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      1 /* $NetBSD: crt0-common.c,v 1.30 2025/05/02 23:04:06 riastradh 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 1.30 2025/05/02 23:04:06 riastradh Exp $");
     40 
     41 #include <sys/types.h>
     42 #include <sys/exec.h>
     43 #include <sys/exec_elf.h>
     44 #include <sys/syscall.h>
     45 
     46 #include <machine/profile.h>
     47 
     48 #include <limits.h>
     49 #include <stdlib.h>
     50 #include <unistd.h>
     51 
     52 #include "csu-common.h"
     53 
     54 extern int main(int, char **, char **);
     55 
     56 typedef void (*fptr_t)(void);
     57 #ifndef HAVE_INITFINI_ARRAY
     58 extern void	_init(void);
     59 extern void	_fini(void);
     60 #endif
     61 
     62 /*
     63  * Arrange for _DYNAMIC to be weak and undefined (and therefore to show up
     64  * as being at address zero, unless something else defines it).  That way,
     65  * if we happen to be compiling without -static but with without any
     66  * shared libs present, things will still work.
     67  */
     68 
     69 __weakref_visible int rtld_DYNAMIC __weak_reference(_DYNAMIC);
     70 
     71 #ifdef MCRT0
     72 extern void	monstartup(u_long, u_long);
     73 extern void	_mcleanup(void);
     74 extern unsigned char __etext, __eprol;
     75 #endif /* MCRT0 */
     76 
     77 static char	 empty_string[] = "";
     78 
     79 char		**environ __common;
     80 struct ps_strings *__ps_strings __common = 0;
     81 char		*__progname __common = empty_string;
     82 
     83 __dead __dso_hidden void ___start(void (*)(void), struct ps_strings *);
     84 
     85 #define	write(fd, s, n)	__syscall(SYS_write, (fd), (s), (n))
     86 
     87 #define	_FATAL(str)				\
     88 do {						\
     89 	write(2, str, sizeof(str)-1);		\
     90 	_exit(1);				\
     91 } while (0)
     92 
     93 /*
     94  * If we are using INIT_ARRAY/FINI_ARRAY and we are linked statically,
     95  * we have to process these instead of relying on RTLD to do it for us.
     96  *
     97  * Since we don't need .init or .fini sections, just code them in C
     98  * to make life easier.
     99  */
    100 extern const fptr_t __preinit_array_start[] __dso_hidden;
    101 extern const fptr_t __preinit_array_end[] __dso_hidden __weak;
    102 extern const fptr_t __init_array_start[] __dso_hidden;
    103 extern const fptr_t __init_array_end[] __dso_hidden __weak;
    104 extern const fptr_t __fini_array_start[] __dso_hidden;
    105 extern const fptr_t __fini_array_end[] __dso_hidden __weak;
    106 
    107 static inline void
    108 _preinit(void)
    109 {
    110 	for (const fptr_t *f = __preinit_array_start; f < __preinit_array_end; f++) {
    111 		(*f)();
    112 	}
    113 }
    114 
    115 static inline void
    116 _initarray(void)
    117 {
    118 	for (const fptr_t *f = __init_array_start; f < __init_array_end; f++) {
    119 		(*f)();
    120 	}
    121 }
    122 
    123 static void
    124 _finiarray(void)
    125 {
    126 	for (const fptr_t *f = __fini_array_start; f < __fini_array_end; f++) {
    127 		(*f)();
    128 	}
    129 }
    130 
    131 #if \
    132     defined(__aarch64__) || \
    133     defined(__powerpc__) || \
    134     defined(__sparc__) || \
    135     defined(__x86_64__)
    136 #define HAS_IPLTA
    137 static void fix_iplta(void) __noinline;
    138 #elif \
    139     defined(__arm__) || \
    140     defined(__i386__)
    141 #define HAS_IPLT
