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Subject[PATCH 2.5.12] x86 Boot enhancements, boot params 1/11
From
Date
This is the first in a set of 11 patches that enhance the x86 boot
process.

This takes work that I am using everyday and makes a good version
of it that can be included in the kernel.

The major themes are:
- cleanups
- setup.c splitting to handle multiple BIOS flavors.
- Needed to handle LinuxBIOS.
- a 32bit entry point.
- Needed if you don't have a traditional x86 BIOS
- Needed for reliable linux booting linux patches until
the kernel can be fixed. On some systems running linux trashes
he BIOS.
- bean counting of the bootimage.
- Needed for computing the lowest possible ramdisk address about
2.6M with my test kernels.
- Useful for knowing what is actually happening in the boot
process.

If you'd like I'll rip out support for zImages.

The last time I posted this code I heard no criticism of it.
Since last time I posted this code I have made 2 functional changes.
- make clean now deletes the bzElf images
- The linker script now reserves room for the bootmem bitmap,
and with that information I have enough information to load
the ramdisk immediately after the kernel in ram.


#1 boot.boot_params
============================================================
- Introduce asm-i386/boot_param.h and struct boot_params
- Implement struct boot_params in misc.c & setup.c
This removes a lot of magic macros and by keeping all of the
boot parameters in a structure it becomes much easier to track
which boot_paramters we have and where they live. Additionally
this keeps the names more uniform making grepping easier.


#2 boot.vmlinuxlds
============================================================
- i386/Makefile remove bogus linker command line of -e stext
- Fix vmlinux.lds so vmlinux knows it loads at 0x100000 (1MB)
- Fix vmlinux.lds so we correctly use startup_32 for our entry point
- Fix vmlinux.lds so we reserve the bootmem bitmap at the end
of the bss segment.
- Make startup_32 global
#3 boot.spring-cleaning
============================================================
Some pieces of code only make sense if we are a bzImage or
a zImage. Since size is relatively important use conditional
compilation to select between the two.
Plus this clearly marks dead code that we can kill we we drop
support for the zImage format.


#4 boot.syntax
============================================================
All changes are syntactic the generated code is not affected.
- e820.h Add define E820ENTRY_SIZE

- boot.h Add defines for address space divisions.

- Add define KERNEL_START in setup.S so if I need this
value more than once it is easy to get at.

#5 boot.heap
============================================================
Modify video.S so that mode_list is also allocated from
the boot time heap. This probably saves a little memory,
and makes a compiled in command line a sane thing to implement.
- Made certain we don't overwrite code with the E820_MAP
Previously we actually reserved to much memory.

- Changed the lables around the setup.S to _setup && _esetup

The Effective the bootsector size is reduced by 200 bytes.

#6 boot.clean_32bit_entries
============================================================
In general allow any kernel entry point to work given any set of
initial register values, while saving the original registers
values so the C code can do something with it if we desire.
- trampoline.S fix comments, and enter the kernel at
secondary_startup_32 instead of startup_32
- trampoline.S fix gdt_48 to have the correct gdt limit
- Save all of the registers we get from any 32bit entry point,
and don't assume they have any particular value.
- head.S split up startup_32
- secondary_startup_32 handles the SMP case
- move finding the command line to startup.c
- Don't copy the kernel parameters to the initial_zero_page,
instead just pass setup.c where they are located.
- Seperate the segments used by setup.S from the rest of the kernel.
This way bootloader can continue to make assumptions about
which segments setup.S uses while the rest of the kernel
can do whatever is convinient.
- Move boot specific defines into boot.h

#7 boot.footprint
============================================================
Solve the space/reliability tradeoff misc.c asks bootloaders
to make, with belt and suspenders.
- modify misc.c to relocate the real mode code to maximize low
memory usage.
- modify misc.c to do inplace decompression
- modify setup.S to query int12 to get the low memory size
- Introduce STAY_PUT flag for bootloaders that don't pass a
command_line but still don't need the bootsector to relocate
itself.

The kernel now uses approximately 78KB of memory below 1MB and 8 bytes
more than the decompressesed kernel above 1MB. And if required
everything except the 5KB of real mode code can go above 1MB.

