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// SPDX-License-Identifier: GPL-2.0
/*
* Decompression and self-relocation for the compressed kernel boot stub,
* based on arch/parisc/boot/compressed/misc.c.
*
* aboot loads the stub as an ordinary ELF at START_ADDR and jumps to it
* with the parameter page and stack already set up; vmlinux.lds.S
* explains why the stub has to be linked there. We decompress above our
* own bss and never write below START_ADDR, so what aboot prepared stays
* valid for the real kernel.
*/
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/types.h>
#include <asm/hwrpb.h>
#include <asm/page.h>
#include <asm/pal.h>
#include <asm/setup.h>
#define STATIC static
#define memzero(s, n) memset((s), 0, (n))
/*
* decompress_unxz.c supplies its own memmove() unless the identifier is
* already a macro. We link our own build of arch/alpha/lib/memmove.S,
* which is better, so take that instead.
*/
#define memmove memmove
extern char input_data[];
extern int input_len;
/* output_len is inserted by the linker, possibly at an unaligned address */
extern char output_len;
extern char _ebss[];
extern char trampoline_start[], trampoline_end[];
static unsigned long free_mem_ptr;
static unsigned long free_mem_end_ptr;
static unsigned long mem_end;
/* The stub has no console, so the message is only for debuggers. */
void __noreturn error(char *m)
{
while (1)
__halt();
}
#ifdef CONFIG_KERNEL_BZIP2
#include "../../../../lib/decompress_bunzip2.c"
#endif
#ifdef CONFIG_KERNEL_GZIP
#include "../../../../lib/decompress_inflate.c"
#endif
#ifdef CONFIG_KERNEL_LZ4
#include "../../../../lib/decompress_unlz4.c"
#endif
#ifdef CONFIG_KERNEL_LZMA
#include "../../../../lib/decompress_unlzma.c"
#endif
#ifdef CONFIG_KERNEL_LZO
#include "../../../../lib/decompress_unlzo.c"
#endif
#ifdef CONFIG_KERNEL_XZ
#include "../../../../lib/decompress_unxz.c"
#endif
#ifdef CONFIG_KERNEL_ZSTD
#include "../../../../lib/decompress_unzstd.c"
#endif
/* Scratch heap for the decompressors, larger than any of them needs. */
#define STUB_HEAP_SIZE (4 * 1024 * 1024)
/*
* Type punning through a packed struct, to avoid the warnings the regular
* get_unaligned_le32() produces when reading a char-typed symbol as an
* integer.
*/
static u32 punned_get_unaligned_le32(const void *p)
{
const struct { __le32 x; } __packed *pp = p;
return le32_to_cpu(pp->x);
}
/*
* End of the usable memory cluster that holds the kernel, or 0 if the
* HWRPB does not describe one. Used to check that the decompressed image
* and the stub's scratch space fit before anything is written.
*/
static unsigned long usable_memory_end(void)
{
struct hwrpb_struct *hwrpb;
struct memdesc_struct *memdesc;
unsigned long pfn = (START_ADDR - PAGE_OFFSET) >> PAGE_SHIFT;
unsigned long i;
hwrpb = (struct hwrpb_struct *)(PAGE_OFFSET + INIT_HWRPB->phys_addr);
memdesc = (struct memdesc_struct *)((unsigned long)hwrpb +
hwrpb->mddt_offset);
for (i = 0; i < memdesc->numclusters; i++) {
struct memclust_struct *cluster = &memdesc->cluster[i];
unsigned long end_pfn = cluster->start_pfn + cluster->numpages;
if (cluster->usage)
continue;
if (pfn >= cluster->start_pfn && pfn < end_pfn)
return PAGE_OFFSET + (end_pfn << PAGE_SHIFT);
}
return 0;
}
/*
* Move the decompressed kernel's single PT_LOAD segment down onto
* START_ADDR and jump to its entry point. The kernel is always linked
* with exactly one PT_LOAD whose p_vaddr equals its e_entry equals
* START_ADDR (see arch/alpha/kernel/vmlinux.lds.S); anything else we do
* not know how to boot.
*
* The copy cannot run from this stub, which is itself executing at
* START_ADDR; see trampoline.S.
*/
static void __noreturn relocate_and_jump(void *image)
{
void (*trampoline)(unsigned long dest, unsigned long src,
unsigned long filesz, unsigned long memsz,
unsigned long entry);
unsigned long tramp_len = trampoline_end - trampoline_start;
Elf64_Phdr phdr, load_phdr = {};
Elf64_Ehdr ehdr;
int i, found_load = 0;
unsigned long tramp;
memcpy(&ehdr, image, sizeof(ehdr));
if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
ehdr.e_ident[EI_MAG3] != ELFMAG3 ||
ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
ehdr.e_ident[EI_DATA] != ELFDATA2LSB ||
ehdr.e_machine != EM_ALPHA ||
ehdr.e_type != ET_EXEC ||
ehdr.e_entry != START_ADDR)
error("Not a bootable Alpha kernel image");
for (i = 0; i < ehdr.e_phnum; i++) {
memcpy(&phdr, image + ehdr.e_phoff + i * ehdr.e_phentsize,
sizeof(phdr));
if (phdr.p_type != PT_LOAD)
continue;
if (found_load || phdr.p_vaddr != START_ADDR)
error("Unexpected kernel segment layout");
found_load = 1;
load_phdr = phdr;
}
if (!found_load)
error("Kernel image has no PT_LOAD segment");
/*
* The trampoline has to outlive both the scratch heap it is copied
* into and the region it is about to write, which extends past the
* kernel's file image to the end of its bss.
*/
tramp = ALIGN(max(free_mem_end_ptr, START_ADDR + load_phdr.p_memsz), 8);
if (mem_end && tramp + tramp_len > mem_end)
error("Not enough memory to relocate the kernel");
memcpy((void *)tramp, trampoline_start, tramp_len);
imb();
trampoline = (void *)tramp;
trampoline(load_phdr.p_vaddr,
(unsigned long)image + load_phdr.p_offset,
load_phdr.p_filesz, load_phdr.p_memsz, ehdr.e_entry);
unreachable();
}
void __noreturn decompress_and_boot(void)
{
unsigned long image_len = punned_get_unaligned_le32(&output_len);
void *image = (void *)ALIGN((unsigned long)_ebss, PAGE_SIZE);
free_mem_ptr = ALIGN((unsigned long)image + image_len, PAGE_SIZE);
free_mem_end_ptr = free_mem_ptr + STUB_HEAP_SIZE;
mem_end = usable_memory_end();
if (mem_end && free_mem_end_ptr > mem_end)
error("Not enough memory to decompress the kernel");
/* Some decompressors report failure only through the return value. */
if (__decompress(input_data, input_len, NULL, NULL, image, image_len,
NULL, error))
error("Kernel decompression failed");
relocate_and_jump(image);
}
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