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x86/boot/Documentation: Fix whitespace noise in boot.rst

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There's a lot of unnecessary whitespace damage in this
file: space before tabs, etc., that has no formatting
or readability effect or advantages.

Fix them.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/176535283007.498.16442167388418039352.tip-bot2@tip-bot2
This commit is contained in:
Ingo Molnar 2025-12-10 08:36:18 +01:00
parent c8161e5304
commit ac87efcf9e
1 changed files with 94 additions and 94 deletions
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188
Documentation/arch/x86/boot.rst
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@ -95,26 +95,26 @@ Memory Layout
The traditional memory map for the kernel loader, used for Image or The traditional memory map for the kernel loader, used for Image or
zImage kernels, typically looks like:: zImage kernels, typically looks like::
| | | |
0A0000 +------------------------+ 0A0000 +------------------------+
| Reserved for BIOS | Do not use. Reserved for BIOS EBDA. | Reserved for BIOS | Do not use. Reserved for BIOS EBDA.
09A000 +------------------------+ 09A000 +------------------------+
| Command line | | Command line |
| Stack/heap | For use by the kernel real-mode code. | Stack/heap | For use by the kernel real-mode code.
098000 +------------------------+ 098000 +------------------------+
| Kernel setup | The kernel real-mode code. | Kernel setup | The kernel real-mode code.
090200 +------------------------+ 090200 +------------------------+
| Kernel boot sector | The kernel legacy boot sector. | Kernel boot sector | The kernel legacy boot sector.
090000 +------------------------+ 090000 +------------------------+
| Protected-mode kernel | The bulk of the kernel image. | Protected-mode kernel | The bulk of the kernel image.
010000 +------------------------+ 010000 +------------------------+
| Boot loader | <- Boot sector entry point 0000:7C00 | Boot loader | <- Boot sector entry point 0000:7C00
001000 +------------------------+ 001000 +------------------------+
| Reserved for MBR/BIOS | | Reserved for MBR/BIOS |
000800 +------------------------+ 000800 +------------------------+
| Typically used by MBR | | Typically used by MBR |
000600 +------------------------+ 000600 +------------------------+
| BIOS use only | | BIOS use only |
000000 +------------------------+ 000000 +------------------------+
When using bzImage, the protected-mode kernel was relocated to When using bzImage, the protected-mode kernel was relocated to
@ -142,27 +142,27 @@ above the 0x9A000 point; too many BIOSes will break above that point.
For a modern bzImage kernel with boot protocol version >= 2.02, a For a modern bzImage kernel with boot protocol version >= 2.02, a
memory layout like the following is suggested:: memory layout like the following is suggested::
~ ~ ~ ~
| Protected-mode kernel | | Protected-mode kernel |
100000 +------------------------+ 100000 +------------------------+
| I/O memory hole | | I/O memory hole |
0A0000 +------------------------+ 0A0000 +------------------------+
| Reserved for BIOS | Leave as much as possible unused | Reserved for BIOS | Leave as much as possible unused
~ ~ ~ ~
| Command line | (Can also be below the X+10000 mark) | Command line | (Can also be below the X+10000 mark)
X+10000 +------------------------+ X+10000 +------------------------+
| Stack/heap | For use by the kernel real-mode code. | Stack/heap | For use by the kernel real-mode code.
X+08000 +------------------------+ X+08000 +------------------------+
| Kernel setup | The kernel real-mode code. | Kernel setup | The kernel real-mode code.
| Kernel boot sector | The kernel legacy boot sector. | Kernel boot sector | The kernel legacy boot sector.
X +------------------------+ X +------------------------+
| Boot loader | <- Boot sector entry point 0000:7C00 | Boot loader | <- Boot sector entry point 0000:7C00
001000 +------------------------+ 001000 +------------------------+
| Reserved for MBR/BIOS | | Reserved for MBR/BIOS |
000800 +------------------------+ 000800 +------------------------+
| Typically used by MBR | | Typically used by MBR |
000600 +------------------------+ 000600 +------------------------+
| BIOS use only | | BIOS use only |
000000 +------------------------+ 000000 +------------------------+
... where the address X is as low as the design of the boot loader permits. ... where the address X is as low as the design of the boot loader permits.
