diff options
Diffstat (limited to 'qemu/roms/ipxe/src/arch/i386/prefix/romprefix.S')
| -rw-r--r-- | qemu/roms/ipxe/src/arch/i386/prefix/romprefix.S | 872 |
1 files changed, 872 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/i386/prefix/romprefix.S b/qemu/roms/ipxe/src/arch/i386/prefix/romprefix.S new file mode 100644 index 000000000..7bc4fe8cd --- /dev/null +++ b/qemu/roms/ipxe/src/arch/i386/prefix/romprefix.S @@ -0,0 +1,872 @@ +/* At entry, the processor is in 16 bit real mode and the code is being + * executed from an address it was not linked to. Code must be pic and + * 32 bit sensitive until things are fixed up. + * + * Also be very careful as the stack is at the rear end of the interrupt + * table so using a noticeable amount of stack space is a no-no. + */ + +FILE_LICENCE ( GPL2_OR_LATER ) + +#include <config/general.h> + +#define PNP_SIGNATURE ( '$' + ( 'P' << 8 ) + ( 'n' << 16 ) + ( 'P' << 24 ) ) +#define PMM_SIGNATURE ( '$' + ( 'P' << 8 ) + ( 'M' << 16 ) + ( 'M' << 24 ) ) +#define PCI_SIGNATURE ( 'P' + ( 'C' << 8 ) + ( 'I' << 16 ) + ( ' ' << 24 ) ) +#define STACK_MAGIC ( 'L' + ( 'R' << 8 ) + ( 'E' << 16 ) + ( 'T' << 24 ) ) +#define PMM_ALLOCATE 0x0000 +#define PMM_FIND 0x0001 +#define PMM_HANDLE_BASE ( ( ( 'F' - 'A' + 1 ) << 26 ) + \ + ( ( 'E' - 'A' + 1 ) << 21 ) + \ + ( ( 'N' - 'A' + 1 ) << 16 ) ) +#define PMM_HANDLE_BASE_IMAGE_SOURCE \ + ( PMM_HANDLE_BASE | 0x00001000 ) +#define PMM_HANDLE_BASE_DECOMPRESS_TO \ + ( PMM_HANDLE_BASE | 0x00002000 ) +#define PCI_FUNC_MASK 0x07 + +/* ROM banner timeout, converted to a number of (18Hz) timer ticks. */ +#define ROM_BANNER_TIMEOUT_TICKS ( ( 18 * ROM_BANNER_TIMEOUT ) / 10 ) + +/* Allow payload to be excluded from ROM size + */ +#if ROMPREFIX_EXCLUDE_PAYLOAD +#define ZINFO_TYPE_ADxB "ADHB" +#define ZINFO_TYPE_ADxW "ADHW" +#else +#define ZINFO_TYPE_ADxB "ADDB" +#define ZINFO_TYPE_ADxW "ADDW" +#endif + +/* Allow ROM to be marked as containing multiple images + */ +#if ROMPREFIX_MORE_IMAGES +#define INDICATOR 0x00 +#else +#define INDICATOR 0x80 +#endif + +/* Default to building a PCI ROM if no bus type is specified + */ +#ifndef BUSTYPE +#define BUSTYPE "PCIR" +#endif + + .text + .code16 + .arch i386 + .section ".prefix", "ax", @progbits + .globl _rom_start +_rom_start: + + .org 0x00 +romheader: + .word 0xAA55 /* BIOS extension signature */ +romheader_size: .byte 0 /* Size in 512-byte blocks */ + jmp init /* Initialisation vector */ +checksum: + .byte 0 + .org 0x10 + .word ipxeheader + .org 0x16 + .word undiheader +.ifeqs BUSTYPE, "PCIR" + .org 0x18 + .word pciheader +.endif + .org 0x1a + .word pnpheader + .size romheader, . - romheader + + .section ".zinfo.fixup", "a", @progbits /* Compressor fixups */ + .ascii ZINFO_TYPE_ADxB + .long romheader_size + .long 512 + .long 0 + .previous + +.ifeqs BUSTYPE, "PCIR" +pciheader: + .ascii "PCIR" /* Signature */ + .word pci_vendor_id /* Vendor identification */ + .word pci_device_id /* Device identification */ + .word 0x0000 /* Device list pointer */ + .word pciheader_len /* PCI data structure length */ + .byte 0x03 /* PCI data structure revision */ + .byte 0x02, 0x00, 0x00 /* Class code */ +pciheader_image_length: + .word 0 /* Image length */ + .word 0x0001 /* Revision level */ + .byte 0x00 /* Code type */ + .byte INDICATOR /* Last image indicator */ +pciheader_runtime_length: + .word 0 /* Maximum run-time image length */ + .word 0x0000 /* Configuration utility code header */ + .word 0x0000 /* DMTF CLP entry point */ + .equ pciheader_len, . - pciheader + .size pciheader, . - pciheader + + .section ".zinfo.fixup", "a", @progbits /* Compressor fixups */ + .ascii ZINFO_TYPE_ADxW + .long pciheader_image_length + .long 512 + .long 0 + .ascii ZINFO_TYPE_ADxW + .long pciheader_runtime_length + .long 512 + .long 0 + .previous +.endif /* PCIR */ + + /* PnP doesn't require any particular alignment, but IBM + * BIOSes will scan on 16-byte boundaries rather than using + * the offset stored at 0x1a + */ + .align 16 +pnpheader: + .ascii "$PnP" /* Signature */ + .byte 0x01 /* Structure revision */ + .byte ( pnpheader_len / 16 ) /* Length (in 16 byte increments) */ + .word 0x0000 /* Offset of next header */ + .byte 0x00 /* Reserved */ + .byte 0x00 /* Checksum */ + .long 0x00000000 /* Device identifier */ + .word mfgstr /* Manufacturer string */ + .word prodstr /* Product name */ + .byte 0x02 /* Device base type code */ + .byte 0x00 /* Device sub-type code */ + .byte 0x00 /* Device interface type code */ + .byte 0xf4 /* Device indicator */ + .word 0x0000 /* Boot connection vector */ + .word 0x0000 /* Disconnect vector */ + .word bev_entry /* Boot execution vector */ + .word 0x0000 /* Reserved */ + .word 0x0000 /* Static resource information vector*/ + .equ pnpheader_len, . - pnpheader + .size pnpheader, . - pnpheader + +/* Manufacturer string */ +mfgstr: + .asciz "http://ipxe.org" + .size mfgstr, . - mfgstr + +/* Product string + * + * Defaults to PRODUCT_SHORT_NAME. If the ROM image is writable at + * initialisation time, it will be filled in to include the PCI + * bus:dev.fn number of the card as well. + */ +prodstr: + .ascii PRODUCT_SHORT_NAME +.ifeqs BUSTYPE, "PCIR" +prodstr_separator: + .byte 0 + .ascii "(PCI " +prodstr_pci_id: + .ascii "xx:xx.x)" /* Filled in by init code */ +.endif /* PCIR */ + .byte 0 + .size prodstr, . - prodstr + + .globl undiheader + .weak undiloader +undiheader: + .ascii "UNDI" /* Signature */ + .byte undiheader_len /* Length of structure */ + .byte 0 /* Checksum */ + .byte 0 /* Structure revision */ + .byte 0,1,2 /* PXE version: 2.1.0 */ + .word undiloader /* Offset to loader routine */ + .word _data16_memsz /* Stack segment size */ + .word _data16_memsz /* Data segment size */ + .word _text16_memsz /* Code segment size */ + .ascii BUSTYPE /* Bus type */ + .equ undiheader_len, . - undiheader + .size undiheader, . - undiheader + +ipxeheader: + .ascii "iPXE" /* Signature */ + .byte ipxeheader_len /* Length of structure */ + .byte 0 /* Checksum */ +shrunk_rom_size: + .byte 0 /* Shrunk size (in 512-byte blocks) */ + .byte 0 /* Reserved */ +build_id: + .long _build_id /* Randomly-generated build ID */ + .equ ipxeheader_len, . - ipxeheader + .size ipxeheader, . - ipxeheader + + .section ".zinfo.fixup", "a", @progbits /* Compressor fixups */ + .ascii "ADHB" + .long shrunk_rom_size + .long 512 + .long 0 + .previous + +/* Initialisation (called once during POST) + * + * Determine whether or not this is a PnP system via a signature + * check. If it is PnP, return to the PnP BIOS indicating that we are + * a boot-capable device; the BIOS will call our boot execution vector + * if it wants to boot us. If it is not PnP, hook INT 19. + */ +init: + /* Preserve registers, clear direction flag, set %ds=%cs */ + pushaw + pushw %ds + pushw %es + pushw %fs + pushw %gs + cld + pushw %cs + popw %ds + + /* Print message as early as possible */ + movw $init_message, %si + xorw %di, %di + call print_message + + /* Store PCI 3.0 runtime segment address for later use, if + * applicable. + */ +.ifeqs BUSTYPE, "PCIR" + movw %bx, %gs +.endif + + /* Store PCI bus:dev.fn address, print PCI bus:dev.fn, and add + * PCI bus:dev.fn to product name string, if applicable. + */ +.ifeqs BUSTYPE, "PCIR" + xorw %di, %di + call print_space + movw %ax, init_pci_busdevfn + call print_pci_busdevfn + movw $prodstr_pci_id, %di + call print_pci_busdevfn + movb $( ' ' ), prodstr_separator +.endif + + /* Print segment address */ + xorw %di, %di + call print_space + movw %cs, %ax + call print_hex_word + + /* Check for PCI BIOS version, if applicable */ +.ifeqs BUSTYPE, "PCIR" + pushl %ebx + pushl %edx + pushl %edi + stc + movw $0xb101, %ax + int $0x1a + jc no_pci3 + cmpl $PCI_SIGNATURE, %edx + jne no_pci3 + testb %ah, %ah + jnz no_pci3 + movw $init_message_pci, %si + xorw %di, %di + call print_message + movb %bh, %al + call print_hex_nibble + movb $( '.' ), %al + call print_character + movb %bl, %al + call print_hex_byte + cmpb $3, %bh + jb no_pci3 + /* PCI >=3.0: leave %gs as-is if sane */ + movw %gs, %ax + cmpw $0xa000, %ax /* Insane if %gs < 0xa000 */ + jb pci3_insane + movw %cs, %bx /* Sane if %cs == %gs */ + cmpw %bx, %ax + je 1f + movzbw romheader_size, %cx /* Sane if %cs+len <= %gs */ + shlw $5, %cx + addw %cx, %bx + cmpw %bx, %ax + jae 1f + movw %cs, %bx /* Sane if %gs+len <= %cs */ + addw %cx, %ax + cmpw %bx, %ax + jbe 1f +pci3_insane: /* PCI 3.0 with insane %gs value: print error and ignore %gs */ + movb $( '!' ), %al + call print_character + movw %gs, %ax + call print_hex_word +no_pci3: + /* PCI <3.0: set %gs (runtime segment) = %cs (init-time segment) */ + pushw %cs + popw %gs +1: popl %edi + popl %edx + popl %ebx +.endif /* PCIR */ + + /* Check for PnP BIOS. Although %es:di should point to the + * PnP BIOS signature on entry, some BIOSes fail to do this. + */ + movw $( 0xf000 - 1 ), %bx +pnp_scan: + incw %bx + jz no_pnp + movw %bx, %es + cmpl $PNP_SIGNATURE, %es:0 + jne pnp_scan + xorw %dx, %dx + xorw %si, %si + movzbw %es:5, %cx +1: es lodsb + addb %al, %dl + loop 1b + jnz pnp_scan + /* Is PnP: print PnP message */ + movw $init_message_pnp, %si + xorw %di, %di + call print_message + jmp pnp_done +no_pnp: /* Not PnP-compliant - hook INT 19 */ +#ifdef NONPNP_HOOK_INT19 + movw $init_message_int19, %si + xorw %di, %di + call print_message + xorw %ax, %ax + movw %ax, %es + pushl %es:( 0x19 * 4 ) + popl orig_int19 + pushw %gs /* %gs contains runtime %cs */ + pushw $int19_entry + popl %es:( 0x19 * 4 ) +#endif /* NONPNP_HOOK_INT19 */ +pnp_done: + + /* Check for PMM */ + movw $( 0xe000 - 1 ), %bx +pmm_scan: + incw %bx + jz no_pmm + movw %bx, %es + cmpl $PMM_SIGNATURE, %es:0 + jne pmm_scan + xorw %dx, %dx + xorw %si, %si + movzbw %es:5, %cx +1: es lodsb + addb %al, %dl + loop 1b + jnz pmm_scan + /* PMM found: print PMM message */ + movw $init_message_pmm, %si + xorw %di, %di + call print_message + /* We have PMM and so a 1kB stack: preserve whole registers */ + pushal + /* Allocate image source PMM block. Round up the size to the + * nearest 4kB (8 512-byte sectors) to work around AMI BIOS bugs. + */ + movzbl romheader_size, %ecx + addw extra_size, %cx + addw $0x0007, %cx /* Round up to multiple of 8 512-byte sectors */ + andw $0xfff8, %cx + shll $5, %ecx + movl $PMM_HANDLE_BASE_IMAGE_SOURCE, %ebx + movw $get_pmm_image_source, %bp + call get_pmm + movl %esi, image_source + jz 1f + /* Copy ROM to image source PMM block */ + pushw %es + xorw %ax, %ax + movw %ax, %es + movl %esi, %edi + xorl %esi, %esi + movzbl romheader_size, %ecx + shll $7, %ecx + addr32 rep movsl /* PMM presence implies flat real mode */ + popw %es + /* Shrink ROM */ + movb shrunk_rom_size, %al + movb %al, romheader_size +1: /* Allocate decompression PMM block. Round up the size to the + * nearest 128kB and use the size within the PMM handle; this + * allows the same decompression area to be shared between + * multiple iPXE ROMs even with differing build IDs + */ + movl $_textdata_memsz_pgh, %ecx + addl $0x00001fff, %ecx + andl $0xffffe000, %ecx + movl %ecx, %ebx + shrw $12, %bx + orl $PMM_HANDLE_BASE_DECOMPRESS_TO, %ebx + movw $get_pmm_decompress_to, %bp + call get_pmm + movl %esi, decompress_to + /* Restore registers */ + popal +no_pmm: + + /* Update checksum */ + xorw %bx, %bx + xorw %si, %si + movzbw romheader_size, %cx + shlw $9, %cx +1: lodsb + addb %al, %bl + loop 1b + subb %bl, checksum + + /* Copy self to option ROM space, if applicable. Required for + * PCI3.0, which loads us to a temporary location in low + * memory. Will be a no-op for lower PCI versions. + */ +.ifeqs BUSTYPE, "PCIR" + xorw %di, %di + call print_space + movw %gs, %ax + call print_hex_word + movzbw romheader_size, %cx + shlw $9, %cx + movw %ax, %es + xorw %si, %si + xorw %di, %di + cs rep movsb +.endif + + /* Skip prompt if this is not the first PCI function, if applicable */ +.ifeqs BUSTYPE, "PCIR" + testb $PCI_FUNC_MASK, init_pci_busdevfn + jnz no_shell +.endif + /* Prompt for POST-time shell */ + movw $init_message_prompt, %si + xorw %di, %di + call print_message + movw $prodstr, %si + call print_message + movw $init_message_dots, %si + call print_message + /* Wait for Ctrl-B */ + movw $0xff02, %bx + call wait_for_key + /* Clear prompt */ + pushf + xorw %di, %di + call print_kill_line + movw $init_message_done, %si + call print_message + popf + jnz no_shell + /* Ctrl-B was pressed: invoke iPXE. The keypress will be + * picked up by the initial shell prompt, and we will drop + * into a shell. + */ + xorl %ebp, %ebp /* Inhibit use of INT 15,e820 and INT 15,e801 */ + pushw %cs + call exec +no_shell: + movb $( '\n' ), %al + xorw %di, %di + call print_character + + /* Restore registers */ + popw %gs + popw %fs + popw %es + popw %ds + popaw + + /* Indicate boot capability to PnP BIOS, if present */ + movw $0x20, %ax + lret + .size init, . - init + +/* Attempt to find or allocate PMM block + * + * Parameters: + * %ecx : size of block to allocate, in paragraphs + * %ebx : PMM handle base + * %bp : routine to check acceptability of found blocks + * %es:0000 : PMM structure + * Returns: + * %ebx : PMM handle + * %esi : allocated block address, or zero (with ZF set) if allocation failed + */ +get_pmm: + /* Preserve registers */ + pushl %eax + pushw %di + movw $( ' ' ), %di +get_pmm_find: + /* Try to find existing block */ + pushl %ebx /* PMM handle */ + pushw $PMM_FIND + lcall *%es:7 + addw $6, %sp + pushw %dx + pushw %ax + popl %esi + /* Treat 0xffffffff (not supported) as 0x00000000 (not found) */ + incl %esi + jz get_pmm_allocate + decl %esi + jz get_pmm_allocate + /* Block found - check acceptability */ + call *%bp + jnc get_pmm_done + /* Block not acceptable - increment handle and retry */ + incl %ebx + jmp get_pmm_find +get_pmm_allocate: + /* Block not found - try to allocate new block */ + pushw $0x0002 /* Extended memory */ + pushl %ebx /* PMM handle */ + pushl %ecx /* Length */ + pushw $PMM_ALLOCATE + lcall *%es:7 + addw $12, %sp + pushw %dx + pushw %ax + popl %esi + movw $( '+' ), %di /* Indicate allocation attempt */ +get_pmm_done: + /* Print block address */ + movw %di, %ax + xorw %di, %di + call print_character + movl %esi, %eax + call print_hex_dword + /* Treat 0xffffffff (not supported) as 0x00000000 (allocation + * failed), and set ZF to indicate a zero result. + */ + incl %esi + jz 1f + decl %esi +1: /* Restore registers and return */ + popw %di + popl %eax + ret + .size get_pmm, . - get_pmm + + /* Check acceptability of image source block */ +get_pmm_image_source: + pushw %es + xorw %ax, %ax + movw %ax, %es + movl build_id, %eax + addr32 cmpl %es:build_id(%esi), %eax + je 1f + stc +1: popw %es + ret + .size get_pmm_image_source, . - get_pmm_image_source + + /* Check acceptability of decompression block */ +get_pmm_decompress_to: + clc + ret + .size get_pmm_decompress_to, . - get_pmm_decompress_to + +/* + * Note to hardware vendors: + * + * If you wish to brand this boot ROM, please do so by defining the + * strings PRODUCT_NAME and PRODUCT_SHORT_NAME in config/general.h. + * + * While nothing in the GPL prevents you from removing all references + * to iPXE or http://ipxe.org, we prefer you not to do so. + * + * If you have an OEM-mandated branding requirement that cannot be + * satisfied simply by defining PRODUCT_NAME and PRODUCT_SHORT_NAME, + * please contact us. + * + * [ Including an ASCII NUL in PRODUCT_NAME is considered to be + * bypassing the spirit of this request! ] + */ +init_message: + .ascii "\n" + .ascii PRODUCT_NAME + .ascii "\n" + .asciz "iPXE (http://ipxe.org)" + .size init_message, . - init_message +.ifeqs BUSTYPE, "PCIR" +init_message_pci: + .asciz " PCI" + .size init_message_pci, . - init_message_pci +.endif /* PCIR */ +init_message_pnp: + .asciz " PnP" + .size init_message_pnp, . - init_message_pnp +init_message_pmm: + .asciz " PMM" + .size init_message_pmm, . - init_message_pmm +init_message_int19: + .asciz " INT19" + .size init_message_int19, . - init_message_int19 +init_message_prompt: + .asciz "\nPress Ctrl-B to configure " + .size init_message_prompt, . - init_message_prompt +init_message_dots: + .asciz "..." + .size init_message_dots, . - init_message_dots +init_message_done: + .asciz "\n\n" + .size init_message_done, . - init_message_done + +/* PCI bus:dev.fn + * + */ +.ifeqs BUSTYPE, "PCIR" +init_pci_busdevfn: + .word 0 + .size init_pci_busdevfn, . - init_pci_busdevfn +.endif /* PCIR */ + +/* Image source area + * + * May be either zero (indicating to use option ROM space as source), + * or within a PMM-allocated block. + */ + .globl image_source +image_source: + .long 0 + .size image_source, . - image_source + +/* Additional image source size (in 512-byte sectors) + * + */ +extra_size: + .word 0 + .size extra_size, . - extra_size + +/* Temporary decompression area + * + * May be either zero (indicating to use default decompression area in + * high memory), or within a PMM-allocated block. + */ + .globl decompress_to +decompress_to: + .long 0 + .size decompress_to, . - decompress_to + +/* Boot Execution Vector entry point + * + * Called by the PnP BIOS when it wants to boot us. + */ +bev_entry: + orl $0xffffffff, %ebp /* Allow arbitrary relocation */ + pushw %cs + call exec + lret + .size bev_entry, . - bev_entry + +/* INT19 entry point + * + * Called via the hooked INT 19 if we detected a non-PnP BIOS. We + * attempt to return via the original INT 19 vector (if we were able + * to store it). + */ +int19_entry: + pushw %cs + popw %ds + /* Prompt user to press B to boot */ + movw $int19_message_prompt, %si + xorw %di, %di + call print_message + movw $prodstr, %si + call print_message + movw $int19_message_dots, %si + call print_message + movw $0xdf4e, %bx + call wait_for_key + pushf + xorw %di, %di + call print_kill_line + movw $int19_message_done, %si + call print_message + popf + jz 1f + /* Leave keypress in buffer and start iPXE. The keypress will + * cause the usual initial Ctrl-B prompt to be skipped. + */ + orl $0xffffffff, %ebp /* Allow arbitrary relocation */ + pushw %cs + call exec +1: /* Try to call original INT 19 vector */ + movl %cs:orig_int19, %eax + testl %eax, %eax + je 2f + ljmp *%cs:orig_int19 +2: /* No chained vector: issue INT 18 as a last resort */ + int $0x18 + .size