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• PC boot: dl register and drive number

  - by kikou

  I read somewhere in the internet that, before jumping to 0x7c00, the BIOS loads into %dl the "drive number" of the booted device. But what is this "drive number"? Each device attached to the computer is assigned a number by the BIOS? If so, how can I know which number is a given device assigned to? Reading GRUB's source code I found when %dl has bits 0x80 and 0x70 set, it overwrites the whole register with 0x80. Why is that? Here is the code: jmp 3f /* grub-setup may overwrite this jump */ testb $0x80, %dl jz 2f 3: /* Ignore %dl different from 0-0x0f and 0x80-0x8f. */ testb $0x70, %dl jz 1f 2: movb $0x80, %dl 1: By the way. Is there any detailed resource on the boot process of PC's in the web? Specially about what the BIOS does before giving the control to the bootloader and also the standard codes used to communicate with it (like that "drive numer"). I was hoping to write my own bootloader and everything I found is a bit too vague, not technical enough to the point of informing of the exact state of the computer when my bootloader starts to run.

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• Is there a way to encode a URL in velocity template

  - by fermatthrm2

  Hi, Excuse my ignorance but I am new to Velocity and trying to fix someone else's problem. I need to encode a URL inside the velocity template. I create a url and as part of the query string I pass in a page name a user created. This page can contain special characters like ëðû. The url would look like http://foo.com/page1/jz?page=SpecialChars_ëðû

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• Why is a 16-bit register used with BSR instruction in this code snippet?

  - by sharptooth

  In this hardcore article there's a function find_maskwidth() that basically detects the number of bits required to represent itemCount dictinct values: unsigned int find_maskwidth( unsigned int itemCount ) { unsigned int maskWidth, count = itemCount; __asm { mov eax, count mov ecx, 0 mov maskWidth, ecx dec eax bsr cx, ax jz next inc cx mov maskWidth, ecx next: } return maskWidth; } the question is why do they use ax and cx registers instead of eax and ecx?

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• How to run boot loader in VMWare?

  - by Asim Haroon

  I am using Ubuntu as a virtual machine in VMWare. I have used this code to write a boot loader which would write Hello world on the screen. [BITS 16] [ORG 0x7C00] MOV SI, HelloString CALL PrintString JMP $ PrintCharacter: MOV AH, 0x0E MOV BH, 0x00 MOV BL, 0x07 INT 0x10 RET PrintString: next_character: MOV AL, [SI] INC SI OR AL, AL JZ exit_function CALL PrintCharacter JMP next_character exit_function: RET HelloString db 'Hello World', 0 TIMES 510 - ($ - $$) db 0 DW 0xAA55 I wrote this code in the text editor in Ubuntu and saved the file as Boot.asm Then I compiled the Boot.asm to boot.bin file by using this command nasm -f bin -o boot.bin Boot.asm and it didn't gave me any errors. After that I copied the boot.bin file to my usb and took it to my Windows OS. After this I burned the boot.bin file to boot.img and boot.iso files. Then I created a new virtual machine and named it booter, when it asked for the .iso file of the OS I want to run I gave it the boot.iso file, about which I told above, then I powered on that virtual machine but it gave me this error PXE-M0F: No boot filename received PXE-M0F: Exiting Intel PXE ROM Operating System not found Please tell me what is the main problem and how can I overcome that problem.

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• [Assembly] jnz after xor?

  - by kotarou3

  After using IDA Pro to disassemble a x86 dll, I found this code (Comments added by me in pusedo-c code. I hope they're correct): test ebx, ebx ; if (ebx == false) jz short loc_6385A34B ; Jump to 0x6385a34b mov eax, [ebx+84h] ; eax = *(ebx+0x84) mov ecx, [esi+84h] ; ecx = *(esi+0x84) mov al, [eax+30h] ; al = *(*(ebx+0x84)+0x30) xor al, [ecx+30h] ; al = al XOR *(*(esi+0x84)+0x30) jnz loc_6385A453 Lets make it simpler for me to understand: mov eax, b3h xor eax, d6h jnz ... How does the conditional jump instruction work after a xor instruction?

