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.
Signed-off-by: Zhangjin Wu falcon@tinylab.org --- tools/include/nolibc/crt.h | 44 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)
diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h index 221b7c5346ca..b269294e9664 100644 --- a/tools/include/nolibc/crt.h +++ b/tools/include/nolibc/crt.h @@ -13,4 +13,48 @@ char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak));
+int main(int argc, char *argv[], char **envp); +static void exit(int); + +void _start_c(long *sp) +{ + int argc, i; + char **argv; + char **envp; + + /* + * 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); + + /* find envp */ + envp = argv + argc + 1; + environ = envp; + + /* find auxv */ + i = 0; + while (envp[i]) + i++; + _auxv = (void *)(envp + i + 1); + + /* go to application */ + exit(main(argc, argv, envp)); +} + #endif /* _NOLIBC_CRT_H */