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%cs at entry to decompressor varies a _lot_ among Linux 2.4.x, 2.6.y kernels.

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Decompressor must adapt; no universal constants exist for __BOOT_CS, _BOOT_DS.
	p_vmlinx.cpp stub/l_vmlinz.asm

committer: jreiser <jreiser> 1103605278 +0000
This commit is contained in:
John Reiser
2004-12-21 05:01:18 +00:00
parent f0c21c7203
commit 36b852e6bf
2 changed files with 53 additions and 41 deletions
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src/stub/l_vmlinz.asm
+27 -14
View File
@@ -34,25 +34,38 @@
SECTION .text
ORG 0
; gdt segment 3 is flat data
%define __BOOT_DS 3*8
; gdt segment 2 is flat code
%define __BOOT_CS 2*8
; =============
; ============= ENTRY POINT
; =============
start:
; __LINUZ000__
cli
xor eax, eax
mov al, __BOOT_DS
mov ds, eax
mov es, eax
; fs, gs set by startup_32 in arch/i386/kernel/head.S
mov ss, eax
lea esp, ['STAK' + esi] ; (0x9000 + 0x90000) typical
;cli ;this must be true already
; The only facts about segments here, that are true for all kernels:
; %cs is a valid "flat" code segment; no other segment reg is valid;
; the next segment after %cs is a valid "flat" data segment, but
; no segment register designates it yet.
mov eax, cs
add eax, byte 1<<3 ; the next segment after %cs
mov ds, eax
mov es, eax
; fs, gs set by startup_32 in arch/i386/kernel/head.S
; Linux Documentation/i386/boot.txt "SAMPLE BOOT CONFIGURATION" says
; 0x8000-0x8FFF Stack and heap [inside the "real mode segment",
; just below the command line at offset 0x9000].
; arch/i386/boot/compressed/head.S "Do the decompression ..." says
; %esi contains the "real mode pointer" [as a 32-bit addr].
; In any case, avoid EBDA (Extended BIOS Data Area) below 0xA0000.
; boot.txt says 0x9A000 is the limit. LILO goes up to 0x9B000.
lea ecx, ['STAK' + esi] ; (0x9000 + 0x90000) typical
mov [-8 + ecx], ecx ; 32-bit offset for stack pointer
mov [-4 + ecx], eax ; segment for stack
lss esp, [-8 + ecx] ; %ss:%esp= %ds:0x99000
push byte 0
popf ; BIOS can leave random flags (such as NT)
@@ -62,7 +75,7 @@ start:
or ebp, byte -1 ; decompressor assumption
mov eax, 'KEIP' ; 0x100000 : address of startup_32
push byte __BOOT_CS ; MATCH00
push cs ; MATCH00
push eax ; MATCH00 entry address
push edi ; MATCH01 save
push esi ; MATCH02 save