diff options
Diffstat (limited to 'roms/ipxe/src/arch/i386/firmware/pcbios/e820mangler.S')
| -rw-r--r-- | roms/ipxe/src/arch/i386/firmware/pcbios/e820mangler.S | 585 |
1 files changed, 585 insertions, 0 deletions
diff --git a/roms/ipxe/src/arch/i386/firmware/pcbios/e820mangler.S b/roms/ipxe/src/arch/i386/firmware/pcbios/e820mangler.S new file mode 100644 index 00000000..cea17ef8 --- /dev/null +++ b/roms/ipxe/src/arch/i386/firmware/pcbios/e820mangler.S @@ -0,0 +1,585 @@ +/* + * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +FILE_LICENCE ( GPL2_OR_LATER ) + + .text + .arch i386 + .code16 + +#define SMAP 0x534d4150 + +/* Most documentation refers to the E820 buffer as being 20 bytes, and + * the API makes it perfectly legitimate to pass only a 20-byte buffer + * and expect to get valid data. However, some morons at ACPI decided + * to extend the data structure by adding an extra "extended + * attributes" field and by including critical information within this + * field, such as whether or not the region is enabled. A caller who + * passes in only a 20-byte buffer therefore risks getting very, very + * misleading information. + * + * I have personally witnessed an HP BIOS that returns a value of + * 0x0009 in the extended attributes field. If we don't pass this + * value through to the caller, 32-bit WinPE will die, usually with a + * PAGE_FAULT_IN_NONPAGED_AREA blue screen of death. + * + * Allow a ridiculously large maximum value (64 bytes) for the E820 + * buffer as a guard against insufficiently creative idiots in the + * future. + */ +#define E820MAXSIZE 64 + +/**************************************************************************** + * + * Allowed memory windows + * + * There are two ways to view this list. The first is as a list of + * (non-overlapping) allowed memory regions, sorted by increasing + * address. The second is as a list of (non-overlapping) hidden + * memory regions, again sorted by increasing address. The second + * view is offset by half an entry from the first: think about this + * for a moment and it should make sense. + * + * xxx_memory_window is used to indicate an "allowed region" + * structure, hidden_xxx_memory is used to indicate a "hidden region" + * structure. Each structure is 16 bytes in length. + * + **************************************************************************** + */ + .section ".data16", "aw", @progbits + .align 16 + .globl hidemem_base + .globl hidemem_umalloc + .globl hidemem_textdata +memory_windows: +base_memory_window: .long 0x00000000, 0x00000000 /* Start of memory */ + +hidemem_base: .long 0x000a0000, 0x00000000 /* Changes at runtime */ +ext_memory_window: .long 0x000a0000, 0x00000000 /* 640kB mark */ + +hidemem_umalloc: .long 0xffffffff, 0xffffffff /* Changes at runtime */ + .long 0xffffffff, 0xffffffff /* Changes at runtime */ + +hidemem_textdata: .long 0xffffffff, 0xffffffff /* Changes at runtime */ + .long 0xffffffff, 0xffffffff /* Changes at runtime */ + + .long 0xffffffff, 0xffffffff /* End of memory */ +memory_windows_end: + +/**************************************************************************** + * Truncate region to memory window + * + * Parameters: + * %edx:%eax Start of region + * %ecx:%ebx Length of region + * %si Memory window + * Returns: + * %edx:%eax Start of windowed region + * %ecx:%ebx Length of windowed region + **************************************************************************** + */ + .section ".text16", "ax", @progbits +window_region: + /* Convert (start,len) to (start, end) */ + addl %eax, %ebx + adcl %edx, %ecx + /* Truncate to window start */ + cmpl 4(%si), %edx + jne 1f + cmpl 0(%si), %eax +1: jae 2f + movl 4(%si), %edx + movl 0(%si), %eax +2: /* Truncate to window end */ + cmpl 12(%si), %ecx + jne 1f + cmpl 8(%si), %ebx +1: jbe 2f + movl 12(%si), %ecx + movl 8(%si), %ebx +2: /* Convert (start, end) back to (start, len) */ + subl %eax, %ebx + sbbl %edx, %ecx + /* If