@ -809,12 +809,12 @@ Protocol: 2.09+
as follow:: as follow::
struct setup_data { struct setup_data {
__u64 next; __u64 next;
__u32 type; __u32 type;
__u32 len; __u32 len;
__u8 data[]; __u8 data[];
} }
Where, the next is a 64-bit physical pointer to the next node of Where, the next is a 64-bit physical pointer to the next node of
linked list, the next field of the last node is 0; the type is used linked list, the next field of the last node is 0; the type is used
to identify the contents of data; the len is the length of data to identify the contents of data; the len is the length of data
@ -835,10 +835,10 @@ Protocol: 2.09+
protocol 2.15:: protocol 2.15::
struct setup_indirect { struct setup_indirect {
__u32 type; __u32 type;
__u32 reserved; /* Reserved, must be set to zero. */ __u32 reserved; /* Reserved, must be set to zero. */
__u64 len; __u64 len;
__u64 addr; __u64 addr;
}; };
The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be
@ -850,15 +850,15 @@ Protocol: 2.09+
In this case setup_data and setup_indirect will look like this:: In this case setup_data and setup_indirect will look like this::
struct setup_data { struct setup_data {
.next = 0, /* or <addr_of_next_setup_data_struct> */ .next = 0, /* or <addr_of_next_setup_data_struct> */
.type = SETUP_INDIRECT, .type = SETUP_INDIRECT,
.len = sizeof(setup_indirect), .len = sizeof(setup_indirect),
.data[sizeof(setup_indirect)] = (struct setup_indirect) { .data[sizeof(setup_indirect)] = (struct setup_indirect) {
.type = SETUP_INDIRECT | SETUP_E820_EXT, .type = SETUP_INDIRECT | SETUP_E820_EXT,
.reserved = 0, .reserved = 0,
.len = <len_of_SETUP_E820_EXT_data>, .len = <len_of_SETUP_E820_EXT_data>,
.addr = <addr_of_SETUP_E820_EXT_data>, .addr = <addr_of_SETUP_E820_EXT_data>,
}, },
} }
.. note:: .. note::
@ -897,11 +897,11 @@ Offset/size: 0x260/4
The kernel runtime start address is determined by the following algorithm:: The kernel runtime start address is determined by the following algorithm::
if (relocatable_kernel) { if (relocatable_kernel) {
if (load_address < pref_address) if (load_address < pref_address)
load_address = pref_address; load_address = pref_address;
runtime_start = align_up(load_address, kernel_alignment); runtime_start = align_up(load_address, kernel_alignment);
} else { } else {
runtime_start = pref_address; runtime_start = pref_address;
} }
Hence the necessary memory window location and size can be estimated by Hence the necessary memory window location and size can be estimated by
@ -975,22 +975,22 @@ after kernel_info_var_len_data label. Each chunk of variable size data has to
be prefixed with header/magic and its size, e.g.:: be prefixed with header/magic and its size, e.g.::
kernel_info: kernel_info:
.ascii "LToP" /* Header, Linux top (structure). */ .ascii "LToP" /* Header, Linux top (structure). */
.long kernel_info_var_len_data - kernel_info .long kernel_info_var_len_data - kernel_info
.long kernel_info_end - kernel_info .long kernel_info_end - kernel_info
.long 0x01234567 /* Some fixed size data for the bootloaders. */ .long 0x01234567 /* Some fixed size data for the bootloaders. */
kernel_info_var_len_data: kernel_info_var_len_data:
example_struct: /* Some variable size data for the bootloaders. */ example_struct: /* Some variable size data for the bootloaders. */