    142 static void fix_iplt(void) __noinline;
    143 #endif
    144 
    145 
    146 #ifdef HAS_IPLTA
    147 #include <stdio.h>
    148 extern const Elf_Rela __rela_iplt_start[] __dso_hidden __weak;
    149 extern const Elf_Rela __rela_iplt_end[] __dso_hidden __weak;
    150 #ifdef __sparc__
    151 #define IFUNC_RELOCATION R_TYPE(JMP_IREL)
    152 #include <machine/elf_support.h>
    153 #define write_plt(where, value) sparc_write_branch((void *)where, (void *)value)
    154 #else
    155 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    156 #define write_plt(where, value) *where = value
    157 #endif
    158 
    159 static void
    160 fix_iplta(void)
    161 {
    162 	const Elf_Rela *rela, *relalim;
    163 	uintptr_t relocbase = 0;
    164 	Elf_Addr *where, target;
    165 
    166 	rela = __rela_iplt_start;
    167 	relalim = __rela_iplt_end;
    168 	for (; rela < relalim; ++rela) {
    169 		if (ELF_R_TYPE(rela->r_info) != IFUNC_RELOCATION)
    170 			abort();
    171 		where = (Elf_Addr *)(relocbase + rela->r_offset);
    172 		target = (Elf_Addr)(relocbase + rela->r_addend);
    173 		target = ((Elf_Addr(*)(void))target)();
    174 		write_plt(where, target);
    175 	}
    176 }
    177 #endif
    178 #ifdef HAS_IPLT
    179 extern const Elf_Rel __rel_iplt_start[] __dso_hidden __weak;
    180 extern const Elf_Rel __rel_iplt_end[] __dso_hidden __weak;
    181 #define IFUNC_RELOCATION R_TYPE(IRELATIVE)
    182 
    183 static void
    184 fix_iplt(void)
    185 {
    186 	const Elf_Rel *rel, *rellim;
    187 	uintptr_t relocbase = 0;
    188 	Elf_Addr *where, target;
    189 
    190 	rel = __rel_iplt_start;
    191 	rellim = __rel_iplt_end;
    192 	for (; rel < rellim; ++rel) {
    193 		if (ELF_R_TYPE(rel->r_info) != IFUNC_RELOCATION)
    194 			abort();
    195 		where = (Elf_Addr *)(relocbase + rel->r_offset);
    196 		target = ((Elf_Addr(*)(void))*where)();
    197 		*where = target;
    198 	}
    199 }
    200 #endif
    201 
    202 #if defined(__x86_64__) || defined(__i386__)
    203 #  define HAS_RELOCATE_SELF
    204 #  if defined(__x86_64__)
    205 #  define RELA
    206 #  define REL_TAG DT_RELA
    207 #  define RELSZ_TAG DT_RELASZ
    208 #  define REL_TYPE Elf_Rela
    209 #  else
    210 #  define REL_TAG DT_REL
    211 #  define RELSZ_TAG DT_RELSZ
    212 #  define REL_TYPE Elf_Rel
    213 #  endif
    214 
    215 #include <elf.h>
    216 
    217 static void relocate_self(struct ps_strings *) __noinline;
    218 
    219 static void
    220 relocate_self(struct ps_strings *ps_strings)
    221 {
    222 	AuxInfo *aux = (AuxInfo *)(ps_strings->ps_argvstr + ps_strings->ps_nargvstr +
    223 	    ps_strings->ps_nenvstr + 2);
    224 	uintptr_t relocbase = (uintptr_t)~0U;
    225 	const Elf_Phdr *phdr = NULL;
    226 	Elf_Half phnum = (Elf_Half)~0;
    227 
    228 	for (; aux->a_type != AT_NULL; ++aux) {
    229 		switch (aux->a_type) {
    230 		case AT_BASE:
    231 			if (aux->a_v)
    232 				return;
    233 			break;
    234 		case AT_PHDR:
    235 			phdr = (void *)aux->a_v;
    236 			break;
    237 		case AT_PHNUM:
    238 			phnum = (Elf_Half)aux->a_v;
    239 			break;
    240 		}
    241 	}
    242 
    243 	if (phdr == NULL || phnum == (Elf_Half)~0)
    244 		return;
    245 
    246 	const Elf_Phdr *phlimit = phdr + phnum, *dynphdr = NULL;
    247 
    248 	for (; phdr < phlimit; ++phdr) {
    249 		if (phdr->p_type == PT_DYNAMIC)
    250 			dynphdr = phdr;
    251 		if (phdr->p_type == PT_PHDR)
