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crt0-common.c revision 1.24 
      1 /* $NetBSD: crt0-common.c,v 1.24 2021/04/20 21:42:31 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 1.24 2021/04/20 21:42:31 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 #include "csu-common.h"
     50 
     51 extern int main(int, char **, char **);
     52 
     53 typedef void (*fptr_t)(void);
     54 #ifndef HAVE_INITFINI_ARRAY
     55 extern void	_init(void);
     56 extern void	_fini(void);
     57 #endif
     58 extern void	_libc_init(void);
     59 
     60 /*
     61  * Arrange for _DYNAMIC to be weak and undefined (and therefore to show up
     62  * as being at address zero, unless something else defines it).  That way,
     63  * if we happen to be compiling without -static but with without any
     64  * shared libs present, things will still work.
     65  */
     66 
     67 __weakref_visible int rtld_DYNAMIC __weak_reference(_DYNAMIC);
     68 
     69 #ifdef MCRT0
     70 extern void	monstartup(u_long, u_long);
     71 extern void	_mcleanup(void);
     72 extern unsigned char __etext, __eprol;
     73 #endif /* MCRT0 */
     74 
     75 static char	 empty_string[] = "";
     76 
     77 char		**environ __common;
     78 struct ps_strings *__ps_strings __common = 0;
     79 char		*__progname __common = empty_string;
     80 
     81 __dead __dso_hidden void ___start(void (*)(void), struct ps_strings *);
     82 
     83 #define	write(fd, s, n)	__syscall(SYS_write, (fd), (s), (n))
     84 
     85 #define	_FATAL(str)				\
     86 do {						\
     87 	write(2, str, sizeof(str)-1);		\
     88 	_exit(1);				\
     89 } while (0)
     90 
     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 _initarray(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 _finiarray(void)
    123 {
    124 	for (const fptr_t *f = __fini_array_start; f < __fini_array_end; f++) {
    125 		(*f)();
    126 	}
    127 }
    128 
    129 #if defined(__x86_64__) || defined(__powerpc__) || defined(__sparc__)
    130 #define HAS_IPLTA
    131 static void fix_iplta(void) __noinline;
    132 #elif defined(__i386__) || defined(__arm__)
    133 #define HAS_IPLT
    134 static void fix_iplt(void) __noinline;
    135 #endif
    136 
    137 
    138 #ifdef HAS_IPLTA
    139 #include <stdio.h>
    140 extern const Elf_Rela __rela_iplt_start[] __dso_hidden __weak;
    141 extern const Elf_Rela __rela_iplt_end[] __dso_hidden __weak;
    142 #ifdef __sparc__
    143 #define IFUNC_RELOCATION R_TYPE(JMP_IREL)
    144 #include <machine/elf_support.h>
    145 #define write_plt(where, value) sparc_write_branch((void *)where, (void *)value)
    146 #else
    147 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    148 #define write_plt(where, value) *where = value
    149 #endif
    150 
    151 static void
    152 fix_iplta(void)
    153 {
    154 	const Elf_Rela *rela, *relalim;
    155 	uintptr_t relocbase = 0;
    156 	Elf_Addr *where, target;
    157 
    158 	rela = __rela_iplt_start;
    159 	relalim = __rela_iplt_end;
    160 	for (; rela < relalim; ++rela) {
    161 		if (ELF_R_TYPE(rela->r_info) != IFUNC_RELOCATION)
    162 			abort();
    163 		where = (Elf_Addr *)(relocbase + rela->r_offset);
    164 		target = (Elf_Addr)(relocbase + rela->r_addend);
    165 		target = ((Elf_Addr(*)(void))target)();
    166 		write_plt(where, target);
    167 	}
    168 }
    169 #endif
    170 #ifdef HAS_IPLT
    171 extern const Elf_Rel __rel_iplt_start[] __dso_hidden __weak;
    172 extern const Elf_Rel __rel_iplt_end[] __dso_hidden __weak;
    173 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    174 
    175 static void
    176 fix_iplt(void)
    177 {
    178 	const Elf_Rel *rel, *rellim;
    179 	uintptr_t relocbase = 0;
    180 	Elf_Addr *where, target;
    181 
    182 	rel = __rel_iplt_start;
    183 	rellim = __rel_iplt_end;
    184 	for (; rel < rellim; ++rel) {
    185 		if (ELF_R_TYPE(rel->r_info) != IFUNC_RELOCATION)
    186 			abort();
    187 		where = (Elf_Addr *)(relocbase + rel->r_offset);
    188 		target = ((Elf_Addr(*)(void))*where)();
    189 		*where = target;
    190 	}
    191 }
    192 #endif
    193 
    194 #if defined(__x86_64__) || defined(__i386__)