The 78KB below 1MB is 5KB real mode code 10KB decompressor code 61KB bss.

The change is especially nice because now in my worst case of only
using 5KB real mode data, I do better than the best case with previous
kernels (assuming it isn't a zImage). With the the bootmem bitmap
reserved in vmlinux.lds I can put initrds down at 2.6MB and not have
to worry about them getting stomped :)

#8 boot.build
============================================================
Rework the actual build/link step for kernel images.
- remove the need for objcopy
- Kill the ROOT_DEV Makefile variable, the implementation
was only half correct and there are much better ways
to specify your root device than modifying the kernel Makefile.
- Don't loose information when the executable is built
Except for a few extra fields in setup.S the binary image
is unchanged.

#9 boot.proto
============================================================
Update the boot protocol to include:
- A compiled in command line
- A 32bit entry point
- File and memory usage information enabling a 1 to 1
conversion between the bzImage format and the static ELF
executable file format.
- In setup.c split the parameters between those that
are compiled in or specified by the bootloader and
those that are queried from the BIOS.

#10 boot.linuxbios
============================================================
Support for reading information from the linuxbios table.
For now I just get the memory size more to come as things
evolve.
#11 boot.elf
============================================================
Add support for generating an ELF executable kernel. External
tools are only needed now to manipulate the command line,
and to add a ramdisk. For netbooting this is very handy.
To revert to a bzImgae you simply strip off the the ELF header.
This should keep the kinds of kernel images floating around low.


diff -uNr linux-2.5.12/Documentation/i386/zero-page.txt linux-2.5.12.boot.boot_params/Documentation/i386/zero-page.txt
--- linux-2.5.12/Documentation/i386/zero-page.txt Mon Aug 30 11:47:02 1999
+++ linux-2.5.12.boot.boot_params/Documentation/i386/zero-page.txt Wed May 1 09:38:29 2002
@@ -9,7 +9,11 @@
arch/i386/boot/video.S
arch/i386/kernel/head.S
arch/i386/kernel/setup.c
-
+
+See include/asm-i386/boot_param.h a structure is kept there with
+uptodate information. The kernel no longer copies this information
+into the empty zero page, but instead uses it directly.
+

Offset Type Description
------ ---- -----------
@@ -65,7 +69,7 @@
0x21c unsigned long INITRD_SIZE, size in bytes of ramdisk image
0x220 4 bytes (setup.S)
0x224 unsigned short setup.S heap end pointer
-0x2d0 - 0x600 E820MAP
+0x2d0 - 0x550 E820MAP

0x800 string, 2K max COMMAND_LINE, the kernel commandline as
copied using CL_OFFSET.
diff -uNr linux-2.5.12/arch/i386/boot/compressed/misc.c linux-2.5.12.boot.boot_params/arch/i386/boot/compressed/misc.c
--- linux-2.5.12/arch/i386/boot/compressed/misc.c Mon Nov 12 10:59:43 2001
+++ linux-2.5.12.boot.boot_params/arch/i386/boot/compressed/misc.c Wed May 1 09:38:29 2002
@@ -13,6 +13,9 @@
#include <linux/vmalloc.h>
#include <linux/tty.h>
#include <asm/io.h>
+#include <linux/apm_bios.h>
+#include <asm/e820.h>
+#include <asm/boot_param.h>

/*
* gzip declarations
@@ -84,13 +87,9 @@
/*
* This is set up by the setup-routine at boot-time
*/
-static unsigned char *real_mode; /* Pointer to real-mode data */
-
-#define EXT_MEM_K (*(unsigned short *)(real_mode + 0x2))
-#ifndef STANDARD_MEMORY_BIOS_CALL
-#define ALT_MEM_K (*(unsigned long *)(real_mode + 0x1e0))
-#endif
-#define SCREEN_INFO (*(struct screen_info *)(real_mode+0))
+static struct boot_params *real_mode; /* Pointer to real-mode data */
+/* Amount of memory in kilobytes, if it isn't set assume enough */
+static unsigned long mem_k = 0xFFFFFFFF;

extern char input_data[];
extern int input_len;
@@ -176,8 +175,8 @@
int x,y,pos;
char c;

