cregit-Linux how code gets into the kernel

Release 4.14 arch/x86/boot/tools/build.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 Martin Mares
 *  Copyright (C) 2007 H. Peter Anvin
 */

/*
 * This file builds a disk-image from three different files:
 *
 * - setup: 8086 machine code, sets up system parm
 * - system: 80386 code for actual system
 * - zoffset.h: header with ZO_* defines
 *
 * It does some checking that all files are of the correct type, and writes
 * the result to the specified destination, removing headers and padding to
 * the right amount. It also writes some system data to stdout.
 */

/*
 * Changes by tytso to allow root device specification
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
 * Cross compiling fixes by Gertjan van Wingerde, July 1996
 * Rewritten by Martin Mares, April 1997
 * Substantially overhauled by H. Peter Anvin, April 2007
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <tools/le_byteshift.h>


typedef unsigned char  u8;

typedef unsigned short u16;

typedef unsigned int   u32;


#define DEFAULT_MAJOR_ROOT 0

#define DEFAULT_MINOR_ROOT 0

#define DEFAULT_ROOT_DEV (DEFAULT_MAJOR_ROOT << 8 | DEFAULT_MINOR_ROOT)

/* Minimal number of setup sectors */

#define SETUP_SECT_MIN 5

#define SETUP_SECT_MAX 64

/* This must be large enough to hold the entire setup */

u8 buf[SETUP_SECT_MAX*512];


#define PECOFF_RELOC_RESERVE 0x20


unsigned long efi32_stub_entry;

unsigned long efi64_stub_entry;

unsigned long efi_pe_entry;

unsigned long startup_64;

/*----------------------------------------------------------------------*/


static const u32 crctab32[] = {
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
	0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
	0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
	0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
	0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
	0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
	0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
	0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
	0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
	0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
	0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
	0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
	0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
	0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
	0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
	0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
	0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
	0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
	0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
	0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
	0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
	0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
	0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
	0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
	0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
	0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
	0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
	0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
	0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
	0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
	0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
	0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
	0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
	0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
	0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
	0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
	0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
	0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
	0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
	0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
	0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
	0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
	0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
	0x2d02ef8d
};


static u32 partial_crc32_one(u8 c, u32 crc) { return crctab32[(crc ^ c) & 0xff] ^ (crc >> 8); }

Contributors

PersonTokensPropCommitsCommitProp
Ian Campbell30100.00%1100.00%
Total30100.00%1100.00%


static u32 partial_crc32(const u8 *s, int len, u32 crc) { while (len--) crc = partial_crc32_one(*s++, crc); return crc; }

Contributors

PersonTokensPropCommitsCommitProp
Ian Campbell36100.00%1100.00%
Total36100.00%1100.00%


static void die(const char * str, ...) { va_list args; va_start(args, str); vfprintf(stderr, str, args); fputc('\n', stderr); exit(1); }

Contributors

PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)4397.73%266.67%
H. Peter Anvin12.27%133.33%
Total44100.00%3100.00%


static void usage(void) { die("Usage: build setup system zoffset.h image"); }

Contributors

PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)1184.62%133.33%
Kees Cook17.69%133.33%
H. Peter Anvin17.69%133.33%
Total13100.00%3100.00%

#ifdef CONFIG_EFI_STUB
static void update_pecoff_section_header_fields(char *section_name, u32 vma, u32 size, u32 datasz, u32 offset) { unsigned int pe_header; unsigned short num_sections; u8 *section; pe_header = get_unaligned_le32(&buf[0x3c]); num_sections = get_unaligned_le16(&buf[pe_header + 6]); #ifdef CONFIG_X86_32 section = &buf[pe_header + 0xa8]; #else section = &buf[pe_header + 0xb8]; #endif while (num_sections > 0) { if (strncmp((char*)section, section_name, 8) == 0) { /* section header size field */ put_unaligned_le32(size, section + 0x8); /* section header vma field */ put_unaligned_le32(vma, section + 0xc); /* section header 'size of initialised data' field */ put_unaligned_le32(datasz, section + 0x10); /* section header 'file offset' field */ put_unaligned_le32(offset, section + 0x14); break; } section += 0x28; num_sections--; } }

Contributors

PersonTokensPropCommitsCommitProp
Jordan Justen10364.38%19.09%
Linus Torvalds (pre-git)2918.12%654.55%
H. Peter Anvin138.12%19.09%
Michael Brown106.25%19.09%
Matt Fleming42.50%19.09%
Ian Campbell10.62%19.09%
Total160100.00%11100.00%


static void update_pecoff_section_header(char *section_name, u32 offset, u32 size) { update_pecoff_section_header_fields(section_name, offset, size, size, offset); }

