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 |
88 | T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS, |
89 | SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2) |
90 | # else |
91 | T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS) |
92 | # endif |
93 | ret_NOERRNO |
94 | T_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 |
103 | T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS, |
104 | SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2) |
105 | # else |
106 | T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS) |
107 | # endif |
108 | ret_ERRVAL |
109 | T_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 |
117 | T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS, |
118 | SYSCALL_ULONG_ARG_1, SYSCALL_ULONG_ARG_2) |
119 | # else |
120 | T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS) |
121 | # endif |
122 | ret |
123 | T_PSEUDO_END (SYSCALL_SYMBOL) |
124 | |
125 | #endif |
126 | |
127 | syscall_hidden_def (SYSCALL_SYMBOL) |
128 | |