- x = SCREEN_INFO.orig_x;
- y = SCREEN_INFO.orig_y;
+ x = real_mode->screen.info.orig_x;
+ y = real_mode->screen.info.orig_y;

while ( ( c = *s++ ) != '\0' ) {
if ( c == '\n' ) {
@@ -198,8 +197,8 @@
}
}

- SCREEN_INFO.orig_x = x;
- SCREEN_INFO.orig_y = y;
+ real_mode->screen.info.orig_x = x;
+ real_mode->screen.info.orig_y = y;

pos = (x + cols * y) * 2; /* Update cursor position */
outb_p(14, vidport);
@@ -208,6 +207,20 @@
outb_p(0xff & (pos >> 1), vidport+1);
}

+static void vid_puts_init(void)
+{
+ if (real_mode->screen.info.orig_video_mode == 7) {
+ vidmem = (char *) 0xb0000;
+ vidport = 0x3b4;
+ } else {
+ vidmem = (char *) 0xb8000;
+ vidport = 0x3d4;
+ }
+
+ lines = real_mode->screen.info.orig_video_lines;
+ cols = real_mode->screen.info.orig_video_cols;
+}
+
static void* memset(void* s, int c, size_t n)
{
int i;
@@ -307,11 +320,7 @@

static void setup_normal_output_buffer(void)
{
-#ifdef STANDARD_MEMORY_BIOS_CALL
- if (EXT_MEM_K < 1024) error("Less than 2MB of memory.\n");
-#else
- if ((ALT_MEM_K > EXT_MEM_K ? ALT_MEM_K : EXT_MEM_K) < 1024) error("Less than 2MB of memory.\n");
-#endif
+ if (mem_k < 2048) error("Less than 2MB of memory.\n");
output_data = (char *)0x100000; /* Points to 1M */
free_mem_end_ptr = (long)real_mode;
}
@@ -324,11 +333,7 @@
static void setup_output_buffer_if_we_run_high(struct moveparams *mv)
{
high_buffer_start = (uch *)(((ulg)&end) + HEAP_SIZE);
-#ifdef STANDARD_MEMORY_BIOS_CALL
- if (EXT_MEM_K < (3*1024)) error("Less than 4MB of memory.\n");
-#else
- if ((ALT_MEM_K > EXT_MEM_K ? ALT_MEM_K : EXT_MEM_K) < (3*1024)) error("Less than 4MB of memory.\n");
-#endif
+ if (mem_k < (4*1024)) error("Less than 4MB of memory.\n");
mv->low_buffer_start = output_data = (char *)LOW_BUFFER_START;
low_buffer_end = ((unsigned int)real_mode > LOW_BUFFER_MAX
? LOW_BUFFER_MAX : (unsigned int)real_mode) & ~0xfff;
@@ -360,16 +365,15 @@
{
real_mode = rmode;

- if (SCREEN_INFO.orig_video_mode == 7) {
- vidmem = (char *) 0xb0000;
- vidport = 0x3b4;
- } else {
- vidmem = (char *) 0xb8000;
- vidport = 0x3d4;
- }
+ vid_puts_init();

- lines = SCREEN_INFO.orig_video_lines;
- cols = SCREEN_INFO.orig_video_cols;
+ mem_k = real_mode->screen.overlap.ext_mem_k;
+#ifndef STANDARD_MEMORY_BIOS_CALL
+ if (real_mode->alt_mem_k > mem_k) {
+ mem_k = real_mode->alt_mem_k;
+ }
+#endif
+ mem_k += 1024;

if (free_mem_ptr < 0x100000) setup_normal_output_buffer();
else setup_output_buffer_if_we_run_high(mv);
diff -uNr linux-2.5.12/arch/i386/kernel/setup.c linux-2.5.12.boot.boot_params/arch/i386/kernel/setup.c
--- linux-2.5.12/arch/i386/kernel/setup.c Mon Apr 29 00:17:11 2002
+++ linux-2.5.12.boot.boot_params/arch/i386/kernel/setup.c Wed May 1 09:38:30 2002
@@ -116,6 +116,7 @@
#include <asm/dma.h>
#include <asm/mpspec.h>
#include <asm/mmu_context.h>
+#include <asm/boot_param.h>

