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 .entry.text, "ax" 16 17# define function_hook __fentry__ 18EXPORT_SYMBOL(__fentry__) 19 20#ifdef CONFIG_FRAME_POINTER 21/* Save parent and function stack frames (rip and rbp) */ 22# define MCOUNT_FRAME_SIZE (8+16*2) 23#else 24/* No need to save a stack frame */ 25# define MCOUNT_FRAME_SIZE 0 26#endif /* CONFIG_FRAME_POINTER */ 27 28/* Size of stack used to save mcount regs in save_mcount_regs */ 29#define MCOUNT_REG_SIZE (SS+8 + MCOUNT_FRAME_SIZE) 30 31/* 32 * gcc -pg option adds a call to 'mcount' in most functions. 33 * When -mfentry is used, the call is to 'fentry' and not 'mcount' 34 * and is done before the function's stack frame is set up. 35 * They both require a set of regs to be saved before calling 36 * any C code and restored before returning back to the function. 37 * 38 * On boot up, all these calls are converted into nops. When tracing 39 * is enabled, the call can jump to either ftrace_caller or 40 * ftrace_regs_caller. Callbacks (tracing functions) that require 41 * ftrace_regs_caller (like kprobes) need to have pt_regs passed to 42 * it. For this reason, the size of the pt_regs structure will be 43 * allocated on the stack and the required mcount registers will 44 * be saved in the locations that pt_regs has them in. 45 */ 46 47/* 48 * @added: the amount of stack added before calling this 49 * 50 * After this is called, the following registers contain: 51 * 52 * %rdi - holds the address that called the trampoline 53 * %rsi - holds the parent function (traced function's return address) 54 * %rdx - holds the original %rbp 55 */ 56.macro save_mcount_regs added=0 57 58#ifdef CONFIG_FRAME_POINTER 59 /* Save the original rbp */ 60 pushq %rbp 61 62 /* 63 * Stack traces will stop at the ftrace trampoline if the frame pointer 64 * is not set up properly. If fentry is used, we need to save a frame 65 * pointer for the parent as well as the function traced, because the 66 * fentry is called before the stack frame is set up, where as mcount 67 * is called afterward. 68 */ 69 70 /* Save the parent pointer (skip orig rbp and our return address) */ 71 pushq \added+8*2(%rsp) 72 pushq %rbp 73 movq %rsp, %rbp 74 /* Save the return address (now skip orig rbp, rbp and parent) */ 75 pushq \added+8*3(%rsp) 76 pushq %rbp 77 movq %rsp, %rbp 78#endif /* CONFIG_FRAME_POINTER */ 79 80 /* 81 * We add enough stack to save all regs. 82 */ 83 subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp 84 movq %rax, RAX(%rsp) 85 movq %rcx, RCX(%rsp) 86 movq %rdx, RDX(%rsp) 87 movq %rsi, RSI(%rsp) 88 movq %rdi, RDI(%rsp) 89 movq %r8, R8(%rsp) 90 movq %r9, R9(%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 118 movq R9(%rsp), %r9 119 movq R8(%rsp), %r8 120 movq RDI(%rsp), %rdi 121 movq RSI(%rsp), %rsi 122 movq RDX(%rsp), %rdx 123 movq RCX(%rsp), %rcx 124 movq RAX(%rsp), %rax 125 126 /* ftrace_regs_caller can modify %rbp */ 127 movq RBP(%rsp), %rbp 128 129 addq $MCOUNT_REG_SIZE, %rsp 130 131 .endm 132 133#ifdef CONFIG_DYNAMIC_FTRACE 134 135ENTRY(function_hook) 136 retq 137ENDPROC(function_hook) 138 139ENTRY(ftrace_caller) 140 /* save_mcount_regs fills in first two parameters */ 141 save_mcount_regs 142 143GLOBAL(ftrace_caller_op_ptr) 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 150GLOBAL(ftrace_call) 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 */ 160GLOBAL(ftrace_epilogue) 161 162#ifdef CONFIG_FUNCTION_GRAPH_TRACER 163GLOBAL(ftrace_graph_call) 164 jmp ftrace_stub 165#endif 166 167/* 168 * This is weak to keep gas from relaxing the jumps. 