1#include <elf.h>
 2#include <poll.h>
 3#include <fcntl.h>
 4#include <signal.h>
 5#include <unistd.h>
 6#include "syscall.h"
 7#include "atomic.h"
 8#include "libc.h"
 9
10static void dummy(void) {}
11weak_alias(dummy, _init);
12
13extern weak hidden void (*const __init_array_start)(void), (*const __init_array_end)(void);
14
15static void dummy1(void *p) {}
16weak_alias(dummy1, __init_ssp);
17
18#define AUX_CNT 38
19
20#ifdef __GNUC__
21__attribute__((__noinline__))
22#endif
23void __init_libc(char **envp, char *pn)
24{
25	size_t i, *auxv, aux[AUX_CNT] = { 0 };
26	__environ = envp;
27	for (i=0; envp[i]; i++);
28	libc.auxv = auxv = (void *)(envp+i+1);
29	for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
30	__hwcap = aux[AT_HWCAP];
31	if (aux[AT_SYSINFO]) __sysinfo = aux[AT_SYSINFO];
32	libc.page_size = aux[AT_PAGESZ];
33
34	if (!pn) pn = (void*)aux[AT_EXECFN];
35	if (!pn) pn = "";
36	__progname = __progname_full = pn;
37	for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
38
39	__init_tls(aux);
40	__init_ssp((void *)aux[AT_RANDOM]);
41
42	if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
43		&& !aux[AT_SECURE]) return;
44
45	struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
46	int r =
47#ifdef SYS_poll
48	__syscall(SYS_poll, pfd, 3, 0);
49#else
50	__syscall(SYS_ppoll, pfd, 3, &(struct timespec){0}, 0, _NSIG/8);
51#endif
52	if (r<0) a_crash();
53	for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
54		if (__sys_open("/dev/null", O_RDWR)<0)
55			a_crash();
56	libc.secure = 1;
57}
58
59static void libc_start_init(void)
60{
61	_init();
62	uintptr_t a = (uintptr_t)&__init_array_start;
63	for (; a<(uintptr_t)&__init_array_end; a+=sizeof(void(*)()))
64		(*(void (**)(void))a)();
65}
66
67weak_alias(libc_start_init, __libc_start_init);
68
69typedef int lsm2_fn(int (*)(int,char **,char **), int, char **);
70static lsm2_fn libc_start_main_stage2;
71
72int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv,
73	void (*init_dummy)(), void(*fini_dummy)(), void(*ldso_dummy)())
74{
75	char **envp = argv+argc+1;
76
77	/* External linkage, and explicit noinline attribute if available,
78	 * are used to prevent the stack frame used during init from
79	 * persisting for the entire process lifetime. */
80	__init_libc(envp, argv[0]);
81
82	/* Barrier against hoisting application code or anything using ssp
83	 * or thread pointer prior to its initialization above. */
84	lsm2_fn *stage2 = libc_start_main_stage2;
85	__asm__ ( "" : "+r"(stage2) : : "memory" );
86	return stage2(main, argc, argv);
87}
88
89static int libc_start_main_stage2(int (*main)(int,char **,char **), int argc, char **argv)
90{
91	char **envp = argv+argc+1;
92	__libc_start_init();
93
94	/* Pass control to the application */
95	exit(main(argc, argv, envp));
96	return 0;
97}