/*
* Machine setup..
@@ -146,14 +147,9 @@
/*
* Setup options
*/
-struct drive_info_struct { char dummy[32]; } drive_info;
+struct drive_info_struct drive_info;
struct screen_info screen_info;
struct apm_info apm_info;
-struct sys_desc_table_struct {
- unsigned short length;
- unsigned char table[0];
-};
-
struct e820map e820;

unsigned char aux_device_present;
@@ -168,34 +164,9 @@
static int disable_x86_serial_nr __initdata = 1;
static int disable_x86_fxsr __initdata = 0;

-/*
- * This is set up by the setup-routine at boot-time
- */
-#define PARAM ((unsigned char *)empty_zero_page)
-#define SCREEN_INFO (*(struct screen_info *) (PARAM+0))
-#define EXT_MEM_K (*(unsigned short *) (PARAM+2))
-#define ALT_MEM_K (*(unsigned long *) (PARAM+0x1e0))
-#define E820_MAP_NR (*(char*) (PARAM+E820NR))
-#define E820_MAP ((struct e820entry *) (PARAM+E820MAP))
-#define APM_BIOS_INFO (*(struct apm_bios_info *) (PARAM+0x40))
-#define DRIVE_INFO (*(struct drive_info_struct *) (PARAM+0x80))
-#define SYS_DESC_TABLE (*(struct sys_desc_table_struct*)(PARAM+0xa0))
-#define MOUNT_ROOT_RDONLY (*(unsigned short *) (PARAM+0x1F2))
-#define RAMDISK_FLAGS (*(unsigned short *) (PARAM+0x1F8))
-#define ORIG_ROOT_DEV (*(unsigned short *) (PARAM+0x1FC))
-#define AUX_DEVICE_INFO (*(unsigned char *) (PARAM+0x1FF))
-#define LOADER_TYPE (*(unsigned char *) (PARAM+0x210))
-#define KERNEL_START (*(unsigned long *) (PARAM+0x214))
-#define INITRD_START (*(unsigned long *) (PARAM+0x218))
-#define INITRD_SIZE (*(unsigned long *) (PARAM+0x21c))
-#define COMMAND_LINE ((char *) (PARAM+2048))
+#define COMMAND_LINE (((char *)empty_zero_page)+2048)
#define COMMAND_LINE_SIZE 256

-#define RAMDISK_IMAGE_START_MASK 0x07FF
-#define RAMDISK_PROMPT_FLAG 0x8000
-#define RAMDISK_LOAD_FLAG 0x4000
-
-
static char command_line[COMMAND_LINE_SIZE];
char saved_command_line[COMMAND_LINE_SIZE];

@@ -557,7 +528,7 @@
*/
#define LOWMEMSIZE() (0x9f000)

-static void __init setup_memory_region(void)
+static void __init setup_memory_region(struct boot_params *params)
{
char *who = "BIOS-e820";

@@ -567,16 +538,16 @@
* Otherwise fake a memory map; one section from 0k->640k,
* the next section from 1mb->appropriate_mem_k
*/
- sanitize_e820_map(E820_MAP, &E820_MAP_NR);
- if (copy_e820_map(E820_MAP, E820_MAP_NR) < 0) {
+ sanitize_e820_map(params->e820_map, &params->e820_map_nr);
+ if (copy_e820_map(params->e820_map, params->e820_map_nr) < 0) {
unsigned long mem_size;

/* compare results from other methods and take the greater */
- if (ALT_MEM_K < EXT_MEM_K) {
- mem_size = EXT_MEM_K;
+ if (params->alt_mem_k < params->screen.overlap.ext_mem_k) {
+ mem_size = params->screen.overlap.ext_mem_k;
who = "BIOS-88";
} else {
- mem_size = ALT_MEM_K;
+ mem_size = params->alt_mem_k;
who = "BIOS-e801";
}

@@ -672,31 +643,36 @@
unsigned long bootmap_size, low_mem_size;
unsigned long start_pfn, max_low_pfn;
int i;
+ struct boot_params *params;

