Mon 14 Oct 23:06:38 CEST 2024
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kernel/elf.c
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187
kernel/elf.c
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/*
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Copyright (C) 2015-2019 The University of Notre Dame
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This software is distributed under the GNU General Public License.
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See the file LICENSE for details.
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*/
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#include "elf.h"
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#include "fs.h"
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#include "string.h"
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#include "console.h"
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#include "process.h"
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#include "kernel/syscall.h"
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#include "memorylayout.h"
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struct elf_header {
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char ident[16];
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uint16_t type;
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uint16_t machine;
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uint32_t version;
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uint32_t entry;
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uint32_t program_offset;
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uint32_t section_offset;
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uint32_t flags;
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uint16_t header_size;
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uint16_t phentsize;
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uint16_t phnum;
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uint16_t shentsize;
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uint16_t shnum;
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uint16_t shstrndx;
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};
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#define ELF_HEADER_TYPE_NONE 0
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#define ELF_HEADER_TYPE_OBJECT 1
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#define ELF_HEADER_TYPE_EXECUTABLE 2
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#define ELF_HEADER_TYPE_DYNAMIC 3
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#define ELF_HEADER_TYPE_CORE 4
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#define ELF_HEADER_MACHINE_I386 3
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#define ELF_HEADER_MACHINE_ARM 40
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#define ELF_HEADER_MACHINE_X86_64 62
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#define ELF_HEADER_VERSION 1
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struct elf_program {
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uint32_t type;
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uint32_t offset;
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uint32_t vaddr;
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uint32_t paddr;
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uint32_t file_size;
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uint32_t memory_size;
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uint32_t flags;
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uint32_t align;
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};
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#define ELF_PROGRAM_TYPE_LOADABLE 1
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struct elf_section {
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uint32_t name;
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uint32_t type;
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uint32_t flags;
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uint32_t address;
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uint32_t offset;
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uint32_t size;
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uint32_t link;
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uint32_t info;
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uint32_t alignment;
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uint32_t entry_size;
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};
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#define ELF_SECTION_TYPE_NULL 0
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#define ELF_SECTION_TYPE_PROGRAM 1
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#define ELF_SECTION_TYPE_SYMBOL_TABLE 2
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#define ELF_SECTION_TYPE_STRING_TABLE 3
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#define ELF_SECTION_TYPE_RELA 4
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#define ELF_SECTION_TYPE_HASH 5
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#define ELF_SECTION_TYPE_DYNAMIC 6
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#define ELF_SECTION_TYPE_NOTE 7
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#define ELF_SECTION_TYPE_BSS 8
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#define ELF_SECTION_FLAGS_WRITE 1
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#define ELF_SECTION_FLAGS_MEMORY 2
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#define ELF_SECTION_FLAGS_EXEC 8
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#define ELF_SECTION_FLAGS_MERGE 16
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#define ELF_SECTION_FLAGS_STRINGS 32
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#define ELF_SECTION_FLAGS_INFO_LINK 64
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#define ELF_SECTION_FLAGS_LINK_ORDER 128
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#define ELF_SECTION_FLAGS_NONSTANDARD 256
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#define ELF_SECTION_FLAGS_GROUP 512
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#define ELF_SECTION_FLAGS_TLS 1024
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/* Ensure that the current process has address space up to this value. */
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static int elf_ensure_address_space( struct process *p, uint32_t addr )
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{
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/* Size of user data area, ignoring start addr */
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uint32_t limit = addr - PROCESS_ENTRY_POINT;
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/* Round up to next page size. */
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uint32_t overflow = limit % PAGE_SIZE;
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limit += (PAGE_SIZE-overflow);
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/* Extend virtual memory if needed. */
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if(limit > p->vm_data_size) {
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return process_data_size_set(p,limit);
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} else {
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return 0;
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}
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/* Return zero on success. */
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}
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int elf_load(struct process *p, struct fs_dirent *d, addr_t * entry)
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{
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struct elf_header header;
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struct elf_program program;
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struct elf_section section;
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int i;
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uint32_t actual;
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actual = fs_dirent_read(d, (char *) &header, sizeof(header), 0);
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if(actual != sizeof(header))
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goto noload;
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if(strncmp(header.ident, "\177ELF", 4) || header.machine != ELF_HEADER_MACHINE_I386 || header.version != ELF_HEADER_VERSION)
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goto noexec;
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actual = fs_dirent_read(d, (char *) &program, sizeof(program), header.program_offset);
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if(actual != sizeof(program))
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goto noload;
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// @blab+ fix first empty section with vaddr=0 (after newly needed objcopy removing unnessary symbols and sections)
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if (program.vaddr==0) program.vaddr=header.entry;
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//printf("elf: text %x bytes from offset %x at address %x length %x\n",program.file_size,program.offset,program.vaddr,program.memory_size);
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if(program.type != ELF_PROGRAM_TYPE_LOADABLE || program.vaddr < PROCESS_ENTRY_POINT || program.memory_size > 0x8000000 || program.memory_size != program.file_size)
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goto noexec;
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process_data_size_set(p, program.memory_size);
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actual = fs_dirent_read(d, (char *) program.vaddr, program.memory_size, program.offset);
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if(actual != program.memory_size)
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goto mustdie;
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for(i = 0; i < header.shnum; i++) {
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actual = fs_dirent_read(d, (char *) §ion, sizeof(section), header.section_offset + i * header.shentsize);
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if(actual != sizeof(section))
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goto mustdie;
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if(section.type == ELF_SECTION_TYPE_BSS) {
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/* For BSS, just clear that address space to zero. */
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actual = elf_ensure_address_space(p,section.address+section.size);
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if(actual!=0) goto nomem;
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memset((void *) section.address, section.size, 0);
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} else if(section.type == ELF_SECTION_TYPE_PROGRAM && section.address!=0) {
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/* For other loadable section types (usually data), load from file. */
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actual = elf_ensure_address_space(p,section.address+section.size);
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if(actual!=0) goto nomem;
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actual = fs_dirent_read(d,(char*)section.address,section.size,section.offset);
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if(actual != section.size) goto mustdie;
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} else {
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/* skip all other section types */
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}
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}
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*entry = header.entry;
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return 0;
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noload:
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printf("elf: failed to load correctly!\n");
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return KERROR_NOT_FOUND;
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noexec:
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printf("elf: not a valid i386 ELF executable [%c%c%c%c:%x(%x):%x(%x):%d(%d)]\n",
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header.ident[0],header.ident[1],header.ident[2],header.ident[3],
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program.type,ELF_PROGRAM_TYPE_LOADABLE,program.vaddr,PROCESS_ENTRY_POINT,program.memory_size,program.file_size); // @blab+
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return KERROR_NOT_EXECUTABLE;
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nomem:
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printf("elf: failed to allocate memory\n");
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return KERROR_OUT_OF_MEMORY;
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mustdie:
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printf("elf: did not load correctly\n");
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return KERROR_EXECUTION_FAILED;
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}
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