1 /* Copyright (C) 1992-2022 Free Software Foundation, Inc. 2 This file is part of the GNU C Library. 3 4 The GNU C Library is free software; you can redistribute it and/or 5 modify it under the terms of the GNU Lesser General Public 6 License as published by the Free Software Foundation; either 7 version 2.1 of the License, or (at your option) any later version. 8 9 The GNU C Library is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public 15 License along with the GNU C Library; if not, see 16 <https://www.gnu.org/licenses/>. */ 17 18 #ifndef _LINUX_I386_SYSDEP_H 19 #define _LINUX_I386_SYSDEP_H 1 20 21 /* There is some commonality. */ 22 #include <sysdeps/unix/sysv/linux/sysdep.h> 23 #include <sysdeps/unix/i386/sysdep.h> 24 /* Defines RTLD_PRIVATE_ERRNO and USE_DL_SYSINFO. */ 25 #include <dl-sysdep.h> 26 #include <tls.h> 27 28 29 /* For Linux we can use the system call table in the header file 30 /usr/include/asm/unistd.h 31 of the kernel. But these symbols do not follow the SYS_* syntax 32 so we have to redefine the `SYS_ify' macro here. */ 33 #undef SYS_ify 34 #define SYS_ify(syscall_name) __NR_##syscall_name 35 36 #ifndef I386_USE_SYSENTER 37 # if defined USE_DL_SYSINFO \ 38 && (IS_IN (libc) || IS_IN (libpthread)) 39 # define I386_USE_SYSENTER 1 40 # else 41 # define I386_USE_SYSENTER 0 42 # endif 43 #endif 44 45 #if !I386_USE_SYSENTER && IS_IN (libc) && !defined SHARED 46 /* Inside static libc, we have two versions. For compilation units 47 with !I386_USE_SYSENTER, the vDSO entry mechanism cannot be 48 used. */ 49 # define I386_DO_SYSCALL_STRING "__libc_do_syscall_int80" 50 #else 51 # define I386_DO_SYSCALL_STRING "__libc_do_syscall" 52 #endif 53 54 #ifdef __ASSEMBLER__ 55 56 /* Linux uses a negative return value to indicate syscall errors, 57 unlike most Unices, which use the condition codes' carry flag. 58 59 Since version 2.1 the return value of a system call might be 60 negative even if the call succeeded. E.g., the `lseek' system call 61 might return a large offset. Therefore we must not anymore test 62 for < 0, but test for a real error by making sure the value in %eax 63 is a real error number. Linus said he will make sure the no syscall 64 returns a value in -1 .. -4095 as a valid result so we can savely 65 test with -4095. */ 66 67 /* We don't want the label for the error handle to be global when we define 68 it here. */ 69 #undef SYSCALL_ERROR_LABEL 70 #define SYSCALL_ERROR_LABEL __syscall_error 71 72 #undef PSEUDO 73 #define PSEUDO(name, syscall_name, args) \ 74 .text; \ 75 ENTRY (name) \ 76 DO_CALL (syscall_name, args); \ 77 cmpl $-4095, %eax; \ 78 jae SYSCALL_ERROR_LABEL 79 80 #undef PSEUDO_END 81 #define PSEUDO_END(name) \ 82 SYSCALL_ERROR_HANDLER \ 83 END (name) 84 85 #undef PSEUDO_NOERRNO 86 #define PSEUDO_NOERRNO(name, syscall_name, args) \ 87 .text; \ 88 ENTRY (name) \ 89 DO_CALL (syscall_name, args) 90 91 #undef PSEUDO_END_NOERRNO 92 #define PSEUDO_END_NOERRNO(name) \ 93 END (name) 94 95 #define ret_NOERRNO ret 96 97 /* The function has to return the error code. */ 98 #undef PSEUDO_ERRVAL 99 #define PSEUDO_ERRVAL(name, syscall_name, args) \ 100 .text; \ 101 ENTRY (name) \ 102 DO_CALL (syscall_name, args); \ 103 negl %eax 104 105 #undef PSEUDO_END_ERRVAL 106 #define PSEUDO_END_ERRVAL(name) \ 107 END (name) 108 109 #define ret_ERRVAL ret 110 111 #define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.c