I have been working with Linux in areas where the usual booting
process is inadequate, or simply falls short.
I regularly boot in an environment that does not have a 16bit BIOS
so I cannot use the current 16bit entry point. This is environment
is LinuxBIOS but I know of several other embedded platforms have this
property as well.
I routinely use very stupid non-interactive boot loaders where it is
convinient to precompute the command line, and where the ramdisk is
loaded in memory. The kernel does not currently export enough
information about it's boot process to do this properly.
To address these needs I have come up with a series of patches that
moves the x86 boot protocol to version 2.04. This retains backwards
compatibility while introducing enough flexibility to handle the
strange cases cleanly, and enough information to actually describe
what memory the kernel boot process is using.
This first patch introduces a structure of boot parameters placed
in asm-i386/boot_param.h and implemented in misc.c and 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.
Eric
diff -uNr linux-2.5.7/Documentation/i386/zero-page.txt linux-2.5.7.boot2.boot_params/Documentation/i386/zero-page.txt
--- linux-2.5.7/Documentation/i386/zero-page.txt Mon Aug 30 11:47:02 1999
+++ linux-2.5.7.boot2.boot_params/Documentation/i386/zero-page.txt Tue Apr 2 11:41:31 2002
@@ -9,6 +9,8 @@
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.
Offset Type Description
@@ -65,7 +67,7 @@
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-2.5.7/arch/i386/boot/compressed/misc.c linux-2.5.7.boot2.boot_params/arch/i386/boot/compressed/misc.c
--- linux-2.5.7/arch/i386/boot/compressed/misc.c Mon Nov 12 10:59:43 2001
+++ linux-2.5.7.boot2.boot_params/arch/i386/boot/compressed/misc.c Tue Apr 2 11:41:31 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-2.5.7/arch/i386/kernel/setup.c linux-2.5.7.boot2.boot_params/arch/i386/kernel/setup.c
--- linux-2.5.7/arch/i386/kernel/setup.c Wed Mar 20 07:18:31 2002
+++ linux-2.5.7.boot2.boot_params/arch/i386/kernel/setup.c Tue Apr 2 11:41:31 2002
@@ -114,6 +114,7 @@
#include <asm/dma.h>
#include <asm/mpspec.h>
#include <asm/mmu_context.h>
+#include <asm/boot_param.h>
/*
* Machine setup..
@@ -147,14 +148,9 @@
/*
* 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;
@@ -169,34 +165,9 @@
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];
@@ -554,7 +525,7 @@
*/
#define LOWMEMSIZE() (0x9f000)
-static void __init setup_memory_region(void)
+static void __init setup_memory_region(struct boot_params *params)
{
char *who = "BIOS-e820";
@@ -564,16 +535,16 @@
* 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, ¶ms->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";
}
@@ -669,31 +640,36 @@
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;
@@ -878,18 +854,21 @@
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->loader_type && 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-2.5.7/include/asm-i386/boot_param.h linux-2.5.7.boot2.boot_params/include/asm-i386/boot_param.h
--- linux-2.5.7/include/asm-i386/boot_param.h Wed Dec 31 17:00:00 1969
+++ linux-2.5.7.boot2.boot_params/include/asm-i386/boot_param.h Tue Apr 2 11:41:31 2002
@@ -0,0 +1,73 @@
+#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 reserved10[2]; /* 0x200 */
+ __u8 header_magic[4]; /* 0x202 */
+ __u16 protocol_version; /* 0x206 */
+ __u8 reserved11[8]; /* 0x208 */
+ __u8 loader_type; /* 0x210 */
+#define LOADER_TYPE_LOADLIN 1
+#define LOADER_TYPE_BOOTSECT_LOADER 2
+#define LOADER_TYPE_SYSLINUX 3
+#define LOADER_TYPE_ETHERBOOT 4
+#define LOADER_TYPE_UNKNOWN 0xFF
+ __u8 loader_flags; /* 0x211 */
+ __u8 reserved12[2]; /* 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 reserved14[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 */
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/