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• Interrupt On GAS

  - by Nathan Campos

  I'm trying to convert my simple program from Intel syntax to the AT&T(to compile it with GAS). I've successfully converted a big part of my application, but I'm still getting an error with the int(the interrupts). My function is like this: printf: mov $0x0e, %ah mov $0x07, %bl nextchar: lodsb or %al, %al jz return int 10 jmp nextchar return: ret msg db "Welcome To Track!", 0Ah But when I compile it, I got this: hello.S: Assembler messages: hello.S:13: Error: operand size mismatch for int' hello.S:19: Error: no such instruction:msg db "Hello, World!",0Ah' What I need to do?

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• top Tweets SOA Partner Community &ndash; June 2012

  - by JuergenKress

  Send your tweets @soacommunity #soacommunity and follow us at http://twitter.com/soacommunity Simone Geib Contact me directly for ideas how to improve http://bit.ly/advancedsoasuite and additional posts, presentations, white papers, #soasuite SOA CommunitySOA Community Newsletter May 2012 https://soacommunity.wordpress.com /2012/05/28/soa-community-newsletter-may-2012/ #soacommunity Simone Geib #soasuite advanced OTN page has become too cluttered. Broke it into separate pages to start with. http://bit.ly/advancedsoasuite SOA CommunitySOA Management with Enterprise Manager Cloud Control 12c and Business Transaction Management 12c Demo https://soacommunity.wordpress.com /2012/05/21/soa-management-with-enterprise-manager-cloud-control-12c-and-business-transaction-management-12c-demo/ #soacommunity OracleBlogs June Webcast: SOA Gateway Implementation and Troubleshooting (2 sessions) http://ow.ly/1kbRFA OTNArchBeatEvery cloud needs an SOA lining: analyst | @JoeMcKendrick http://zd.net/KTgMHk ServiceTechSymposium New session just posted to calendar: "NoSQL for Data Services, Data Virtualization & Big Data" by Guido Schmutz, Trivadis AG ://ow.ly/bjjOe OTNArchBeat?Every cloud needs an SOA lining: analyst | @JoeMcKendrick http://zd.net/KTgMHk Debra Lilley looks good - real proof people are using the apps ! RT @fteter:Very cool Fusion Applications Help site: http://bit.ly/L3nvOR #FusionApps OTNArchBeat How to Set JVM Parameters in Oracle SOA 11G | Francis Ip http://bit.ly/JBDYPj demed"rapid proliferation of cloud computing will drive convergence of SOA and cloud paradigms" http://ovum.com/2012/05/18/soa-paves-the-way-for-cloud/ SOA Community Sending out invitations to our advanced Fusion Middleware Summer Camps! Want to learn more register for the community http://www.oracle.com/goto/emea/soa SOA Community Middleware Oracle Excellence Awards 2012 - HAPPY NEW YEAR! https://soacommunity.wordpress.com/ 2012/05/31/middleware-oracle-excellence-awards-2012 happy-new-year/ #soacommunity #opn #opnaward #specialization #oracle Simone Geib #oraclesoa performance tuning resources. All in one: docs, blogs, WPs, ppts: http://bit.ly/soa_resources OracleBlogs Middleware Oracle Excellence Awards 2012 - HAPPY NEW YEAR! http://ow.ly/1k9ri0 ServiceTechSymposiumNew session just posted to Symposium calendar: "Service Modeling & BPM Business Value Patterns" by Jürgen Kress, Oracle http://www.servicetechsymposium.com/ agenda2012.php #service_modeling_and_bpm _business_value_patterns SOA Community Happy New Year #soacommunity thanks for the business! Time for a drink ;-) http://pic.twitter.com/zkK08KWB Jan van ZoggelUsing execute-sql() function for Name-Value pair lookups in Oracle Service Bus http://wp.me/p1H430-jZ SOA Community Middleware Oracle Excellence Awards 2012&ndash;HAPPY NEW YEAR! http://wp.me/p10C8u-q4 orclateamsoa A-Team Blog #ateam: BPM 11g Deployment & Instance Migration - I have seen a number of request lately asking how to http://ow.ly/1jZ0h8 OTNArchBeat Who should ‘own’ the Enterprise Architecture? | Michael Glas http://bit.ly/K0ge0Q Oracle UPK & Tutor TOMORROW! (June 23rd) - UPK Professional Webinar at Noon ET: Discover why user adoption is a key factor for the http://bit.ly/LjZjdx Sabine Leitner Finance Event im Design-Hotel beim Barbeque: 21. Juni FRA mit Kunden SV Informatik, Schufa, LBBW http://bit.ly/JtwE3v #Oracle @itevent OracleEnterpriseMgr SOA Management with Enterprise Manager Cloud Control 12c and Business Transaction Management 12c Demo http://ow.ly/b3WP1 #em12c ServiceTechSymposium New session just posted to Symposium calendar: "Elastic SOA in the Cloud" by Steve Millidge, C2B2 Consulting http://www.servicetechsymposium.com /agenda2012.php #elastic_soa_in_the_cloud OTNArchBeat Securing Heterogeneous Systems Using Oracle Web Services Manager by @rluttikhuizen & Jens Peters http://bit.ly/KjShFi Oracleteamsoa A-Team Blog #ateam: How to Set JVM Parameters in Oracle SOA 11G http://ow.ly/1k2cnl SOA Community Oracle Service Registry in an automated (Maven) SOA/BPM build http://redstack.wordpress.com /2012/05/22/using-oracle-service-registry-in-an-automated-maven-soabpm-build/ #soacommunity #redstack #soa #osr #opn SOA CommunityHigh demand for advanced Fusion Middleware Summer Camps! Want to learn more register for the #soacommunity http://www.oracle.com/goto/emea/soa OracleBlogs? How to Set JVM Parameters in Oracle SOA 11G http://ow.ly/1k1UTv SOA Community top Tweets SOA Partner Community &ndash; May 2012 http://wp.me/p10C8u-pP ServiceTechSymposium New session just posted to Symposium calendar: "SOA Governance at EDP: A Global Energy Company" by Manuel Rosa, Link http://www.servicetechsymposium.com/ agenda2012.php #soa_governance_at_edp For regular information on Oracle SOA Suite become a member in the SOA Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) Blog Twitter LinkedIn Mix Forum Technorati Tags: soacommunity,twitter,Oracle,SOA Community,Jürgen Kress,OPN,SOA,BPM

