[292] | 1 | /** |
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| 2 | * \file : boot_loader_entry.c |
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| 3 | * \date : August 2012 |
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| 4 | * \author : Cesar Fuguet |
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| 5 | * |
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| 6 | * This file defines an elf file loader which reads an executable elf file |
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| 7 | * starting at a sector passed as argument of a disk and copy the different |
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| 8 | * ELF program segments in the appropriate memory address using as information |
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| 9 | * the virtual address read from the elf file. |
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| 10 | */ |
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| 11 | |
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| 12 | #include <boot_ioc.h> |
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| 13 | #include <elf-types.h> |
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| 14 | #include <boot_tty.h> |
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| 15 | #include <boot_memcpy.h> |
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| 16 | #include <defs.h> |
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| 17 | |
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| 18 | void * boot_elf_loader(unsigned int lba) |
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| 19 | { |
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| 20 | /** |
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| 21 | * Temporary variables used by the boot loader |
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| 22 | */ |
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| 23 | unsigned char boot_elf_loader_buffer[512]; |
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| 24 | Elf32_Ehdr elf_header; |
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| 25 | Elf32_Phdr elf_pht[PHDR_ARRAY_SIZE]; |
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| 26 | |
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| 27 | unsigned char * buffer_ptr; |
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| 28 | Elf32_Ehdr * elf_header_ptr; |
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| 29 | Elf32_Phdr * elf_pht_ptr; |
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| 30 | |
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| 31 | unsigned int nb_available; |
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| 32 | unsigned int nb_rest; |
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| 33 | unsigned int nb_read; |
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| 34 | unsigned int nb_block; |
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| 35 | unsigned int offset; |
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| 36 | unsigned int pseg; |
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| 37 | unsigned int i; |
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| 38 | unsigned int segment_req; |
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| 39 | |
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| 40 | /* |
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| 41 | * Loader state machine definition |
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| 42 | */ |
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| 43 | enum |
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| 44 | { |
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| 45 | ELF_HEADER_STATE, |
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| 46 | ELF_PROGRAM_HEADER_STATE, |
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| 47 | ELF_OFFSET_STATE, |
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| 48 | ELF_SEGMENT_STATE, |
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| 49 | ELF_END_STATE |
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| 50 | } init_state; |
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| 51 | |
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| 52 | boot_puts("Starting boot_elf_loader function...\n\r"); |
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| 53 | |
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| 54 | nb_block = lba; |
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| 55 | |
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| 56 | pseg = 0; |
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| 57 | nb_available = 0; |
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| 58 | nb_rest = sizeof(Elf32_Ehdr); |
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| 59 | offset = 0; |
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| 60 | |
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| 61 | elf_header_ptr = (Elf32_Ehdr *) &elf_header; |
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| 62 | elf_pht_ptr = (Elf32_Phdr *) &elf_pht[0]; |
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| 63 | |
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| 64 | init_state = ELF_HEADER_STATE; |
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| 65 | |
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| 66 | while(init_state != ELF_END_STATE) |
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| 67 | { |
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| 68 | if (nb_available == 0) |
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| 69 | { |
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| 70 | buffer_ptr = &boot_elf_loader_buffer[0]; |
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| 71 | |
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| 72 | if ( boot_ioc_read(nb_block , buffer_ptr, 1) ) |
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| 73 | { |
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| 74 | boot_puts ( |
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| 75 | "ERROR: " |
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| 76 | "IOC_FAILED" |
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| 77 | "\n" |
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| 78 | ); |
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| 79 | |
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| 80 | boot_exit(); |
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| 81 | } |
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| 82 | |
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| 83 | nb_block += 1; |
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| 84 | nb_available = 512; |
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| 85 | } |
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| 86 | |
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| 87 | nb_read = (nb_rest <= nb_available) ? nb_rest : nb_available; |
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| 88 | offset += nb_read; |
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| 89 | |
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| 90 | switch(init_state) |
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| 91 | { |
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| 92 | /** |
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| 93 | * Reading ELF executable header |
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| 94 | */ |
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| 95 | case ELF_HEADER_STATE: |
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| 96 | boot_memcpy(elf_header_ptr, buffer_ptr, nb_read); |
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| 97 | |
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| 98 | nb_rest -= nb_read; |
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| 99 | |
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| 100 | if(nb_rest == 0) |
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| 101 | { |
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| 102 | nb_rest = elf_header_ptr->e_phnum * elf_header_ptr->e_phentsize; |
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| 103 | |
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| 104 | /* Verification of ELF Magic Number */ |
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| 105 | if ( |
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| 106 | (elf_header_ptr->e_ident[EI_MAG0] != ELFMAG0) || |
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| 107 | (elf_header_ptr->e_ident[EI_MAG1] != ELFMAG1) || |
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| 108 | (elf_header_ptr->e_ident[EI_MAG2] != ELFMAG2) || |
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| 109 | (elf_header_ptr->e_ident[EI_MAG3] != ELFMAG3) ) |
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| 110 | { |
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| 111 | boot_puts( |
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| 112 | "ERROR: " |
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| 113 | "Input file does not use ELF format" |
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| 114 | "\n" |
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| 115 | ); |
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| 116 | |
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| 117 | boot_exit(); |
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| 118 | } |
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| 119 | |
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| 120 | /* |
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| 121 | * Verification of Program Headers table size. It must be |
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| 122 | * smaller than the work size allocated for the |
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| 123 | * elf_pht[PHDR_ARRAY_SIZE] array |
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| 124 | **/ |
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| 125 | if (elf_header_ptr->e_phnum > PHDR_ARRAY_SIZE) |
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| 126 | { |
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| 127 | boot_puts( |
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| 128 | "ERROR: " |
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| 129 | "ELF PHDR table size is bigger than " |
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| 130 | "the allocated work space" |
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| 131 | "\n" |
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| 132 | ); |
