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move elf in dedicated file

This commit is contained in:
Mathieu Maret 2022-07-25 17:10:28 +02:00
parent db0d3dff14
commit 7891554d8b
3 changed files with 187 additions and 175 deletions
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182
core/elf.c Normal file
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@ -0,0 +1,182 @@
#include "elf.h"
#include "kernel.h"
#include "klibc.h"
#include "mem.h"
#include "paging.h"
/**
* Make sure the program is in a valid ELF format, map it into memory,
* and return the address of its entry point (ie _start function)
*
* @return 0 when the program is not a valid ELF
*/
uaddr_t loadElfProg(const char *prog)
{
int i;
/**
* Typedefs, constants and structure definitions as given by the ELF
* standard specifications.
*/
typedef unsigned long Elf32_Addr;
typedef unsigned long Elf32_Word;
typedef unsigned short Elf32_Half;
typedef unsigned long Elf32_Off;
// typedef signed long Elf32_Sword;
/* Elf identification */
#define EI_NIDENT 16
typedef struct {
unsigned char e_ident[EI_NIDENT];
Elf32_Half e_type;
Elf32_Half e_machine;
Elf32_Word e_version;
Elf32_Addr e_entry;
Elf32_Off e_phoff;
Elf32_Off e_shoff;
Elf32_Word e_flags;
Elf32_Half e_ehsize;
Elf32_Half e_phentsize;
Elf32_Half e_phnum;
Elf32_Half e_shentsize;
Elf32_Half e_shnum;
Elf32_Half e_shstrndx;
} __attribute__((packed)) Elf32_Ehdr_t;
/* e_ident value */
#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'
/* e_ident offsets */
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define EI_PAD 7
/* e_ident[EI_CLASS] */
#define ELFCLASSNONE 0
#define ELFCLASS32 1
#define ELFCLASS64 2
/* e_ident[EI_DATA] */
#define ELFDATANONE 0
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2
/* e_type */
#define ET_NONE 0 /* No file type */
#define ET_REL 1 /* Relocatable file */
#define ET_EXEC 2 /* Executable file */
#define ET_DYN 3 /* Shared object file */
#define ET_CORE 4 /* Core file */
#define ET_LOPROC 0xff00 /* Processor-specific */
#define ET_HIPROC 0xffff /* Processor-specific */
/* e_machine */
#define EM_NONE 0 /* No machine */
#define EM_M32 1 /* AT&T WE 32100 */
#define EM_SPARC 2 /* SPARC */
#define EM_386 3 /* Intel 80386 */
#define EM_68K 4 /* Motorola 68000 */
#define EM_88K 5 /* Motorola 88000 */
#define EM_860 7 /* Intel 80860 */
#define EM_MIPS 8 /* MIPS RS3000 */
/* e_version */
#define EV_NONE 0 /* invalid version */
#define EV_CURRENT 1 /* current version */
typedef struct {
Elf32_Word p_type;
Elf32_Off p_offset;
Elf32_Addr p_vaddr;
Elf32_Addr p_paddr;
Elf32_Word p_filesz;
Elf32_Word p_memsz;
Elf32_Word p_flags;
Elf32_Word p_align;
} __attribute__((packed)) Elf32_Phdr_t;
/* Reserved segment types p_type */
#define PT_NULL 0
#define PT_LOAD 1
#define PT_DYNAMIC 2
#define PT_INTERP 3
#define PT_NOTE 4
#define PT_SHLIB 5
#define PT_PHDR 6
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff
/* p_flags */
#define PF_X 1
#define PF_W 2
#define PF_R 4
Elf32_Ehdr_t *elf_hdr = (Elf32_Ehdr_t *)prog;
Elf32_Phdr_t *elf_phdrs;
/* Macro to check expected values for some fields in the ELF header */
#define ELF_CHECK(hdr, field, expected_value) \
({ \
