OSCL-LXR linux-6.0.1/​tools/​include/​nolibc/​nolibc.h	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
 /* nolibc.h
  * Copyright (C) 2017-2018 Willy Tarreau <w@1wt.eu>
  */
 
 /*
  * This file is designed to be used as a libc alternative for minimal programs
  * with very limited requirements. It consists of a small number of syscall and
  * type definitions, and the minimal startup code needed to call main().
  * All syscalls are declared as static functions so that they can be optimized
  * away by the compiler when not used.
  *
  * Syscalls are split into 3 levels:
  *   - The lower level is the arch-specific syscall() definition, consisting in
  *     assembly code in compound expressions. These are called my_syscall0() to
  *     my_syscall6() depending on the number of arguments. The MIPS
  *     implementation is limited to 5 arguments. All input arguments are cast
  *     to a long stored in a register. These expressions always return the
  *     syscall's return value as a signed long value which is often either a
  *     pointer or the negated errno value.
  *
  *   - The second level is mostly architecture-independent. It is made of
  *     static functions called sys_<name>() which rely on my_syscallN()
  *     depending on the syscall definition. These functions are responsible
  *     for exposing the appropriate types for the syscall arguments (int,
  *     pointers, etc) and for setting the appropriate return type (often int).
  *     A few of them are architecture-specific because the syscalls are not all
  *     mapped exactly the same among architectures. For example, some archs do
  *     not implement select() and need pselect6() instead, so the sys_select()
  *     function will have to abstract this.
  *
  *   - The third level is the libc call definition. It exposes the lower raw
  *     sys_<name>() calls in a way that looks like what a libc usually does,
  *     takes care of specific input values, and of setting errno upon error.
  *     There can be minor variations compared to standard libc calls. For
  *     example the open() call always takes 3 args here.
  *
  * The errno variable is declared static and unused. This way it can be
  * optimized away if not used. However this means that a program made of
  * multiple C files may observe different errno values (one per C file). For
  * the type of programs this project targets it usually is not a problem. The
  * resulting program may even be reduced by defining the NOLIBC_IGNORE_ERRNO
  * macro, in which case the errno value will never be assigned.
  *
  * Some stdint-like integer types are defined. These are valid on all currently
  * supported architectures, because signs are enforced, ints are assumed to be
  * 32 bits, longs the size of a pointer and long long 64 bits. If more
  * architectures have to be supported, this may need to be adapted.
  *
  * Some macro definitions like the O_* values passed to open(), and some
  * structures like the sys_stat struct depend on the architecture.
  *
  * The definitions start with the architecture-specific parts, which are picked
  * based on what the compiler knows about the target architecture, and are
  * completed with the generic code. Since it is the compiler which sets the
  * target architecture, cross-compiling normally works out of the box without
  * having to specify anything.
  *
  * Finally some very common libc-level functions are provided. It is the case
  * for a few functions usually found in string.h, ctype.h, or stdlib.h.
  *
  * The nolibc.h file is only a convenient entry point which includes all other
  * files. It also defines the NOLIBC macro, so that it is possible for a
  * program to check this macro to know if it is being built against and decide
  * to disable some features or simply not to include some standard libc files.
  *
  * A simple static executable may be built this way :
  *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
  *            -static -include nolibc.h -o hello hello.c -lgcc
  *
  * Simple programs meant to be reasonably portable to various libc and using
  * only a few common includes, may also be built by simply making the include
  * path point to the nolibc directory:
  *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
  *            -I../nolibc -o hello hello.c -lgcc
  *
  * The available standard (but limited) include files are:
  *   ctype.h, errno.h, signal.h, stdio.h, stdlib.h, string.h, time.h
  *
  * In addition, the following ones are expected to be provided by the compiler:
  *   float.h, stdarg.h, stddef.h
  *
  * The following ones which are part to the C standard are not provided:
  *   assert.h, locale.h, math.h, setjmp.h, limits.h
  *
  * A very useful calling convention table may be found here :
  *      http://man7.org/linux/man-pages/man2/syscall.2.html
  *
  * This doc is quite convenient though not necessarily up to date :
  *      https://w3challs.com/syscalls/
  *
  */
 #ifndef _NOLIBC_H
 #define _NOLIBC_H
 
 #include "std.h"
 #include "arch.h"
 #include "types.h"
 #include "sys.h"
 #include "ctype.h"
 #include "signal.h"
 #include "stdio.h"
 #include "stdlib.h"
 #include "string.h"
 #include "time.h"
 #include "unistd.h"
 
 /* Used by programs to avoid std includes */
 #define NOLIBC
 
 #endif /* _NOLIBC_H */

This page was automatically generated by the 2.1.0 LXR engine. The LXR team