#ifdef CONFIG_VISWS
visws_get_board_type_and_rev();
#endif

- ROOT_DEV = to_kdev_t(ORIG_ROOT_DEV);
- drive_info = DRIVE_INFO;
- screen_info = SCREEN_INFO;
- apm_info.bios = APM_BIOS_INFO;
- if( SYS_DESC_TABLE.length != 0 ) {
- MCA_bus = SYS_DESC_TABLE.table[3] &0x2;
- machine_id = SYS_DESC_TABLE.table[0];
- machine_submodel_id = SYS_DESC_TABLE.table[1];
- BIOS_revision = SYS_DESC_TABLE.table[2];
+ /*
+ * This is set up by the setup-routine at boot-time
+ */
+ params = (struct boot_params *)empty_zero_page;
+ ROOT_DEV = to_kdev_t(params->root_dev);
+ drive_info = params->drive_info;
+ screen_info = params->screen.info;
+ apm_info.bios = params->apm_bios_info;
+ if( params->sys_desc_table.length != 0 ) {
+ MCA_bus = params->sys_desc_table.table[3] &0x2;
+ machine_id = params->sys_desc_table.table[0];
+ machine_submodel_id = params->sys_desc_table.table[1];
+ BIOS_revision = params->sys_desc_table.table[2];
}
- aux_device_present = AUX_DEVICE_INFO;
+ aux_device_present = params->aux_device_info;

#ifdef CONFIG_BLK_DEV_RAM
- rd_image_start = RAMDISK_FLAGS & RAMDISK_IMAGE_START_MASK;
- rd_prompt = ((RAMDISK_FLAGS & RAMDISK_PROMPT_FLAG) != 0);
- rd_doload = ((RAMDISK_FLAGS & RAMDISK_LOAD_FLAG) != 0);
+ rd_image_start = params->ramdisk_flags & RAMDISK_IMAGE_START_MASK;
+ rd_prompt = ((params->ramdisk_flags & RAMDISK_PROMPT_FLAG) != 0);
+ rd_doload = ((params->ramdisk_flags & RAMDISK_LOAD_FLAG) != 0);
#endif
- setup_memory_region();
+ setup_memory_region(params);