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• What is Causing This Memory Leak in Delphi?

  - by lkessler

  I just can't figure out this memory leak that EurekaLog is reporting for my program. I'm using Delphi 2009. Here it is: Memory Leak: Type=Data; Total size=26; Count=1; The stack is: System.pas _UStrSetLength 17477 System.pas _UStrCat 17572 Process.pas InputGedcomFile 1145 That is all there is in the stack. EurekaLog is pointing me to the location where the memory that was not released was first allocated. According to it, the line in my program is line 1145 of InputGedcomFile. That line is: CurStruct0Key := 'HEAD' + Level0Key; where CurStruct0Key and Level0Key are simply defined in the procedure as local variables that should be dynamically handled by the Delphi memory manager when entering and leaving the procedure: var CurStruct0Key, Level0Key: string; So now I look at the _UStrCat procedure in the System Unit. Line 17572 is: CALL _UStrSetLength // Set length of Dest and I go to the _UStrSetLength procedure in the System Unit, and the relevant lines are: @@isUnicode: CMP [EAX-skew].StrRec.refCnt,1 // !!! MT safety JNE @@copyString // not unique, so copy SUB EAX,rOff // Offset EAX "S" to start of memory block ADD EDX,EDX // Double length to get size JO @@overflow ADD EDX,rOff+2 // Add string rec size JO @@overflow PUSH EAX // Put S on stack MOV EAX,ESP // to pass by reference CALL _ReallocMem POP EAX ADD EAX,rOff // Readjust MOV [EBX],EAX // Store MOV [EAX-skew].StrRec.length,ESI MOV WORD PTR [EAX+ESI*2],0 // Null terminate TEST EDI,EDI // Was a temp created? JZ @@exit PUSH EDI MOV EAX,ESP CALL _LStrClr POP EDI JMP @@exit where line 17477 is the "CALL _ReallocMem" line. So then what is the memory leak? Surely a simple concatenate of a string constant to a local string variable should not be causing a memory leak. Why is EurekaLog pointing me to the ReallocMem line in a _UStrSetLength routine that is part of Delphi? This is Delphi 2009 and I am using the new unicode strings. Any help or explanation here will be much appreciated.

