1/* Assembly code template for system call stubs.
2 Copyright (C) 2009-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/* The real guts of this work are in the macros defined in the
20 machine- and kernel-specific sysdep.h header file. Cancellable syscalls
21 should be implemented using C implementation with SYSCALL_CANCEL macro.
22
23 Each system call's object is built by a rule in sysd-syscalls
24 generated by make-syscalls.sh that #include's this file after
25 defining a few macros:
26 SYSCALL_NAME syscall name
27 SYSCALL_NARGS number of arguments this call takes
28 SYSCALL_ULONG_ARG_1 the first unsigned long int argument this
29 call takes. 0 means that there are no
30 unsigned long int arguments.
31 SYSCALL_ULONG_ARG_2 the second unsigned long int argument this
32 call takes. 0 means that there is at most
33 one unsigned long int argument.
34 SYSCALL_SYMBOL primary symbol name
35 SYSCALL_NOERRNO 1 to define a no-errno version (see below)
36 SYSCALL_ERRVAL 1 to define an error-value version (see below)
37
38 We used to simply pipe the correct three lines below through cpp into
39 the assembler. The main reason to have this file instead is so that
40 stub objects can be assembled with -g and get source line information
41 that leads a user back to a source file and these fine comments. The
42 average user otherwise has a hard time knowing which "syscall-like"
43 functions in libc are plain stubs and which have nontrivial C wrappers.
44 Some versions of the "plain" stub generation macros are more than a few
45 instructions long and the untrained eye might not distinguish them from
46 some compiled code that inexplicably lacks source line information. */
47
48#include <sysdep.h>
49
50/* This indirection is needed so that SYMBOL gets macro-expanded. */
51#define syscall_hidden_def(SYMBOL) hidden_def (SYMBOL)
52
53/* If PSEUDOS_HAVE_ULONG_INDICES is defined, PSEUDO and T_PSEUDO macros
54 have 2 extra arguments for unsigned long int arguments:
55 Extra argument 1: Position of the first unsigned long int argument.
56 Extra argument 2: Position of the second unsigned long int argument.
57 */
58#ifndef PSEUDOS_HAVE_ULONG_INDICES
59# undef SYSCALL_ULONG_ARG_1
60# define SYSCALL_ULONG_ARG_1 0
61#endif
62
63#if SYSCALL_ULONG_ARG_1
64# define T_PSEUDO(SYMBOL, NAME, N, U1, U2) \
65 PSEUDO (SYMBOL, NAME, N, U1, U2)
66# define T_PSEUDO_NOERRNO(SYMBOL, NAME, N, U1, U2) \
67 PSEUDO_NOERRNO (SYMBOL, NAME, N, U1, U2)
68# define T_PSEUDO_ERRVAL(SYMBOL, NAME, N, U1, U2) \
69 PSEUDO_ERRVAL (SYMBOL, NAME, N, U1, U2)
70#else
71# define T_PSEUDO(SYMBOL, NAME, N) \
72 PSEUDO (SYMBOL, NAME, N)
73# define T_PSEUDO_NOERRNO(SYMBOL, NAME, N) \
74 PSEUDO_NOERRNO (SYMBOL, NAME, N)
75# define T_PSEUDO_ERRVAL(SYMBOL, NAME, N) \
76 PSEUDO_ERRVAL (SYMBOL, NAME, N)
77#endif
78#define T_PSEUDO_END(SYMBOL) PSEUDO_END (SYMBOL)
79#define T_PSEUDO_END_NOERRNO(SYMBOL) PSEUDO_END_NOERRNO (SYMBOL)
80#define T_PSEUDO_END_ERRVAL(SYMBOL) PSEUDO_END_ERRVAL (SYMBOL)
81
82#if SYSCALL_NOERRNO
83
84/* This kind of system call stub never returns an error.
85 We return the return value register to the caller unexamined. */
86
87# if SYSCALL_ULONG_ARG_1
88T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
89 SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2)
90# else
91T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
92# endif
93 ret_NOERRNO
94T_PSEUDO_END_NOERRNO (SYSCALL_SYMBOL)
95
96#elif SYSCALL_ERRVAL
97
98/* This kind of system call stub returns the errno code as its return
99 value, or zero for success. We may massage the kernel's return value
100 to meet that ABI, but we never set errno here. */
101
102# if SYSCALL_ULONG_ARG_1
103T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
104 SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2)
105# else
106T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
107# endif
108 ret_ERRVAL
109T_PSEUDO_END_ERRVAL (SYSCALL_SYMBOL)
110
111#else
112
113/* This is a "normal" system call stub: if there is an error,
114 it returns -1 and sets errno. */
115
116# if SYSCALL_ULONG_ARG_1
117T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
118 SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2)
119# else
120T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
121# endif
122 ret
123T_PSEUDO_END (SYSCALL_SYMBOL)
124
125#endif
126
127syscall_hidden_def (SYSCALL_SYMBOL)
128

source code of glibc/sysdeps/unix/syscall-template.S