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crt0-common.c revision 1.22 
      1 /* $NetBSD: crt0-common.c,v 1.22 2018/12/28 18:17:11 christos Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1998 Christos Zoulas
      5  * Copyright (c) 1995 Christopher G. Demetriou
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *          This product includes software developed for the
     19  *          NetBSD Project.  See http://www.NetBSD.org/ for
     20  *          information about NetBSD.
     21  * 4. The name of the author may not be used to endorse or promote products
     22  *    derived from this software without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     27  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     28  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     29  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     30  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     33  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     34  *
     35  * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
     36  */
     37 
     38 #include <sys/cdefs.h>
     39 __RCSID("$NetBSD: crt0-common.c,v 1.22 2018/12/28 18:17:11 christos Exp $");
     40 
     41 #include <sys/types.h>
     42 #include <sys/exec.h>
     43 #include <sys/exec_elf.h>
     44 #include <sys/syscall.h>
     45 #include <machine/profile.h>
     46 #include <stdlib.h>
     47 #include <unistd.h>
     48 
     49 extern int main(int, char **, char **);
     50 
     51 #ifdef HAVE_INITFINI_ARRAY
     52 typedef void (*fptr_t)(void);
     53 #else
     54 extern void	_init(void);
     55 extern void	_fini(void);
     56 #endif
     57 extern void	_libc_init(void);
     58 
     59 /*
     60  * Arrange for _DYNAMIC to be weak and undefined (and therefore to show up
     61  * as being at address zero, unless something else defines it).  That way,
     62  * if we happen to be compiling without -static but with without any
     63  * shared libs present, things will still work.
     64  */
     65 
     66 __weakref_visible int rtld_DYNAMIC __weak_reference(_DYNAMIC);
     67 
     68 #ifdef MCRT0
     69 extern void	monstartup(u_long, u_long);
     70 extern void	_mcleanup(void);
     71 extern unsigned char __etext, __eprol;
     72 #endif /* MCRT0 */
     73 
     74 char		**environ;
     75 struct ps_strings *__ps_strings = 0;
     76 
     77 static char	 empty_string[] = "";
     78 char		*__progname = empty_string;
     79 
     80 __dead __dso_hidden void ___start(void (*)(void), struct ps_strings *);
     81 
     82 #define	write(fd, s, n)	__syscall(SYS_write, (fd), (s), (n))
     83 
     84 #define	_FATAL(str)				\
     85 do {						\
     86 	write(2, str, sizeof(str)-1);		\
     87 	_exit(1);				\
     88 } while (0)
     89 
     90 #ifdef HAVE_INITFINI_ARRAY
     91 /*
     92  * If we are using INIT_ARRAY/FINI_ARRAY and we are linked statically,
     93  * we have to process these instead of relying on RTLD to do it for us.
     94  *
     95  * Since we don't need .init or .fini sections, just code them in C
     96  * to make life easier.
     97  */
     98 extern const fptr_t __preinit_array_start[] __dso_hidden;
     99 extern const fptr_t __preinit_array_end[] __dso_hidden __weak;
    100 extern const fptr_t __init_array_start[] __dso_hidden;
    101 extern const fptr_t __init_array_end[] __dso_hidden __weak;
    102 extern const fptr_t __fini_array_start[] __dso_hidden;
    103 extern const fptr_t __fini_array_end[] __dso_hidden __weak;
