Re: [PATCH] treewide: remove current_text_addr

["H. Peter Anvin" <hpa@xxxxxxxxx>]

On 08/25/18 19:38, H. Peter Anvin wrote:
>
> If it was worthwhile it would make more sense to at least force this
> into the rodata section with the string, something like the attached
> file for an example; however, I have a hunch it doesn't matter.
> 

An even nuttier version which avoids the extra pointer indirection.
Read it and fear.

	-hpa

#include <stddef.h>
#include <string.h>

#define _RET_IP_ ((unsigned long)__builtin_return_address(0))
#define no_inline __attribute__((noinline))
#define must_inline __attribute__((always_inline)) inline

struct myputs_string {
	unsigned short len;
	char str[0];
};

int _myputs_struct(const struct myputs_string * const strs);
int _myputs_string(const char *str);
int __myputs(unsigned long ip, const char *str, size_t len);

int no_inline _myputs_struct(const struct myputs_string * const strs)
{
	return __myputs(_RET_IP_, strs->str, strs->len);
}

int no_inline _myputs_string(const char *str)
{
	return __myputs(_RET_IP_, str, strlen(str)+1);
}

#define ifconst(x,y)	__builtin_choose_expr(__builtin_constant_p(x),(x),(y))

#define myputs(s)							\
({									\
	int _rv;							\
	if (__builtin_constant_p(s) &&					\
	    __builtin_constant_p(strlen(s)) &&				\
	    strlen(s)+1 == sizeof(s) &&					\
	    sizeof(s) <= (size_t)65535) {				\
	static const struct {						\
		struct myputs_string _mps_hdr;				\
		char _mps_str[sizeof(s)];				\
	} _mps = {							\
		._mps_hdr.len = sizeof(s),				\
		._mps_str = ifconst(s,""),				\
	};								\
		_rv = _myputs_struct(&_mps._mps_hdr);			\
	} else {							\
		_rv = _myputs_string(s);				\
	}								\
	_rv;								\
})

int test1(void);
int test2(const char *strx);

int test1(void)
{
	return myputs("Foobar");
}

int test2(const char *strx)
{
	return myputs(strx);
}