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elf: Always do ASLR when loading relocatable ELFs and handle unavailable memory ranges instead of crashing

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This commit is contained in:
mintsuki 2021-03-26 15:47:59 +01:00
parent 621a004bf2
commit 30b750a2ad
8 changed files with 97 additions and 76 deletions
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2
stage23/fs/file.s2.c
View File

@ -113,7 +113,7 @@ int fread(struct file_handle *fd, void *buf, uint64_t loc, uint64_t count) {
void *freadall(struct file_handle *fd, uint32_t type) {
if (fd->is_memfile) {
memmap_alloc_range((uint64_t)(size_t)fd->fd, fd->size, type, false, true);
memmap_alloc_range((uint64_t)(size_t)fd->fd, fd->size, type, false, true, false);
return fd->fd;
} else {
void *ret = ext_mem_alloc_aligned_type(fd->size, 4096, type);

67
stage23/lib/elf.c
View File

@ -4,9 +4,12 @@
#include <lib/libc.h>
#include <lib/elf.h>
#include <lib/print.h>
#include <lib/rand.h>
#include <mm/pmm.h>
#include <fs/file.h>
#define KASLR_SLIDE_BITMASK ((uintptr_t)0x3ffff000)
#define PT_LOAD 0x00000001
#define PT_INTERP 0x00000003
#define PT_PHDR 0x00000006
@ -133,6 +136,27 @@ int elf_bits(struct file_handle *fd) {
}
}
static bool elf64_is_relocatable(struct file_handle *fd, struct elf64_hdr *hdr) {
// Find RELA sections
for (uint16_t i = 0; i < hdr->sh_num; i++) {
struct elf64_shdr section;
fread(fd, &section, hdr->shoff + i * sizeof(struct elf64_shdr),
sizeof(struct elf64_shdr));
if (section.sh_type != SHT_RELA)
continue;
if (section.sh_entsize != sizeof(struct elf64_rela)) {
print("elf: Unknown sh_entsize for RELA section!\n");
continue;
}
return true;
}
return false;
}
static int elf64_apply_relocations(struct file_handle *fd, struct elf64_hdr *hdr, void *buffer, uint64_t vaddr, size_t size, uint64_t slide) {
// Find RELA sections
for (uint16_t i = 0; i < hdr->sh_num; i++) {
@ -268,7 +292,7 @@ int elf32_load_section(struct file_handle *fd, void *buffer, const char *name, s
return 2;
}
int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uint64_t slide, uint32_t alloc_type) {
int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *_slide, uint32_t alloc_type) {
struct elf64_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf64_hdr));
@ -287,8 +311,20 @@ int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uin
return -1;
}
*top = 0;
uint64_t slide = 0;
bool simulation = true;
size_t try_count = 0;
size_t max_simulated_tries = 250;
if (!elf64_is_relocatable(fd, &hdr)) {
simulation = false;
goto final;
}
again:
slide = rand64() & KASLR_SLIDE_BITMASK;
final:
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
fread(fd, &phdr, hdr.phoff + i * sizeof(struct elf64_phdr),
@ -304,12 +340,11 @@ int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uin
load_vaddr += slide;
uint64_t this_top = load_vaddr + phdr.p_memsz;
if (this_top > *top)
*top = this_top;
memmap_alloc_range((size_t)load_vaddr, (size_t)phdr.p_memsz, alloc_type, true, true);
if (!memmap_alloc_range((size_t)load_vaddr, (size_t)phdr.p_memsz, alloc_type, true, false, simulation)) {
if (++try_count == max_simulated_tries || simulation == false)
return -1;
goto again;
}
fread(fd, (void *)(uintptr_t)load_vaddr, phdr.p_offset, phdr.p_filesz);
@ -324,12 +359,18 @@ int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uin
return -1;
}
if (simulation) {
simulation = false;
goto final;
}
*entry_point = hdr.entry + slide;
*_slide = slide;
return 0;
}
int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t *top, uint32_t alloc_type) {
int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t alloc_type) {
struct elf32_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf32_hdr));
@ -348,8 +389,6 @@ int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t *top, uin
return -1;
}
*top = 0;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf32_phdr phdr;
fread(fd, &phdr, hdr.phoff + i * sizeof(struct elf32_phdr),
@ -358,11 +397,7 @@ int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t *top, uin
if (phdr.p_type != PT_LOAD)
continue;
uint32_t this_top = phdr.p_vaddr + phdr.p_memsz;
if (this_top > *top)
*top = this_top;
memmap_alloc_range((size_t)phdr.p_paddr, (size_t)phdr.p_memsz, alloc_type, true, true);
memmap_alloc_range((size_t)phdr.p_paddr, (size_t)phdr.p_memsz, alloc_type, true, true, false);
fread(fd, (void *)(uintptr_t)phdr.p_paddr, phdr.p_offset, phdr.p_filesz);

