Cope with regions bigger than 4GB.
We now split e820 regions around ourselves, rather than just truncating the e820 region. This avoids the worst-case scenario of losing all memory over 4GB. It's more important to get the memory map right now that we're expecting to still be loaded when the OS starts in several situations (e.g. Linux with UNDI driver, any OS with iSCSI/AoE boot, etc.).
This commit is contained in:
Michael Brown
parent
bef8874842
commit
5ec2b2c251
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@ -1,296 +1,423 @@
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#undef CODE16
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#if defined(PCBIOS)
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#define CODE16
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#endif
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#ifdef CODE16
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#define BOCHSBP xchgw %bx,%bx
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/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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.text
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.arch i386
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.section ".text16", "ax", @progbits
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.section ".data16", "aw", @progbits
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.section ".text16.data", "aw", @progbits
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.code16
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/****************************************************************************
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* Memory map mangling code
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****************************************************************************
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*/
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#define SMAP 0x534d4150
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.globl e820mangler
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e820mangler:
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/* Macro to calculate offset of labels within code segment in
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* installed copy of code.
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*/
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#define INSTALLED(x) ( (x) - e820mangler )
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/****************************************************************************
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* Intercept INT 15 memory calls and remove the hidden memory ranges
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* from the resulting memory map.
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****************************************************************************
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*/
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.globl _intercept_int15
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_intercept_int15:
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/* Preserve registers */
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pushw %bp
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/* Store %ax for future reference */
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pushw %ax
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/* Make INT-style call to old INT15 routine */
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pushfw
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lcall %cs:*INSTALLED(_intercepted_int15)
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/* Preserve flags returned by original E820 routine */
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pushfw
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/* Check for valid INT15 routine */
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jc intercept_int15_exit
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/* Check for a routine we want to intercept */
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movw %sp, %bp
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cmpw $0xe820, 2(%bp)
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je intercept_e820
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cmpw $0xe801, 2(%bp)
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je intercept_e801
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cmpb $0x88, 3(%bp)
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je intercept_88
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intercept_int15_exit:
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/* Restore registers and return */
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popfw
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popw %bp /* discard original %ax */
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popw %bp
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lret $2 /* 'iret' - flags already loaded */
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.globl _intercepted_int15
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_intercepted_int15: .word 0,0
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/****************************************************************************
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* Exclude an address range from a potentially overlapping address range
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*
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* Note: this *can* be called even if the range doesn't overlap; it
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* will simply return the range unaltered. It copes with all the
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* possible cases of overlap, including total overlap (which will
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* modify the range to length zero). If the to-be-excluded range is
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* in the middle of the target range, then the larger remaining
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* portion will be returned. If %di is nonzero on entry then the
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* range will only be truncated from the high end, i.e. the base
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* address will never be altered. All this in less than 30
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* instructions. :)
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* Check for overlap
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*
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* Parameters:
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* %eax Base address of memory range
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* %ecx Length of memory range
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* %ebx Base address of memory range to exclude
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* %edx Length of memory range to exclude
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* %di 0 => truncate either end, 1 => truncate high end only
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* %eax Updated base address of range
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* %ecx Updated length of range
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* %ebx,%edx Undefined
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* All other registers (including %di) preserved
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*
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* Note: "ja" is used rather than "jg" because we are comparing
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* unsigned ints
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* CF set Region overlaps
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* CF clear No overlap
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****************************************************************************
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*/
