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ELFLoader: Read the ELF file header by header using the VFS

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Instead of just allocating one big redundant blob of memory and reading into it, then having to free it...
This commit is contained in:
apio 2022-10-12 18:23:52 +02:00
parent 7a2e313a20
commit 261fc73146
2 changed files with 30 additions and 37 deletions
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3
kernel/include/sys/elf/ELFLoader.h
View File

@ -1,10 +1,11 @@
#pragma once
#include "fs/VFS.h"
#include "sys/elf/Image.h"
#include <stdint.h>
namespace ELFLoader
{
ELFImage* load_elf_from_address(uintptr_t addr);
ELFImage* load_elf_from_vfs(VFS::Node* node);
ELFImage* load_elf_from_filesystem(const char* filename);
void release_elf_image(ELFImage* image);
}

64
kernel/src/sys/elf/ELFLoader.cpp
View File

@ -36,80 +36,72 @@ ELFImage* ELFLoader::load_elf_from_filesystem(const char* filename)
return 0;
}
void* file = kmalloc(node->length);
if (VFS::read(node, 0, node->length, (char*)file) < 0)
{
kwarnln("Failed to read ELF image from file");
kfree(file);
return 0;
}
ELFImage* result =
load_elf_from_address((uintptr_t)file); // FIXME: Read headers and sections as we go along the file, to avoid
// loading the entire file at once into memory.
kfree(file);
ELFImage* result = load_elf_from_vfs(node);
return result;
}
ELFImage* ELFLoader::load_elf_from_address(uintptr_t addr)
ELFImage* ELFLoader::load_elf_from_vfs(VFS::Node* node)
{
Elf64_Ehdr* elf_ehdr = (Elf64_Ehdr*)addr;
if (strncmp((const char*)elf_ehdr->e_ident, ELFMAG, SELFMAG) != 0)
Elf64_Ehdr elf_ehdr;
if (VFS::read(node, 0, sizeof(elf_ehdr), (char*)&elf_ehdr) < 0)
{
kwarnln("Unable to read ELF header");
return 0;
}
if (strncmp((const char*)elf_ehdr.e_ident, ELFMAG, SELFMAG) != 0)
{
kwarnln("ELF file has invalid magic, skipping");
return 0;
}
if (elf_ehdr->e_ident[EI_CLASS] != ELFCLASS64)
if (elf_ehdr.e_ident[EI_CLASS] != ELFCLASS64)
{
kwarnln("ELF file is not ELF64, skipping");
return 0;
}
if (elf_ehdr->e_ident[EI_DATA] != ELFDATA2LSB)
if (elf_ehdr.e_ident[EI_DATA] != ELFDATA2LSB)
{
kwarnln("ELF file is not little-endian, skipping");
return 0;
}
if (elf_ehdr->e_type != ET_EXEC)
if (elf_ehdr.e_type != ET_EXEC)
{
kwarnln("not supported: ELF file is not an executable");
return 0;
}
if (elf_ehdr->e_machine != EM_MACH)
if (elf_ehdr.e_machine != EM_MACH)
{
kwarnln("Unsupported target machine");
return 0;
}
if (elf_ehdr->e_phnum == 0)
if (elf_ehdr.e_phnum == 0)
{
kwarnln("ELF file has no PHDRS");
return 0;
}
ELFImage* image = (ELFImage*)kmalloc(sizeof(ELFImage) - sizeof(ELFSection));
memset(image, 0, sizeof(ELFImage) - sizeof(ELFSection));
image->entry = elf_ehdr->e_entry;
image->entry = elf_ehdr.e_entry;
int i;
Elf64_Phdr* phdr;
for (phdr = (Elf64_Phdr*)((uint64_t)addr + elf_ehdr->e_phoff), i = 0; i < elf_ehdr->e_phnum;
i++, phdr = (Elf64_Phdr*)((uint8_t*)phdr + elf_ehdr->e_phentsize))
Elf64_Phdr phdr;
for (VFS::read(node, elf_ehdr.e_phoff, sizeof(Elf64_Phdr), (char*)&phdr), i = 0; i < elf_ehdr.e_phnum;
i++, VFS::read(node, elf_ehdr.e_phoff + (i * elf_ehdr.e_phentsize), sizeof(Elf64_Phdr), (char*)&phdr))
{
if (phdr->p_type == PT_LOAD)
if (phdr.p_type == PT_LOAD)
{
kdbgln("Loading loadable segment at address %lx, file size %ld, mem size %ld, permissions %s",
phdr->p_vaddr, phdr->p_filesz, phdr->p_memsz, format_permissions(phdr->p_flags));
if (!phdr->p_vaddr)
kdbgln("Loading loadable segment at address %lx, file size %ld, mem size %ld, permissions %s", phdr.p_vaddr,
phdr.p_filesz, phdr.p_memsz, format_permissions(phdr.p_flags));
if (!phdr.p_vaddr)
{
kerrorln("Address is NULL, this is invalid :(");
return 0;
}
uint64_t pages = Utilities::get_blocks_from_size(PAGE_SIZE, (phdr->p_vaddr % PAGE_SIZE) + phdr->p_memsz);
uint64_t pages = Utilities::get_blocks_from_size(PAGE_SIZE, (phdr.p_vaddr % PAGE_SIZE) + phdr.p_memsz);
void* buffer = (void*)((uint64_t)MemoryManager::get_pages_at(
Utilities::round_down_to_nearest_page(phdr->p_vaddr), pages,
phdr->p_flags & 2 ? MAP_READ_WRITE | MAP_USER : MAP_USER) +
(phdr->p_vaddr % PAGE_SIZE));
memcpy(buffer, (void*)(addr + phdr->p_offset), phdr->p_filesz);
memset((void*)((uint64_t)buffer + phdr->p_filesz), 0, phdr->p_memsz - phdr->p_filesz);
Utilities::round_down_to_nearest_page(phdr.p_vaddr), pages,
phdr.p_flags & 2 ? MAP_READ_WRITE | MAP_USER : MAP_USER) +
(phdr.p_vaddr % PAGE_SIZE));
VFS::read(node, phdr.p_offset, phdr.p_filesz, (char*)buffer);
memset((void*)((uint64_t)buffer + phdr.p_filesz), 0, phdr.p_memsz - phdr.p_filesz);
image = (ELFImage*)krealloc(image, (sizeof(ELFImage) - sizeof(ELFSection)) +
(image->section_count + 1) * sizeof(ELFSection));
ELFSection& section = image->sections[image->section_count];