is used. */ 112 113 /* The original calling convention for system calls on Linux/i386 is 114 to use int $0x80. */ 115 #if I386_USE_SYSENTER 116 # ifdef PIC 117 # define ENTER_KERNEL call *%gs:SYSINFO_OFFSET 118 # else 119 # define ENTER_KERNEL call *_dl_sysinfo 120 # endif 121 #else 122 # define ENTER_KERNEL int $0x80 123 #endif 124 125 /* Linux takes system call arguments in registers: 126 127 syscall number %eax call-clobbered 128 arg 1 %ebx call-saved 129 arg 2 %ecx call-clobbered 130 arg 3 %edx call-clobbered 131 arg 4 %esi call-saved 132 arg 5 %edi call-saved 133 arg 6 %ebp call-saved 134 135 The stack layout upon entering the function is: 136 137 24(%esp) Arg# 6 138 20(%esp) Arg# 5 139 16(%esp) Arg# 4 140 12(%esp) Arg# 3 141 8(%esp) Arg# 2 142 4(%esp) Arg# 1 143 (%esp) Return address 144 145 (Of course a function with say 3 arguments does not have entries for 146 arguments 4, 5, and 6.) 147 148 The following code tries hard to be optimal. A general assumption 149 (which is true according to the data books I have) is that 150 151 2 * xchg is more expensive than pushl + movl + popl 152 153 Beside this a neat trick is used. The calling conventions for Linux 154 tell that among the registers used for parameters %ecx and %edx need 155 not be saved. Beside this we may clobber this registers even when 156 they are not used for parameter passing. 157 158 As a result one can see below that we save the content of the %ebx 159 register in the %edx register when we have less than 3 arguments 160 (2 * movl is less expensive than pushl + popl). 161 162 Second unlike for the other registers we don't save the content of 163 %ecx and %edx when we have more than 1 and 2 registers resp. 164 165 The code below might look a bit long but we have to take care for 166 the pipelined processors (i586). Here the `pushl' and `popl' 167 instructions are marked as NP (not pairable) but the exception is 168 two consecutive of these instruction. This gives no penalty on 169 other processors though. */ 170 171 #undef DO_CALL 172 #define DO_CALL(syscall_name, args) \ 173 PUSHARGS_##args \ 174 DOARGS_##args \ 175 movl $SYS_ify (syscall_name), %eax; \ 176 ENTER_KERNEL \ 177 POPARGS_##args 178 179 #define PUSHARGS_0 /* No arguments to push. */ 180 #define DOARGS_0 /* No arguments to frob. */ 181 #define POPARGS_0 /* No arguments to pop. */ 182 #define _PUSHARGS_0 /* No arguments to push. */ 183 #define _DOARGS_0(n) /* No arguments to frob. */ 184 #define _POPARGS_0 /* No arguments to pop. */ 185 186 #define PUSHARGS_1 movl %ebx, %edx; L(SAVEBX1): PUSHARGS_0 187 #define DOARGS_1 _DOARGS_1 (4) 188 #define POPARGS_1 POPARGS_0; movl %edx, %ebx; L(RESTBX1): 189 #define _PUSHARGS_1 pushl %ebx; cfi_adjust_cfa_offset (4); \ 190 cfi_rel_offset (ebx, 0); L(PUSHBX1): _PUSHARGS_0 191 #define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4) 192 #define _POPARGS_1 _POPARGS_0; popl %ebx; cfi_adjust_cfa_offset (-4); \ 193 cfi_restore (ebx); L(POPBX1): 194 195 #define PUSHARGS_2 PUSHARGS_1 196 #define DOARGS_2 _DOARGS_2 (8) 197 #define POPARGS_2 POPARGS_1 198 #define _PUSHARGS_2 _PUSHARGS_1 199 #define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4) 200 #define _POPARGS_2 _POPARGS_1 201 202 #define PUSHARGS_3 _PUSHARGS_2 203 #define DOARGS_3 _DOARGS_3 (16) 204 #define POPARGS_3 _POPARGS_3 205 #define _PUSHARGS_3 _PUSHARGS_2 206 #define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4) 207 #define _POPARGS_3 _POPARGS_2 208 209 #define PUSHARGS_4 _PUSHARGS_4 210 #define DOARGS_4 _DOARGS_4 (24) 211 #define POPARGS_4 _POPARGS_4 212 #define _PUSHARGS_4 pushl %esi; cfi_adjust_cfa_offset (4); \ 213 cfi_rel_offset (esi, 0); L(PUSHSI1): _PUSHARGS_3 214 #define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4) 215 #define _POPARGS_4 _POPARGS_3; popl %esi; cfi_adjust_cfa_offset (-4); \ 216 cfi_restore (esi); L(POPSI1): 217 218 #define PUSHARGS_5 _PUSHARGS_5 219 #define DOARGS_5 _DOARGS_5 (32) 220 #define POPARGS_5 _POPARGS_5 221 #define _PUSHARGS_5 pushl %edi; cfi_adjust_cfa_offset (4); \ 222 cfi_rel_offset (edi, 0); L(PUSHDI1): _PUSHARGS_4 223 #define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4) 224 #define _POPARGS_5 _POPARGS_4; popl %edi; cfi_adjust_cfa_offset (-4); \ 225 cfi_restore (edi); L(POPDI1): 226 227 #define PUSHARGS_6 _PUSHARGS_6 228 #define DOARGS_6 _DOARGS_6 (40) 229 #define POPARGS_6 _POPARGS_6 230 #define _PUSHARGS_6 pushl %ebp; cfi_adjust_cfa_offset (4); \ 231 cfi_rel_offset (ebp, 0); L(PUSHBP1): _PUSHARGS_5 232 #define _DOARGS_6(n) movl n(%esp), %ebp; _DOARGS_5 (n-4) 233 #define _POPARGS_6 _POPARGS_5; popl %ebp; cfi_adjust_cfa_offset (-4); \ 234 cfi_restore (ebp); L(POPBP1): 235 236 #else /* !__ASSEMBLER__ */ 237 238 extern int __syscall_error (int) 239 attribute_hidden __attribute__ ((__regparm__ (1))); 240 241 /* Six-argument syscalls use an out-of-line helper, because an inline 242 asm using all registers apart from %esp cannot work reliably and 243 the assembler does not support describing an asm that saves and 244 restores %ebp itself as a separate stack frame. This structure 245 stores the arguments not passed in registers; %edi is passed with a 246 pointer to this structure. */ 247 struct libc_do_syscall_args 248 { 249 int ebx, edi, ebp; 250 }; 251 252 # define VDSO_NAME "LINUX_2.6" 253 # define VDSO_HASH 61765110 254 255 /* List of system calls which are supported as vsyscalls. */ 256 # define HAVE_CLOCK_GETTIME_VSYSCALL "__vdso_clock_gettime" 257 # define HAVE_CLOCK_GETTIME64_VSYSCALL "__vdso_clock_gettime64" 258 # define HAVE_GETTIMEOFDAY_VSYSCALL "__vdso_gettimeofday" 259 # define HAVE_TIME_VSYSCALL "__vdso_time" 260 # define HAVE_CLOCK_GETRES_VSYSCALL "__vdso_clock_getres" 261 262 # define HAVE_CLONE3_WRAPPER 1 263 264 # undef HAVE_INTERNAL_BRK_ADDR_SYMBOL 265 # define HAVE_INTERNAL_BRK_ADDR_SYMBOL 1 266 267 /* Define a macro which expands inline into the wrapper code for a system 268 call. This use is for internal calls that do not need to handle errors 269 normally. It will never touch errno. This returns just what the kernel 270 gave back. 271 272 The _NCS variant allows non-constant syscall numbers but it is not 273 possible to use more than four parameters. */ 274 #undef INTERNAL_SYSCALL 275 #define INTERNAL_SYSCALL_MAIN_0(name, args...) \ 276 INTERNAL_SYSCALL_MAIN_INLINE(name, 0, args) 277 #define INTERNAL_SYSCALL_MAIN_1(name, args...) \ 278 INTERNAL_SYSCALL_MAIN_INLINE(name, 1, args) 279 #define INTERNAL_SYSCALL_MAIN_2(name, args...) \ 280 INTERNAL_SYSCALL_MAIN_INLINE(name, 2, args) 281 #define INTERNAL_SYSCALL_MAIN_3(name, args...) \ 282 INTERNAL_SYSCALL_MAIN_INLINE(name, 3, args) 283 #define INTERNAL_SYSCALL_MAIN_4(name, args...) \ 284 INTERNAL_SYSCALL_MAIN_INLINE(name, 4, args) 285 #define