if ((hdr)->field != (expected_value)) { \
printf("ELF prog : for %s, expected %x, got %x\n", #field, \
(unsigned)(expected_value), (unsigned)(hdr)->field); \
return 0; \
} \
})
ELF_CHECK(elf_hdr, e_ident[EI_MAG0], ELFMAG0);
ELF_CHECK(elf_hdr, e_ident[EI_MAG1], ELFMAG1);
ELF_CHECK(elf_hdr, e_ident[EI_MAG2], ELFMAG2);
ELF_CHECK(elf_hdr, e_ident[EI_MAG3], ELFMAG3);
ELF_CHECK(elf_hdr, e_ident[EI_CLASS], ELFCLASS32);
ELF_CHECK(elf_hdr, e_ident[EI_DATA], ELFDATA2LSB);
ELF_CHECK(elf_hdr, e_type, ET_EXEC);
ELF_CHECK(elf_hdr, e_version, EV_CURRENT);
/* Get the begining of the program header table */
elf_phdrs = (Elf32_Phdr_t *)(prog + elf_hdr->e_phoff);
/* Map the program segment in R/W mode. To make things clean, we
should iterate over the sections, not the program header */
for (i = 0; i < elf_hdr->e_phnum; i++) {
uaddr_t uaddr;
/* Ignore the empty program headers that are not marked "LOAD" */
if (elf_phdrs[i].p_type != PT_LOAD) {
continue;
}
if (elf_phdrs[i].p_vaddr < PAGING_BASE_USER_ADDRESS) {
printf("User program has an incorrect address 0x%x\n", elf_phdrs[i].p_vaddr);
return (uaddr_t)NULL;
}
/* Map pages of physical memory into user space */
for (uaddr = ALIGN_DOWN(elf_phdrs[i].p_vaddr, PAGE_SIZE);
uaddr < elf_phdrs[i].p_vaddr + elf_phdrs[i].p_memsz; uaddr += PAGE_SIZE) {
paddr_t ppage;
ppage = allocPhyPage(1);
assert(pageMap(uaddr, ppage,
PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
unrefPhyPage(ppage);
}
/* Copy segment into memory */
memcpy((void *)elf_phdrs[i].p_vaddr, (void *)(prog + elf_phdrs[i].p_offset),
elf_phdrs[i].p_filesz);
}
return elf_hdr->e_entry;
}

4
core/elf.h Normal file
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@ -0,0 +1,4 @@
#pragma once
#include "types.h"
uaddr_t loadElfProg(const char *prog);

176
core/main.c
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@ -1,6 +1,7 @@
#include "alloc.h"
#include "allocArea.h"
#include "ata.h"
#include "elf.h"
#include "exception.h"
#include "gdt.h"
#include "idt.h"
@ -39,181 +40,6 @@ void idleThread(void *arg)
}
}
/**
* Make sure the program is in a valid ELF format, map it into memory,
* and return the address of its entry point (ie _start function)
*
* @return 0 when the program is not a valid ELF
*/
static uaddr_t loadElfProg(const char *prog)
{
int i;
/**
* Typedefs, constants and structure definitions as given by the ELF
* standard specifications.
*/
typedef unsigned long Elf32_Addr;
typedef unsigned long Elf32_Word;
typedef unsigned short Elf32_Half;
typedef unsigned long Elf32_Off;
// typedef signed long Elf32_Sword;
/* Elf identification */
#define EI_NIDENT 16
typedef struct {
unsigned char e_ident[EI_NIDENT];
Elf32_Half e_type;
Elf32_Half e_machine;
Elf32_Word e_version;
Elf32_Addr e_entry;
Elf32_Off e_phoff;
Elf32_Off e_shoff;
Elf32_Word e_flags;
Elf32_Half e_ehsize;
Elf32_Half e_phentsize;
Elf32_Half e_phnum;
Elf32_Half e_shentsize;
Elf32_Half e_shnum;
Elf32_Half e_shstrndx;
} __attribute__((packed)) Elf32_Ehdr_t;
/* e_ident value */
#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'
/* e_ident offsets */
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define EI_PAD 7
/* e_ident[EI_CLASS] */
#define ELFCLASSNONE 0
#define ELFCLASS32 1