    195 #  define HAS_RELOCATE_SELF
    196 #  if defined(__x86_64__)
    197 #  define RELA
    198 #  define REL_TAG DT_RELA
    199 #  define RELSZ_TAG DT_RELASZ
    200 #  define REL_TYPE Elf_Rela
    201 #  else
    202 #  define REL_TAG DT_REL
    203 #  define RELSZ_TAG DT_RELSZ
    204 #  define REL_TYPE Elf_Rel
    205 #  endif
    206 
    207 #include <elf.h>
    208 
    209 static void relocate_self(struct ps_strings *) __noinline;
    210 
    211 static void
    212 relocate_self(struct ps_strings *ps_strings)
    213 {
    214 	AuxInfo *aux = (AuxInfo *)(ps_strings->ps_argvstr + ps_strings->ps_nargvstr +
    215 	    ps_strings->ps_nenvstr + 2);
    216 	uintptr_t relocbase = (uintptr_t)~0U;
    217 	const Elf_Phdr *phdr = NULL;
    218 	Elf_Half phnum = (Elf_Half)~0;
    219 
    220 	for (; aux->a_type != AT_NULL; ++aux) {
    221 		switch (aux->a_type) {
    222 		case AT_BASE:
    223 			if (aux->a_v)
    224 				return;
    225 			break;
    226 		case AT_PHDR:
    227 			phdr = (void *)aux->a_v;
    228 			break;
    229 		case AT_PHNUM:
    230 			phnum = (Elf_Half)aux->a_v;
    231 			break;
    232 		}
    233 	}
    234 
    235 	if (phdr == NULL || phnum == (Elf_Half)~0)
    236 		return;
    237 
    238 	const Elf_Phdr *phlimit = phdr + phnum, *dynphdr = NULL;
    239 
    240 	for (; phdr < phlimit; ++phdr) {
    241 		if (phdr->p_type == PT_DYNAMIC)
    242 			dynphdr = phdr;
    243 		if (phdr->p_type == PT_PHDR)
    244 			relocbase = (uintptr_t)phdr - phdr->p_vaddr;
    245 	}
    246 	if (dynphdr == NULL || relocbase == (uintptr_t)~0U)
    247 		return;
    248 
    249 	Elf_Dyn *dynp = (Elf_Dyn *)((uint8_t *)dynphdr->p_vaddr + relocbase);
    250 
    251 	const REL_TYPE *relocs = 0, *relocslim;
    252 	Elf_Addr relocssz = 0;
    253 
    254 	for (; dynp->d_tag != DT_NULL; dynp++) {
    255 		switch (dynp->d_tag) {
    256 		case REL_TAG:
    257 			relocs =
    258 			    (const REL_TYPE *)(relocbase + dynp->d_un.d_ptr);
    259 			break;
    260 		case RELSZ_TAG:
    261 			relocssz = dynp->d_un.d_val;
    262 			break;
    263 		}
    264 	}
    265 	relocslim = (const REL_TYPE *)((const uint8_t *)relocs + relocssz);
    266 	for (; relocs < relocslim; ++relocs) {
    267 		Elf_Addr *where;
    268 
    269 		where = (Elf_Addr *)(relocbase + relocs->r_offset);
    270 
    271 		switch (ELF_R_TYPE(relocs->r_info)) {
    272 		case R_TYPE(RELATIVE):  /* word64 B + A */
    273 #ifdef RELA
    274 			*where = (Elf_Addr)(relocbase + relocs->r_addend);
    275 #else
    276 			*where += (Elf_Addr)relocbase;
    277 #endif
    278 			break;
    279 #ifdef IFUNC_RELOCATION
    280 		case IFUNC_RELOCATION:
    281 			break;
    282 #endif
    283 		default:
    284 			abort();
    285 		}
    286 	}
    287 }
    288 #endif
    289 
    290 void
    291 ___start(void (*cleanup)(void),			/* from shared loader */
    292     struct ps_strings *ps_strings)
    293 {
    294 #if defined(HAS_RELOCATE_SELF)
    295 	relocate_self(ps_strings);
    296 #endif
    297 
    298 	if (ps_strings == NULL)
    299 		_FATAL("ps_strings missing\n");
    300 	__ps_strings = ps_strings;
    301 
    302 	environ = ps_strings->ps_envstr;
    303 
    304 	if (ps_strings->ps_argvstr[0] != NULL) {
    305 		char *c;
    306 		__progname = ps_strings->ps_argvstr[0];
    307 		for (c = ps_strings->ps_argvstr[0]; *c; ++c) {
    308 			if (*c == '/')
    309 				__progname = c + 1;
    310 		}
    311 	} else {
    312 		__progname = empty_string;
    313 	}
    314 
    315 	if (cleanup != NULL)
    316 		atexit(cleanup);
    317 
    318 	_libc_init();
    319 
    320 	if (&rtld_DYNAMIC == NULL) {
    321 #ifdef HAS_IPLTA
    322 		fix_iplta();
    323 #endif
    324 #ifdef HAS_IPLT
    325 		fix_iplt();
    326 #endif
    327 	}
    328 
    329 	_preinit();
    330 
    331 #ifdef MCRT0
    332 	atexit(_mcleanup);
    333 	monstartup((u_long)&__eprol, (u_long)&__etext);
    334 #endif
    335 
    336 	atexit(_finiarray);
    337 	_initarray();
    338 
    339 #ifndef HAVE_INITFINI_ARRAY
    340 	atexit(_fini);
    341 	_init();
    342 #endif
    343 
    344 	exit(main(ps_strings->ps_nargvstr, ps_strings->ps_argvstr, environ));
    345 }
    346