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#ifdef TEST_EXCLUDE_ALGORITHM
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.code32
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#endif /* TEST_EXCLUDE_ALGORITHM */
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exclude_memory_range:
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/* Convert (start,length) to (start,end) */
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addl %eax, %ecx
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addl %ebx, %edx
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/* Calculate "prefix" length */
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subl %eax, %ebx /* %ebx = "prefix" length */
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ja 1f
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xorl %ebx, %ebx /* Truncate to zero if negative */
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1: /* %di == 0 => truncate either end
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* %di != 0 => truncate only high end
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*/
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testw %di, %di
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je use_either
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cmpl %eax, %edx
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jbe 99f /* excl. range is below target range */
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use_prefix: /* Use prefix, discard suffix */
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addl %eax, %ebx /* %ebx = candidate end address */
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cmpl %ecx, %ebx /* %ecx = min ( %ebx, %ecx ) */
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ja 1f
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movl %ebx, %ecx
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1: jmp 99f
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use_either:
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/* Calculate "suffix" length */
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subl %ecx, %edx /* %edx = -( "suffix" length ) */
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jb 1f
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xorl %edx, %edx /* Truncate to zero if negative */
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1: negl %edx /* %edx = "suffix" length */
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/* Use whichever is longest of "prefix" and "suffix" */
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cmpl %ebx, %edx
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jbe use_prefix
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use_suffix: /* Use suffix, discard prefix */
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negl %edx
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addl %ecx, %edx /* %edx = candidate start address */
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cmpl %eax, %edx /* %eax = max ( %eax, %edx ) */
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jb 1f
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movl %edx, %eax
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1:
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99: subl %eax, %ecx /* Convert back to (start,length) */
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*/
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.section ".text16"
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check_overlap:
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/* If start >= hidden_end, there is no overlap. */
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testl %edx, %edx
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jnz no_overlap
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cmpl 4(%si), %eax
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jae no_overlap
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/* If end <= hidden_start, there is no overlap; equivalently,
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* if end > hidden_start, there is overlap.
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*/
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testl %ecx, %ecx
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jnz overlap
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cmpl 0(%si), %ebx
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ja overlap
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no_overlap:
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clc
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ret
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overlap:
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stc
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ret
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.size check_overlap, . - check_overlap
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#ifdef TEST_EXCLUDE_ALGORITHM
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.globl __test_exclude
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__test_exclude:
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pushl %ebx
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pushl %edi
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movl 12(%esp), %eax
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movl 16(%esp), %ecx
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movl 20(%esp), %ebx
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movl 24(%esp), %edx
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movl 28(%esp), %edi
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call exclude_memory_range
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shll $16, %eax
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orl %ecx, %eax
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popl %edi
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popl %ebx
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ret
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.code16
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#endif /* TEST_EXCLUDE_ALGORITHM */
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/****************************************************************************
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* Exclude Etherboot-reserved address ranges from a potentially
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* overlapping address range
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* Check for overflow/underflow
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*
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* Parameters:
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* %eax Base address of memory range
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* %ecx Length of memory range
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* %di 0 => truncate either end, 1 => truncate high end only
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* Returns:
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* %eax Updated base address of range
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* %ecx Updated length of range
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* All other registers (including %di) preserved
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* CF set start < end
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* CF clear start >= end
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****************************************************************************
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*/
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exclude_hidden_memory_ranges:
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pushw %si
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.section ".text16"
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check_overflow:
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pushl %ecx
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pushl %ebx
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pushl %edx
