x86: add extension fields for bootloader type and version
A long ago, in days of yore, it all began with a god named Thor. There were vikings and boats and some plans for a Linux kernel header. Unfortunately, a single 8-bit field was used for bootloader type and version. This has generally worked without *too* much pain, but we're getting close to flat running out of ID fields. Add extension fields for both type and version. The type will be extended if it the old field is 0xE; the version is a simple MSB extension. Keep /proc/sys/kernel/bootloader_type containing (type << 4) + (ver & 0xf) for backwards compatiblity, but also add /proc/sys/kernel/bootloader_version which contains the full version number. [ Impact: new feature to support more bootloaders ] Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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H. Peter Anvin
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fe83fcc0a1
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5031296c57
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@ -50,10 +50,9 @@ Protocol 2.08: (Kernel 2.6.26) Added crc32 checksum and ELF format
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Protocol 2.09: (Kernel 2.6.26) Added a field of 64-bit physical
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pointer to single linked list of struct setup_data.
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Protocol 2.10: (Kernel 2.6.31) A protocol for relaxed alignment
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Protocol 2.10: (Kernel 2.6.31) Added a protocol for relaxed alignment
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beyond the kernel_alignment added, new init_size and
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pref_address fields.
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pref_address fields. Added extended boot loader IDs.
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**** MEMORY LAYOUT
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@ -173,7 +172,8 @@ Offset Proto Name Meaning
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021C/4 2.00+ ramdisk_size initrd size (set by boot loader)
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0220/4 2.00+ bootsect_kludge DO NOT USE - for bootsect.S use only
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0224/2 2.01+ heap_end_ptr Free memory after setup end
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0226/2 N/A pad1 Unused
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0226/1 2.02+(3 ext_loader_ver Extended boot loader version
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0227/1 2.02+(3 ext_loader_type Extended boot loader ID
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0228/4 2.02+ cmd_line_ptr 32-bit pointer to the kernel command line
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022C/4 2.03+ ramdisk_max Highest legal initrd address
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0230/4 2.05+ kernel_alignment Physical addr alignment required for kernel
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@ -197,6 +197,8 @@ Offset Proto Name Meaning
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field are unusable, which means the size of a bzImage kernel
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cannot be determined.
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(3) Ignored, but safe to set, for boot protocols 2.02-2.09.
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If the "HdrS" (0x53726448) magic number is not found at offset 0x202,
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the boot protocol version is "old". Loading an old kernel, the
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following parameters should be assumed:
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@ -350,18 +352,32 @@ Protocol: 2.00+
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0xTV here, where T is an identifier for the boot loader and V is
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a version number. Otherwise, enter 0xFF here.
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For boot loader IDs above T = 0xD, write T = 0xE to this field and
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write the extended ID minus 0x10 to the ext_loader_type field.
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Similarly, the ext_loader_ver field can be used to provide more than
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four bits for the bootloader version.
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For example, for T = 0x15, V = 0x234, write:
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type_of_loader <- 0xE4
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ext_loader_type <- 0x05
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ext_loader_ver <- 0x23
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Assigned boot loader ids:
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0 LILO (0x00 reserved for pre-2.00 bootloader)
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1 Loadlin
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2 bootsect-loader (0x20, all other values reserved)
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3 SYSLINUX
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4 EtherBoot
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3 Syslinux
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4 Etherboot/gPXE
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5 ELILO
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7 GRUB
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8 U-BOOT
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8 U-Boot
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9 Xen
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A Gujin
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B Qemu
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C Arcturus Networks uCbootloader
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E Extended (see ext_loader_type)
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F Special (0xFF = undefined)
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Please contact <hpa@zytor.com> if you need a bootloader ID
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value assigned.
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@ -460,6 +476,35 @@ Protocol: 2.01+
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Set this field to the offset (from the beginning of the real-mode
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code) of the end of the setup stack/heap, minus 0x0200.
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Field name: ext_loader_ver
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Type: write (optional)
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Offset/size: 0x226/1
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Protocol: 2.02+
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This field is used as an extension of the version number in the
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type_of_loader field. The total version number is considered to be
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(type_of_loader & 0x0f) + (ext_loader_ver << 4).
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The use of this field is boot loader specific. If not written, it
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is zero.
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Kernels prior to 2.6.31 did not recognize this field, but it is safe
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to write for protocol version 2.02 or higher.
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Field name: ext_loader_type
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Type: write (obligatory if (type_of_loader & 0xf0) == 0xe0)
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Offset/size: 0x227/1
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Protocol: 2.02+
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This field is used as an extension of the type number in
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type_of_loader field. If the type in type_of_loader is 0xE, then
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the actual type is (ext_loader_type + 0x10).
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This field is ignored if the type in type_of_loader is not 0xE.
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Kernels prior to 2.6.31 did not recognize this field, but it is safe
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to write for protocol version 2.02 or higher.
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Field name: cmd_line_ptr
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Type: write (obligatory)
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Offset/size: 0x228/4
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@ -169,7 +169,11 @@ heap_end_ptr: .word _end+STACK_SIZE-512
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# end of setup code can be used by setup
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# for local heap purposes.
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pad1: .word 0
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ext_loader_ver:
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.byte 0 # Extended boot loader version
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ext_loader_type:
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.byte 0 # Extended boot loader type
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cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
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# If nonzero, a 32-bit pointer
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# to the kernel command line.
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@ -50,7 +50,8 @@ struct setup_header {
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__u32 ramdisk_size;
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__u32 bootsect_kludge;
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__u16 heap_end_ptr;
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__u16 _pad1;
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__u8 ext_loader_ver;
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__u8 ext_loader_type;
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__u32 cmd_line_ptr;
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__u32 initrd_addr_max;
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__u32 kernel_alignment;
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@ -814,6 +814,7 @@ extern unsigned int BIOS_revision;
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/* Boot loader type from the setup header: */
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extern int bootloader_type;
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extern int bootloader_version;
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extern char ignore_fpu_irq;
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@ -214,8 +214,8 @@ unsigned long mmu_cr4_features;
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unsigned long mmu_cr4_features = X86_CR4_PAE;
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#endif
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/* Boot loader ID as an integer, for the benefit of proc_dointvec */
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int bootloader_type;
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/* Boot loader ID and version as integers, for the benefit of proc_dointvec */
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int bootloader_type, bootloader_version;
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/*
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* Setup options
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@ -706,6 +706,12 @@ void __init setup_arch(char **cmdline_p)
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#endif
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saved_video_mode = boot_params.hdr.vid_mode;
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bootloader_type = boot_params.hdr.type_of_loader;
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if ((bootloader_type >> 4) == 0xe) {
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bootloader_type &= 0xf;
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bootloader_type |= (boot_params.hdr.ext_loader_type+0x10) << 4;
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}
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bootloader_version = bootloader_type & 0xf;
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bootloader_version |= boot_params.hdr.ext_loader_ver << 4;
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#ifdef CONFIG_BLK_DEV_RAM
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rd_image_start = boot_params.hdr.ram_size & RAMDISK_IMAGE_START_MASK;
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@ -727,6 +727,14 @@ static struct ctl_table kern_table[] = {
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.mode = 0444,
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.proc_handler = &proc_dointvec,
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},
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "bootloader_version",
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.data = &bootloader_version,
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.maxlen = sizeof (int),
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.mode = 0444,
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.proc_handler = &proc_dointvec,
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},
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "kstack_depth_to_print",
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