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• No Program Entry Point TASM Error

  - by Nathan Campos

  I'm trying to develop a simple kernel using TASM, using this code: ; beroset.asm ; ; This is a primitive operating system. ; ;********************************************************************** code segment para public use16 '_CODE' .386 assume cs:code, ds:code, es:code, ss:code org 0 Start: mov ax,cs mov ds,ax mov es,ax mov si,offset err_msg call DisplayMsg spin: jmp spin ;**************************************************************************** ; DisplayMsg ; ; displays the ASCIIZ message to the screen using int 10h calls ; ; Entry: ; ds:si ==> ASCII string ; ; Exit: ; ; Destroyed: ; none ; ; ;**************************************************************************** DisplayMsg proc push ax bx si cld nextchar: lodsb or al,al jz alldone mov bx,0007h mov ah,0eh int 10h jmp nextchar alldone: pop si bx ax ret DisplayMsg endp err_msg db "Operating system found and loaded.",0 code ends END Then I compile it like this: C:\DOCUME~1\Nathan\Desktop tasm /la /m2 beroset.asm Turbo Assembler Version 4.1 Copyright (c) 1988, 1996 Borland International Assembling file: beroset.asm Error messages: None Warning messages: None Passes: 2 Remaining memory: 406k C:\DOCUME~1\Nathan\Desktop tlink beroset, loader.bin Turbo Link Version 7.1.30.1. Copyright (c) 1987, 1996 Borland International Fatal: No program entry point C:\DOCUME~1\Nathan\Desktop What can I to correct this error?

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• Decompiling a *.DLL to assembly for .net in delphi 4