169 * It is also used to copy the retq for trampolines. 170 */ 171WEAK(ftrace_stub) 172 retq 173ENDPROC(ftrace_caller) 174 175ENTRY(ftrace_regs_caller) 176 /* Save the current flags before any operations that can change them */ 177 pushfq 178 179 /* added 8 bytes to save flags */ 180 save_mcount_regs 8 181 /* save_mcount_regs fills in first two parameters */ 182 183GLOBAL(ftrace_regs_caller_op_ptr) 184 /* Load the ftrace_ops into the 3rd parameter */ 185 movq function_trace_op(%rip), %rdx 186 187 /* Save the rest of pt_regs */ 188 movq %r15, R15(%rsp) 189 movq %r14, R14(%rsp) 190 movq %r13, R13(%rsp) 191 movq %r12, R12(%rsp) 192 movq %r11, R11(%rsp) 193 movq %r10, R10(%rsp) 194 movq %rbx, RBX(%rsp) 195 /* Copy saved flags */ 196 movq MCOUNT_REG_SIZE(%rsp), %rcx 197 movq %rcx, EFLAGS(%rsp) 198 /* Kernel segments */ 199 movq $__KERNEL_DS, %rcx 200 movq %rcx, SS(%rsp) 201 movq $__KERNEL_CS, %rcx 202 movq %rcx, CS(%rsp) 203 /* Stack - skipping return address and flags */ 204 leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx 205 movq %rcx, RSP(%rsp) 206 207 ENCODE_FRAME_POINTER 208 209 /* regs go into 4th parameter */ 210 leaq (%rsp), %rcx 211 212GLOBAL(ftrace_regs_call) 213 call ftrace_stub 214 215 /* Copy flags back to SS, to restore them */ 216 movq EFLAGS(%rsp), %rax 217 movq %rax, MCOUNT_REG_SIZE(%rsp) 218 219 /* Handlers can change the RIP */ 220 movq RIP(%rsp), %rax 221 movq %rax, MCOUNT_REG_SIZE+8(%rsp) 222 223 /* restore the rest of pt_regs */ 224 movq R15(%rsp), %r15 225 movq R14(%rsp), %r14 226 movq R13(%rsp), %r13 227 movq R12(%rsp), %r12 228 movq R10(%rsp), %r10 229 movq RBX(%rsp), %rbx 230 231 restore_mcount_regs 232 233 /* Restore flags */ 234 popfq 235 236 /* 237 * As this jmp to ftrace_epilogue can be a short jump 238 * it must not be copied into the trampoline. 239 * The trampoline will add the code to jump 240 * to the return. 241 */ 242GLOBAL(ftrace_regs_caller_end) 243 244 jmp ftrace_epilogue 245 246ENDPROC(ftrace_regs_caller) 247 248 249#else /* ! CONFIG_DYNAMIC_FTRACE */ 250 251ENTRY(function_hook) 252 cmpq $ftrace_stub, ftrace_trace_function 253 jnz trace 254 255fgraph_trace: 256#ifdef CONFIG_FUNCTION_GRAPH_TRACER 257 cmpq $ftrace_stub, ftrace_graph_return 258 jnz ftrace_graph_caller 259 260 cmpq $ftrace_graph_entry_stub, ftrace_graph_entry 261 jnz ftrace_graph_caller 262#endif 263 264GLOBAL(ftrace_stub) 265 retq 266 267trace: 268 /* save_mcount_regs fills in first two parameters */ 269 save_mcount_regs 270 271 /* 272 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not 273 * set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the 274 * ip and parent ip are used and the list function is called when 275 * function tracing is enabled. 276 */ 277 movq ftrace_trace_function, %r8 278 CALL_NOSPEC %r8 279 restore_mcount_regs 280 281 jmp fgraph_trace 282ENDPROC(function_hook) 283#endif /* CONFIG_DYNAMIC_FTRACE */ 284 285#ifdef CONFIG_FUNCTION_GRAPH_TRACER 286ENTRY(ftrace_graph_caller) 287 /* Saves rbp into %rdx and fills first parameter */ 288 save_mcount_regs 289 290 leaq MCOUNT_REG_SIZE+8(%rsp), %rsi 291 movq $0, %rdx /* No framepointers needed */ 292 call prepare_ftrace_return 293 294 restore_mcount_regs 295 296 retq 297ENDPROC(ftrace_graph_caller) 298 299ENTRY(return_to_handler) 300 UNWIND_HINT_EMPTY 301 subq $24, %rsp 302 303 /* Save the return values */ 304 movq %rax, (%rsp) 305 movq %rdx, 8(%rsp) 306 movq %rbp, %rdi 307 308 call ftrace_return_to_handler 309 310 movq %rax, %rdi 311 movq 8(%rsp), %rdx 312 movq (%rsp), %rax 313 addq $24, %rsp 314 JMP_NOSPEC %rdi 315END(return_to_handler) 316#endif 317