    104 
    105 static inline void
    106 _preinit(void)
    107 {
    108 	for (const fptr_t *f = __preinit_array_start; f < __preinit_array_end; f++) {
    109 		(*f)();
    110 	}
    111 }
    112 
    113 static inline void
    114 _init(void)
    115 {
    116 	for (const fptr_t *f = __init_array_start; f < __init_array_end; f++) {
    117 		(*f)();
    118 	}
    119 }
    120 
    121 static void
    122 _fini(void)
    123 {
    124 	for (const fptr_t *f = __fini_array_start; f < __fini_array_end; f++) {
    125 		(*f)();
    126 	}
    127 }
    128 #endif /* HAVE_INITFINI_ARRAY */
    129 
    130 #if defined(__x86_64__) || defined(__powerpc__) || defined(__sparc__)
    131 #define HAS_IPLTA
    132 static void fix_iplta(void) __noinline;
    133 #elif defined(__i386__) || defined(__arm__)
    134 #define HAS_IPLT
    135 static void fix_iplt(void) __noinline;
    136 #endif
    137 
    138 
    139 #ifdef HAS_IPLTA
    140 #include <stdio.h>
    141 extern const Elf_Rela __rela_iplt_start[] __dso_hidden __weak;
    142 extern const Elf_Rela __rela_iplt_end[] __dso_hidden __weak;
    143 #ifdef __sparc__
    144 #define IFUNC_RELOCATION R_TYPE(JMP_IREL)
    145 #include <machine/elf_support.h>
    146 #define write_plt(where, value) sparc_write_branch((void *)where, (void *)value)
    147 #else
    148 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    149 #define write_plt(where, value) *where = value
    150 #endif
    151 
    152 static void
    153 fix_iplta(void)
    154 {
    155 	const Elf_Rela *rela, *relalim;
    156 	uintptr_t relocbase = 0;
    157 	Elf_Addr *where, target;
    158 
    159 	rela = __rela_iplt_start;
    160 	relalim = __rela_iplt_end;
    161 	for (; rela < relalim; ++rela) {
    162 		if (ELF_R_TYPE(rela->r_info) != IFUNC_RELOCATION)
    163 			abort();
    164 		where = (Elf_Addr *)(relocbase + rela->r_offset);
    165 		target = (Elf_Addr)(relocbase + rela->r_addend);
    166 		target = ((Elf_Addr(*)(void))target)();
    167 		write_plt(where, target);
    168 	}
    169 }
    170 #endif
    171 #ifdef HAS_IPLT
    172 extern const Elf_Rel __rel_iplt_start[] __dso_hidden __weak;
    173 extern const Elf_Rel __rel_iplt_end[] __dso_hidden __weak;
    174 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    175 
    176 static void
    177 fix_iplt(void)
    178 {
    179 	const Elf_Rel *rel, *rellim;
    180 	uintptr_t relocbase = 0;
    181 	Elf_Addr *where, target;
    182 
    183 	rel = __rel_iplt_start;
    184 	rellim = __rel_iplt_end;
    185 	for (; rel < rellim; ++rel) {
    186 		if (ELF_R_TYPE(rel->r_info) != IFUNC_RELOCATION)
    187 			abort();
    188 		where = (Elf_Addr *)(relocbase + rel->r_offset);
    189 		target = ((Elf_Addr(*)(void))*where)();
    190 		*where = target;
    191 	}
    192 }
    193 #endif
    194 
    195 #if defined(__x86_64__) || defined(__i386__)
    196 #  define HAS_RELOCATE_SELF
    197 #  if defined(__x86_64__)
    198 #  define RELA
    199 #  define REL_TAG DT_RELA
    200 #  define RELSZ_TAG DT_RELASZ
    201 #  define REL_TYPE Elf_Rela
    202 #  else
    203 #  define REL_TAG DT_REL
    204 #  define RELSZ_TAG DT_RELSZ
    205 #  define REL_TYPE Elf_Rel
    206 #  endif
    207 
    208 #include <elf.h>
    209 
    210 static void relocate_self(struct ps_strings *) __noinline;
    211 
    212 static void
    213 relocate_self(struct ps_strings *ps_strings)
    214 {
    215 	AuxInfo *aux = (AuxInfo *)(ps_strings->ps_argvstr + ps_strings->ps_nargvstr +