Contributors

PersonTokensPropCommitsCommitProp
Michael Brown29100.00%1100.00%
Total29100.00%1100.00%


static void update_pecoff_setup_and_reloc(unsigned int size) { u32 setup_offset = 0x200; u32 reloc_offset = size - PECOFF_RELOC_RESERVE; u32 setup_size = reloc_offset - setup_offset; update_pecoff_section_header(".setup", setup_offset, setup_size); update_pecoff_section_header(".reloc", reloc_offset, PECOFF_RELOC_RESERVE); /* * Modify .reloc section contents with a single entry. The * relocation is applied to offset 10 of the relocation section. */ put_unaligned_le32(reloc_offset + 10, &buf[reloc_offset]); put_unaligned_le32(10, &buf[reloc_offset + 4]); }

Contributors

PersonTokensPropCommitsCommitProp
Jordan Justen6385.14%116.67%
Linus Torvalds (pre-git)56.76%350.00%
H. Peter Anvin34.05%116.67%
Matt Fleming34.05%116.67%
Total74100.00%6100.00%


static void update_pecoff_text(unsigned int text_start, unsigned int file_sz) { unsigned int pe_header; unsigned int text_sz = file_sz - text_start; pe_header = get_unaligned_le32(&buf[0x3c]); /* * Size of code: Subtract the size of the first sector (512 bytes) * which includes the header. */ put_unaligned_le32(file_sz - 512, &buf[pe_header + 0x1c]); /* * Address of entry point for PE/COFF executable */ put_unaligned_le32(text_start + efi_pe_entry, &buf[pe_header + 0x28]); update_pecoff_section_header(".text", text_start, text_sz); }

Contributors

PersonTokensPropCommitsCommitProp
Jordan Justen7697.44%150.00%
David Woodhouse22.56%150.00%
Total78100.00%2100.00%


static void update_pecoff_bss(unsigned int file_sz, unsigned int init_sz) { unsigned int pe_header; unsigned int bss_sz = init_sz - file_sz; pe_header = get_unaligned_le32(&buf[0x3c]); /* Size of uninitialized data */ put_unaligned_le32(bss_sz, &buf[pe_header + 0x24]); /* Size of image */ put_unaligned_le32(init_sz, &buf[pe_header + 0x50]); update_pecoff_section_header_fields(".bss", file_sz, bss_sz, 0, 0); }

Contributors

PersonTokensPropCommitsCommitProp
Michael Brown78100.00%1100.00%
Total78100.00%1100.00%


static int reserve_pecoff_reloc_section(int c) { /* Reserve 0x20 bytes for .reloc section */ memset(buf+c, 0, PECOFF_RELOC_RESERVE); return PECOFF_RELOC_RESERVE; }

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming24100.00%1100.00%
Total24100.00%1100.00%


static void efi_stub_defaults(void) { /* Defaults for old kernel */ #ifdef CONFIG_X86_32 efi_pe_entry = 0x10; #else efi_pe_entry = 0x210; startup_64 = 0x200; #endif }

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming28100.00%1100.00%
Total28100.00%1100.00%


static void efi_stub_entry_update(void) { unsigned long addr = efi32_stub_entry; #ifdef CONFIG_X86_64 /* Yes, this is really how we defined it :( */ addr = efi64_stub_entry - 0x200; #endif #ifdef CONFIG_EFI_MIXED if (efi32_stub_entry != addr) die("32-bit and 64-bit EFI entry points do not match\n"); #endif put_unaligned_le32(addr, &buf[0x264]); }

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming53100.00%2100.00%
Total53100.00%2100.00%

#else
static inline void update_pecoff_setup_and_reloc(unsigned int size) {}

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming10100.00%2100.00%
Total10100.00%2100.00%


static inline void update_pecoff_text(unsigned int text_start, unsigned int file_sz) {}

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming14100.00%2100.00%
Total14100.00%2100.00%


static inline void update_pecoff_bss(unsigned int file_sz, unsigned int init_sz) {}

Contributors

PersonTokensPropCommitsCommitProp
Michael Brown14100.00%1100.00%
Total14100.00%1100.00%


static inline void efi_stub_defaults(void) {}

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PersonTokensPropCommitsCommitProp
Matt Fleming8100.00%1100.00%
Total8100.00%1100.00%


static inline void efi_stub_entry_update(void) {}

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming8100.00%2100.00%
Total8100.00%2100.00%


static inline int reserve_pecoff_reloc_section(int c) { return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Matt Fleming13100.00%1100.00%
Total13100.00%1100.00%

#endif /* CONFIG_EFI_STUB */ /* * Parse zoffset.h and find the entry points. We could just #include zoffset.h * but that would mean tools/build would have to be rebuilt every time. It's * not as if parsing it is hard... */ #define PARSE_ZOFS(p, sym) do { \ if (!strncmp(p, "#define ZO_" #sym " ", 11+sizeof(#sym))) \ sym = strtoul(p + 11 + sizeof(#sym), NULL, 16); \ } while (0)
static void parse_zoffset(char *fname) { FILE *file; char *p; int c; file = fopen(fname, "r"); if (!file) die("Unable to open `%s': %m", fname); c = fread(buf, 1, sizeof(buf) - 1, file); if (ferror(file)) die("read-error on `zoffset.h'"); fclose(file); buf[c] = 0; p = (char *)buf; while (p && *p) { PARSE_ZOFS(p, efi32_stub_entry); PARSE_ZOFS(p, efi64_stub_entry); PARSE_ZOFS(p, efi_pe_entry); PARSE_ZOFS(p, startup_64); p = strchr(p, '\n'); while (p && (*p == '\r' || *p == '\n')) p++; } }

