Hi, Thomas > 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? > With the extra comment added, this is not required anymore, will remove this typedef. > > +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. > Ok, which gcc version supports stackprotector? seems the test even skip on gcc 10, I will find one to verify the code change. > > + > > + /* > > + * 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. > This 'argc = *sp;' may be better ;-) > > + > > + /* find envp */ > > + envp = argv + argc + 1; > > + environ = envp; > > Is envp really needed? Could just be assigned directly to environ. > Ok, let's save one variable, envp is used to be consistent with the frequenty declaration of main(). > > + > > + /* find auxv */ > > + i = 0; > > + while (envp[i]) > > + i++; > > + _auxv = (void *)(envp + i + 1); > > Could be simplified a bit: > > _auxv = (void *) envp; > while (_auxv) > _auxv++; > Yeah, it is better, but needs a little change. _auxv = (void *) envp; while (*_auxv) _auxv++; _auxv++; Thanks, Zhangjin > > + > > + /* go to application */ > > + exit(_nolibc_main(argc, argv, envp)); > > +} > > + > > +#endif /* _NOLIBC_CRT_H */ > > -- > > 2.25.1 > >