    252 			relocbase = (uintptr_t)phdr - phdr->p_vaddr;
    253 	}
    254 	if (dynphdr == NULL || relocbase == (uintptr_t)~0U)
    255 		return;
    256 
    257 	Elf_Dyn *dynp = (Elf_Dyn *)((uint8_t *)dynphdr->p_vaddr + relocbase);
    258 
    259 	const Elf_Relr *relr = 0, *relrlim;
    260 	const REL_TYPE *relocs = 0, *relocslim;
    261 	Elf_Addr relrsz = 0, relocssz = 0;
    262 
    263 	for (; dynp->d_tag != DT_NULL; dynp++) {
    264 		switch (dynp->d_tag) {
    265 		case DT_RELR:
    266 			relr =
    267 			    (const Elf_Relr *)(relocbase + dynp->d_un.d_ptr);
    268 			break;
    269 		case DT_RELRSZ:
    270 			relrsz = dynp->d_un.d_val;
    271 			break;
    272 		case REL_TAG:
    273 			relocs =
    274 			    (const REL_TYPE *)(relocbase + dynp->d_un.d_ptr);
    275 			break;
    276 		case RELSZ_TAG:
    277 			relocssz = dynp->d_un.d_val;
    278 			break;
    279 		}
    280 	}
    281 	relrlim = (const Elf_Relr *)((const uint8_t *)relr + relrsz);
    282 	relocslim = (const REL_TYPE *)((const uint8_t *)relocs + relocssz);
    283 	while (relr < relrlim) {
    284 		Elf_Addr *where;
    285 
    286 		where = (Elf_Addr *)(relocbase + *relr);
    287 		*where++ += relocbase;
    288 		while (++relr < relrlim && *relr & 1) {
    289 			unsigned i;
    290 
    291 			for (i = 1; i < CHAR_BIT*sizeof(*relr); i++, where++) {
    292 				if (*relr & ((Elf_Relr)1 << i))
    293 					*where += relocbase;
    294 			}
    295 		}
    296 	}
    297 	for (; relocs < relocslim; ++relocs) {
    298 		Elf_Addr *where;
    299 
    300 		where = (Elf_Addr *)(relocbase + relocs->r_offset);
    301 
    302 		switch (ELF_R_TYPE(relocs->r_info)) {
    303 		case R_TYPE(RELATIVE):  /* word64 B + A */
    304 #ifdef RELA
    305 			*where = (Elf_Addr)(relocbase + relocs->r_addend);
    306 #else
    307 			*where += (Elf_Addr)relocbase;
    308 #endif
    309 			break;
    310 #ifdef IFUNC_RELOCATION
    311 		case IFUNC_RELOCATION:
    312 			break;
    313 #endif
    314 		default:
    315 			abort();
    316 		}
    317 	}
    318 }
    319 #endif
    320 
    321 void
    322 ___start(void (*cleanup)(void),			/* from shared loader */
    323     struct ps_strings *ps_strings)
    324 {
    325 #if defined(HAS_RELOCATE_SELF)
    326 	relocate_self(ps_strings);
    327 #endif
    328 
    329 	if (ps_strings == NULL)
    330 		_FATAL("ps_strings missing\n");
    331 	__ps_strings = ps_strings;
    332 
    333 	environ = ps_strings->ps_envstr;
    334 
    335 	if (ps_strings->ps_argvstr[0] != NULL) {
    336 		char *c;
    337 		__progname = ps_strings->ps_argvstr[0];
    338 		for (c = ps_strings->ps_argvstr[0]; *c; ++c) {
    339 			if (*c == '/')
    340 				__progname = c + 1;
    341 		}
    342 	} else {
    343 		__progname = empty_string;
    344 	}
    345 
    346 	_libc_init();
    347 
    348 	if (&rtld_DYNAMIC == NULL) {
    349 #ifdef HAS_IPLTA
    350 		fix_iplta();
    351 #endif
    352 #ifdef HAS_IPLT
    353 		fix_iplt();
    354 #endif
    355 	}
    356 
    357 	_preinit();
    358 
    359 	if (cleanup != NULL)
    360 		atexit(cleanup);
    361 
    362 #ifdef MCRT0
    363 	atexit(_mcleanup);
    364 	monstartup((u_long)&__eprol, (u_long)&__etext);
    365 #endif
    366 
    367 	atexit(_finiarray);
    368 	_initarray();
    369 
    370 #ifndef HAVE_INITFINI_ARRAY
    371 	atexit(_fini);
    372 	_init();
    373 #endif
    374 
    375 	exit(main(ps_strings->ps_nargvstr, ps_strings->ps_argvstr, environ));
    376 }
    377