.ascii "0123" /* Header/Magic. */ .ascii "0123" /* Header/Magic. */
.long example_struct_end - example_struct .long example_struct_end - example_struct
.ascii "Struct" .ascii "Struct"
.long 0x89012345 .long 0x89012345
example_struct_end: example_struct_end:
example_strings: /* Some variable size data for the bootloaders. */ example_strings: /* Some variable size data for the bootloaders. */
.ascii "ABCD" /* Header/Magic. */ .ascii "ABCD" /* Header/Magic. */
.long example_strings_end - example_strings .long example_strings_end - example_strings
.asciz "String_0" .asciz "String_0"
.asciz "String_1" .asciz "String_1"
example_strings_end: example_strings_end:
kernel_info_end: kernel_info_end:
@ -1132,53 +1132,53 @@ Such a boot loader should enter the following fields in the header::
unsigned long base_ptr; /* base address for real-mode segment */ unsigned long base_ptr; /* base address for real-mode segment */
if (setup_sects == 0) if (setup_sects == 0)
setup_sects = 4; setup_sects = 4;
if (protocol >= 0x0200) { if (protocol >= 0x0200) {
type_of_loader = <type code>; type_of_loader = <type code>;
if (loading_initrd) { if (loading_initrd) {
ramdisk_image = <initrd_address>; ramdisk_image = <initrd_address>;
ramdisk_size = <initrd_size>; ramdisk_size = <initrd_size>;
} }
if (protocol >= 0x0202 && loadflags & 0x01) if (protocol >= 0x0202 && loadflags & 0x01)
heap_end = 0xe000; heap_end = 0xe000;
else else
heap_end = 0x9800; heap_end = 0x9800;
if (protocol >= 0x0201) { if (protocol >= 0x0201) {
heap_end_ptr = heap_end - 0x200; heap_end_ptr = heap_end - 0x200;
loadflags |= 0x80; /* CAN_USE_HEAP */ loadflags |= 0x80; /* CAN_USE_HEAP */
} }
if (protocol >= 0x0202) { if (protocol >= 0x0202) {
cmd_line_ptr = base_ptr + heap_end; cmd_line_ptr = base_ptr + heap_end;
strcpy(cmd_line_ptr, cmdline); strcpy(cmd_line_ptr, cmdline);
} else { } else {
cmd_line_magic = 0xA33F; cmd_line_magic = 0xA33F;
cmd_line_offset = heap_end; cmd_line_offset = heap_end;
setup_move_size = heap_end + strlen(cmdline) + 1; setup_move_size = heap_end + strlen(cmdline) + 1;
strcpy(base_ptr + cmd_line_offset, cmdline); strcpy(base_ptr + cmd_line_offset, cmdline);
} }
} else { } else {
/* Very old kernel */ /* Very old kernel */
heap_end = 0x9800; heap_end = 0x9800;
cmd_line_magic = 0xA33F; cmd_line_magic = 0xA33F;
cmd_line_offset = heap_end; cmd_line_offset = heap_end;
/* A very old kernel MUST have its real-mode code loaded at 0x90000 */ /* A very old kernel MUST have its real-mode code loaded at 0x90000 */
if (base_ptr != 0x90000) { if (base_ptr != 0x90000) {
/* Copy the real-mode kernel */ /* Copy the real-mode kernel */
memcpy(0x90000, base_ptr, (setup_sects + 1) * 512); memcpy(0x90000, base_ptr, (setup_sects + 1) * 512);
base_ptr = 0x90000; /* Relocated */ base_ptr = 0x90000; /* Relocated */
} }
strcpy(0x90000 + cmd_line_offset, cmdline); strcpy(0x90000 + cmd_line_offset, cmdline);
/* It is recommended to clear memory up to the 32K mark */ /* It is recommended to clear memory up to the 32K mark */
memset(0x90000 + (setup_sects + 1) * 512, 0, (64 - (setup_sects + 1)) * 512); memset(0x90000 + (setup_sects + 1) * 512, 0, (64 - (setup_sects + 1)) * 512);
} }