1 /* Assembly code template for system call stubs.
2 Copyright (C) 2009 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
20 /* The real guts of this work are in the macros defined in the
21 machine- and kernel-specific sysdep.h header file. When we
22 are defining a cancellable system call, the sysdep-cancel.h
23 versions of those macros are what we really use.
25 Each system call's object is built by a rule in sysd-syscalls
26 generated by make-syscalls.sh that #include's this file after
27 defining a few macros:
28 SYSCALL_NAME syscall name
29 SYSCALL_NARGS number of arguments this call takes
30 SYSCALL_SYMBOL primary symbol name
31 SYSCALL_CANCELLABLE 1 if the call is a cancelation point
32 SYSCALL_NOERRNO 1 to define a no-errno version (see below)
33 SYSCALL_ERRVAL 1 to define an error-value version (see below)
35 We used to simply pipe the correct three lines below through cpp into
36 the assembler. The main reason to have this file instead is so that
37 stub objects can be assembled with -g and get source line information
38 that leads a user back to a source file and these fine comments. The
39 average user otherwise has a hard time knowing which "syscall-like"
40 functions in libc are plain stubs and which have nontrivial C wrappers.
41 Some versions of the "plain" stub generation macros are more than a few
42 instructions long and the untrained eye might not distinguish them from
43 some compiled code that inexplicably lacks source line information. */
45 #if SYSCALL_CANCELLABLE
46 # include <sysdep-cancel.h>
51 #define T_PSEUDO(SYMBOL, NAME, N) PSEUDO (SYMBOL, NAME, N)
52 #define T_PSEUDO_NOERRNO(SYMBOL, NAME, N) PSEUDO_NOERRNO (SYMBOL, NAME, N)
53 #define T_PSEUDO_ERRVAL(SYMBOL, NAME, N) PSEUDO_ERRVAL (SYMBOL, NAME, N)
54 #define T_PSEUDO_END(SYMBOL) PSEUDO_END (SYMBOL)
55 #define T_PSEUDO_END_NOERRNO(SYMBOL) PSEUDO_END_NOERRNO (SYMBOL)
56 #define T_PSEUDO_END_ERRVAL(SYMBOL) PSEUDO_END_ERRVAL (SYMBOL)
60 /* This kind of system call stub never returns an error.
61 We return the return value register to the caller unexamined. */
63 T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
65 T_PSEUDO_END_NOERRNO (SYSCALL_SYMBOL)
69 /* This kind of system call stub returns the errno code as its return
70 value, or zero for success. We may massage the kernel's return value
71 to meet that ABI, but we never set errno here. */
73 T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
75 T_PSEUDO_END_ERRVAL (SYSCALL_SYMBOL)
79 /* This is a "normal" system call stub: if there is an error,
80 it returns -1 and sets errno. */
82 T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
84 T_PSEUDO_END (SYSCALL_SYMBOL)
88 libc_hidden_def (SYSCALL_SYMBOL)