elf_trampoline.c revision 202908 
1/*-
2 * Copyright (c) 2005 Olivier Houchard.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include <sys/cdefs.h>
26__FBSDID("$FreeBSD: head/sys/mips/mips/elf_trampoline.c 202908 2010-01-24 02:59:22Z gonzo $");
27#include <machine/asm.h>
28#include <sys/param.h>
29
30#ifdef __mips_n64
31#include <sys/elf64.h>
32#else
33#include <sys/elf32.h>
34#endif
35#include <sys/inflate.h>
36#include <machine/elf.h>
37#include <machine/cpufunc.h>
38#include <machine/stdarg.h>
39
40/*
41 * Since we are compiled outside of the normal kernel build process, we
42 * need to include opt_global.h manually.
43 */
44#include "opt_global.h"
45#include "opt_kernname.h"
46
47extern char kernel_start[];
48extern char kernel_end[];
49
50static __inline void *
51memcpy(void *dst, const void *src, size_t len)
52{
53	const char *s = src;
54    	char *d = dst;
55
56	while (len) {
57		if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
58		    !((vm_offset_t)s & 3)) {
59			*(uint32_t *)d = *(uint32_t *)s;
60			s += 4;
61			d += 4;
62			len -= 4;
63		} else {
64			*d++ = *s++;
65			len--;
66		}
67	}
68	return (dst);
69}
70
71static __inline void
72bzero(void *addr, size_t count)
73{
74	char *tmp = (char *)addr;
75
76	while (count > 0) {
77		if (count >= 4 && !((vm_offset_t)tmp & 3)) {
78			*(uint32_t *)tmp = 0;
79			tmp += 4;
80			count -= 4;
81		} else {
82			*tmp = 0;
83			tmp++;
84			count--;
85		}
86	}
87}
88
89/*
90 * Relocate PT_LOAD segements of kernel ELF image to their respective
91 * virtual addresses and return entry point
92 */
93void *
94load_kernel(void * kstart)
95{
96#ifdef __mips_n64
97	Elf64_Ehdr *eh;
98	Elf64_Phdr phdr[64] /* XXX */;
99	Elf64_Phdr shdr[64] /* XXX */;
100#else
101	Elf32_Ehdr *eh;
102	Elf32_Phdr phdr[64] /* XXX */;
103	Elf32_Shdr shdr[64] /* XXX */;
104#endif
105	int i, j;
106	void *entry_point;
107	vm_offset_t lastaddr = 0;
108	int symtabindex = -1;
109	int symstrindex = -1;
110
111#ifdef __mips_n64
112	eh = (Elf64_Ehdr *)kstart;
113#else
114	eh = (Elf32_Ehdr *)kstart;
115#endif
116	entry_point = (void*)eh->e_entry;
117	memcpy(phdr, (void *)(kstart + eh->e_phoff ),
118	    eh->e_phnum * sizeof(phdr[0]));
119
120	memcpy(shdr, (void *)(kstart + eh->e_shoff),
121	    sizeof(*shdr) * eh->e_shnum);
122
123	if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
124		for (i = 0; i < eh->e_shnum; i++) {
125			if (shdr[i].sh_type == SHT_SYMTAB) {
126				/*
127				 * XXX: check if .symtab is in PT_LOAD?
128				 */
129				if (shdr[i].sh_offset != 0 &&
130				    shdr[i].sh_size != 0) {
131					symtabindex = i;
132					symstrindex = shdr[i].sh_link;
133				}
134			}
135		}
136	}
137
138	/*
139	 * Copy loadable segments
140	 */
141	for (i = 0; i < eh->e_phnum; i++) {
142		volatile char c;
143
144		if (phdr[i].p_type != PT_LOAD)
145			continue;
146
147		memcpy((void *)(phdr[i].p_vaddr),
148		    (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
149
150		/* Clean space from oversized segments, eg: bss. */
151		if (phdr[i].p_filesz < phdr[i].p_memsz)
152			bzero((void *)(phdr[i].p_vaddr + phdr[i].p_filesz),
153			    phdr[i].p_memsz - phdr[i].p_filesz);
154
155		if (lastaddr < phdr[i].p_vaddr + phdr[i].p_memsz)
156			lastaddr = phdr[i].p_vaddr + phdr[i].p_memsz;
157	}
158
159	/* Now grab the symbol tables. */
160	if (symtabindex >= 0 && symstrindex >= 0) {
161		*(Elf_Size *)lastaddr = SYMTAB_MAGIC;
162		lastaddr += sizeof(Elf_Size);
163		*(Elf_Size *)lastaddr = shdr[symtabindex].sh_size +
164		    shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
165		lastaddr += sizeof(Elf_Size);
166		/* .symtab size */
167		*(Elf_Size *)lastaddr = shdr[symtabindex].sh_size;
168		lastaddr += sizeof(shdr[symtabindex].sh_size);
169		/* .symtab data */
170		memcpy((void*)lastaddr,
171		    shdr[symtabindex].sh_offset + kstart,
172		    shdr[symtabindex].sh_size);
173		lastaddr += shdr[symtabindex].sh_size;
174
175		/* .strtab size */
176		*(Elf_Size *)lastaddr = shdr[symstrindex].sh_size;
177		lastaddr += sizeof(shdr[symstrindex].sh_size);
178
179		/* .strtab data */
180		memcpy((void*)lastaddr,
181		    shdr[symstrindex].sh_offset + kstart,
182		    shdr[symstrindex].sh_size);
183	} else
184		/* Do not take any chances */
185		*(Elf_Size *)lastaddr = 0;
186
187	return entry_point;
188}
189
190void
191_startC(register_t a0, register_t a1, register_t a2, register_t a3)
192{
193	unsigned int * code;
194	int i;
195	void (*entry_point)(register_t, register_t, register_t, register_t);
196
197	/*
198	 * Relocate segment to the predefined memory location
199	 * Most likely it will be KSEG0/KSEG1 address
200	 */
201	entry_point = load_kernel(kernel_start);
202
203	/* Pass saved registers to original _start */
204	entry_point(a0, a1, a2, a3);
205}
206