 /* Handlers can change the RIP */ 224 movq RIP(%rsp), %rax 225 movq %rax, MCOUNT_REG_SIZE+8(%rsp) 226 227 /* restore the rest of pt_regs */ 228 movq R15(%rsp), %r15 229 movq R14(%rsp), %r14 230 movq R13(%rsp), %r13 231 movq R12(%rsp), %r12 232 movq R10(%rsp), %r10 233 movq RBX(%rsp), %rbx 234 235 movq ORIG_RAX(%rsp), %rax 236 movq %rax, MCOUNT_REG_SIZE-8(%rsp) 237 238 /* 239 * If ORIG_RAX is anything but zero, make this a call to that. 240 * See arch_ftrace_set_direct_caller(). 241 */ 242 movq ORIG_RAX(%rsp), %rax 243 testq %rax, %rax 244SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL) 245 jnz 1f 246 247 restore_mcount_regs 248 /* Restore flags */ 249 popfq 250 251 /* 252 * As this jmp to ftrace_epilogue can be a short jump 253 * it must not be copied into the trampoline. 254 * The trampoline will add the code to jump 255 * to the return. 256 */ 257SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL) 258 jmp ftrace_epilogue 259 260 /* Swap the flags with orig_rax */ 2611: movq MCOUNT_REG_SIZE(%rsp), %rdi 262 movq %rdi, MCOUNT_REG_SIZE-8(%rsp) 263 movq %rax, MCOUNT_REG_SIZE(%rsp) 264 265 restore_mcount_regs 8 266 /* Restore flags */ 267 popfq 268 UNWIND_HINT_RET_OFFSET 269 jmp ftrace_epilogue 270 271SYM_FUNC_END(ftrace_regs_caller) 272 273 274#else /* ! CONFIG_DYNAMIC_FTRACE */ 275 276SYM_FUNC_START(__fentry__) 277 cmpq $ftrace_stub, ftrace_trace_function 278 jnz trace 279 280fgraph_trace: 281#ifdef CONFIG_FUNCTION_GRAPH_TRACER 282 cmpq $ftrace_stub, ftrace_graph_return 283 jnz ftrace_graph_caller 284 285 cmpq $ftrace_graph_entry_stub, ftrace_graph_entry 286 jnz ftrace_graph_caller 287#endif 288 289SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL) 290 retq 291 292trace: 293 /* save_mcount_regs fills in first two parameters */ 294 save_mcount_regs 295 296 /* 297 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not 298 * set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the 299 * ip and parent ip are used and the list function is called when 300 * function tracing is enabled. 301 */ 302 movq ftrace_trace_function, %r8 303 CALL_NOSPEC r8 304 restore_mcount_regs 305 306 jmp fgraph_trace 307SYM_FUNC_END(__fentry__) 308EXPORT_SYMBOL(__fentry__) 309#endif /* CONFIG_DYNAMIC_FTRACE */ 310 311#ifdef CONFIG_FUNCTION_GRAPH_TRACER 312SYM_FUNC_START(ftrace_graph_caller) 313 /* Saves rbp into %rdx and fills first parameter */ 314 save_mcount_regs 315 316 leaq MCOUNT_REG_SIZE+8(%rsp), %rsi 317 movq $0, %rdx /* No framepointers needed */ 318 call prepare_ftrace_return 319 320 restore_mcount_regs 321 322 retq 323SYM_FUNC_END(ftrace_graph_caller) 324 325SYM_CODE_START(return_to_handler) 326 UNWIND_HINT_EMPTY 327 subq $24, %rsp 328 329 /* Save the return values */ 330 movq %rax, (%rsp) 331 movq %rdx, 8(%rsp) 332 movq %rbp, %rdi 333 334 call ftrace_return_to_handler 335 336 movq %rax, %rdi 337 movq 8(%rsp), %rdx 338 movq (%rsp), %rax 339 addq $24, %rsp 340 JMP_NOSPEC rdi 341SYM_CODE_END(return_to_handler) 342#endif 343