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movw $INSTALLED(_hide_memory), %si
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2: movl %cs:0(%si), %ebx
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movl %cs:4(%si), %edx
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call exclude_memory_range
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addw $8, %si
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cmpw $INSTALLED(_hide_memory_end), %si
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jl 2b
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popl %edx
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subl %eax, %ebx
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sbbl %edx, %ecx
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popl %ebx
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popl %ecx
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ret
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.size check_overflow, . - check_overflow
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/****************************************************************************
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* Truncate towards start of region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region end
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate_to_start:
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/* If overlaps, set region end = hidden region start */
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call check_overlap
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jnc 99f
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movl 0(%si), %ebx
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xorl %ecx, %ecx
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/* If region end < region start, set region end = region start */
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call check_overflow
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jnc 1f
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movl %eax, %ebx
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movl %edx, %ecx
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1: stc
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99: ret
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.size truncate_to_start, . - truncate_to_start
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/****************************************************************************
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* Truncate towards end of region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region end
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate_to_end:
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/* If overlaps, set region start = hidden region end */
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call check_overlap
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jnc 99f
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movl 4(%si), %eax
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xorl %edx, %edx
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/* If region start > region end, set region start = region end */
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call check_overflow
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jnc 1f
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movl %ebx, %eax
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movl %ecx, %edx
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1: stc
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99: ret
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.size truncate_to_end, . - truncate_to_end
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/****************************************************************************
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* Truncate region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region length (*not* region end)
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* %bp truncate_to_start or truncate_to_end
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region length
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate:
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pushw %si
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pushfw
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/* Convert (start,len) to (start,end) */
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addl %eax, %ebx
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adcl %edx, %ecx
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/* Hide all hidden regions, truncating as directed */
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movw $hidden_regions, %si
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1: call *%bp
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jnc 2f
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popfw /* If CF was set, set stored CF in flags word on stack */
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||||
stc
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||||
pushfw
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||||
2: addw $8, %si
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cmpl $0, 0(%si)
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||||
jne 1b
|
||||
/* Convert modified (start,end) back to (start,len) */
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subl %eax, %ebx
|
||||
sbbl %edx, %ecx
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popfw
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||||
popw %si
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||||
ret
|
||||
|
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.globl _hide_memory
|
||||
_hide_memory:
|
||||
.long 0,0 /* Etherboot text (base,length) */
|
||||
.long 0,0 /* Heap (base,length) */
|
||||
_hide_memory_end:
|
||||
.size truncate, . - truncate
|
||||
|
||||
/****************************************************************************
|
||||
* Intercept INT 15,E820 calls and remove the hidden memory ranges
|
||||
* from the resulting memory map.
|
||||
* Patch "memory above 1MB" figure
|
||||
*
|
||||
* Parameters:
|
||||
* %ax Memory above 1MB, in 1kB blocks
|
||||
* Returns:
|
||||
* %ax Modified memory above 1M in 1kB blocks
|
||||
* CF set Region was truncated
|
||||
* CF clear Region was not truncated
|
||||
****************************************************************************
|
||||
*/
|
||||
#define SMAP ( 0x534d4150 )
|
||||
intercept_e820:
|
||||
/* Check for valid E820 routine */
|
||||
cmpl $SMAP, %eax
|
||||
jne intercept_int15_exit
|
||||
/* If base address isn't in the low 4GB, return unaltered
|
||||
* (since we never claim memory above 4GB). WARNING: we cheat
|
||||
* by assuming that no E820 region will straddle the 4GB
|
||||
* boundary: if this is not a valid assumption then things
|
||||
* will probably break.
|
||||
*/
|
||||
cmpl $0, %es:4(%di)
|
||||
jne intercept_int15_exit
|
||||
/* Preserve registers */
|
||||
pushl %eax
|
||||
pushl %ecx
|
||||
/* Update returned memory range */
|
||||
movl %es:0(%di), %eax /* Base */
|
||||
movl %es:8(%di), %ecx /* Length */
|
||||
pushw %di
|
||||
xorw %di, %di /* "truncate either end" flag */
|
||||
call exclude_hidden_memory_ranges
|
||||
popw %di
|
||||
movl %eax, %es:0(%di) /* Store updated base */
|
||||
movl %ecx, %es:8(%di) /* Store updated length */
|
||||
/* Restore registers and return */
|
||||
popl %ecx
|
||||
popl %eax
|
||||
jmp intercept_int15_exit
|
||||
|
||||
/****************************************************************************
|
||||
* Intercept INT 15,E801 calls and remove the hidden memory ranges
|
||||
* from the resulting memory map.
|
||||
****************************************************************************
|
||||
*/
|
||||
intercept_e801:
|
||||
/* Adjust return values */
|
||||
call e801_adjust
|
||||
xchgw %ax, %cx
|
||||
xchgw %bx, %dx
|
||||
call e801_adjust
|
||||
xchgw %ax, %cx
|
||||
xchgw %bx, %dx
|
||||
jmp intercept_int15_exit
|
||||
|
||||
/* %ax = #KB from 1MB+, %bx = #64KB from 16MB+
|
||||
* Return with modified values in %ax, %bx. Preserver other regs.
