158 lines
4.9 KiB
C
158 lines
4.9 KiB
C
#include "elf.h"
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#include "kernel.h"
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#include "klibc.h"
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#include "mem.h"
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#include "paging.h"
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#include "thread.h"
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#include "types.h"
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#include "zero.h"
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/**
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* Make sure the program is in a valid ELF format, map it into memory,
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* and return the address of its entry point (ie _start function)
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*
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* @return 0 when the program is not a valid ELF
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*/
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uaddr_t loadElfProg(const char *prog, struct process *proc)
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{
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int i;
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uaddr_t lastUserAddr = 0;
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struct uAddrSpace *as = processGetAddrSpace(proc);
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/* e_ident value */
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#define ELFMAG0 0x7f
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#define ELFMAG1 'E'
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#define ELFMAG2 'L'
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#define ELFMAG3 'F'
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/* e_ident offsets */
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#define EI_MAG0 0
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#define EI_MAG1 1
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#define EI_MAG2 2
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#define EI_MAG3 3
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#define EI_CLASS 4
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#define EI_DATA 5
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#define EI_VERSION 6
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#define EI_PAD 7
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/* e_ident[EI_CLASS] */
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#define ELFCLASSNONE 0
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#define ELFCLASS32 1
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#define ELFCLASS64 2
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/* e_ident[EI_DATA] */
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#define ELFDATANONE 0
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#define ELFDATA2LSB 1
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#define ELFDATA2MSB 2
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/* e_type */
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#define ET_NONE 0 /* No file type */
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#define ET_REL 1 /* Relocatable file */
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#define ET_EXEC 2 /* Executable file */
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#define ET_DYN 3 /* Shared object file */
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#define ET_CORE 4 /* Core file */
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#define ET_LOPROC 0xff00 /* Processor-specific */
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#define ET_HIPROC 0xffff /* Processor-specific */
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/* e_machine */
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#define EM_NONE 0 /* No machine */
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#define EM_M32 1 /* AT&T WE 32100 */
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#define EM_SPARC 2 /* SPARC */
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#define EM_386 3 /* Intel 80386 */
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#define EM_68K 4 /* Motorola 68000 */
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#define EM_88K 5 /* Motorola 88000 */
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#define EM_860 7 /* Intel 80860 */
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#define EM_MIPS 8 /* MIPS RS3000 */
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/* e_version */
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#define EV_NONE 0 /* invalid version */
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#define EV_CURRENT 1 /* current version */
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/* Reserved segment types p_type */
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#define PT_NULL 0
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#define PT_LOAD 1
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#define PT_DYNAMIC 2
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#define PT_INTERP 3
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#define PT_NOTE 4
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#define PT_SHLIB 5
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#define PT_PHDR 6
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#define PT_LOPROC 0x70000000
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#define PT_HIPROC 0x7fffffff
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/* p_flags */
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#define PF_X 1
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#define PF_W 2
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#define PF_R 4
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Elf32_Ehdr_t *elf_hdr = (Elf32_Ehdr_t *)prog;
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Elf32_Phdr_t *elf_phdrs;
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/* Macro to check expected values for some fields in the ELF header */
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#define ELF_CHECK(hdr, field, expected_value) \
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({ \
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if ((hdr)->field != (expected_value)) { \
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printf("ELF prog : for %s, expected %x, got %x\n", #field, \
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(unsigned)(expected_value), (unsigned)(hdr)->field); \
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return 0; \
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} \
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})
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ELF_CHECK(elf_hdr, e_ident[EI_MAG0], ELFMAG0);
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ELF_CHECK(elf_hdr, e_ident[EI_MAG1], ELFMAG1);
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ELF_CHECK(elf_hdr, e_ident[EI_MAG2], ELFMAG2);
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ELF_CHECK(elf_hdr, e_ident[EI_MAG3], ELFMAG3);
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ELF_CHECK(elf_hdr, e_ident[EI_CLASS], ELFCLASS32);
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ELF_CHECK(elf_hdr, e_ident[EI_DATA], ELFDATA2LSB);
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ELF_CHECK(elf_hdr, e_type, ET_EXEC);
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ELF_CHECK(elf_hdr, e_version, EV_CURRENT);
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/* Get the begining of the program header table */
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elf_phdrs = (Elf32_Phdr_t *)(prog + elf_hdr->e_phoff);
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/* Map the program segment in R/W mode. To make things clean, we
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should iterate over the sections, not the program header */
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for (i = 0; i < elf_hdr->e_phnum; i++) {
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uaddr_t uaddr;
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/* Ignore the empty program headers that are not marked "LOAD" */
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if (elf_phdrs[i].p_type != PT_LOAD) {
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continue;
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}
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if (elf_phdrs[i].p_vaddr < PAGING_BASE_USER_ADDRESS) {
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printf("User program has an incorrect address 0x%p\n", (void *)elf_phdrs[i].p_vaddr);
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return (uaddr_t)NULL;
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}
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/* Map pages of physical memory into user space */
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for (uaddr = ALIGN_DOWN(elf_phdrs[i].p_vaddr, PAGE_SIZE);
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uaddr < elf_phdrs[i].p_vaddr + elf_phdrs[i].p_memsz; uaddr += PAGE_SIZE) {
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paddr_t ppage;
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ppage = allocPhyPage(1);
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assert(pageMap(uaddr, ppage,
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PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
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unrefPhyPage(ppage);
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}
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/* Copy segment into memory */
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memcpy((void *)elf_phdrs[i].p_vaddr, (void *)(prog + elf_phdrs[i].p_offset),
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elf_phdrs[i].p_filesz);
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if (lastUserAddr < uaddr) {
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lastUserAddr = uaddr;
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}
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// Hack: Even if already allocated mark the adresse space as managed by a ressource
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// So this address space is not used by another ressource.
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uaddr = elf_phdrs[i].p_vaddr;
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assert(zeroMmap(as, &uaddr, elf_phdrs[i].p_memsz, PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ, 0) == 0);
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}
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processInitHeap(proc, lastUserAddr);
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return elf_hdr->e_entry;
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}
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