  - by Lex Dean

  I love my Delphi 4 but at the same time I see the need to talk to windows .net This is a recompiled dll that I found on sourceforge.net/projects/delphinet/ (DelphiNet03.zip) by some nice people that fund the dll from some were. The real answer is to make this dll so that fits into Delphi as true Delphi code, and not a dll clip on. So we can make objects that use dot net in Delphi. Because I’m not an assembly freak, I’m freaking out a little with a wee sweek for help! 1/ How do I link the asm code with the data info at the bottom of this code. Can some one show me which calls to look for to make this link to data. 2/ I need to find the beginning of all the procedures and functions, but I cannot find a ‘RET’ statement. And what line is the beginning statement in this code. 3/ How do I identify were the jump statements go to, put them into Delphi format In this code it looks I can do:- jle 402890h \1000:00402854 7e3a add [eax], al \1000:00402856 0000 …………………………………………….. or ch, [edi+3eh] \1000:0040288d 0a6f3e xrefs first: 1000:00402854 number : 1 \; add [eax], al \1000:00402890 0000 //******************************* jle @@21 \\1000:00402854 7e3a add [eax], al \\1000:00402856 0000 …………………………………………….. or ch, [edi+3eh] \1000:0040288d 0a6f3e xrefs first: 1000:00402854 number : 1 \; @@21 add [eax], al \1000:00402890 0000 Is that a correct conversion. I think a xrefs first: 1000:004021d1 number : 1 is the best to follow 4/ I need a good reference on 8086 up assembly code that I can print out and get to learn properly. I found this asm decomplier of http://www.cronos.cc/ that is so similar to Delphi that it only needs a little more convertion to get it into Delphi asm I think. It’s only taken me 3 hours to get the file into TMemo and to write a few lines to chop the line over in a stream and reload the memo. Help please Email: [email protected] xrefs first: 1000:004041ae number : 1 \\; dd 4190h \\1000:00402000 90410000 dd 00h \\1000:00402004 00000000 dec eax \\1000:00402008 48 add [eax], al \\1000:00402009 0000 add [edx], al \\1000:0040200b 0002 add [eax], al \\1000:0040200d 0000 add [eax-2bffffd2h], al \\1000:0040200f 00802e0000d4 adc al, [eax] \\1000:00402015 1200 add [ecx], al \\1000:00402017 0001 add [eax], al \\1000:00402019 0000 add [eax], al \\1000:0040201b 0000 add [eax], al \\1000:0040201d 0000 add [eax], al \\1000:0040201f 0000 add [eax], al \\1000:00402021 0000 add [eax], al \\1000:00402023 0000 add [eax], al \\1000:00402025 0000 add [eax], al \\1000:00402027 0000 add [eax], al \\1000:00402029 0000 add [eax], al \\1000:0040202b 0000 add [eax], al \\1000:0040202d 0000 add [eax], al \\1000:0040202f 0000 add [eax], al \\1000:00402031 0000 add [eax], al \\1000:00402033 0000 add [eax], al \\1000:00402035 0000 add [eax], al \\1000:00402037 0000 add [eax], al \\1000:00402039 0000 add [eax], al \\1000:0040203b 0000 add [eax], al \\1000:0040203d 0000 add [eax], al \\1000:0040203f 0000 add [eax], al \\1000:00402041 0000 add [eax], al \\1000:00402043 0000 add [eax], al \\1000:00402045 0000 add [eax], al \\1000:00402047 0000 add [eax], al \\1000:00402049 0000 add [eax], al \\1000:0040204b 0000 add [eax], al \\1000:0040204d 0000 add [ebx], dl \\1000:0040204f 0013 xor [eax+eax], al \\1000:00402051 300400 or al, [ecx] \\1000:00402054 0a01 add [eax], al \\1000:00402056 0000 add [eax], eax \\1000:00402058 0100 add [ecx], dl \\1000:0040205a 0011 push cs \\1000:0040205c 0e add al, 50h \\1000:0040205d 0450 mov gs, [ecx+05h] \\1000:0040205f 8e6905 push eax \\1000:00402062 50 mov gs, [ecx+2eh] \\1000:00402063 8e692e add eax, f938h \\1000:00402066 0538f90000 add [ebx], al \\1000:0040206b 0003 jc 402070h \\1000:0040206d 7201 add [eax], al \\1000:0040206f 0000 jo 40209bh \\1000:00402071 7028 add al, [eax] \\1000:00402073 0200 add [edx], cl \\1000:00402075 000a sub eax, 36f0408h \\1000:00402077 2d08046f03 add [eax], al \\1000:0040207c 0000 or ch, [ebx] \\1000:0040207e 0a2b push es \\1000:00402080 06 add al, 6fh \\1000:00402081 046f add al, 00h \\1000:00402083 0400 add [edx], cl \\1000:00402085 000a adc eax, [edi] \\1000:00402087 1307 push ss \\1000:00402089 16 adc ecx, [eax] \\1000:0040208a 1308 cmp cl, cl \\1000:0040208c 38c9 add [eax], al \\1000:0040208e 0000 add [ecx], dl \\1000:00402090 0011 pop es \\1000:00402092 07 adc [eax], ecx \\1000:00402093 1108 callf 056f:060a9a08h \\1000:00402095 9a0a066f05 add [eax], al \\1000:0040209a 0000 or cl, [ebx] \\1000:0040209c 0a0b push es \\1000:0040209e 06 outsd \\1000:0040209f 6f push es \\1000:004020a0 06 add [eax], al \\1000:004020a1 0000 or al, [ebx] \\1000:004020a3 0a03 sub [edx], al \\1000:004020a5 2802 add [eax], al \\1000:004020a7 0000 or bh, [ecx] \\1000:004020a9 0a39 movsd \\1000:004020ab a5 add [eax], al \\1000:004020ac 0000 add [edi], al \\1000:004020ae 0007 mov gs, [ecx+0eh] \\1000:004020b0 8e690e add al, 50h \\1000:004020b3 0450 mov gs, [ecx+40h] \\1000:004020b5 8e6940 cwde \\1000:004020b8 98 add [eax], al \\1000:004020b9 0000 add [edi], dl \\1000:004020bb 0017 or al, 16h \\1000:004020bd 0c16 or eax, 9072b2bh \\1000:004020bf 0d2b2b0709 callf 0000:076f9a09h \\1000:004020c4 9a6f070000 or ch, [edi+08h] \\1000:004020c9 0a6f08 add [eax], al \\1000:004020cc 0000 or ch, [eax+ebx] \\1000:004020ce 0a2c18 push cs \\1000:004020d1 0e add al, 50h \\1000:004020d2 0450 or [edx+d72h], ebx \\1000:004020d4 099a720d0000 jo 402104h \\1000:004020da 7028 or [eax], eax \\1000:004020dc 0900 add [edx], cl \\1000:004020de 000a add dl, cs:[esi] \\1000:004020e0 2e0216 or al, 08h \\1000:004020e3 0c08 sub eax, 90c2b02h \\1000:004020e5 2d022b0c09 pop ss \\1000:004020ea 17 pop eax \\1000:004020eb 58 or eax, 50040e09h \\1000:004020ec 0d090e0450 mov gs, [ecx+32h] \\1000:004020f1 8e6932 int 08h \\1000:004020f4 cd08 sub al, 5ch \\1000:004020f6 2c5c push ss \\1000:004020f8 16 adc eax, [ebx+ebp] \\1000:004020f9 13042b dec esi \\1000:004020fc 4e push cs \\1000:004020fd 0e add al, 50h \\1000:004020fe 0450 adc [edx+ebx*4], eax \\1000:00402100 11049a jc 402112h \\1000:00402103 720d add [eax], al \\1000:00402105 0000 jo 402131h \\1000:00402107 7028 or [eax], eax \\1000:00402109 0900 add [edx], cl \\1000:0040210b 000a xor esi, [esi] \\1000:0040210d 3336 pop es \\1000:0040210f 07 adc [edx+ebx*4], eax \\1000:00402110 11049a outsd \\1000:00402113 6f pop es \\1000:00402114 07 add [eax], al \\1000:00402115 0000 or ch, [edi+0ah] \\1000:00402117 0a6f0a add [eax], al \\1000:0040211a 0000 or dl, [ebx] \\1000:0040211c 0a13 push es \\1000:0040211e 06 add eax, 9a041150h \\1000:0040211f 055011049a sub [ebx], cl \\1000:00402124 280b add [eax], al \\1000:00402126 0000 or dl, [edx] \\1000:00402128 0a12 push es \\1000:0040212a 06 adc al, [c28h] \\1000:0040212b 1205280c0000 xrefs first: 