1 // SPDX-License-Identifier: GPL-2.0
5 * This is a collection of several routines used to extract the kernel
6 * which includes KASLR relocation, decompression, ELF parsing, and
7 * relocation processing. Additionally included are the screen and serial
8 * output functions and related debugging support functions.
10 * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
11 * puts by Nick Holloway 1993, better puts by Martin Mares 1995
12 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
18 #include "../string.h"
19 #include "../voffset.h"
20 #include <asm/bootparam_utils.h>
24 * This code is compiled with -fPIC and it is relocated dynamically at
25 * run time, but no relocation processing is performed. This means that
26 * it is not safe to place pointers in static structures.
29 /* Macros used by the included decompressor code below. */
31 /* Define an externally visible malloc()/free(). */
32 #define MALLOC_VISIBLE
33 #include <linux/decompress/mm.h>
36 * Provide definitions of memzero and memmove as some of the decompressors will
37 * try to define their own functions if these are not defined as macros.
39 #define memzero(s, n) memset((s), 0, (n))
41 #define memmove memmove
42 /* Functions used by the included decompressor code below. */
43 void *memmove(void *dest, const void *src, size_t n);
47 * This is set up by the setup-routine at boot-time
49 struct boot_params *boot_params_ptr;
51 struct port_io_ops pio_ops;
54 memptr free_mem_end_ptr;
59 /* These might be accessed before .bss is cleared, so use .data instead. */
60 static int lines __section(".data");
61 static int cols __section(".data");
63 #ifdef CONFIG_KERNEL_GZIP
64 #include "../../../../lib/decompress_inflate.c"
67 #ifdef CONFIG_KERNEL_BZIP2
68 #include "../../../../lib/decompress_bunzip2.c"
71 #ifdef CONFIG_KERNEL_LZMA
72 #include "../../../../lib/decompress_unlzma.c"
75 #ifdef CONFIG_KERNEL_XZ
76 #include "../../../../lib/decompress_unxz.c"
79 #ifdef CONFIG_KERNEL_LZO
80 #include "../../../../lib/decompress_unlzo.c"
83 #ifdef CONFIG_KERNEL_LZ4
84 #include "../../../../lib/decompress_unlz4.c"
87 #ifdef CONFIG_KERNEL_ZSTD
88 #include "../../../../lib/decompress_unzstd.c"
91 * NOTE: When adding a new decompressor, please update the analysis in
95 static void scroll(void)
99 memmove(vidmem, vidmem + cols * 2, (lines - 1) * cols * 2);
100 for (i = (lines - 1) * cols * 2; i < lines * cols * 2; i += 2)
106 #define TXR 0 /* Transmit register (WRITE) */
107 #define LSR 5 /* Line Status */
108 static void serial_putchar(int ch)
110 unsigned timeout = 0xffff;
112 while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
115 outb(ch, early_serial_base + TXR);
118 void __putstr(const char *s)
123 if (early_serial_base) {
127 serial_putchar('\r');
128 serial_putchar(*str++);
132 if (lines == 0 || cols == 0)
135 x = boot_params_ptr->screen_info.orig_x;
136 y = boot_params_ptr->screen_info.orig_y;
138 while ((c = *s++) != '\0') {
146 vidmem[(x + cols * y) * 2] = c;
157 boot_params_ptr->screen_info.orig_x = x;
158 boot_params_ptr->screen_info.orig_y = y;
160 pos = (x + cols * y) * 2; /* Update cursor position */
162 outb(0xff & (pos >> 9), vidport+1);
164 outb(0xff & (pos >> 1), vidport+1);
167 void __puthex(unsigned long value)
172 for (bits = sizeof(value) * 8 - 4; bits >= 0; bits -= 4) {
173 unsigned long digit = (value >> bits) & 0xf;
176 alpha[0] = '0' + digit;
178 alpha[0] = 'a' + (digit - 0xA);
184 #ifdef CONFIG_X86_NEED_RELOCS
185 static void handle_relocations(void *output, unsigned long output_len,
186 unsigned long virt_addr)
189 unsigned long delta, map, ptr;
190 unsigned long min_addr = (unsigned long)output;
191 unsigned long max_addr = min_addr + (VO___bss_start - VO__text);
194 * Calculate the delta between where vmlinux was linked to load
195 * and where it was actually loaded.