int19_entry, . - int19_entry +orig_int19: + .long 0 + .size orig_int19, . - orig_int19 + +int19_message_prompt: + .asciz "Press N to skip booting from " + .size int19_message_prompt, . - int19_message_prompt +int19_message_dots: + .asciz "..." + .size int19_message_dots, . - int19_message_dots +int19_message_done: + .asciz "\n\n" + .size int19_message_done, . - int19_message_done + +/* Execute as a boot device + * + */ +exec: /* Set %ds = %cs */ + pushw %cs + popw %ds + + /* Print message as soon as possible */ + movw $prodstr, %si + xorw %di, %di + call print_message + movw $exec_message_pre_install, %si + call print_message + + /* Store magic word on BIOS stack and remember BIOS %ss:sp */ + pushl $STACK_MAGIC + movw %ss, %cx + movw %sp, %dx + + /* Obtain a reasonably-sized temporary stack */ + xorw %bx, %bx + movw %bx, %ss + movw $0x7c00, %sp + + /* Install iPXE */ + call alloc_basemem + movl image_source, %esi + movl decompress_to, %edi + call install_prealloc + + /* Print message indicating successful installation */ + movw $exec_message_post_install, %si + xorw %di, %di + call print_message + + /* Set up real-mode stack */ + movw %bx, %ss + movw $_estack16, %sp + + /* Jump to .text16 segment */ + pushw %ax + pushw $1f + lret + .section ".text16", "awx", @progbits +1: + /* Retrieve PCI bus:dev.fn, if applicable */ +.ifeqs BUSTYPE, "PCIR" + movw init_pci_busdevfn, %ax +.endif + + /* Set up %ds for access to .data16 */ + movw %bx, %ds + + /* Store PCI bus:dev.fn, if applicable */ +.ifeqs BUSTYPE, "PCIR" + movw %ax, autoboot_busdevfn +.endif + + /* Call main() */ + pushl $main + pushw %cs + call prot_call + popl %eax /* discard */ + + /* Set up flat real mode for return to BIOS */ + call flatten_real_mode + + /* Uninstall iPXE */ + call uninstall + + /* Restore BIOS stack */ + movw %cx, %ss + movw %dx, %sp + + /* Check magic word on BIOS stack */ + popl %eax + cmpl $STACK_MAGIC, %eax + jne 1f + /* BIOS stack OK: return to caller */ + lret +1: /* BIOS stack corrupt: use INT 18 */ + int $0x18 + .previous + +exec_message_pre_install: + .asciz " starting execution..." + .size exec_message_pre_install, . - exec_message_pre_install +exec_message_post_install: + .asciz "ok\n" + .size exec_message_post_install, . - exec_message_post_install + +/* Wait for key press specified by %bl (masked by %bh) + * + * Used by init and INT19 code when prompting user. If the specified + * key is pressed, it is left in the keyboard buffer. + * + * Returns with ZF set iff specified key is pressed. + */ +wait_for_key: + /* Preserve registers */ + pushw %cx + pushw %ax +1: /* Empty the keyboard buffer before waiting for input */ + movb $0x01, %ah + int $0x16 + jz 2f + xorw %ax, %ax + int $0x16 + jmp 1b +2: /* Wait for a key press */ + movw $ROM_BANNER_TIMEOUT_TICKS, %cx +3: decw %cx + js 99f /* Exit with ZF clear */ + /* Wait for timer tick to be updated */ + call wait_for_tick + /* Check to see if a key was pressed */ + movb $0x01, %ah + int $0x16 + jz 3b + /* Check to see if key was the specified key */ + andb %bh, %al + cmpb %al, %bl + je 99f /* Exit with ZF set */ + /* Not the specified key: remove from buffer and stop waiting */ + pushfw + xorw %ax, %ax + int $0x16 + popfw /* Exit with ZF clear */ +99: /* Restore registers and return */ + popw %ax + popw %cx + ret + .size wait_for_key, . - wait_for_key + +/* Wait for timer tick + * + * Used by wait_for_key + */ +wait_for_tick: + pushl %eax + pushw %fs + movw $0x40, %ax + movw %ax, %fs + movl %fs:(0x6c), %eax +1: pushf + sti + hlt + popf + cmpl %fs:(0x6c), %eax + je 1b + popw %fs + popl %eax + ret + .size wait_for_tick, . - wait_for_tick |