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