1700efc1bSEric W. Biederman /* 2700efc1bSEric W. Biederman * linux/arch/i386/kernel/head32.c -- prepare to run common code 3700efc1bSEric W. Biederman * 4700efc1bSEric W. Biederman * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE 5700efc1bSEric W. Biederman * Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com> 6700efc1bSEric W. Biederman */ 7700efc1bSEric W. Biederman 8700efc1bSEric W. Biederman #include <linux/init.h> 9700efc1bSEric W. Biederman #include <linux/start_kernel.h> 10700efc1bSEric W. Biederman 11a4c81cf6SYinghai Lu #include <asm/setup.h> 12a4c81cf6SYinghai Lu #include <asm/sections.h> 13a4c81cf6SYinghai Lu #include <asm/e820.h> 14a4c81cf6SYinghai Lu #include <asm/bios_ebda.h> 15a4c81cf6SYinghai Lu 16a4c81cf6SYinghai Lu #define BIOS_LOWMEM_KILOBYTES 0x413 17a4c81cf6SYinghai Lu 18a4c81cf6SYinghai Lu /* 19a4c81cf6SYinghai Lu * The BIOS places the EBDA/XBDA at the top of conventional 20a4c81cf6SYinghai Lu * memory, and usually decreases the reported amount of 21a4c81cf6SYinghai Lu * conventional memory (int 0x12) too. This also contains a 22a4c81cf6SYinghai Lu * workaround for Dell systems that neglect to reserve EBDA. 23a4c81cf6SYinghai Lu * The same workaround also avoids a problem with the AMD768MPX 24a4c81cf6SYinghai Lu * chipset: reserve a page before VGA to prevent PCI prefetch 25a4c81cf6SYinghai Lu * into it (errata #56). Usually the page is reserved anyways, 26a4c81cf6SYinghai Lu * unless you have no PS/2 mouse plugged in. 27a4c81cf6SYinghai Lu */ 28a4c81cf6SYinghai Lu static void __init reserve_ebda_region(void) 29a4c81cf6SYinghai Lu { 30a4c81cf6SYinghai Lu unsigned int lowmem, ebda_addr; 31a4c81cf6SYinghai Lu 32a4c81cf6SYinghai Lu /* To determine the position of the EBDA and the */ 33a4c81cf6SYinghai Lu /* end of conventional memory, we need to look at */ 34a4c81cf6SYinghai Lu /* the BIOS data area. In a paravirtual environment */ 35a4c81cf6SYinghai Lu /* that area is absent. We'll just have to assume */ 36a4c81cf6SYinghai Lu /* that the paravirt case can handle memory setup */ 37a4c81cf6SYinghai Lu /* correctly, without our help. */ 38a4c81cf6SYinghai Lu if (paravirt_enabled()) 39a4c81cf6SYinghai Lu return; 40a4c81cf6SYinghai Lu 41a4c81cf6SYinghai Lu /* end of low (conventional) memory */ 42a4c81cf6SYinghai Lu lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); 43a4c81cf6SYinghai Lu lowmem <<= 10; 44a4c81cf6SYinghai Lu 45a4c81cf6SYinghai Lu /* start of EBDA area */ 46a4c81cf6SYinghai Lu ebda_addr = get_bios_ebda(); 47a4c81cf6SYinghai Lu 48a4c81cf6SYinghai Lu /* Fixup: bios puts an EBDA in the top 64K segment */ 49a4c81cf6SYinghai Lu /* of conventional memory, but does not adjust lowmem. */ 50a4c81cf6SYinghai Lu if ((lowmem - ebda_addr) <= 0x10000) 51a4c81cf6SYinghai Lu lowmem = ebda_addr; 52a4c81cf6SYinghai Lu 53a4c81cf6SYinghai Lu /* Fixup: bios does not report an EBDA at all. */ 54a4c81cf6SYinghai Lu /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */ 55a4c81cf6SYinghai Lu if ((ebda_addr == 0) && (lowmem >= 0x9f000)) 56a4c81cf6SYinghai Lu lowmem = 0x9f000; 57a4c81cf6SYinghai Lu 58a4c81cf6SYinghai Lu /* Paranoia: should never happen, but... */ 59a4c81cf6SYinghai Lu if ((lowmem == 0) || (lowmem >= 0x100000)) 60a4c81cf6SYinghai Lu lowmem = 0x9f000; 61a4c81cf6SYinghai Lu 62a4c81cf6SYinghai Lu /* reserve all memory between lowmem and the 1MB mark */ 63a4c81cf6SYinghai Lu reserve_early(lowmem, 0x100000, "BIOS reserved"); 64a4c81cf6SYinghai Lu } 65a4c81cf6SYinghai Lu 66700efc1bSEric W. Biederman void __init i386_start_kernel(void) 67700efc1bSEric W. Biederman { 68a4c81cf6SYinghai Lu reserve_early(__pa_symbol(&_text), __pa_symbol(&_end), "TEXT DATA BSS"); 69a4c81cf6SYinghai Lu 70a4c81cf6SYinghai Lu #ifdef CONFIG_BLK_DEV_INITRD 71a4c81cf6SYinghai Lu /* Reserve INITRD */ 72a4c81cf6SYinghai Lu if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) { 73a4c81cf6SYinghai Lu u64 ramdisk_image = boot_params.hdr.ramdisk_image; 74a4c81cf6SYinghai Lu u64 ramdisk_size = boot_params.hdr.ramdisk_size; 75a4c81cf6SYinghai Lu u64 ramdisk_end = ramdisk_image + ramdisk_size; 76a4c81cf6SYinghai Lu reserve_early(ramdisk_image, ramdisk_end, "RAMDISK"); 77a4c81cf6SYinghai Lu } 78a4c81cf6SYinghai Lu #endif 79a4c81cf6SYinghai Lu reserve_early(__pa_symbol(&_end), init_pg_tables_end, "INIT_PG_TABLE"); 80a4c81cf6SYinghai Lu 81a4c81cf6SYinghai Lu reserve_ebda_region(); 82a4c81cf6SYinghai Lu 83a4c81cf6SYinghai Lu /* 84a4c81cf6SYinghai Lu * At this point everything still needed from the boot loader 85a4c81cf6SYinghai Lu * or BIOS or kernel text should be early reserved or marked not 86a4c81cf6SYinghai Lu * RAM in e820. All other memory is free game. 87a4c81cf6SYinghai Lu */ 88a4c81cf6SYinghai Lu 89700efc1bSEric W. Biederman start_kernel(); 90700efc1bSEric W. Biederman } 91