1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 2014 Steven Rostedt, Red Hat Inc 4 */ 5 6 #include <linux/cfi_types.h> 7 #include <linux/linkage.h> 8 #include <asm/asm-offsets.h> 9 #include <asm/ptrace.h> 10 #include <asm/ftrace.h> 11 #include <asm/export.h> 12 #include <asm/nospec-branch.h> 13 #include <asm/unwind_hints.h> 14 #include <asm/frame.h> 15 16 .code64 17 .section .text, "ax" 18 19 #ifdef CONFIG_FRAME_POINTER 20 /* Save parent and function stack frames (rip and rbp) */ 21 # define MCOUNT_FRAME_SIZE (8+16*2) 22 #else 23 /* No need to save a stack frame */ 24 # define MCOUNT_FRAME_SIZE 0 25 #endif /* CONFIG_FRAME_POINTER */ 26 27 /* Size of stack used to save mcount regs in save_mcount_regs */ 28 #define MCOUNT_REG_SIZE (FRAME_SIZE + MCOUNT_FRAME_SIZE) 29 30 /* 31 * gcc -pg option adds a call to 'mcount' in most functions. 32 * When -mfentry is used, the call is to 'fentry' and not 'mcount' 33 * and is done before the function's stack frame is set up. 34 * They both require a set of regs to be saved before calling 35 * any C code and restored before returning back to the function. 36 * 37 * On boot up, all these calls are converted into nops. When tracing 38 * is enabled, the call can jump to either ftrace_caller or 39 * ftrace_regs_caller. Callbacks (tracing functions) that require 40 * ftrace_regs_caller (like kprobes) need to have pt_regs passed to 41 * it. For this reason, the size of the pt_regs structure will be 42 * allocated on the stack and the required mcount registers will 43 * be saved in the locations that pt_regs has them in. 44 */ 45 46 /* 47 * @added: the amount of stack added before calling this 48 * 49 * After this is called, the following registers contain: 50 * 51 * %rdi - holds the address that called the trampoline 52 * %rsi - holds the parent function (traced function's return address) 53 * %rdx - holds the original %rbp 54 */ 55 .macro save_mcount_regs added=0 56 57 #ifdef CONFIG_FRAME_POINTER 58 /* Save the original rbp */ 59 pushq %rbp 60 61 /* 62 * Stack traces will stop at the ftrace trampoline if the frame pointer 63 * is not set up properly. If fentry is used, we need to save a frame 64 * pointer for the parent as well as the function traced, because the 65 * fentry is called before the stack frame is set up, where as mcount 66 * is called afterward. 67 */ 68 69 /* Save the parent pointer (skip orig rbp and our return address) */ 70 pushq \added+8*2(%rsp) 71 pushq %rbp 72 movq %rsp, %rbp 73 /* Save the return address (now skip orig rbp, rbp and parent) */ 74 pushq \added+8*3(%rsp) 75 pushq %rbp 76 movq %rsp, %rbp 77 #endif /* CONFIG_FRAME_POINTER */ 78 79 /* 80 * We add enough stack to save all regs. 81 */ 82 subq $(FRAME_SIZE), %rsp 83 movq %rax, RAX(%rsp) 84 movq %rcx, RCX(%rsp) 85 movq %rdx, RDX(%rsp) 86 movq %rsi, RSI(%rsp) 87 movq %rdi, RDI(%rsp) 88 movq %r8, R8(%rsp) 89 movq %r9, R9(%rsp) 90 movq $0, ORIG_RAX(%rsp) 91 /* 92 * Save the original RBP. Even though the mcount ABI does not 93 * require this, it helps out callers. 94 */ 95 #ifdef CONFIG_FRAME_POINTER 96 movq MCOUNT_REG_SIZE-8(%rsp), %rdx 97 #else 98 movq %rbp, %rdx 99 #endif 100 movq %rdx, RBP(%rsp) 101 102 /* Copy the parent address into %rsi (second parameter) */ 103 movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi 104 105 /* Move RIP to its proper location */ 106 movq MCOUNT_REG_SIZE+\added(%rsp), %rdi 107 movq %rdi, RIP(%rsp) 108 109 /* 110 * Now %rdi (the first parameter) has the return address of 111 * where ftrace_call returns. But the callbacks expect the 112 * address of the call itself. 