length is <0, set length to 0 */ + jae 1f + xorl %ebx, %ebx + xorl %ecx, %ecx + ret + .size window_region, . - window_region + +/**************************************************************************** + * Patch "memory above 1MB" figure + * + * Parameters: + * %ax Memory above 1MB, in 1kB blocks + * Returns: + * %ax Modified memory above 1M in 1kB blocks + **************************************************************************** + */ + .section ".text16", "ax", @progbits +patch_1m: + pushal + /* Convert to (start,len) format and call truncate */ + xorl %ecx, %ecx + movzwl %ax, %ebx + shll $10, %ebx + xorl %edx, %edx + movl $0x100000, %eax + movw $ext_memory_window, %si + call window_region + /* Convert back to "memory above 1MB" format and return via %ax */ + pushfw + shrl $10, %ebx + popfw + movw %sp, %bp + movw %bx, 28(%bp) + popal + ret + .size patch_1m, . - patch_1m + +/**************************************************************************** + * Patch "memory above 16MB" figure + * + * Parameters: + * %bx Memory above 16MB, in 64kB blocks + * Returns: + * %bx Modified memory above 16M in 64kB blocks + **************************************************************************** + */ + .section ".text16", "ax", @progbits +patch_16m: + pushal + /* Convert to (start,len) format and call truncate */ + xorl %ecx, %ecx + shll $16, %ebx + xorl %edx, %edx + movl $0x1000000, %eax + movw $ext_memory_window, %si + call window_region + /* Convert back to "memory above 16MB" format and return via %bx */ + pushfw + shrl $16, %ebx + popfw + movw %sp, %bp + movw %bx, 16(%bp) + popal + ret + .size patch_16m, . - patch_16m + +/**************************************************************************** + * Patch "memory between 1MB and 16MB" and "memory above 16MB" figures + * + * Parameters: + * %ax Memory between 1MB and 16MB, in 1kB blocks + * %bx Memory above 16MB, in 64kB blocks + * Returns: + * %ax Modified memory between 1MB and 16MB, in 1kB blocks + * %bx Modified memory above 16MB, in 64kB blocks + **************************************************************************** + */ + .section ".text16", "ax", @progbits +patch_1m_16m: + call patch_1m + call patch_16m + /* If 1M region is no longer full-length, kill off the 16M region */ + cmpw $( 15 * 1024 ), %ax + je 1f + xorw %bx, %bx +1: ret + .size patch_1m_16m, . - patch_1m_16m + +/**************************************************************************** + * Get underlying e820 memory region to underlying_e820 buffer + * + * Parameters: + * As for INT 15,e820 + * Returns: + * As for INT 15,e820 + * + * Wraps the underlying INT 15,e820 call so that the continuation + * value (%ebx) is a 16-bit simple sequence counter (with the high 16 + * bits ignored), and termination is always via CF=1 rather than + * %ebx=0. + * + **************************************************************************** + */ + .section ".text16", "ax", @progbits +get_underlying_e820: + + /* If the requested region is in the cache, return it */ + cmpw %bx, underlying_e820_index + jne 2f + pushw %di + pushw %si + movw $underlying_e820_cache, %si + cmpl underlying_e820_cache_size, %ecx + jbe 1f + movl underlying_e820_cache_size, %ecx +1: pushl %ecx + rep movsb + popl %ecx + popw %si + popw %di + incw %bx + movl %edx, %eax + clc + ret +2: + /* If the requested region is earlier than the cached region, + * invalidate the cache. + */ + cmpw %bx, underlying_e820_index + jbe 1f + movw $0xffff, underlying_e820_index +1: + /* If the cache is invalid, reset the underlying %ebx */ + cmpw $0xffff, underlying_e820_index + jne 1f + andl $0, underlying_e820_ebx +1: + /* If the cache is valid but the continuation value is zero, + * this means that the previous underlying call returned with + * %ebx=0. Return with CF=1 in this case. + */ + cmpw $0xffff, underlying_e820_index + je 1f + cmpl $0, underlying_e820_ebx + jne 1f + stc + ret +1: + /* Get the next