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| 133 | |
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| 134 | boot_exit(); |
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| 135 | } |
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| 136 | |
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| 137 | init_state = ELF_PROGRAM_HEADER_STATE; |
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| 138 | } |
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| 139 | |
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| 140 | break; |
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| 141 | |
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| 142 | /** |
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| 143 | * Reading ELF program headers |
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| 144 | */ |
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| 145 | case ELF_PROGRAM_HEADER_STATE: |
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| 146 | boot_memcpy(elf_pht_ptr, buffer_ptr, nb_read); |
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| 147 | |
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| 148 | elf_pht_ptr = (Elf32_Phdr *)((unsigned char *) elf_pht_ptr + nb_read); |
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| 149 | nb_rest -= nb_read; |
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| 150 | |
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| 151 | if(nb_rest == 0) |
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| 152 | { |
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| 153 | elf_pht_ptr = (Elf32_Phdr *) &elf_pht[0]; |
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| 154 | |
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| 155 | /* |
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| 156 | * Search the first not NULL segment in the ELF file |
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| 157 | */ |
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| 158 | for (pseg = 0; pseg < elf_header_ptr->e_phnum; pseg++) |
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| 159 | { |
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| 160 | if(elf_pht_ptr[pseg].p_type == PT_LOAD) |
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| 161 | { |
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| 162 | nb_rest = elf_pht_ptr[pseg].p_offset - offset; |
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| 163 | break; |
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| 164 | } |
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| 165 | } |
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| 166 | |
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| 167 | init_state = ELF_OFFSET_STATE; |
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| 168 | } |
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| 169 | |
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| 170 | break; |
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| 171 | |
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| 172 | /** |
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| 173 | * Go to the offset of the first not null program segment in the ELF file |
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| 174 | */ |
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| 175 | case ELF_OFFSET_STATE: |
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| 176 | nb_rest -= nb_read; |
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| 177 | |
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| 178 | if (nb_rest == 0) |
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| 179 | { |
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| 180 | nb_rest = elf_pht_ptr[pseg].p_filesz; |
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| 181 | init_state = ELF_SEGMENT_STATE; |
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| 182 | } |
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| 183 | |
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| 184 | break; |
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| 185 | |
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| 186 | /** |
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| 187 | * Reading ELF segments |
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| 188 | */ |
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| 189 | case ELF_SEGMENT_STATE: |
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| 190 | /** |
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| 191 | * Copying ELF segment data in memory segments using the virtual |
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| 192 | * address got from the ELF file |
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| 193 | */ |
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| 194 | segment_req = ((elf_pht_ptr[pseg].p_vaddr & 0xBFC00000) != 0xBFC00000); |
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| 195 | |
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| 196 | if ( segment_req ) |
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| 197 | { |
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| 198 | boot_memcpy((unsigned char *) elf_pht_ptr[pseg].p_vaddr + |
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| 199 | (elf_pht_ptr[pseg].p_filesz - nb_rest), |
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| 200 | buffer_ptr, |
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| 201 | nb_read); |
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| 202 | } |
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| 203 | |
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| 204 | nb_rest -= nb_read; |
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| 205 | |
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| 206 | if ( nb_rest == 0 ) |
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| 207 | { |
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| 208 | if ( segment_req ) |
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| 209 | { |
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| 210 | boot_puts("Copied segment at address "); |
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| 211 | boot_putx(elf_pht_ptr[pseg].p_vaddr); |
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| 212 | boot_puts("\n"); |
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| 213 | |
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| 214 | /* |
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| 215 | * Fill remaining bytes with zeros (filesz < memsz) |
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| 216 | */ |
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| 217 | for ( i = 0 ; |
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| 218 | i < (elf_pht_ptr[pseg].p_memsz - elf_pht_ptr[pseg].p_filesz) ; |
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| 219 | i-- ) |
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| 220 | { |
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| 221 | *(unsigned char *) |
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| 222 | (elf_pht_ptr[pseg].p_vaddr + elf_pht_ptr[pseg].p_filesz + i) = 0; |
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| 223 | } |
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| 224 | } |
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| 225 | |
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| 226 | /* |
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| 227 | * Search the first not NULL segment in the ELF file |
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| 228 | */ |
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| 229 | for ( pseg = pseg + 1; pseg < elf_header_ptr->e_phnum; pseg++) { |
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| 230 | if(elf_pht_ptr[pseg].p_type == PT_LOAD) |
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| 231 | { |
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| 232 | nb_rest = elf_pht_ptr[pseg].p_offset - offset; |
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| 233 | break; |
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| 234 | } |
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| 235 | } |
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| 236 | |
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| 237 | /* |
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| 238 | * Program loading finished |
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| 239 | */ |
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| 240 | if(pseg == elf_header_ptr->e_phnum) |
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| 241 | { |
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| 242 | init_state = ELF_END_STATE; |
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| 243 | break; |
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| 244 | } |
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| 245 | |
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| 246 | init_state = ELF_OFFSET_STATE; |
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| 247 | } |
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| 248 | break; |
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| 249 | |
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| 250 | default: |
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| 251 | break; |
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| 252 | } |
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| 253 | |
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| 254 | buffer_ptr += nb_read; |
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| 255 | nb_available -= nb_read; |
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| 256 | } |
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| 257 | |
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| 258 | boot_puts ( |
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| 259 | "Finishing boot_elf_loader function.\n" |
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| 260 | "Entry point address: " |
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| 261 | ); |
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| 262 | boot_putx(elf_header_ptr->e_entry); |
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| 263 | boot_puts("\n"); |
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| 264 | |
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| 265 | return ((void *) elf_header_ptr->e_entry); |
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| 266 | } |
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