113 */ 114 subq $MCOUNT_INSN_SIZE, %rdi 115 .endm 116 117 .macro restore_mcount_regs save=0 118 119 /* ftrace_regs_caller or frame pointers require this */ 120 movq RBP(%rsp), %rbp 121 122 movq R9(%rsp), %r9 123 movq R8(%rsp), %r8 124 movq RDI(%rsp), %rdi 125 movq RSI(%rsp), %rsi 126 movq RDX(%rsp), %rdx 127 movq RCX(%rsp), %rcx 128 movq RAX(%rsp), %rax 129 130 addq $MCOUNT_REG_SIZE-\save, %rsp 131 132 .endm 133 134 SYM_TYPED_FUNC_START(ftrace_stub) 135 CALL_DEPTH_ACCOUNT 136 RET 137 SYM_FUNC_END(ftrace_stub) 138 139 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 140 SYM_TYPED_FUNC_START(ftrace_stub_graph) 141 CALL_DEPTH_ACCOUNT 142 RET 143 SYM_FUNC_END(ftrace_stub_graph) 144 #endif 145 146 #ifdef CONFIG_DYNAMIC_FTRACE 147 148 SYM_FUNC_START(__fentry__) 149 CALL_DEPTH_ACCOUNT 150 RET 151 SYM_FUNC_END(__fentry__) 152 EXPORT_SYMBOL(__fentry__) 153 154 SYM_FUNC_START(ftrace_caller) 155 /* save_mcount_regs fills in first two parameters */ 156 save_mcount_regs 157 158 CALL_DEPTH_ACCOUNT 159 160 /* Stack - skipping return address of ftrace_caller */ 161 leaq MCOUNT_REG_SIZE+8(%rsp), %rcx 162 movq %rcx, RSP(%rsp) 163 164 SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) 165 ANNOTATE_NOENDBR 166 /* Load the ftrace_ops into the 3rd parameter */ 167 movq function_trace_op(%rip), %rdx 168 169 /* regs go into 4th parameter */ 170 leaq (%rsp), %rcx 171 172 /* Only ops with REGS flag set should have CS register set */ 173 movq $0, CS(%rsp) 174 175 /* Account for the function call below */ 176 CALL_DEPTH_ACCOUNT 177 178 SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) 179 ANNOTATE_NOENDBR 180 call ftrace_stub 181 182 /* Handlers can change the RIP */ 183 movq RIP(%rsp), %rax 184 movq %rax, MCOUNT_REG_SIZE(%rsp) 185 186 restore_mcount_regs 187 188 /* 189 * The code up to this label is copied into trampolines so 190 * think twice before adding any new code or changing the 191 * layout here. 192 */ 193 SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL) 194 ANNOTATE_NOENDBR 195 RET 196 SYM_FUNC_END(ftrace_caller); 197 STACK_FRAME_NON_STANDARD_FP(ftrace_caller) 198 199 SYM_FUNC_START(ftrace_regs_caller) 200 /* Save the current flags before any operations that can change them */ 201 pushfq 202 203 /* added 8 bytes to save flags */ 204 save_mcount_regs 8 205 /* save_mcount_regs fills in first two parameters */ 206 207 CALL_DEPTH_ACCOUNT 208 209 SYM_INNER_LABEL(ftrace_regs_caller_op_ptr, SYM_L_GLOBAL) 210 ANNOTATE_NOENDBR 211 /* Load the ftrace_ops into the 3rd parameter */ 212 movq function_trace_op(%rip), %rdx 213 214 /* Save the rest of pt_regs */ 215 movq %r15, R15(%rsp) 216 movq %r14, R14(%rsp) 217 movq %r13, R13(%rsp) 218 movq %r12, R12(%rsp) 219 movq %r11, R11(%rsp) 220 movq %r10, R10(%rsp) 221 movq %rbx, RBX(%rsp) 222 /* Copy saved flags */ 223 movq MCOUNT_REG_SIZE(%rsp), %rcx 224 movq %rcx, EFLAGS(%rsp) 225 /* Kernel segments */ 226 movq $__KERNEL_DS, %rcx 227 movq %rcx, SS(%rsp) 228 movq $__KERNEL_CS, %rcx 229 movq %rcx, CS(%rsp) 230 /* Stack - skipping return address and flags */ 231 leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx 232 movq %rcx, RSP(%rsp) 233 234 ENCODE_FRAME_POINTER 235 236 /* regs go into 4th parameter */ 237 leaq (%rsp), %rcx 238 239 /* Account for the function call below */ 240 CALL_DEPTH_ACCOUNT 241 242 SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL) 243 ANNOTATE_NOENDBR 244 call ftrace_stub 245 246 /* Copy flags back