1000:00402107 number : 1 \\; or ch, [edx+eax] \\1000:00402131 0a2c02 sub ebx, [esi] \\1000:00402134 2b1e push cs \\1000:00402136 0e add al, 50h \\1000:00402137 0450 adc [edi+eax], eax \\1000:00402139 110407 adc [edx+ebx*4], eax \\1000:0040213c 11049a outsd \\1000:0040213f 6f pop es \\1000:00402140 07 add [eax], al \\1000:00402141 0000 or ah, [edx+58170411h] \\1000:00402143 0aa211041758 adc eax, [ecx+edx] \\1000:00402149 130411 add al, 0eh \\1000:0040214c 040e add al, 50h \\1000:0040214e 0450 mov gs, [ecx+32h] \\1000:00402150 8e6932 test eax, 58170811h \\1000:00402153 a911081758 adc ecx, [eax] \\1000:00402158 1308 adc [eax], ecx \\1000:0040215a 1108 adc [edi], eax \\1000:0040215c 1107 mov gs, [ecx+3fh] \\1000:0040215e 8e693f sub al, ffh \\1000:00402161 2cff db ff \\1000:00402163 ff jmp [edx] \\1000:00402164 ff2a add [eax], al \\1000:00402166 0000 adc esi, [eax] \\1000:00402168 1330 add eax, 8100h \\1000:0040216a 0500810000 add [edx], al \\1000:0040216f 0002 add [eax], al \\1000:00402171 0000 adc [edx+esi*2], eax \\1000:00402173 110472 xor eax, [eax] \\1000:00402176 3300 add [eax+28h], dh \\1000:00402178 007028 add al, [eax] \\1000:0040217b 0200 add [edx], cl \\1000:0040217d 000a sub al, 09h \\1000:0040217f 2c09 add ebp, [eax] \\1000:00402181 0328 or eax, a0a0000h \\1000:00402183 0d00000a0a sub eax, [edi] \\1000:00402188 2b07 add al, 28h \\1000:0040218a 0428 push cs \\1000:0040218c 0e add [eax], al \\1000:0040218d 0000 or cl, [edx] \\1000:0040218f 0a0a push es \\1000:00402191 06 add eax, f6f1717h \\1000:00402192 0517176f0f add [eax], al \\1000:00402197 0000 or cl, [ebx] \\1000:00402199 0a0b push ss \\1000:0040219b 16 lea eax, [edx] \\1000:0040219c 8d02 add [eax], al \\1000:0040219e 0000 add [esi+ecx], ecx \\1000:004021a0 010c0e add al, 2ch \\1000:004021a3 042c push cs \\1000:004021a5 260e add al, 8eh \\1000:004021a7 048e c160d imul edi, [eax+28dh], d160c01h \\1000:004021a9 69b88d020000010c sub edx, [eax] \\1000:004021b3 2b10 or [ecx], cl \\1000:004021b5 0809 push cs \\1000:004021b7 0e add al, 09h \\1000:004021b8 0409 callf 0000:106f9a09h \\1000:004021ba 9a6f100000 or ah, [edx+d581709h] \\1000:004021bf 0aa20917580d or [esi], ecx \\1000:004021c5 090e add al, 8eh \\1000:004021c7 048e imul esi, [edx], 17202e9h \\1000:004021c9 6932e9027201 add [eax], al \\1000:004021cf 0000 jo 4021dah \\1000:004021d1 7007 db 0f \\1000:004021d3 0f add al, 12h \\1000:004021d4 0412 add ch, [eax] \\1000:004021d6 0228 add [eax], eax \\1000:004021d8 0100 xrefs first: 1000:004021d1 number : 1 \\; add [esi], al \\1000:004021da 0006 pop es \\1000:004021dc 07 or [edi+11h], ch \\1000:004021dd 086f11 add [eax], al \\1000:004021e0 0000 or dl, [ebx] \\1000:004021e2 0a13 add al, 11h \\1000:004021e4 0411 add al, 0eh \\1000:004021e6 040e add al, 6fh \\1000:004021e8 046f adc al, [eax] \\1000:004021ea 1200 add [edx], cl \\1000:004021ec 000a adc eax, [511002bh] \\1000:004021ee 13052b001105 sub al, [eax] \\1000:004021f4 2a00 add [eax], al \\1000:004021f6 0000 adc esi, [eax] \\1000:004021f8 1330 add eax, 4e00h \\1000:004021fa 05004e0000 add [ebx], al \\1000:004021ff 0003 add [eax], al \\1000:00402201 0000 adc [ebx], eax \\1000:00402203 1103 outsd \\1000:00402205 6f adc [eax], al \\1000:00402206 1000 add [edx], cl \\1000:00402208 000a or al, [8db8698eh] \\1000:0040220a 0a058e69b88d add al, [eax] \\1000:00402210 0200 add [ecx], al \\1000:00402212 