region into the cache */ + pushl %eax + pushl %ebx + pushl %ecx + pushl %edx + pushl %esi /* Some implementations corrupt %esi, so we */ + pushl %edi /* preserve %esi, %edi and %ebp to be paranoid */ + pushl %ebp + pushw %es + pushw %ds + popw %es + movw $underlying_e820_cache, %di + cmpl $E820MAXSIZE, %ecx + jbe 1f + movl $E820MAXSIZE, %ecx +1: movl underlying_e820_ebx, %ebx + stc + pushfw + lcall *%cs:int15_vector + popw %es + popl %ebp + popl %edi + popl %esi + /* Check for error return from underlying e820 call */ + jc 2f /* CF set: error */ + cmpl $SMAP, %eax + je 3f /* 'SMAP' missing: error */ +2: /* An error occurred: return values returned by underlying e820 call */ + stc /* Force CF set if SMAP was missing */ + addr32 leal 16(%esp), %esp /* avoid changing other flags */ + ret +3: /* No error occurred */ + movl %ebx, underlying_e820_ebx + movl %ecx, underlying_e820_cache_size + popl %edx + popl %ecx + popl %ebx + popl %eax + /* Mark cache as containing this result */ + incw underlying_e820_index + + /* Loop until found */ + jmp get_underlying_e820 + .size get_underlying_e820, . - get_underlying_e820 + + .section ".data16", "aw", @progbits +underlying_e820_index: + .word 0xffff /* Initialise to an invalid value */ + .size underlying_e820_index, . - underlying_e820_index + + .section ".bss16", "aw", @nobits +underlying_e820_ebx: + .long 0 + .size underlying_e820_ebx, . - underlying_e820_ebx + + .section ".bss16", "aw", @nobits +underlying_e820_cache: + .space E820MAXSIZE + .size underlying_e820_cache, . - underlying_e820_cache + + .section ".bss16", "aw", @nobits +underlying_e820_cache_size: + .long 0 + .size underlying_e820_cache_size, . - underlying_e820_cache_size + +/**************************************************************************** + * Get windowed e820 region, without empty region stripping + * + * Parameters: + * As for INT 15,e820 + * Returns: + * As for INT 15,e820 + * + * Wraps the underlying INT 15,e820 call so that each underlying + * region is returned N times, windowed to fit within N visible-memory + * windows. Termination is always via CF=1. + * + **************************************************************************** + */ + .section ".text16", "ax", @progbits +get_windowed_e820: + + /* Preserve registers */ + pushl %esi + pushw %bp + + /* Split %ebx into %si:%bx, store original %bx in %bp */ + pushl %ebx + popw %bp + popw %si + + /* %si == 0 => start of memory_windows list */ + testw %si, %si + jne 1f + movw $memory_windows, %si +1: + /* Get (cached) underlying e820 region to buffer */ + call get_underlying_e820 + jc 99f /* Abort on error */ + + /* Preserve registers */ + pushal + /* start => %edx:%eax, len => %ecx:%ebx */ + movl %es:0(%di), %eax + movl %es:4(%di), %edx + movl %es:8(%di), %ebx + movl %es:12(%di), %ecx + /* Truncate region to current window */ + call window_region +1: /* Store modified values in e820 map entry */ + movl %eax, %es:0(%di) + movl %edx, %es:4(%di) + movl %ebx, %es:8(%di) + movl %ecx, %es:12(%di) + /* Restore registers */ + popal + + /* Derive continuation value for next call */ + addw $16, %si + cmpw $memory_windows_end, %si + jne 1f + /* End of memory windows: reset %si and allow %bx to continue */ + xorw %si, %si + jmp 2f +1: /* More memory windows to go: restore original %bx */ + movw %bp, %bx +2: /* Construct %ebx from %si:%bx */ + pushw %si + pushw %bx + popl %ebx + +98: /* Clear CF */ + clc +99: /* Restore registers and return */ + popw %bp + popl %esi + ret + .size get_windowed_e820, . - get_windowed_e820 + +/**************************************************************************** + * Get windowed e820 region, with empty region stripping + * + * Parameters: + * As for INT 15,e820 + * Returns: + * As for INT 15,e820 + * + * Wraps the underlying INT 15,e820 call so that each underlying + * region is returned up to N times, windowed to fit within N + * visible-memory windows. Empty windows are never