Contributors

PersonTokensPropCommitsCommitProp
David Woodhouse14491.72%133.33%
Matt Fleming85.10%133.33%
Jiri Slaby53.18%133.33%
Total157100.00%3100.00%


int main(int argc, char ** argv) { unsigned int i, sz, setup_sectors, init_sz; int c; u32 sys_size; struct stat sb; FILE *file, *dest; int fd; void *kernel; u32 crc = 0xffffffffUL; efi_stub_defaults(); if (argc != 5) usage(); parse_zoffset(argv[3]); dest = fopen(argv[4], "w"); if (!dest) die("Unable to write `%s': %m", argv[4]); /* Copy the setup code */ file = fopen(argv[1], "r"); if (!file) die("Unable to open `%s': %m", argv[1]); c = fread(buf, 1, sizeof(buf), file); if (ferror(file)) die("read-error on `setup'"); if (c < 1024) die("The setup must be at least 1024 bytes"); if (get_unaligned_le16(&buf[510]) != 0xAA55) die("Boot block hasn't got boot flag (0xAA55)"); fclose(file); c += reserve_pecoff_reloc_section(c); /* Pad unused space with zeros */ setup_sectors = (c + 511) / 512; if (setup_sectors < SETUP_SECT_MIN) setup_sectors = SETUP_SECT_MIN; i = setup_sectors*512; memset(buf+c, 0, i-c); update_pecoff_setup_and_reloc(i); /* Set the default root device */ put_unaligned_le16(DEFAULT_ROOT_DEV, &buf[508]); printf("Setup is %d bytes (padded to %d bytes).\n", c, i); /* Open and stat the kernel file */ fd = open(argv[2], O_RDONLY); if (fd < 0) die("Unable to open `%s': %m", argv[2]); if (fstat(fd, &sb)) die("Unable to stat `%s': %m", argv[2]); sz = sb.st_size; printf("System is %d kB\n", (sz+1023)/1024); kernel = mmap(NULL, sz, PROT_READ, MAP_SHARED, fd, 0); if (kernel == MAP_FAILED) die("Unable to mmap '%s': %m", argv[2]); /* Number of 16-byte paragraphs, including space for a 4-byte CRC */ sys_size = (sz + 15 + 4) / 16; /* Patch the setup code with the appropriate size parameters */ buf[0x1f1] = setup_sectors-1; put_unaligned_le32(sys_size, &buf[0x1f4]); update_pecoff_text(setup_sectors * 512, i + (sys_size * 16)); init_sz = get_unaligned_le32(&buf[0x260]); update_pecoff_bss(i + (sys_size * 16), init_sz); efi_stub_entry_update(); crc = partial_crc32(buf, i, crc); if (fwrite(buf, 1, i, dest) != i) die("Writing setup failed"); /* Copy the kernel code */ crc = partial_crc32(kernel, sz, crc); if (fwrite(kernel, 1, sz, dest) != sz) die("Writing kernel failed"); /* Add padding leaving 4 bytes for the checksum */ while (sz++ < (sys_size*16) - 4) { crc = partial_crc32_one('\0', crc); if (fwrite("\0", 1, 1, dest) != 1) die("Writing padding failed"); } /* Write the CRC */ printf("CRC %x\n", crc); put_unaligned_le32(crc, buf); if (fwrite(buf, 1, 4, dest) != 4) die("Writing CRC failed"); /* Catch any delayed write failures */ if (fclose(dest)) die("Writing image failed"); close(fd); /* Everything is OK */ return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Jordan Justen20433.77%14.55%
H. Peter Anvin10216.89%418.18%
Ian Campbell9315.40%14.55%
Linus Torvalds (pre-git)9215.23%940.91%
Kees Cook518.44%14.55%
Michael Brown254.14%14.55%
Matt Fleming233.81%418.18%
David Woodhouse142.32%14.55%
Total604100.00%22100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Ian Campbell68132.23%13.12%
Jordan Justen45621.58%13.12%
Linus Torvalds (pre-git)23210.98%1546.88%
Matt Fleming2099.89%618.75%
David Woodhouse1818.57%13.12%
Michael Brown1567.38%13.12%
H. Peter Anvin1396.58%412.50%
Kees Cook532.51%13.12%
Jiri Slaby50.24%13.12%
Greg Kroah-Hartman10.05%13.12%
Total2113100.00%32100.00%
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