|
||||
*/
|
||||
e801_adjust:
|
||||
pushw %di
|
||||
pushl %ecx
|
||||
pushl %eax
|
||||
movw $1, %di /* "truncate only high end" flag */
|
||||
|
||||
/* Truncate #64KB from 16MB+ as appropriate */
|
||||
movw %bx, %cx /* (no need to zero high word) */
|
||||
shll $16, %ecx /* %ecx = length in bytes */
|
||||
movl $(1<<24), %eax /* 16MB start address */
|
||||
call exclude_hidden_memory_ranges
|
||||
shrl $16, %ecx /* %cx = updated length in 64KB */
|
||||
movw %cx, %bx /* Return in %bx */
|
||||
|
||||
/* Truncate #KB from 1MB+ as appropriate */
|
||||
popw %cx /* Orig. %ax (high word already 0) */
|
||||
shll $10, %ecx /* %ecx = length in bytes */
|
||||
shrl $4, %eax /* 1MB start address */
|
||||
call exclude_hidden_memory_ranges
|
||||
shrl $10, %ecx /* %cx = updated length in KB */
|
||||
pushw %cx /* Will be picked up in %eax */
|
||||
|
||||
popl %eax
|
||||
popl %ecx
|
||||
popw %di
|
||||
.section ".text16"
|
||||
patch_1m:
|
||||
pushal
|
||||
/* Convert to (start,len) format and call truncate */
|
||||
movw $truncate_to_start, %bp
|
||||
xorl %ecx, %ecx
|
||||
movzwl %ax, %ebx
|
||||
shll $10, %ebx
|
||||
xorl %edx, %edx
|
||||
movl $0x100000, %eax
|
||||
call truncate
|
||||
/* 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
|
||||
|
||||
/****************************************************************************
|
||||
* Intercept INT 15,88 calls and remove the hidden memory ranges
|
||||
* from the resulting memory map.
|
||||
* Patch "memory above 16MB" figure
|
||||
*
|
||||
* Parameters:
|
||||
* %bx Memory above 16MB, in 64kB blocks
|
||||
* Returns:
|
||||
* %bx Modified memory above 16M in 64kB blocks
|
||||
* CF set Region was truncated
|
||||
* CF clear Region was not truncated
|
||||
****************************************************************************
|
||||
*/
|
||||
intercept_88:
|
||||
pushw %bx /* E801 adjust, ignore %bx */
|
||||
call e801_adjust
|
||||
popw %bx
|
||||
jmp intercept_int15_exit
|
||||
.section ".text16"
|
||||
patch_16m:
|
||||
pushal
|
||||
/* Convert to (start,len) format and call truncate */
|
||||
movw $truncate_to_start, %bp
|
||||
xorl %ecx, %ecx
|
||||
shll $16, %ebx
|
||||
xorl %edx, %edx
|
||||
movl $0x1000000, %eax
|
||||
call truncate
|
||||
/* Convert back to "memory above 16MB" format and return via %bx */
|
||||
pushfw
|
||||
shrl $16, %ebx
|
||||
popfw
|
||||
movw %sp, %bp
|
||||
movw %bx, 24(%bp)
|
||||
popal
|
||||
ret
|
||||
.size patch_16m, . - patch_16m
|
||||
|
||||
.globl e820mangler_end
|
||||
e820mangler_end:
|
||||
/****************************************************************************
|
||||
* 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
|
||||
* CF set Region was truncated
|
||||
* CF clear Region was not truncated
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
patch_1m_16m:
|
||||
call patch_1m
|
||||
jc 1f
|
||||
call patch_16m
|
||||
ret
|
||||
1: /* 1m region was truncated; kill the 16m region */
|
||||
xorw %bx, %bx
|
||||
ret
|
||||
.size patch_1m_16m, . - patch_1m_16m
|
||||
|
||||
.globl _e820mangler_size
|
||||
.equ _e820mangler_size, e820mangler_end - e820mangler
|
||||
.globl e820mangler_size
|
||||
e820mangler_size:
|
||||
.word _e820mangler_size
|
||||
/****************************************************************************
|
||||
* Patch E820 memory map entry
|
||||
*
|
||||
* Parameters:
|
||||
* %es:di Pointer to E820 memory map descriptor
|
||||
* %bp truncate_to_start or truncate_to_end
|
||||
* Returns:
|
||||
* %es:di Pointer to now-modified E820 memory map descriptor
|
||||
* CF set Region was truncated
|
||||
* CF clear Region was not truncated
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
patch_e820:
|
||||
pushal
|
||||
movl %es:0(%di), %eax
|
||||
movl %es:4(%di), %edx
|
||||
movl %es:8(%di), %ebx
|
||||
movl %es:12(%di), %ecx
|
||||
call truncate
|
||||
movl %eax, %es:0(%di)
|
||||
movl %edx, %es:4(%di)
|
||||
movl %ebx, %es:8(%di)
|
||||
movl %ecx, %es:12(%di)
|
||||
popal
|
||||
ret
|
||||
.size patch_e820, . - patch_e820
|
||||
|
||||
#else
|
||||
/****************************************************************************
|
||||
* INT 15,e820 handler
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
int15_e820:
|
||||
pushw %si
|
||||
pushw %bp
|
||||
/* Caller's %bx => %si, real %ebx to %ebx, call previous handler */
|
||||
pushfw
|
||||
movw %bx, %si
|
||||
testl %ebx, %ebx
|
||||
jnz 1f
|
||||
movl %ebx, %cs:real_ebx
|
||||
1: movl %cs:real_ebx, %ebx
|
||||
lcall *%cs:int15_vector
|
||||
pushfw
|
||||
/* Edit result */
|
||||
pushw %ds
|
||||
pushw %cs:rm_ds
|
||||
popw %ds
|
||||
movw $truncate_to_start, %bp
|
||||
incw %si
|
||||
jns 2f
|
||||
movw $truncate_to_end, %bp
|
||||
2: call patch_e820
|
||||
jnc 3f
|
||||
xorw $0x8000, %si
|
||||
3: testw %si, %si
|
||||
js 4f
|
||||
movl %ebx, %cs:real_ebx
|
||||
testl %ebx, %ebx
|
||||
jz 5f
|
||||
4: movw %si, %bx
|
||||
5: popw %ds
|
||||
/* Restore flags returned by previous handler and return */
|
||||
popfw
|
||||
popw %bp
|
||||
popw %si
|
||||
lret $2
|
||||
.size int15_e820, . - int15_e820
|
||||
|
||||
.globl _e820mangler_size
|
||||
.equ _e820mangler_size, 0
|
||||
.section ".text16.data"
|
||||
real_ebx:
|
||||
.long 0
|
||||
.size real_ebx, . - real_ebx
|
||||
|
||||
#endif /* CODE16 */
|
||||
/****************************************************************************
|
||||
* INT 15,e801 handler
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
int15_e801:
|
||||
/* Call previous handler */
|
||||
pushfw
|
||||
lcall *%cs:int15_vector
|
||||
pushfw
|
||||
/* 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
|
||||
/* Restore flags returned by previous handler and return */
|
||||
popfw
|
||||
lret $2
|
||||
.size int15_e801, . - int15_e801
|
||||
|
||||
/****************************************************************************
|
||||
* INT 15,88 handler
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
int15_88:
|
||||
/* Call previous handler */
|
||||
pushfw
|
||||
lcall *%cs:int15_vector
|
||||
pushfw
|
||||
/* Edit result */
|
||||
pushw %ds
|
||||
pushw %cs:rm_ds
|
||||
popw %ds
|
||||
call patch_1m
|
||||
popw %ds
|
||||
/* Restore flags returned by previous handler and return */
|
||||
popfw
|
||||
lret $2
|
||||
.size int15_88, . - int15_88
|
||||
|
||||
/****************************************************************************
|
||||
* INT 15 handler
|
||||
****************************************************************************
|
||||
*/
|
||||
.section ".text16"
|
||||
.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"
|
||||
.globl int15_vector
|
||||
int15_vector:
|
||||
.long 0
|
||||
.size int15_vector, . - int15_vector
|
||||
|
|
|
|||
Reference in New Issue