    216 	    ps_strings->ps_nenvstr + 2);
    217 	uintptr_t relocbase = (uintptr_t)~0U;
    218 	const Elf_Phdr *phdr = NULL;
    219 	Elf_Half phnum = (Elf_Half)~0;
    220 
    221 	for (; aux->a_type != AT_NULL; ++aux) {
    222 		switch (aux->a_type) {
    223 		case AT_BASE:
    224 			if (aux->a_v)
    225 				return;
    226 			break;
    227 		case AT_PHDR:
    228 			phdr = (void *)aux->a_v;
    229 			break;
    230 		case AT_PHNUM:
    231 			phnum = (Elf_Half)aux->a_v;
    232 			break;
    233 		}
    234 	}
    235 
    236 	if (phdr == NULL || phnum == (Elf_Half)~0)
    237 		return;
    238 
    239 	const Elf_Phdr *phlimit = phdr + phnum, *dynphdr = NULL;
    240 
    241 	for (; phdr < phlimit; ++phdr) {
    242 		if (phdr->p_type == PT_DYNAMIC)
    243 			dynphdr = phdr;
    244 		if (phdr->p_type == PT_PHDR)
    245 			relocbase = (uintptr_t)phdr - phdr->p_vaddr;
    246 	}
    247 	if (dynphdr == NULL || relocbase == (uintptr_t)~0U)
    248 		return;
    249 
    250 	Elf_Dyn *dynp = (Elf_Dyn *)((uint8_t *)dynphdr->p_vaddr + relocbase);
    251 
    252 	const REL_TYPE *relocs = 0, *relocslim;
    253 	Elf_Addr relocssz = 0;
    254 
    255 	for (; dynp->d_tag != DT_NULL; dynp++) {
    256 		switch (dynp->d_tag) {
    257 		case REL_TAG:
    258 			relocs =
    259 			    (const REL_TYPE *)(relocbase + dynp->d_un.d_ptr);
    260 			break;
    261 		case RELSZ_TAG:
    262 			relocssz = dynp->d_un.d_val;
    263 			break;
    264 		}
    265 	}
    266 	relocslim = (const REL_TYPE *)((const uint8_t *)relocs + relocssz);
    267 	for (; relocs < relocslim; ++relocs) {
    268 		Elf_Addr *where;
    269 
    270 		where = (Elf_Addr *)(relocbase + relocs->r_offset);
    271 
    272 		switch (ELF_R_TYPE(relocs->r_info)) {
    273 		case R_TYPE(RELATIVE):  /* word64 B + A */
    274 #ifdef RELA
    275 			*where = (Elf_Addr)(relocbase + relocs->r_addend);
    276 #else
    277 			*where += (Elf_Addr)relocbase;
    278 #endif
    279 			break;
    280 #ifdef IFUNC_RELOCATION
    281 		case IFUNC_RELOCATION:
    282 			break;
    283 #endif
    284 		default:
    285 			abort();
    286 		}
    287 	}
    288 }
    289 #endif
    290 
    291 void
    292 ___start(void (*cleanup)(void),			/* from shared loader */
    293     struct ps_strings *ps_strings)
    294 {
    295 #if defined(HAS_RELOCATE_SELF)
    296 	relocate_self(ps_strings);
    297 #endif
    298 
    299 	if (ps_strings == NULL)
    300 		_FATAL("ps_strings missing\n");
    301 	__ps_strings = ps_strings;
    302 
    303 	environ = ps_strings->ps_envstr;
    304 
    305 	if (ps_strings->ps_argvstr[0] != NULL) {
    306 		char *c;
    307 		__progname = ps_strings->ps_argvstr[0];
    308 		for (c = ps_strings->ps_argvstr[0]; *c; ++c) {
    309 			if (*c == '/')
    310 				__progname = c + 1;
    311 		}
    312 	} else {
    313 		__progname = empty_string;
    314 	}
    315 
    316 	if (cleanup != NULL)
    317 		atexit(cleanup);
    318 
    319 	_libc_init();
    320 
    321 	if (&rtld_DYNAMIC == NULL) {
    322 #ifdef HAS_IPLTA
    323 		fix_iplta();
    324 #endif
    325 #ifdef HAS_IPLT
    326 		fix_iplt();
    327 #endif
    328 	}
    329 
    330 #ifdef HAVE_INITFINI_ARRAY
    331 	_preinit();
    332 #endif
    333 
    334 #ifdef MCRT0
    335 	atexit(_mcleanup);
    336 	monstartup((u_long)&__eprol, (u_long)&__etext);
    337 #endif
    338 
    339 	atexit(_fini);
    340 	_init();
    341 
    342 	exit(main(ps_strings->ps_nargvstr, ps_strings->ps_argvstr, environ));
    343 }
    344