- if (!MOUNT_ROOT_RDONLY)
+ if (!params->mount_root_rdonly)
root_mountflags &= ~MS_RDONLY;
init_mm.start_code = (unsigned long) &_text;
init_mm.end_code = (unsigned long) &_etext;
@@ -881,18 +857,21 @@
find_smp_config();
#endif
#ifdef CONFIG_BLK_DEV_INITRD
- if (LOADER_TYPE && INITRD_START) {
- if (INITRD_START + INITRD_SIZE <= (max_low_pfn << PAGE_SHIFT)) {
- reserve_bootmem(INITRD_START, INITRD_SIZE);
- initrd_start =
- INITRD_START ? INITRD_START + PAGE_OFFSET : 0;
- initrd_end = initrd_start+INITRD_SIZE;
+ if (params->type_of_loader && params->initrd_start) {
+ initrd_start = params->initrd_start ?
+ params->initrd_start + PAGE_OFFSET : 0;
+ initrd_end = initrd_start + params->initrd_size;
+ }
+ if (initrd_start) {
+ if ((initrd_end - PAGE_OFFSET) <= (max_low_pfn << PAGE_SHIFT)) {
+ reserve_bootmem(initrd_start - PAGE_OFFSET,
+ initrd_end - initrd_start);
}
else {
printk(KERN_ERR "initrd extends beyond end of memory "
- "(0x%08lx > 0x%08lx)\ndisabling initrd\n",
- INITRD_START + INITRD_SIZE,
- max_low_pfn << PAGE_SHIFT);
+ "(0x%08lx > 0x%08lx)\ndisabling initrd\n",
+ initrd_end - PAGE_OFFSET,
+ max_low_pfn << PAGE_SHIFT);
initrd_start = 0;
}
}
diff -uNr linux-2.5.12/include/asm-i386/boot_param.h linux-2.5.12.boot.boot_params/include/asm-i386/boot_param.h
--- linux-2.5.12/include/asm-i386/boot_param.h Wed Dec 31 17:00:00 1969
+++ linux-2.5.12.boot.boot_params/include/asm-i386/boot_param.h Wed May 1 09:38:30 2002
@@ -0,0 +1,79 @@
+#ifndef __I386_BOOT_PARAM_H
+#define __I386_BOOT_PARAM_H
+
+struct drive_info_struct { __u8 dummy[32]; };
+struct sys_desc_table {
+ __u16 length;
+ __u8 table[318];
+};
+struct screen_info_overlap {
+ __u8 reserved1[2]; /* 0x00 */
+ __u16 ext_mem_k; /* 0x02 */
+ __u8 reserved2[0x20 - 0x04]; /* 0x04 */
+ __u16 cl_magic; /* 0x20 */
+#define CL_MAGIC_VALUE 0xA33F
+ __u16 cl_offset; /* 0x22 */
+ __u8 reserved3[0x40 - 0x24]; /* 0x24 */
+};
+
+struct boot_params {
+ union { /* 0x00 */
+ struct screen_info info;
+ struct screen_info_overlap overlap;
+ } screen;
+
+ struct apm_bios_info apm_bios_info; /* 0x40 */
+ __u8 reserved4[0x80 - 0x54]; /* 0x54 */
+ struct drive_info_struct drive_info; /* 0x80 */
+ struct sys_desc_table sys_desc_table; /* 0xa0 */
+ __u32 alt_mem_k; /* 0x1e0 */
+ __u8 reserved5[4]; /* 0x1e4 */
+ __u8 e820_map_nr; /* 0x1e8 */
+ __u8 reserved6[8]; /* 0x1e9 */
+ __u8 setup_sects; /* 0x1f1 */
+ __u16 mount_root_rdonly; /* 0x1f2 */
+ __u16 syssize; /* 0x1f4 */
+ __u16 swapdev; /* 0x1f6 */
+ __u16 ramdisk_flags; /* 0x1f8 */
+#define RAMDISK_IMAGE_START_MASK 0x07FF
+#define RAMDISK_PROMPT_FLAG 0x8000
+#define RAMDISK_LOAD_FLAG 0x4000
+ __u16 vid_mode; /* 0x1fa */
+ __u16 root_dev; /* 0x1fc */
+ __u8 reserved9[1]; /* 0x1fe */
+ __u8 aux_device_info; /* 0x1ff */
+ /* 2.00+ */
+ __u8 jump[2]; /* 0x200 */
+ __u8 header_magic[4]; /* 0x202 */
+ __u16 version; /* 0x206 */
+ __u16 realmode_swtch[2]; /* 0x208 */
+ __u16 start_sys_seg; /* 0x20c */
+ __u16 kernel_version; /* 0x20e */
+ __u8 type_of_loader; /* 0x210 */
+#define LOADER_LILO 0x00
+#define LOADER_LOADLIN 0x10
+#define LOADER_BOOTSECT_LOADER 0x20
+#define LOADER_SYSLINUX 0x30
+#define LOADER_ETHERBOOT 0x40
+#define LOADER_UNKNOWN 0xFF
+ __u8 loadflags; /* 0x211 */
+#define LOADFLAG_LOADED_HIGH 1
+#define LOADFLAG_STAY_PUT 0x40
+#define LOADFLAG_CAN_USE_HEAP 0x80
+ __u16 setup_move_size; /* 0x212 */
+ __u32 code32_start; /* 0x214 */
+ __u32 initrd_start; /* 0x218 */
+ __u32 initrd_size; /* 0x21c */
+ __u8 reserved13[4]; /* 0x220 */
+ /* 2.01+ */
+ __u16 heap_end_ptr; /* 0x224 */
+ __u8 pad1[2]; /* 0x226 */
+ /* 2.02+ */
+ __u32 cmd_line_ptr; /* 0x228 */
+ /* 2.03+ */
+ __u32 ramdisk_max; /* 0x22c */
+ __u8 reserved15[0x2d0 - 0x230]; /* 0x230 */
+ struct e820entry e820_map[E820MAX]; /* 0x2d0 */
+ /* 0x550 */
+} __attribute__((packed));
+#endif /* __I386_BOOT_PARAM_H */
-
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