4
stage23/lib/elf.h
View File

@ -8,10 +8,10 @@
int elf_bits(struct file_handle *fd);
int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uint64_t slide, uint32_t alloc_type);
int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *slide, uint32_t alloc_type);
int elf64_load_section(struct file_handle *fd, void *buffer, const char *name, size_t limit, uint64_t slide);
int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t *top, uint32_t alloc_type);
int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t alloc_type);
int elf32_load_section(struct file_handle *fd, void *buffer, const char *name, size_t limit);
#endif

2
stage23/mm/pmm.h
View File

@ -25,7 +25,7 @@ extern size_t memmap_entries;
void init_memmap(void);
struct e820_entry_t *get_memmap(size_t *entries);
void print_memmap(struct e820_entry_t *mm, size_t size);
bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free_only, bool panic);
bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free_only, bool panic, bool simulation);
void *ext_mem_alloc(size_t count);
void *ext_mem_alloc_type(size_t count, uint32_t type);

13
stage23/mm/pmm.s2.c
View File

@ -342,7 +342,7 @@ void init_memmap(void) {
memmap_alloc_range(bump_allocator_base,
bump_allocator_limit - bump_allocator_base,
MEMMAP_REMOVE_RANGE, true, true);
MEMMAP_REMOVE_RANGE, true, true, false);
print("pmm: Conventional mem allocator base: %X\n", bump_allocator_base);
print("pmm: Conventional mem allocator limit: %X\n", bump_allocator_limit);
@ -399,7 +399,7 @@ void *ext_mem_alloc_aligned_type(size_t count, size_t alignment, uint32_t type)
// We now reserve the range we need.
int64_t aligned_length = entry_top - alloc_base;
memmap_alloc_range((uint64_t)alloc_base, (uint64_t)aligned_length, type, true, true);
memmap_alloc_range((uint64_t)alloc_base, (uint64_t)aligned_length, type, true, true, false);
void *ret = (void *)(size_t)alloc_base;
@ -414,7 +414,7 @@ void *ext_mem_alloc_aligned_type(size_t count, size_t alignment, uint32_t type)
panic("High memory allocator: Out of memory");
}
bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free_only, bool do_panic) {
bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free_only, bool do_panic, bool simulation) {
if (length == 0)
return true;
@ -443,6 +443,9 @@ bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free
if (type == MEMMAP_REMOVE_RANGE &&
base == entry_base && top == entry_top) {
if (simulation)
return true;
// Eradicate from memmap
for (size_t j = i; j < memmap_entries - 1; j++) {
memmap[j] = memmap[j+1];
@ -454,6 +457,10 @@ bool memmap_alloc_range(uint64_t base, uint64_t length, uint32_t type, bool free
if (base >= entry_base && base < entry_top &&
top >= entry_base && top <= entry_top) {
if (simulation)
return true;
struct e820_entry_t *target;
memmap[i].length -= entry_top - base;

4
stage23/protos/linux.c
View File

@ -417,7 +417,7 @@ void linux_load(char *config, char *cmdline) {
for (;;) {
if (memmap_alloc_range(kernel_load_addr,
kernel->size - real_mode_code_size,
MEMMAP_BOOTLOADER_RECLAIMABLE, true, false))
MEMMAP_BOOTLOADER_RECLAIMABLE, true, false, false))
break;
kernel_load_addr += 0x100000;
@ -451,7 +451,7 @@ void linux_load(char *config, char *cmdline) {
for (;;) {
if (memmap_alloc_range(modules_mem_base, size_of_all_modules,
MEMMAP_BOOTLOADER_RECLAIMABLE, true, false))
MEMMAP_BOOTLOADER_RECLAIMABLE, true, false, false))
break;
modules_mem_base -= 4096;
}