returned. + * Termination is always via CF=1. + * + **************************************************************************** + */ + .section ".text16", "ax", @progbits +get_nonempty_e820: + + /* Record entry parameters */ + pushl %eax + pushl %ecx + pushl %edx + + /* Get next windowed region */ + call get_windowed_e820 + jc 99f /* abort on error */ + + /* If region is non-empty, finish here */ + cmpl $0, %es:8(%di) + jne 98f + cmpl $0, %es:12(%di) + jne 98f + + /* Region was empty: restore entry parameters and go to next region */ + popl %edx + popl %ecx + popl %eax + jmp get_nonempty_e820 + +98: /* Clear CF */ + clc +99: /* Return values from underlying call */ + addr32 leal 12(%esp), %esp /* avoid changing flags */ + ret + .size get_nonempty_e820, . - get_nonempty_e820 + +/**************************************************************************** + * Get mangled e820 region, with empty region stripping + * + * Parameters: + * As for INT 15,e820 + * Returns: + * As for INT 15,e820 + * + * Wraps the underlying INT 15,e820 call so that underlying regions + * are windowed to the allowed memory regions. Empty regions are + * stripped from the map. Termination is always via %ebx=0. + * + **************************************************************************** + */ + .section ".text16", "ax", @progbits +get_mangled_e820: + + /* Get a nonempty region */ + call get_nonempty_e820 + jc 99f /* Abort on error */ + + /* Peek ahead to see if there are any further nonempty regions */ + pushal + pushw %es + movw %sp, %bp + subw %cx, %sp + movl $0xe820, %eax + movl $SMAP, %edx + pushw %ss + popw %es + movw %sp, %di + call get_nonempty_e820 + movw %bp, %sp + popw %es + popal + jnc 99f /* There are further nonempty regions */ + + /* No futher nonempty regions: zero %ebx and clear CF */ + xorl %ebx, %ebx + +99: /* Return */ + ret + .size get_mangled_e820, . - get_mangled_e820 + +/**************************************************************************** + * INT 15,e820 handler + **************************************************************************** + */ + .section ".text16", "ax", @progbits +int15_e820: + pushw %ds + pushw %cs:rm_ds + popw %ds + call get_mangled_e820 + popw %ds + call patch_cf + iret + .size int15_e820, . - int15_e820 + +/**************************************************************************** + * INT 15,e801 handler + **************************************************************************** + */ + .section ".text16", "ax", @progbits +int15_e801: + /* Call previous handler */ + pushfw + lcall *%cs:int15_vector + call patch_cf + /* Edit result */ + pushw %ds + pushw %cs:rm_ds + popw %ds + call patch_1m_16m + xchgw %ax, %cx + xchgw %bx, %dx + call patch_1m_16m + xchgw %ax, %cx + xchgw %bx, %dx + popw %ds + iret + .size int15_e801, . - int15_e801 + +/**************************************************************************** + * INT 15,88 handler + **************************************************************************** + */ + .section ".text16", "ax", @progbits +int15_88: + /* Call previous handler */ + pushfw + lcall *%cs:int15_vector + call patch_cf + /* Edit result */ + pushw %ds + pushw %cs:rm_ds + popw %ds + call patch_1m + popw %ds + iret + .size int15_88, . - int15_88 + +/**************************************************************************** + * INT 15 handler + **************************************************************************** + */ + .section ".text16", "ax", @progbits + .globl int15 +int15: + /* See if we want to intercept this call */ + pushfw + cmpw $0xe820, %ax + jne 1f + cmpl $SMAP, %edx + jne 1f + popfw + jmp int15_e820 +1: cmpw $0xe801, %ax + jne 2f + popfw + jmp int15_e801 +2: cmpb $0x88, %ah + jne 3f + popfw + jmp int15_88 +3: popfw + ljmp *%cs:int15_vector + .size int15, . - int15 + + .section ".text16.data", "aw", @progbits + .globl int15_vector +int15_vector: + .long 0 + .size int15_vector, . - int15_vector |