INTERNAL_SYSCALL_MAIN_5(name, args...) \ 286 INTERNAL_SYSCALL_MAIN_INLINE(name, 5, args) 287 288 #define INTERNAL_SYSCALL_MAIN_NCS_0(name, args...) \ 289 INTERNAL_SYSCALL_MAIN_NCS(name, 0, args) 290 #define INTERNAL_SYSCALL_MAIN_NCS_1(name, args...) \ 291 INTERNAL_SYSCALL_MAIN_NCS(name, 1, args) 292 #define INTERNAL_SYSCALL_MAIN_NCS_2(name, args...) \ 293 INTERNAL_SYSCALL_MAIN_NCS(name, 2, args) 294 #define INTERNAL_SYSCALL_MAIN_NCS_3(name, args...) \ 295 INTERNAL_SYSCALL_MAIN_NCS(name, 3, args) 296 #define INTERNAL_SYSCALL_MAIN_NCS_4(name, args...) \ 297 INTERNAL_SYSCALL_MAIN_NCS(name, 4, args) 298 #define INTERNAL_SYSCALL_MAIN_NCS_5(name, args...) \ 299 INTERNAL_SYSCALL_MAIN_NCS(name, 5, args) 300 301 /* Each object using 6-argument inline syscalls must include a 302 definition of __libc_do_syscall. */ 303 #define INTERNAL_SYSCALL_MAIN_6(name, arg1, arg2, arg3, \ 304 arg4, arg5, arg6) \ 305 struct libc_do_syscall_args _xv = \ 306 { \ 307 (int) (arg1), \ 308 (int) (arg5), \ 309 (int) (arg6) \ 310 }; \ 311 asm volatile ( \ 312 "movl %1, %%eax\n\t" \ 313 "call " I386_DO_SYSCALL_STRING \ 314 : "=a" (resultvar) \ 315 : "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \ 316 : "memory", "cc") 317 #define INTERNAL_SYSCALL_MAIN_NCS_6(name, arg1, arg2, arg3, \ 318 arg4, arg5, arg6) \ 319 struct libc_do_syscall_args _xv = \ 320 { \ 321 (int) (arg1), \ 322 (int) (arg5), \ 323 (int) (arg6) \ 324 }; \ 325 asm volatile ( \ 326 "movl %1, %%eax\n\t" \ 327 "call " I386_DO_SYSCALL_STRING \ 328 : "=a" (resultvar) \ 329 : "a" (name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \ 330 : "memory", "cc") 331 332 #define INTERNAL_SYSCALL(name, nr, args...) \ 333 ({ \ 334 register unsigned int resultvar; \ 335 INTERNAL_SYSCALL_MAIN_##nr (name, args); \ 336 (int) resultvar; }) 337 #define INTERNAL_SYSCALL_NCS(name, nr, args...) \ 338 ({ \ 339 register unsigned int resultvar; \ 340 INTERNAL_SYSCALL_MAIN_NCS_##nr (name, args); \ 341 (int) resultvar; }) 342 343 #if I386_USE_SYSENTER 344 # ifdef PIC 345 # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ 346 LOADREGS_##nr(args) \ 347 asm volatile ( \ 348 "call *%%gs:%P2" \ 349 : "=a" (resultvar) \ 350 : "a" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo)) \ 351 ASMARGS_##nr(args) : "memory", "cc") 352 # define INTERNAL_SYSCALL_MAIN_NCS(name, nr, args...) \ 353 LOADREGS_##nr(args) \ 354 asm volatile ( \ 355 "call *%%gs:%P2" \ 356 : "=a" (resultvar) \ 357 : "a" (name), "i" (offsetof (tcbhead_t, sysinfo)) \ 358 ASMARGS_##nr(args) : "memory", "cc") 359 # else /* I386_USE_SYSENTER && !PIC */ 360 # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ 361 LOADREGS_##nr(args) \ 362 asm volatile ( \ 363 "call *_dl_sysinfo" \ 364 : "=a" (resultvar) \ 365 : "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc") 366 # define INTERNAL_SYSCALL_MAIN_NCS(name, nr, args...) \ 367 LOADREGS_##nr(args) \ 368 asm volatile ( \ 369 "call *_dl_sysinfo" \ 370 : "=a" (resultvar) \ 371 : "a" (name) ASMARGS_##nr(args) : "memory", "cc") 372 # endif /* I386_USE_SYSENTER && !PIC */ 373 #else /* !I386_USE_SYSENTER */ 374 # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ 375 LOADREGS_##nr(args) \ 376 asm volatile ( \ 377 "int $0x80" \ 378 : "=a" (resultvar) \ 379 : "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc") 380 # define INTERNAL_SYSCALL_MAIN_NCS(name, nr, args...) \ 381 LOADREGS_##nr(args) \ 382 asm volatile ( \ 383 "int $0x80" \ 384 : "=a" (resultvar) \ 385 : "a" (name) ASMARGS_##nr(args) : "memory", "cc") 386 #endif /* !I386_USE_SYSENTER */ 387 388 #define LOADREGS_0() 389 #define ASMARGS_0() 390 #define LOADREGS_1(arg1) \ 391 LOADREGS_0 () 392 #define ASMARGS_1(arg1) \ 393 ASMARGS_0 (), "b" ((unsigned int) (arg1)) 394 #define LOADREGS_2(arg1, arg2) \ 395 LOADREGS_1 (arg1) 396 #define ASMARGS_2(arg1, arg2) \ 397 ASMARGS_1 (arg1), "c" ((unsigned int) (arg2)) 398 #define LOADREGS_3(arg1, arg2, arg3) \ 399 LOADREGS_2 (arg1, arg2) 400 #define ASMARGS_3(arg1, arg2, arg3) \ 401 ASMARGS_2 (arg1, arg2), "d" ((unsigned int) (arg3)) 402 #define LOADREGS_4(arg1, arg2, arg3, arg4) \ 403 LOADREGS_3 (arg1, arg2, arg3) 404 #define ASMARGS_4(arg1, arg2, arg3, arg4) \ 405 ASMARGS_3 (arg1, arg2, arg3), "S" ((unsigned int) (arg4)) 406 #define LOADREGS_5(arg1, arg2, arg3, arg4, arg5) \ 407 LOADREGS_4 (arg1, arg2, arg3, arg4) 408 #define ASMARGS_5(arg1, arg2, arg3, arg4, arg5) \ 409 ASMARGS_4 (arg1, arg2, arg3, arg4), "D" ((unsigned int) (arg5)) 410 411 #define ASMFMT_0() 412 #ifdef __PIC__ 413 # define ASMFMT_1(arg1) \ 414 , "cd" (arg1) 415 # define ASMFMT_2(arg1, arg2) \ 416 , "d" (arg1), "c" (arg2) 417 # define ASMFMT_3(arg1, arg2, arg3) \ 418 , "D" (arg1), "c" (arg2), "d" (arg3) 419 # define ASMFMT_4(arg1, arg2, arg3, arg4) \ 420 , "D" (arg1), "c" (arg2), "d" (arg3), "S" (arg4) 421 # define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \ 422 , "0" (arg1), "m" (_xv), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5) 423 #else 424 # define ASMFMT_1(arg1) \ 425 , "b" (arg1) 426 # define ASMFMT_2(arg1, arg2) \ 427 , "b" (arg1), "c" (arg2) 428 # define ASMFMT_3(arg1, arg2, arg3) \ 429 , "b" (arg1), "c" (arg2), "d" (arg3) 430 # define ASMFMT_4(arg1, arg2, arg3, arg4) \ 431 , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4) 432 # define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \ 433 , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5) 434 #endif 435 436 #define EXTRAVAR_0 437 #define EXTRAVAR_1 438 #define EXTRAVAR_2 439 #define EXTRAVAR_3 440 #define EXTRAVAR_4 441 #ifdef __PIC__ 442 # define EXTRAVAR_5 int _xv; 443 #else 444 # define EXTRAVAR_5 445 #endif 446 447 #endif /* __ASSEMBLER__ */ 448 449 450 /* Pointer mangling support. */ 451 #if IS_IN (rtld) 452 /* We cannot use the thread descriptor because in ld.so we use setjmp 453 earlier than the descriptor is initialized. Using a global variable 454 is too complicated here since we have no PC-relative addressing mode. */ 455 #else 456 # ifdef __ASSEMBLER__ 457 # define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \ 458 roll $9, reg 459 # define PTR_DEMANGLE(reg) rorl $9, reg; \ 460 xorl %gs:POINTER_GUARD, reg 461 # else 462 # define PTR_MANGLE(var) asm ("xorl %%gs:%c2, %0\n" \ 463 "roll $9, %0" \ 464 : "=r" (var) \ 465 : "0" (var), \ 466 "i" (offsetof (tcbhead_t, \ 467 pointer_guard))) 468 # define PTR_DEMANGLE(var) asm ("rorl $9, %0\n" \ 469 "xorl %%gs:%c2, %0" \ 470 : "=r" (var) \ 471 : "0" (var), \ 472 "i" (offsetof (tcbhead_t, \ 473 pointer_guard))) 474 # endif 475 #endif 476 477 /* Each shadow stack slot takes 4 bytes. Assuming that each stack 478 frame takes 128 bytes, this is used to compute shadow stack size 479 from stack size. */ 480 #define STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT 5 481 482 #endif /* linux/i386/sysdep.h */ 483