From 17336755150b19a697079f9c3945eff7882a77c5 Mon Sep 17 00:00:00 2001 From: Zhangjin Wu Date: Sun, 16 Jul 2023 02:21:08 +0800 Subject: tools/nolibc: add new crt.h with _start_c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As the environ and _auxv support added for nolibc, the assembly _start function becomes more and more complex and therefore makes the porting of nolibc to new architectures harder and harder. To simplify portability, this C version of _start_c() is added to do most of the assembly start operations in C, which reduces the complexity a lot and will eventually simplify the porting of nolibc to the new architectures. The new _start_c() only requires a stack pointer argument, it will find argc, argv, envp/environ and _auxv for us, and then call main(), finally, it exit() with main's return status. With this new _start_c(), the future new architectures only require to add very few assembly instructions. As suggested by Thomas, users may use a different signature of main (e.g. void main(void)), a _nolibc_main alias is added for main to silence the warning about potential conflicting types. As suggested by Willy, the code is carefully polished for both smaller size and better readability with local variables and the right types. Suggested-by: Willy Tarreau Link: https://lore.kernel.org/lkml/20230715095729.GC24086@1wt.eu/ Suggested-by: Thomas Weißschuh Link: https://lore.kernel.org/lkml/90fdd255-32f4-4caf-90ff-06456b53dac3@t-8ch.de/ Signed-off-by: Zhangjin Wu Signed-off-by: Willy Tarreau --- tools/include/nolibc/Makefile | 1 + tools/include/nolibc/crt.h | 57 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+) create mode 100644 tools/include/nolibc/crt.h (limited to 'tools/include') diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile index 64d67b080744..909b6eb500fe 100644 --- a/tools/include/nolibc/Makefile +++ b/tools/include/nolibc/Makefile @@ -27,6 +27,7 @@ nolibc_arch := $(patsubst arm64,aarch64,$(ARCH)) arch_file := arch-$(nolibc_arch).h all_files := \ compiler.h \ + crt.h \ ctype.h \ errno.h \ nolibc.h \ diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h new file mode 100644 index 000000000000..92a2a0478cb1 --- /dev/null +++ b/tools/include/nolibc/crt.h @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ +/* + * C Run Time support for NOLIBC + * Copyright (C) 2023 Zhangjin Wu + */ + +#ifndef _NOLIBC_CRT_H +#define _NOLIBC_CRT_H + +char **environ __attribute__((weak)); +const unsigned long *_auxv __attribute__((weak)); + +static void exit(int); + +void _start_c(long *sp) +{ + long argc; + char **argv; + char **envp; + const unsigned long *auxv; + /* silence potential warning: conflicting types for 'main' */ + int _nolibc_main(int, char **, char **) __asm__ ("main"); + + /* + * sp : argc <-- argument count, required by main() + * argv: argv[0] <-- argument vector, required by main() + * argv[1] + * ... + * argv[argc-1] + * null + * environ: environ[0] <-- environment variables, required by main() and getenv() + * environ[1] + * ... + * null + * _auxv: _auxv[0] <-- auxiliary vector, required by getauxval() + * _auxv[1] + * ... + * null + */ + + /* assign argc and argv */ + argc = *sp; + argv = (void *)(sp + 1); + + /* find environ */ + environ = envp = argv + argc + 1; + + /* find _auxv */ + for (auxv = (void *)envp; *auxv++;) + ; + _auxv = auxv; + + /* go to application */ + exit(_nolibc_main(argc, argv, envp)); +} + +#endif /* _NOLIBC_CRT_H */ -- cgit v1.2.3