#define ELFCLASS64 2
/* e_ident[EI_DATA] */
#define ELFDATANONE 0
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2
/* e_type */
#define ET_NONE 0 /* No file type */
#define ET_REL 1 /* Relocatable file */
#define ET_EXEC 2 /* Executable file */
#define ET_DYN 3 /* Shared object file */
#define ET_CORE 4 /* Core file */
#define ET_LOPROC 0xff00 /* Processor-specific */
#define ET_HIPROC 0xffff /* Processor-specific */
/* e_machine */
#define EM_NONE 0 /* No machine */
#define EM_M32 1 /* AT&T WE 32100 */
#define EM_SPARC 2 /* SPARC */
#define EM_386 3 /* Intel 80386 */
#define EM_68K 4 /* Motorola 68000 */
#define EM_88K 5 /* Motorola 88000 */
#define EM_860 7 /* Intel 80860 */
#define EM_MIPS 8 /* MIPS RS3000 */
/* e_version */
#define EV_NONE 0 /* invalid version */
#define EV_CURRENT 1 /* current version */
typedef struct {
Elf32_Word p_type;
Elf32_Off p_offset;
Elf32_Addr p_vaddr;
Elf32_Addr p_paddr;
Elf32_Word p_filesz;
Elf32_Word p_memsz;
Elf32_Word p_flags;
Elf32_Word p_align;
} __attribute__((packed)) Elf32_Phdr_t;
/* Reserved segment types p_type */
#define PT_NULL 0
#define PT_LOAD 1
#define PT_DYNAMIC 2
#define PT_INTERP 3
#define PT_NOTE 4
#define PT_SHLIB 5
#define PT_PHDR 6
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff
/* p_flags */
#define PF_X 1
#define PF_W 2
#define PF_R 4
Elf32_Ehdr_t *elf_hdr = (Elf32_Ehdr_t *)prog;
Elf32_Phdr_t *elf_phdrs;
/* Macro to check expected values for some fields in the ELF header */
#define ELF_CHECK(hdr, field, expected_value) \
({ \
if ((hdr)->field != (expected_value)) { \
printf("ELF prog : for %s, expected %x, got %x\n", #field, \
(unsigned)(expected_value), (unsigned)(hdr)->field); \
return 0; \
} \
})
ELF_CHECK(elf_hdr, e_ident[EI_MAG0], ELFMAG0);
ELF_CHECK(elf_hdr, e_ident[EI_MAG1], ELFMAG1);
ELF_CHECK(elf_hdr, e_ident[EI_MAG2], ELFMAG2);
ELF_CHECK(elf_hdr, e_ident[EI_MAG3], ELFMAG3);
ELF_CHECK(elf_hdr, e_ident[EI_CLASS], ELFCLASS32);
ELF_CHECK(elf_hdr, e_ident[EI_DATA], ELFDATA2LSB);
ELF_CHECK(elf_hdr, e_type, ET_EXEC);
ELF_CHECK(elf_hdr, e_version, EV_CURRENT);
/* Get the begining of the program header table */
elf_phdrs = (Elf32_Phdr_t *)(prog + elf_hdr->e_phoff);
/* Map the program segment in R/W mode. To make things clean, we
should iterate over the sections, not the program header */
for (i = 0; i < elf_hdr->e_phnum; i++) {
uaddr_t uaddr;
/* Ignore the empty program headers that are not marked "LOAD" */
if (elf_phdrs[i].p_type != PT_LOAD) {
continue;
}
if (elf_phdrs[i].p_vaddr < PAGING_BASE_USER_ADDRESS) {
printf("User program has an incorrect address 0x%x\n", elf_phdrs[i].p_vaddr);
return (uaddr_t)NULL;
}
/* Map pages of physical memory into user space */
for (uaddr = ALIGN_DOWN(elf_phdrs[i].p_vaddr, PAGE_SIZE);
uaddr < elf_phdrs[i].p_vaddr + elf_phdrs[i].p_memsz; uaddr += PAGE_SIZE) {
paddr_t ppage;
ppage = allocPhyPage(1);
assert(pageMap(uaddr, ppage,
PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
unrefPhyPage(ppage);
}
/* Copy segment into memory */
memcpy((void *)elf_phdrs[i].p_vaddr, (void *)(prog + elf_phdrs[i].p_offset),
elf_phdrs[i].p_filesz);
}
return elf_hdr->e_entry;
}
#define FILE_HEADER_SIZE 16
#define FILE_MAX_SIZE 64