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Prekernel: Make sure we're not overwriting the ELF header

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This copies the ELF header because we might end up overwriting when
loading the ELF sections.
This commit is contained in:
Gunnar Beutner 2021-07-19 22:34:16 +02:00 • committed by Gunnar Beutner
parent 06468d9794
commit 69fd68b1c8
1 changed files with 11 additions and 7 deletions
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18
Kernel/Prekernel/init.cpp
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@ -68,11 +68,15 @@ extern "C" [[noreturn]] void init()
multiboot_module_entry_t* kernel_module = (multiboot_module_entry_t*)(FlatPtr)multiboot_info_ptr->mods_addr; multiboot_module_entry_t* kernel_module = (multiboot_module_entry_t*)(FlatPtr)multiboot_info_ptr->mods_addr;
u8* kernel_image = (u8*)(FlatPtr)kernel_module->start; u8* kernel_image = (u8*)(FlatPtr)kernel_module->start;
ElfW(Ehdr)* kernel_elf_header = (ElfW(Ehdr)*)kernel_image; // copy the ELF header and program headers because we might end up overwriting them
ElfW(Phdr)* kernel_program_headers = (ElfW(Phdr*))((char*)kernel_elf_header + kernel_elf_header->e_phoff); ElfW(Ehdr) kernel_elf_header = *(ElfW(Ehdr)*)kernel_image;
ElfW(Phdr) kernel_program_headers[16];
if (kernel_elf_header.e_phnum > array_size(kernel_program_headers))
halt();
__builtin_memcpy(kernel_program_headers, kernel_image + kernel_elf_header.e_phoff, sizeof(ElfW(Phdr)) * kernel_elf_header.e_phnum);
FlatPtr kernel_load_base = kernel_program_headers[0].p_vaddr; FlatPtr kernel_load_base = kernel_program_headers[0].p_vaddr;
FlatPtr kernel_load_end = kernel_program_headers[kernel_elf_header->e_phnum - 1].p_vaddr + kernel_program_headers[kernel_elf_header->e_phnum - 1].p_memsz; FlatPtr kernel_load_end = kernel_program_headers[kernel_elf_header.e_phnum - 1].p_vaddr + kernel_program_headers[kernel_elf_header.e_phnum - 1].p_memsz;
// align to 1GB // align to 1GB
kernel_load_base &= ~(FlatPtr)0x3fffffff; kernel_load_base &= ~(FlatPtr)0x3fffffff;
@ -99,7 +103,7 @@ extern "C" [[noreturn]] void init()
for (size_t i = 0; i < (FlatPtr)end_of_prekernel_image / PAGE_SIZE; i++) for (size_t i = 0; i < (FlatPtr)end_of_prekernel_image / PAGE_SIZE; i++)
boot_pd_kernel_pts[i] = i * PAGE_SIZE | 0x3; boot_pd_kernel_pts[i] = i * PAGE_SIZE | 0x3;
for (size_t i = 0; i < kernel_elf_header->e_phnum; i++) { for (size_t i = 0; i < kernel_elf_header.e_phnum; i++) {
auto& kernel_program_header = kernel_program_headers[i]; auto& kernel_program_header = kernel_program_headers[i];
if (kernel_program_header.p_type != PT_LOAD) if (kernel_program_header.p_type != PT_LOAD)
continue; continue;
@ -113,14 +117,14 @@ extern "C" [[noreturn]] void init()
reload_cr3(); reload_cr3();
for (ssize_t i = kernel_elf_header->e_phnum - 1; i >= 0; i--) { for (ssize_t i = kernel_elf_header.e_phnum - 1; i >= 0; i--) {
auto& kernel_program_header = kernel_program_headers[i]; auto& kernel_program_header = kernel_program_headers[i];
if (kernel_program_header.p_type != PT_LOAD) if (kernel_program_header.p_type != PT_LOAD)
continue; continue;
__builtin_memmove((u8*)kernel_program_header.p_vaddr, kernel_image + kernel_program_header.p_offset, kernel_program_header.p_filesz); __builtin_memmove((u8*)kernel_program_header.p_vaddr, kernel_image + kernel_program_header.p_offset, kernel_program_header.p_filesz);
} }
for (ssize_t i = kernel_elf_header->e_phnum - 1; i >= 0; i--) { for (ssize_t i = kernel_elf_header.e_phnum - 1; i >= 0; i--) {
auto& kernel_program_header = kernel_program_headers[i]; auto& kernel_program_header = kernel_program_headers[i];
if (kernel_program_header.p_type != PT_LOAD) if (kernel_program_header.p_type != PT_LOAD)
continue; continue;
@ -166,7 +170,7 @@ extern "C" [[noreturn]] void init()
for (FlatPtr vaddr = (FlatPtr)end_of_prekernel_image; vaddr < MAX_KERNEL_SIZE; vaddr += PAGE_SIZE) for (FlatPtr vaddr = (FlatPtr)end_of_prekernel_image; vaddr < MAX_KERNEL_SIZE; vaddr += PAGE_SIZE)
boot_pd0_pts[vaddr >> 12 & 0x1ff] = 0; boot_pd0_pts[vaddr >> 12 & 0x1ff] = 0;
void (*entry)(BootInfo const&) = (void (*)(BootInfo const&))kernel_elf_header->e_entry; void (*entry)(BootInfo const&) = (void (*)(BootInfo const&))kernel_elf_header.e_entry;
entry(*adjust_by_load_base(&info)); entry(*adjust_by_load_base(&info));
__builtin_unreachable(); __builtin_unreachable();