40
stage23/protos/stivale.c
View File

@ -9,7 +9,6 @@
#include <lib/config.h>
#include <lib/time.h>
#include <lib/print.h>
#include <lib/rand.h>
#include <lib/real.h>
#include <lib/uri.h>
#include <lib/fb.h>
@ -23,8 +22,6 @@
#include <mm/mtrr.h>
#include <stivale/stivale.h>
#define KASLR_SLIDE_BITMASK 0x000FFF000u
struct stivale_struct stivale_struct = {0};
void stivale_load(char *config, char *cmdline) {
@ -50,9 +47,11 @@ void stivale_load(char *config, char *cmdline) {
int ret;
uint64_t slide = 0;
bool level5pg = false;
uint64_t slide = 0;
uint64_t entry_point = 0;
switch (bits) {
case 64: {
// Check if 64 bit CPU
@ -66,19 +65,21 @@ void stivale_load(char *config, char *cmdline) {
level5pg = true;
}
char *s_kaslr = config_get_value(config, 0, "KASLR");
if (s_kaslr != NULL && !strcmp(s_kaslr, "yes")) {
// KASLR is enabled, set the slide
slide = rand64() & KASLR_SLIDE_BITMASK;
}
if (elf64_load(kernel, &entry_point, &slide, 10))
panic("stivale: ELF64 load failure");
ret = elf64_load_section(kernel, &stivale_hdr, ".stivalehdr", sizeof(struct stivale_header), slide);
break;
}
case 32:
case 32: {
if (elf32_load(kernel, (uint32_t *)&entry_point, 10))
panic("stivale: ELF32 load failure");
ret = elf32_load_section(kernel, &stivale_hdr, ".stivalehdr", sizeof(struct stivale_header));
break;
}
default:
panic("stivale: Not 32 nor 64 bit x86 ELF file.");
}
@ -96,26 +97,13 @@ void stivale_load(char *config, char *cmdline) {
panic("stivale: Section .stivalehdr is smaller than size of the struct.");
}
print("stivale: Requested stack at %X\n", stivale_hdr.stack);
uint64_t entry_point = 0;
uint64_t top_used_addr = 0;
switch (bits) {
case 64:
elf64_load(kernel, &entry_point, &top_used_addr, slide, 10);
break;
case 32:
elf32_load(kernel, (uint32_t *)&entry_point, (uint32_t *)&top_used_addr, 10);
break;
}
if (stivale_hdr.entry_point != 0)
entry_point = stivale_hdr.entry_point;
print("stivale: Kernel slide: %X\n", slide);
print("stivale: Top used address in ELF: %X\n", top_used_addr);
print("stivale: Entry point at: %X\n", entry_point);
print("stivale: Requested stack at: %X\n", stivale_hdr.stack);
stivale_struct.module_count = 0;
uint64_t *prev_mod_ptr = &stivale_struct.modules;

41
stage23/protos/stivale2.c
View File

@ -68,35 +68,39 @@ void stivale2_load(char *config, char *cmdline, bool pxe, void *efi_system_table
int ret;
uint64_t slide = 0;
bool level5pg = false;
uint64_t slide = 0;
uint64_t entry_point = 0;
switch (bits) {
case 64: {
// Check if 64 bit CPU
uint32_t eax, ebx, ecx, edx;
if (!cpuid(0x80000001, 0, &eax, &ebx, &ecx, &edx) || !(edx & (1 << 29))) {
panic("stivale: This CPU does not support 64-bit mode.");
panic("stivale2: This CPU does not support 64-bit mode.");
}
// Check if 5-level paging is available
if (cpuid(0x00000007, 0, &eax, &ebx, &ecx, &edx) && (ecx & (1 << 16))) {
print("stivale: CPU has 5-level paging support\n");
print("stivale2: CPU has 5-level paging support\n");
level5pg = true;
}
char *s_kaslr = config_get_value(config, 0, "KASLR");
if (s_kaslr != NULL && !strcmp(s_kaslr, "yes")) {
// KASLR is enabled, set the slide
slide = rand64() & KASLR_SLIDE_BITMASK;
}
if (elf64_load(kernel, &entry_point, &slide, 10))
panic("stivale2: ELF64 load failure");
ret = elf64_load_section(kernel, &stivale2_hdr, ".stivale2hdr", sizeof(struct stivale2_header), slide);
break;
}
case 32:
case 32: {
if (elf32_load(kernel, (uint32_t *)&entry_point, 10))
panic("stivale2: ELF32 load failure");
ret = elf32_load_section(kernel, &stivale2_hdr, ".stivale2hdr", sizeof(struct stivale2_header));
break;
}
default:
panic("stivale2: Not 32 nor 64 bit x86 ELF file.");
}
@ -114,26 +118,13 @@ void stivale2_load(char *config, char *cmdline, bool pxe, void *efi_system_table
panic("stivale2: Section .stivale2hdr is smaller than size of the struct.");
}
print("stivale2: Requested stack at %X\n", stivale2_hdr.stack);
uint64_t entry_point = 0;
uint64_t top_used_addr = 0;
switch (bits) {
case 64:
elf64_load(kernel, &entry_point, &top_used_addr, slide, 0x1001);
break;
case 32:
elf32_load(kernel, (uint32_t *)&entry_point, (uint32_t *)&top_used_addr, 0x1001);
break;
}
if (stivale2_hdr.entry_point != 0)
entry_point = stivale2_hdr.entry_point;
print("stivale2: Kernel slide: %X\n", slide);
print("stivale2: Top used address in ELF: %X\n", top_used_addr);
print("stivale2: Entry point at: %X\n", entry_point);
print("stivale2: Requested stack at: %X\n", stivale2_hdr.stack);
strcpy(stivale2_struct.bootloader_brand, "Limine");
strcpy(stivale2_struct.bootloader_version, LIMINE_VERSION);