On 2023-07-12 17:17:39+0800, Zhangjin Wu wrote: > 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 > argv, envp 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. > > Suggested-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx> > Link: https://lore.kernel.org/lkml/90fdd255-32f4-4caf-90ff-06456b53dac3@xxxxxxxx/ > Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx> > --- > tools/include/nolibc/Makefile | 1 + > tools/include/nolibc/crt.h | 59 +++++++++++++++++++++++++++++++++++ > 2 files changed, 60 insertions(+) > create mode 100644 tools/include/nolibc/crt.h > > 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..f9db2389acd2 > --- /dev/null > +++ b/tools/include/nolibc/crt.h > @@ -0,0 +1,59 @@ > +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ > +/* > + * C Run Time support for NOLIBC > + * Copyright (C) 2023 Zhangjin Wu <falcon@xxxxxxxxxxx> > + */ > + > +#ifndef _NOLIBC_CRT_H > +#define _NOLIBC_CRT_H > + > +char **environ __attribute__((weak)); > +const unsigned long *_auxv __attribute__((weak)); > + > +typedef int (_nolibc_main_fn)(int, char **, char **); What's the advantage of the typedef over using the pointer type inline? > +static void exit(int); > + > +void _start_c(long *sp) > +{ > + int argc, i; > + char **argv; > + char **envp; > + /* silence potential warning: conflicting types for 'main' */ > + _nolibc_main_fn _nolibc_main __asm__ ("main"); What about the stackprotector initialization? It would really fit great into this series. > + > + /* > + * sp : argc <-- argument count, required by main() > + * argv: argv[0] <-- argument vector, required by main() > + * argv[1] > + * ... > + * argv[argc-1] > + * null > + * envp: envp[0] <-- environment variables, required by main() and getenv() > + * envp[1] > + * ... > + * null > + * _auxv: auxv[0] <-- auxiliary vector, required by getauxval() > + * auxv[1] > + * ... > + * null > + */ > + > + /* assign argc and argv */ > + argc = sp[0]; > + argv = (void *)(sp + 1); Bit of a weird mismatch between array syntax and pointer arithmetic. > + > + /* find envp */ > + envp = argv + argc + 1; > + environ = envp; Is envp really needed? Could just be assigned directly to environ. > + > + /* find auxv */ > + i = 0; > + while (envp[i]) > + i++; > + _auxv = (void *)(envp + i + 1); Could be simplified a bit: _auxv = (void *) envp; while (_auxv) _auxv++; > + > + /* go to application */ > + exit(_nolibc_main(argc, argv, envp)); > +} > + > +#endif /* _NOLIBC_CRT_H */ > -- > 2.25.1 >
