usr/klibc/libc_init.c

/*
 * libc_init.c
 *
 * This function takes the raw data block set up by the ELF loader
 * in the kernel and parses it.  It is invoked by crt0.S which makes
 * any necessary adjustments and passes calls this function using
 * the standard C calling convention.
 *
 * The arguments are:
 *  uintptr_t *elfdata	 -- The ELF loader data block; usually from the stack.
 *                          Basically a pointer to argc.
 *  void (*onexit)(void) -- Function to install into onexit
 */

/*
 * Several Linux ABIs don't pass the onexit pointer, and the ones that
 * do never use it.  Therefore, unless USE_ONEXIT is defined, we just
 * ignore the onexit pointer.
 */
/* #define USE_ONEXIT */

#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#include <klibc/compiler.h>
#include <elf.h>
#include "atexit.h"

/* This file is included from __static_init.c or __shared_init.c */
#ifndef SHARED
# error "SHARED should be defined to 0 or 1"
#endif

char **environ;
unsigned int __page_size, __page_shift;

struct auxentry {
	uintptr_t type;
	uintptr_t v;
};

__noreturn __libc_init(uintptr_t * elfdata, void (*onexit) (void))
{
	int argc;
	char **argv, **envp, **envend;
	struct auxentry *auxentry;
#if SHARED
	typedef int (*main_t) (int, char **, char **);
	main_t MAIN = NULL;
#else
	extern int main(int, char **, char **);
#define MAIN main
#endif
	unsigned int page_size = 0, page_shift = 0;

#ifdef USE_ONEXIT
	if (onexit) {
		static struct atexit at_exit;

		at_exit.fctn = (void (*)(int, void *))onexit;
		/* at_exit.next = NULL already */
		__atexit_list = &at_exit;
	}
#else
	(void)onexit;		/* Ignore this... */
#endif

	argc = (int)*elfdata++;
	argv = (char **)elfdata;
	envp = argv + (argc + 1);

	/* The auxillary entry vector is after all the environment vars */
	for (envend = envp; *envend; envend++) ;
	auxentry = (struct auxentry *)(envend + 1);

	while (auxentry->type) {
		switch (auxentry->type) {
#if SHARED
		case AT_ENTRY:
			MAIN = (main_t) (auxentry->v);
			break;
#endif
		case AT_PAGESZ:
			page_size = (unsigned int)(auxentry->v);
			break;
		}
		auxentry++;
	}

	__page_size = page_size;

#if __GNUC__ >= 4
	/* unsigned int is 32 bits on all our architectures */
	page_shift = __builtin_clz(page_size) ^ 31;
#elif defined(__i386__) || defined(__x86_64__)
      asm("bsrl %1,%0": "=r"(page_shift):"r"(page_size));
#else
	while (page_size > 1) {
		page_shift++;
		page_size >>= 1;
	}
#endif
	__page_shift = page_shift;

	environ = envp;
	exit(MAIN(argc, argv, envp));
}
1	/*
2	* libc_init.c
3	*
4	* This function takes the raw data block set up by the ELF loader
5	* in the kernel and parses it. It is invoked by crt0.S which makes
6	* any necessary adjustments and passes calls this function using
7	* the standard C calling convention.
8	*
9	* The arguments are:
10	* uintptr_t *elfdata -- The ELF loader data block; usually from the stack.
11	* Basically a pointer to argc.
12	* void (*onexit)(void) -- Function to install into onexit
13	*/
14
15	/*
16	* Several Linux ABIs don't pass the onexit pointer, and the ones that
17	* do never use it. Therefore, unless USE_ONEXIT is defined, we just
18	* ignore the onexit pointer.
19	*/
20	/* #define USE_ONEXIT */
21
22	#include <stddef.h>
23	#include <stdlib.h>
24	#include <stdint.h>
25	#include <klibc/compiler.h>
26	#include <elf.h>
27	#include "atexit.h"
28
29	/* This file is included from __static_init.c or __shared_init.c */
30	#ifndef SHARED
31	# error "SHARED should be defined to 0 or 1"
32	#endif
33
34	char **environ;
35	unsigned int __page_size, __page_shift;
36
37	struct auxentry {
38	uintptr_t type;
39	uintptr_t v;
40	};
41
42	__noreturn __libc_init(uintptr_t * elfdata, void (*onexit) (void))
43	{
44	int argc;
45	char argv, envp, **envend;
46	struct auxentry *auxentry;
47	#if SHARED
48	typedef int (main_t) (int, char , char *);
49	main_t MAIN = NULL;
50	#else
51	extern int main(int, char , char );
52	#define MAIN main
53	#endif
54	unsigned int page_size = 0, page_shift = 0;
55
56	#ifdef USE_ONEXIT
57	if (onexit) {
58	static struct atexit at_exit;
59
60	at_exit.fctn = (void ()(int, void ))onexit;
61	/* at_exit.next = NULL already */
62	__atexit_list = &at_exit;
63	}
64	#else
65	(void)onexit; /* Ignore this... */
66	#endif
67
68	argc = (int)*elfdata++;
69	argv = (char **)elfdata;
70	envp = argv + (argc + 1);
71
72	/* The auxillary entry vector is after all the environment vars */
73	for (envend = envp; *envend; envend++) ;
74	auxentry = (struct auxentry *)(envend + 1);
75
76	while (auxentry->type) {
77	switch (auxentry->type) {
78	#if SHARED
79	case AT_ENTRY:
80	MAIN = (main_t) (auxentry->v);
81	break;
82	#endif
83	case AT_PAGESZ:
84	page_size = (unsigned int)(auxentry->v);
85	break;
86	}
87	auxentry++;
88	}
89
90	__page_size = page_size;
91
92	#if __GNUC__ >= 4
93	/* unsigned int is 32 bits on all our architectures */
94	page_shift = __builtin_clz(page_size) ^ 31;
95	#elif defined(__i386__) \|\| defined(__x86_64__)
96	asm("bsrl %1,%0": "=r"(page_shift):"r"(page_size));
97	#else
98	while (page_size > 1) {
99	page_shift++;
100	page_size >>= 1;
101	}
102	#endif
103	__page_shift = page_shift;
104
105	environ = envp;
106	exit(MAIN(argc, argv, envp));
107	}