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1/* Copyright (C) 1992-2025 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 safely
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
238extern 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. */
247struct 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#endif /* linux/i386/sysdep.h */