197 delta = min_addr - LOAD_PHYSICAL_ADDR;
200 * The kernel contains a table of relocation addresses. Those
201 * addresses have the final load address of the kernel in virtual
202 * memory. We are currently working in the self map. So we need to
203 * create an adjustment for kernel memory addresses to the self map.
204 * This will involve subtracting out the base address of the kernel.
206 map = delta - __START_KERNEL_map;
209 * 32-bit always performs relocations. 64-bit relocations are only
210 * needed if KASLR has chosen a different starting address offset
211 * from __START_KERNEL_map.
213 if (IS_ENABLED(CONFIG_X86_64))
214 delta = virt_addr - LOAD_PHYSICAL_ADDR;
217 debug_putstr("No relocation needed... ");
220 debug_putstr("Performing relocations... ");
223 * Process relocations: 32 bit relocations first then 64 bit after.
224 * Three sets of binary relocations are added to the end of the kernel
225 * before compression. Each relocation table entry is the kernel
226 * address of the location which needs to be updated stored as a
227 * 32-bit value which is sign extended to 64 bits.
232 * 0 - zero terminator for 64 bit relocations
233 * 64 bit relocation repeated
234 * 0 - zero terminator for inverse 32 bit relocations
235 * 32 bit inverse relocation repeated
236 * 0 - zero terminator for 32 bit relocations
237 * 32 bit relocation repeated
239 * So we work backwards from the end of the decompressed image.
241 for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
242 long extended = *reloc;
245 ptr = (unsigned long)extended;
246 if (ptr < min_addr || ptr > max_addr)
247 error("32-bit relocation outside of kernel!\n");
249 *(uint32_t *)ptr += delta;
253 long extended = *reloc;
256 ptr = (unsigned long)extended;
257 if (ptr < min_addr || ptr > max_addr)
258 error("inverse 32-bit relocation outside of kernel!\n");
260 *(int32_t *)ptr -= delta;
262 for (reloc--; *reloc; reloc--) {
263 long extended = *reloc;
266 ptr = (unsigned long)extended;
267 if (ptr < min_addr || ptr > max_addr)
268 error("64-bit relocation outside of kernel!\n");
270 *(uint64_t *)ptr += delta;
275 static inline void handle_relocations(void *output, unsigned long output_len,
276 unsigned long virt_addr)
280 static size_t parse_elf(void *output)
284 Elf64_Phdr *phdrs, *phdr;
287 Elf32_Phdr *phdrs, *phdr;
292 memcpy(&ehdr, output, sizeof(ehdr));
293 if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
294 ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
295 ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
296 ehdr.e_ident[EI_MAG3] != ELFMAG3)
297 error("Kernel is not a valid ELF file");
299 debug_putstr("Parsing ELF... ");
301 phdrs = malloc(sizeof(*phdrs) * ehdr.e_phnum);
303 error("Failed to allocate space for phdrs");
305 memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
307 for (i = 0; i < ehdr.e_phnum; i++) {
310 switch (phdr->p_type) {
313 if ((phdr->p_align % 0x200000) != 0)
314 error("Alignment of LOAD segment isn't multiple of 2MB");
316 #ifdef CONFIG_RELOCATABLE
318 dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR);
320 dest = (void *)(phdr->p_paddr);
322 memmove(dest, output + phdr->p_offset, phdr->p_filesz);
324 default: /* Ignore other PT_* */ break;
330 return ehdr.e_entry - LOAD_PHYSICAL_ADDR;
333 const unsigned long kernel_total_size = VO__end - VO__text;
335 static u8 boot_heap[BOOT_HEAP_SIZE] __aligned(4);
337 extern unsigned char input_data[];
338 extern unsigned int input_len, output_len;
340 unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
341 void (*error)(char *x))
346 free_mem_ptr = (unsigned long)boot_heap;
347 free_mem_end_ptr = (unsigned long)boot_heap + sizeof(boot_heap);
350 if (__decompress(input_data, input_len, NULL, NULL, outbuf, output_len,
354 entry = parse_elf(outbuf);
355 handle_relocations(outbuf, output_len, virt_addr);
361 * The compressed kernel image (ZO), has been moved so that its position
362 * is against the end of the buffer used to hold the uncompressed kernel