to SS, to restore them */ 247 movq EFLAGS(%rsp), %rax 248 movq %rax, MCOUNT_REG_SIZE(%rsp) 249 250 /* Handlers can change the RIP */ 251 movq RIP(%rsp), %rax 252 movq %rax, MCOUNT_REG_SIZE+8(%rsp) 253 254 /* restore the rest of pt_regs */ 255 movq R15(%rsp), %r15 256 movq R14(%rsp), %r14 257 movq R13(%rsp), %r13 258 movq R12(%rsp), %r12 259 movq R10(%rsp), %r10 260 movq RBX(%rsp), %rbx 261 262 movq ORIG_RAX(%rsp), %rax 263 movq %rax, MCOUNT_REG_SIZE-8(%rsp) 264 265 /* 266 * If ORIG_RAX is anything but zero, make this a call to that. 267 * See arch_ftrace_set_direct_caller(). 268 */ 269 testq %rax, %rax 270 SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL) 271 ANNOTATE_NOENDBR 272 jnz 1f 273 274 restore_mcount_regs 275 /* Restore flags */ 276 popfq 277 278 /* 279 * The trampoline will add the return. 280 */ 281 SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL) 282 ANNOTATE_NOENDBR 283 RET 284 285 /* Swap the flags with orig_rax */ 286 1: movq MCOUNT_REG_SIZE(%rsp), %rdi 287 movq %rdi, MCOUNT_REG_SIZE-8(%rsp) 288 movq %rax, MCOUNT_REG_SIZE(%rsp) 289 290 restore_mcount_regs 8 291 /* Restore flags */ 292 popfq 293 UNWIND_HINT_FUNC 294 295 /* 296 * The above left an extra return value on the stack; effectively 297 * doing a tail-call without using a register. This PUSH;RET 298 * pattern unbalances the RSB, inject a pointless CALL to rebalance. 299 */ 300 ANNOTATE_INTRA_FUNCTION_CALL 301 CALL .Ldo_rebalance 302 int3 303 .Ldo_rebalance: 304 add $8, %rsp 305 ALTERNATIVE __stringify(RET), \ 306 __stringify(ANNOTATE_UNRET_SAFE; ret; int3), \ 307 X86_FEATURE_CALL_DEPTH 308 309 SYM_FUNC_END(ftrace_regs_caller) 310 STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller) 311 312 SYM_FUNC_START(ftrace_stub_direct_tramp) 313 CALL_DEPTH_ACCOUNT 314 RET 315 SYM_FUNC_END(ftrace_stub_direct_tramp) 316 317 #else /* ! CONFIG_DYNAMIC_FTRACE */ 318 319 SYM_FUNC_START(__fentry__) 320 CALL_DEPTH_ACCOUNT 321 322 cmpq $ftrace_stub, ftrace_trace_function 323 jnz trace 324 RET 325 326 trace: 327 /* save_mcount_regs fills in first two parameters */ 328 save_mcount_regs 329 330 /* 331 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not 332 * set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the 333 * ip and parent ip are used and the list function is called when 334 * function tracing is enabled. 335 */ 336 movq ftrace_trace_function, %r8 337 CALL_NOSPEC r8 338 restore_mcount_regs 339 340 jmp ftrace_stub 341 SYM_FUNC_END(__fentry__) 342 EXPORT_SYMBOL(__fentry__) 343 STACK_FRAME_NON_STANDARD_FP(__fentry__) 344 345 #endif /* CONFIG_DYNAMIC_FTRACE */ 346 347 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 348 SYM_CODE_START(return_to_handler) 349 UNWIND_HINT_UNDEFINED 350 ANNOTATE_NOENDBR 351 subq $24, %rsp 352 353 /* Save the return values */ 354 movq %rax, (%rsp) 355 movq %rdx, 8(%rsp) 356 movq %rbp, 16(%rsp) 357 movq %rsp, %rdi 358 359 call ftrace_return_to_handler 360 361 movq %rax, %rdi 362 movq 8(%rsp), %rdx 363 movq (%rsp), %rax 364 365 addq $24, %rsp 366 /* 367 * Jump back to the old return address. This cannot be JMP_NOSPEC rdi 368 * since IBT would demand that contain ENDBR, which simply isn't so for 369 * return addresses. Use a retpoline here to keep the RSB balanced. 370 */ 371 ANNOTATE_INTRA_FUNCTION_CALL 372 call .Ldo_rop 373 int3 374 .Ldo_rop: 375 mov %rdi, (%rsp) 376 ALTERNATIVE __stringify(RET), \ 377 __stringify(ANNOTATE_UNRET_SAFE; ret; int3), \ 378 X86_FEATURE_CALL_DEPTH 379 SYM_CODE_END(return_to_handler) 380 #endif 381