linux/arch/x86/include/asm/boot.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_BOOT_H
#define _ASM_X86_BOOT_H


#include <asm/pgtable_types.h>
#include <uapi/asm/boot.h>

/* Minimum kernel alignment, as a power of two */
#ifdef CONFIG_X86_64
#define MIN_KERNEL_ALIGN_LG2 …
#else
#define MIN_KERNEL_ALIGN_LG2 …
#endif
#define MIN_KERNEL_ALIGN …

#if (CONFIG_PHYSICAL_ALIGN & (CONFIG_PHYSICAL_ALIGN-1)) || \
	(CONFIG_PHYSICAL_ALIGN < MIN_KERNEL_ALIGN)
# error "Invalid value for CONFIG_PHYSICAL_ALIGN"
#endif

#if defined(CONFIG_KERNEL_BZIP2)
#define BOOT_HEAP_SIZE …
#elif defined(CONFIG_KERNEL_ZSTD)
/*
 * Zstd needs to allocate the ZSTD_DCtx in order to decompress the kernel.
 * The ZSTD_DCtx is ~160KB, so set the heap size to 192KB because it is a
 * round number and to allow some slack.
 */
#define BOOT_HEAP_SIZE …
#else
#define BOOT_HEAP_SIZE …
#endif

#ifdef CONFIG_X86_64
#define BOOT_STACK_SIZE …

/*
 * Used by decompressor's startup_32() to allocate page tables for identity
 * mapping of the 4G of RAM in 4-level paging mode:
 * - 1 level4 table;
 * - 1 level3 table;
 * - 4 level2 table that maps everything with 2M pages;
 *
 * The additional level5 table needed for 5-level paging is allocated from
 * trampoline_32bit memory.
 */
#define BOOT_INIT_PGT_SIZE …

/*
 * Total number of page tables kernel_add_identity_map() can allocate,
 * including page tables consumed by startup_32().
 *
 * Worst-case scenario:
 *  - 5-level paging needs 1 level5 table;
 *  - KASLR needs to map kernel, boot_params, cmdline and randomized kernel,
 *    assuming all of them cross 256T boundary:
 *    + 4*2 level4 table;
 *    + 4*2 level3 table;
 *    + 4*2 level2 table;
 *  - X86_VERBOSE_BOOTUP needs to map the first 2M (video RAM):
 *    + 1 level4 table;
 *    + 1 level3 table;
 *    + 1 level2 table;
 * Total: 28 tables
 *
 * Add 4 spare table in case decompressor touches anything beyond what is
 * accounted above. Warn if it happens.
 */
#define BOOT_PGT_SIZE_WARN …
#define BOOT_PGT_SIZE …

#else /* !CONFIG_X86_64 */
#define BOOT_STACK_SIZE …
#endif

#ifndef __ASSEMBLY__
extern unsigned int output_len;
extern const unsigned long kernel_text_size;
extern const unsigned long kernel_total_size;

unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
				void (*error)(char *x));

extern struct boot_params *boot_params_ptr;
#endif

#endif /* _ASM_X86_BOOT_H */