363 * image (VO) and the execution environment (.bss, .brk), which makes sure
364 * there is room to do the in-place decompression. (See header.S for the
367 * |-----compressed kernel image------|
369 * 0 extract_offset +INIT_SIZE
370 * |-----------|---------------|-------------------------|--------|
372 * VO__text startup_32 of ZO VO__end ZO__end
374 * |-------uncompressed kernel image---------|
377 asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
379 unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
380 memptr heap = (memptr)boot_heap;
381 unsigned long needed_size;
384 /* Retain x86 boot parameters pointer passed from startup_32/64. */
385 boot_params_ptr = rmode;
387 /* Clear flags intended for solely in-kernel use. */
388 boot_params_ptr->hdr.loadflags &= ~KASLR_FLAG;
390 sanitize_boot_params(boot_params_ptr);
392 if (boot_params_ptr->screen_info.orig_video_mode == 7) {
393 vidmem = (char *) 0xb0000;
396 vidmem = (char *) 0xb8000;
400 lines = boot_params_ptr->screen_info.orig_video_lines;
401 cols = boot_params_ptr->screen_info.orig_video_cols;
403 init_default_io_ops();
406 * Detect TDX guest environment.
408 * It has to be done before console_init() in order to use
409 * paravirtualized port I/O operations if needed.
416 * Save RSDP address for later use. Have this after console_init()
417 * so that early debugging output from the RSDP parsing code can be
420 boot_params_ptr->acpi_rsdp_addr = get_rsdp_addr();
422 debug_putstr("early console in extract_kernel\n");
424 free_mem_ptr = heap; /* Heap */
425 free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
428 * The memory hole needed for the kernel is the larger of either
429 * the entire decompressed kernel plus relocation table, or the
430 * entire decompressed kernel plus .bss and .brk sections.
432 * On X86_64, the memory is mapped with PMD pages. Round the
433 * size up so that the full extent of PMD pages mapped is
434 * included in the check against the valid memory table
435 * entries. This ensures the full mapped area is usable RAM
436 * and doesn't include any reserved areas.
438 needed_size = max_t(unsigned long, output_len, kernel_total_size);
440 needed_size = ALIGN(needed_size, MIN_KERNEL_ALIGN);
443 /* Report initial kernel position details. */
444 debug_putaddr(input_data);
445 debug_putaddr(input_len);
446 debug_putaddr(output);
447 debug_putaddr(output_len);
448 debug_putaddr(kernel_total_size);
449 debug_putaddr(needed_size);
452 /* Report address of 32-bit trampoline */
453 debug_putaddr(trampoline_32bit);
456 choose_random_location((unsigned long)input_data, input_len,
457 (unsigned long *)&output,
461 /* Validate memory location choices. */
462 if ((unsigned long)output & (MIN_KERNEL_ALIGN - 1))
463 error("Destination physical address inappropriately aligned");
464 if (virt_addr & (MIN_KERNEL_ALIGN - 1))
465 error("Destination virtual address inappropriately aligned");
467 if (heap > 0x3fffffffffffUL)
468 error("Destination address too large");
469 if (virt_addr + needed_size > KERNEL_IMAGE_SIZE)
470 error("Destination virtual address is beyond the kernel mapping area");
472 if (heap > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff))
473 error("Destination address too large");
475 #ifndef CONFIG_RELOCATABLE
476 if (virt_addr != LOAD_PHYSICAL_ADDR)
477 error("Destination virtual address changed when not relocatable");
480 debug_putstr("\nDecompressing Linux... ");
482 if (init_unaccepted_memory()) {
483 debug_putstr("Accepting memory... ");
484 accept_memory(__pa(output), __pa(output) + needed_size);
487 entry_offset = decompress_kernel(output, virt_addr, error);
489 debug_putstr("done.\nBooting the kernel (entry_offset: 0x");
490 debug_puthex(entry_offset);
491 debug_putstr(").\n");
493 /* Disable exception handling before booting the kernel */
494 cleanup_exception_handling();
496 return output + entry_offset;
499 void fortify_panic(const char *name)
501 error("detected buffer overflow");