1 /* 2 * linux/arch/i386/kernel/head32.c -- prepare to run common code 3 * 4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE 5 * Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com> 6 */ 7 8 #include <linux/init.h> 9 #include <linux/start_kernel.h> 10 11 #include <asm/setup.h> 12 #include <asm/sections.h> 13 #include <asm/e820.h> 14 #include <asm/bios_ebda.h> 15 16 #define BIOS_LOWMEM_KILOBYTES 0x413 17 18 /* 19 * The BIOS places the EBDA/XBDA at the top of conventional 20 * memory, and usually decreases the reported amount of 21 * conventional memory (int 0x12) too. This also contains a 22 * workaround for Dell systems that neglect to reserve EBDA. 23 * The same workaround also avoids a problem with the AMD768MPX 24 * chipset: reserve a page before VGA to prevent PCI prefetch 25 * into it (errata #56). Usually the page is reserved anyways, 26 * unless you have no PS/2 mouse plugged in. 27 */ 28 static void __init reserve_ebda_region(void) 29 { 30 unsigned int lowmem, ebda_addr; 31 32 /* To determine the position of the EBDA and the */ 33 /* end of conventional memory, we need to look at */ 34 /* the BIOS data area. In a paravirtual environment */ 35 /* that area is absent. We'll just have to assume */ 36 /* that the paravirt case can handle memory setup */ 37 /* correctly, without our help. */ 38 if (paravirt_enabled()) 39 return; 40 41 /* end of low (conventional) memory */ 42 lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); 43 lowmem <<= 10; 44 45 /* start of EBDA area */ 46 ebda_addr = get_bios_ebda(); 47 48 /* Fixup: bios puts an EBDA in the top 64K segment */ 49 /* of conventional memory, but does not adjust lowmem. */ 50 if ((lowmem - ebda_addr) <= 0x10000) 51 lowmem = ebda_addr; 52 53 /* Fixup: bios does not report an EBDA at all. */ 54 /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */ 55 if ((ebda_addr == 0) && (lowmem >= 0x9f000)) 56 lowmem = 0x9f000; 57 58 /* Paranoia: should never happen, but... */ 59 if ((lowmem == 0) || (lowmem >= 0x100000)) 60 lowmem = 0x9f000; 61 62 /* reserve all memory between lowmem and the 1MB mark */ 63 reserve_early(lowmem, 0x100000, "BIOS reserved"); 64 } 65 66 void __init i386_start_kernel(void) 67 { 68 reserve_early(__pa_symbol(&_text), __pa_symbol(&_end), "TEXT DATA BSS"); 69 70 #ifdef CONFIG_BLK_DEV_INITRD 71 /* Reserve INITRD */ 72 if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) { 73 u64 ramdisk_image = boot_params.hdr.ramdisk_image; 74 u64 ramdisk_size = boot_params.hdr.ramdisk_size; 75 u64 ramdisk_end = ramdisk_image + ramdisk_size; 76 reserve_early(ramdisk_image, ramdisk_end, "RAMDISK"); 77 } 78 #endif 79 reserve_early(init_pg_tables_start, init_pg_tables_end, 80 "INIT_PG_TABLE"); 81 82 reserve_ebda_region(); 83 84 /* 85 * At this point everything still needed from the boot loader 86 * or BIOS or kernel text should be early reserved or marked not 87 * RAM in e820. All other memory is free game. 88 */ 89 90 start_kernel(); 91 } 92