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| 1 | /* SPDX-License-Identifier: LGPL-2.1 OR MIT */ |
|---|---|
| 2 | /* nolibc.h |
| 3 | * Copyright (C) 2017-2018 Willy Tarreau <w@1wt.eu> |
| 4 | */ |
| 5 | |
| 6 | /* |
| 7 | * This file is designed to be used as a libc alternative for minimal programs |
| 8 | * with very limited requirements. It consists of a small number of syscall and |
| 9 | * type definitions, and the minimal startup code needed to call main(). |
| 10 | * All syscalls are declared as static functions so that they can be optimized |
| 11 | * away by the compiler when not used. |
| 12 | * |
| 13 | * Syscalls are split into 3 levels: |
| 14 | * - The lower level is the arch-specific syscall() definition, consisting in |
| 15 | * assembly code in compound expressions. These are called my_syscall0() to |
| 16 | * my_syscall6() depending on the number of arguments. All input arguments |
| 17 | * are castto a long stored in a register. These expressions always return |
| 18 | * the syscall's return value as a signed long value which is often either |
| 19 | * a pointer or the negated errno value. |
| 20 | * |
| 21 | * - The second level is mostly architecture-independent. It is made of |
| 22 | * static functions called sys_<name>() which rely on my_syscallN() |
| 23 | * depending on the syscall definition. These functions are responsible |
| 24 | * for exposing the appropriate types for the syscall arguments (int, |
| 25 | * pointers, etc) and for setting the appropriate return type (often int). |
| 26 | * A few of them are architecture-specific because the syscalls are not all |
| 27 | * mapped exactly the same among architectures. For example, some archs do |
| 28 | * not implement select() and need pselect6() instead, so the sys_select() |
| 29 | * function will have to abstract this. |
| 30 | * |
| 31 | * - The third level is the libc call definition. It exposes the lower raw |
| 32 | * sys_<name>() calls in a way that looks like what a libc usually does, |
| 33 | * takes care of specific input values, and of setting errno upon error. |
| 34 | * There can be minor variations compared to standard libc calls. |
| 35 | * |
| 36 | * The errno variable is declared static and unused. This way it can be |
| 37 | * optimized away if not used. However this means that a program made of |
| 38 | * multiple C files may observe different errno values (one per C file). For |
| 39 | * the type of programs this project targets it usually is not a problem. The |
| 40 | * resulting program may even be reduced by defining the NOLIBC_IGNORE_ERRNO |
| 41 | * macro, in which case the errno value will never be assigned. |
| 42 | * |
| 43 | * Some stdint-like integer types are defined. These are valid on all currently |
| 44 | * supported architectures, because signs are enforced, ints are assumed to be |
| 45 | * 32 bits, longs the size of a pointer and long long 64 bits. If more |
| 46 | * architectures have to be supported, this may need to be adapted. |
| 47 | * |
| 48 | * Some macro definitions like the O_* values passed to open(), and some |
| 49 | * structures like the sys_stat struct depend on the architecture. |
| 50 | * |
| 51 | * The definitions start with the architecture-specific parts, which are picked |
| 52 | * based on what the compiler knows about the target architecture, and are |
| 53 | * completed with the generic code. Since it is the compiler which sets the |
| 54 | * target architecture, cross-compiling normally works out of the box without |
| 55 | * having to specify anything. |
| 56 | * |
| 57 | * Finally some very common libc-level functions are provided. It is the case |
| 58 | * for a few functions usually found in string.h, ctype.h, or stdlib.h. |
| 59 | * |
| 60 | * The nolibc.h file is only a convenient entry point which includes all other |
| 61 | * files. It also defines the NOLIBC macro, so that it is possible for a |
| 62 | * program to check this macro to know if it is being built against and decide |
| 63 | * to disable some features or simply not to include some standard libc files. |
| 64 | * |
| 65 | * A simple static executable may be built this way : |
| 66 | * $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \ |
| 67 | * -static -include nolibc.h -o hello hello.c -lgcc |
| 68 | * |
| 69 | * Simple programs meant to be reasonably portable to various libc and using |
| 70 | * only a few common includes, may also be built by simply making the include |
| 71 | * path point to the nolibc directory: |
| 72 | * $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \ |
| 73 | * -I../nolibc -o hello hello.c -lgcc |
| 74 | * |
| 75 | * The available standard (but limited) include files are: |
| 76 | * ctype.h, errno.h, signal.h, stdarg.h, stdbool.h stdio.h, stdlib.h, |
| 77 | * string.h, time.h |
| 78 | * |
| 79 | * In addition, the following ones are expected to be provided by the compiler: |
| 80 | * float.h, stddef.h |
| 81 | * |
| 82 | * The following ones which are part to the C standard are not provided: |
| 83 | * assert.h, locale.h, math.h, setjmp.h, limits.h |
| 84 | * |
| 85 | * A very useful calling convention table may be found here : |
| 86 | * http://man7.org/linux/man-pages/man2/syscall.2.html |
| 87 | * |
| 88 | * This doc is quite convenient though not necessarily up to date : |
| 89 | * https://w3challs.com/syscalls/ |
| 90 | * |
| 91 | */ |
| 92 | #ifndef _NOLIBC_H |
| 93 | #define _NOLIBC_H |
| 94 | |
| 95 | #include "std.h" |
| 96 | #include "arch.h" |
| 97 | #include "types.h" |
| 98 | #include "sys.h" |
| 99 | #include "sys/auxv.h" |
| 100 | #include "sys/ioctl.h" |
| 101 | #include "sys/mman.h" |
| 102 | #include "sys/mount.h" |
| 103 | #include "sys/prctl.h" |
| 104 | #include "sys/random.h" |
| 105 | #include "sys/reboot.h" |
| 106 | #include "sys/resource.h" |
| 107 | #include "sys/select.h" |
| 108 | #include "sys/stat.h" |
| 109 | #include "sys/syscall.h" |
| 110 | #include "sys/sysmacros.h" |
| 111 | #include "sys/time.h" |
| 112 | #include "sys/timerfd.h" |
| 113 | #include "sys/uio.h" |
| 114 | #include "sys/utsname.h" |
| 115 | #include "sys/wait.h" |
| 116 | #include "ctype.h" |
| 117 | #include "elf.h" |
| 118 | #include "sched.h" |
| 119 | #include "signal.h" |
| 120 | #include "unistd.h" |
| 121 | #include "stdbool.h" |
| 122 | #include "stdio.h" |
| 123 | #include "stdlib.h" |
| 124 | #include "string.h" |
| 125 | #include "time.h" |
| 126 | #include "stackprotector.h" |
| 127 | #include "dirent.h" |
| 128 | #include "fcntl.h" |
| 129 | #include "getopt.h" |
| 130 | #include "poll.h" |
| 131 | #include "math.h" |
| 132 | |
| 133 | /* Used by programs to avoid std includes */ |
| 134 | #define NOLIBC |
| 135 | |
| 136 | #endif /* _NOLIBC_H */ |
| 137 |
Warning: That file was not part of the compilation database. It may have many parsing errors.