1/*	$OpenBSD: boot.h,v 1.35 2023/11/18 16:26:15 deraadt Exp $ */
2
3/*
4 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29/*
30 * IMPORTANT: any functions below are NOT protected by SSP.  Please
31 * do not add anything except what is required to reach GOT with
32 * an adjustment.
33 */
34
35#define	_DYN_LOADER
36
37#include <sys/exec_elf.h>
38#include <sys/mman.h>
39
40#include <machine/reloc.h>
41
42__dead
43void _csu_abort(void);
44
45#include "archdep.h"
46
47/*
48 * Use the internal, hidden name for any syscalls we need, to avoid
49 * accidental override by application code
50 */
51#define REDIRECT_SYSCALL(x)	typeof(x) x asm("_libc_"#x) __dso_hidden
52REDIRECT_SYSCALL(mprotect);
53REDIRECT_SYSCALL(mimmutable);
54
55#if RELOC_TAG == DT_RELA
56typedef	Elf_RelA	RELOC_TYPE;
57#elif RELOC_TAG == DT_REL
58typedef	Elf_Rel		RELOC_TYPE;
59#else
60# error "unknown RELOC_TAG"
61#endif
62
63static void *relro_addr;
64static size_t relro_size;
65#define RCRT0_RELRO()							\
66	do {								\
67		if (relro_addr != NULL && relro_size != 0) {		\
68			mprotect(relro_addr, relro_size, PROT_READ);	\
69			mimmutable(relro_addr, relro_size);		\
70		}							\
71	} while (0)
72
73/*
74 * Local decls.
75 */
76void _dl_boot_bind(const long, long *, Elf_Dyn *);
77
78void
79_dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynp)
80{
81	AuxInfo		*auxstack;
82	long		*stack;
83	int		n, argc;
84	char		**argv, **envp;
85	long		loff;
86	RELOC_TYPE	*dt_reloc, *rend;	/* DT_RELA   or DT_REL */
87	Elf_Word	dt_relocsz;		/* DT_RELASZ or DT_RELSZ */
88	const Elf_Sym	*dt_symtab;
89	Elf_Phdr	*phdp;
90	Elf_Addr	i;
91
92	/*
93	 * Scan argument and environment vectors. Find dynamic
94	 * data vector put after them.
95	 */
96	stack = (long *)sp;
97	argc = *stack++;
98	argv = (char **)stack;
99	envp = &argv[argc + 1];
100	stack = (long *)envp;
101	while (*stack++ != 0L)
102		;
103
104	/*
105	 * Zero out dl_data.
106	 */
107	for (n = 0; n <= AUX_entry; n++)
108		dl_data[n] = 0;
109
110	/*
111	 * Dig out auxiliary data set up by exec call. Move all known
112	 * tags to an indexed local table for easy access.
113	 */
114	for (auxstack = (AuxInfo *)stack; auxstack->au_id != AUX_null;
115	    auxstack++) {
116		if (auxstack->au_id > AUX_entry)
117			continue;
118		dl_data[auxstack->au_id] = auxstack->au_v;
119	}
120	loff = dl_data[AUX_base];	/* XXX assumes ld.so is linked at 0x0 */
121
122	/*
123	 * Scan the DYNAMIC section for the items we need
124	 */
125	dt_reloc = NULL;
126	dt_relocsz = 0;
127	while (dynp->d_tag != DT_NULL) {
128		/* first the tags that are pointers to be relocated */
129		if (dynp->d_tag == DT_SYMTAB)
130			dt_symtab = (void *)(dynp->d_un.d_ptr + loff);
131		else if (dynp->d_tag == RELOC_TAG)	/* DT_{RELA,REL} */
132			dt_reloc = (void *)(dynp->d_un.d_ptr + loff);
133
134		/* Now for the tags that are just sizes or counts */
135		else if (dynp->d_tag == RELOC_TAG+1)	/* DT_{RELA,REL}SZ */
136			dt_relocsz = dynp->d_un.d_val;
137		dynp++;
138	}
139
140	rend = (RELOC_TYPE *)((char *)dt_reloc + dt_relocsz);
141	for (; dt_reloc < rend; dt_reloc++) {
142		Elf_Addr *ra;
143		const Elf_Sym *sp;
144
145		sp = dt_symtab + ELF_R_SYM(dt_reloc->r_info);
146		if (!ELF_R_SYM(dt_reloc->r_info) || sp->st_value != 0) {
147			ra = (Elf_Addr *)(dt_reloc->r_offset + loff);
148			RELOC_DYN(dt_reloc, sp, ra, loff);
149		}
150	}
151
152	/* do any RWX -> RX fixups for executable PLTs and apply GNU_RELRO */
153	phdp = (Elf_Phdr *)dl_data[AUX_phdr];
154	for (i = 0; i < dl_data[AUX_phnum]; i++, phdp++) {
155		switch (phdp->p_type) {
156#if defined(__alpha__) || defined(__powerpc__) || defined(__sparc64__)
157		case PT_LOAD:
158			if ((phdp->p_flags & (PF_X | PF_W)) != (PF_X | PF_W))
159				break;
160			mprotect((void *)(phdp->p_vaddr + loff), phdp->p_memsz,
161			    PROT_READ);
162			break;
163#endif
164		case PT_GNU_RELRO:
165			relro_addr = (void *)(phdp->p_vaddr + loff);
166			relro_size = phdp->p_memsz;
167			/*
168			 * GNU_RELRO (a) covers the GOT, and (b) comes after
169			 * all LOAD sections, so if we found it then we're done
170			 */
171			break;
172		}
173	}
174}
175