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%cs at entry to decompressor varies a _lot_ among Linux 2.4.x, 2.6.y kernels.
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
parent
f0c21c7203
commit
36b852e6bf
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@ -487,39 +487,38 @@ void PackVmlinuxI386::unpack(OutputFile *fo)
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//-----
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//
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//----- arch/i386/boot/compressed/upx-head.S
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//#include <asm/segment.h>
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//#ifndef __BOOT_CS /* Linux 2.4.x */
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//#define __BOOT_CS __KERNEL_CS
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//#define __BOOT_DS __KERNEL_DS
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//#endif
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//
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// .text
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// .text
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//startup_32: .globl startup_32 # In: %esi=0x90000 setup data "real_mode pointer"
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// cli # but if it matters, then there is a race!
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// #cli # this must be true already
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//
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// movl $ __BOOT_DS,%eax
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// movl %eax,%ss; leal 0x9000(%esi),%esp # 0x99000 typical
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// /* Linux Documentation/i386/boot.txt "SAMPLE BOOT CONFIGURATION" says
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// 0x8000-0x8FFF Stack and heap [inside the "real mode segment",
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// just below the command line at offset 0x9000].
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// /* The only facts about segments here, that are true for all kernels:
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// * %cs is a valid "flat" code segment; no other segment reg is valid;
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// * the next segment after %cs is a valid "flat" data segment, but
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// * no segment register designates it yet.
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// */
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// movl %cs,%eax; addl $1<<3,%eax # the next segment after %cs
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// movl %eax,%ds
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// movl %eax,%es
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// leal 0x9000(%esi),%ecx # 0x99000 typical
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// movl %ecx,-8(%ecx) # 32-bit offset for stack pointer
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// movl %eax,-4(%ecx) # segment for stack pointer
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// lss -8(%ecx),%esp # %ss:%esp= %ds:0x99000
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// /* Linux Documentation/i386/boot.txt "SAMPLE BOOT CONFIGURATION" says
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// 0x8000-0x8FFF Stack and heap [inside the "real mode segment",
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// just below the command line at offset 0x9000].
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//
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// arch/i386/boot/compressed/head.S "Do the decompression ..." says
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// %esi contains the "real mode pointer" [as a 32-bit addr].
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// arch/i386/boot/compressed/head.S "Do the decompression ..." says
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// %esi contains the "real mode pointer" [as a 32-bit addr].
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//
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// In any case, avoid EBDA (Extended BIOS Data Area) below 0xA0000.
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// boot.txt says 0x9A000 is the limit. LILO goes up to 0x9B000.
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// */
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// In any case, avoid EBDA (Extended BIOS Data Area) below 0xA0000.
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// boot.txt says 0x9A000 is the limit. LILO goes up to 0x9B000.
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// */
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//
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// pushl $0; popf # subsumes "cli; cld"; also clears NT for buggy BIOS
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// pushl $0; popf # subsumes "cli; cld"; also clears NT for buggy BIOS
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//
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// movl %eax,%ds # all non-code segments identical
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// movl %eax,%es
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// movl %eax,%fs
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// movl %eax,%gs
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//
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// movl $ 0x100000,%eax # destination of uncompression (and entry point)
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// pushl $ __BOOT_CS
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///* Fall into .text of upx-compressed vmlinux. */
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// movl $ 0x100000,%eax # destination of uncompression (and entry point)
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// push %cs
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/* Fall into .text of upx-compressed vmlinux. */
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//-----
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// Approximate translation for Linux 2.4.x:
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@ -34,25 +34,38 @@
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SECTION .text
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ORG 0
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; gdt segment 3 is flat data
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%define __BOOT_DS 3*8
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; gdt segment 2 is flat code
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%define __BOOT_CS 2*8
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; =============
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; ============= ENTRY POINT
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; =============
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start:
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; __LINUZ000__
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cli
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xor eax, eax
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mov al, __BOOT_DS
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mov ds, eax
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mov es, eax
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; fs, gs set by startup_32 in arch/i386/kernel/head.S
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mov ss, eax
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lea esp, ['STAK' + esi] ; (0x9000 + 0x90000) typical
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;cli ;this must be true already
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; The only facts about segments here, that are true for all kernels:
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; %cs is a valid "flat" code segment; no other segment reg is valid;
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; the next segment after %cs is a valid "flat" data segment, but
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; no segment register designates it yet.
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mov eax, cs
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add eax, byte 1<<3 ; the next segment after %cs
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mov ds, eax
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mov es, eax
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; fs, gs set by startup_32 in arch/i386/kernel/head.S
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; Linux Documentation/i386/boot.txt "SAMPLE BOOT CONFIGURATION" says
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; 0x8000-0x8FFF Stack and heap [inside the "real mode segment",
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; just below the command line at offset 0x9000].
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; arch/i386/boot/compressed/head.S "Do the decompression ..." says
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; %esi contains the "real mode pointer" [as a 32-bit addr].
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; In any case, avoid EBDA (Extended BIOS Data Area) below 0xA0000.
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; boot.txt says 0x9A000 is the limit. LILO goes up to 0x9B000.
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lea ecx, ['STAK' + esi] ; (0x9000 + 0x90000) typical
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mov [-8 + ecx], ecx ; 32-bit offset for stack pointer
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mov [-4 + ecx], eax ; segment for stack
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lss esp, [-8 + ecx] ; %ss:%esp= %ds:0x99000
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push byte 0
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popf ; BIOS can leave random flags (such as NT)
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@ -62,7 +75,7 @@ start:
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or ebp, byte -1 ; decompressor assumption
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mov eax, 'KEIP' ; 0x100000 : address of startup_32
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push byte __BOOT_CS ; MATCH00
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push cs ; MATCH00
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push eax ; MATCH00 entry address
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push edi ; MATCH01 save
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push esi ; MATCH02 save
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