0001 or edx, [esi] \\1000:00402214 0b16 or al, 2bh \\1000:00402216 0c2b db 0f \\1000:00402218 0f pop es \\1000:00402219 07 or [106f9a08h], al \\1000:0040221a 0805089a6f10 add [eax], al \\1000:00402220 0000 or ah, [edx+c581708h] \\1000:00402222 0aa20817580c or [eb32698eh], al \\1000:00402228 08058e6932eb add al, [esi+eax] \\1000:0040222e 020406 lsl edx, [edx] \\1000:00402231 0f0312 add [eax], ebp \\1000:00402234 0128 add [eax], eax \\1000:00402236 0100 add [esi], al \\1000:00402238 0006 push es \\1000:0040223a 06 add al, 07h \\1000:0040223b 0407 outsd \\1000:0040223d 6f adc eax, [eax] \\1000:0040223e 1300 add [edx], cl \\1000:00402240 000a or eax, 6f050309h \\1000:00402242 0d0903056f adc al, 00h \\1000:00402247 1400 add [edx], cl \\1000:00402249 000a adc eax, [ebx+ebp] \\1000:0040224b 13042b add [ecx], dl \\1000:0040224e 0011 add al, 2ah \\1000:00402250 042a add [eax], al \\1000:00402252 0000 adc esi, [eax] \\1000:00402254 1330 add eax, 7600h \\1000:00402256 0500760000 add [eax+eax], al \\1000:0040225b 000400 add [ecx], dl \\1000:0040225e 0011 add al, 72h \\1000:00402260 0472 xor eax, [eax] \\1000:00402262 3300 add [eax+28h], dh \\1000:00402264 007028 add al, [eax] \\1000:00402267 0200 add [edx], cl \\1000:00402269 000a sub al, 09h \\1000:0040226b 2c09 add ebp, [eax] \\1000:0040226d 0328 or eax, a0a0000h \\1000:0040226f 0d00000a0a sub eax, [edi] \\1000:00402274 2b07 add al, 28h \\1000:00402276 0428 push cs \\1000:00402278 0e add [eax], al \\1000:00402279 0000 or cl, [edx] \\1000:0040227b 0a0a push es \\1000:0040227d 06 add eax, f6f1717h \\1000:0040227e 0517176f0f add [eax], al \\1000:00402283 0000 or cl, [ebx] \\1000:00402285 0a0b push cs \\1000:00402287 0e add eax, 8db8698eh \\1000:00402288 058e69b88d add al, [eax] \\1000:0040228d 0200 add [ecx], al \\1000:0040228f 0001 or al, 16h \\1000:00402291 0c16 or eax, 908102bh \\1000:00402293 0d2b100809 push cs \\1000:00402298 0e add eax, 106f9a09h \\1000:00402299 05099a6f10 add [eax], al \\1000:0040229e 0000 or ah, [edx+d581709h] \\1000:004022a0 0aa20917580d or [esi], ecx \\1000:004022a6 090e add eax, e932698eh \\1000:004022a8 058e6932e9 add cl, [esi] \\1000:004022ad 020e add al, 07h \\1000:004022af 0407 db 0f \\1000:004022b1 0f add eax, 1280212h \\1000:004022b2 0512022801 add [eax], al \\1000:004022b7 0000 push es \\1000:004022b9 06 pop es \\1000:004022ba 07 push cs \\1000:004022bb 0e add al, 08h \\1000:004022bc 0408 outsd \\1000:004022be 6f adc eax, [eax] \\1000:004022bf 1300 add [edx], cl \\1000:004022c1 000a adc eax, [ecx+edx] \\1000:004022c3 130411 add al, 14h \\1000:004022c6 0414 push cs \\1000:004022c8 0e add eax, 146fh \\1000:004022c9 056f140000 or dl, [ebx] \\1000:004022ce 0a13 add eax, 511002bh \\1000:004022d0 052b001105 sub al, [eax] \\1000:004022d5 2a00 add [ebx], dl \\1000:004022d7 0013 xor [eax+eax], al \\1000:004022d9 300400 jbe 4022deh \\1000:004022dc 7600 xrefs first: 1000:004022dc number : 1 \\; add fs:[esi+45h], cl \\1000:004034fc 64004e45 push esp \\1000:00403500 54 dec ecx \\1000:00403501 49 xrefs first: 1000:004034b2 number : 1 \\; outsb \\1000:00403502 6e jbe 403574h \\1000:00403503 766f imul esp, [ebp+43h], 6ch \\1000:00403505 6b65436c popad \\1000:00403509 61 jnc 40357fh \\1000:0040350a 7373 dec ebp \\1000:0040350c 4d jz 403578h \\1000:0040350d 657468 outsd \\1000:00403510 6f add fs:[esi+45h], cl \\1000:00403511 64004e45 push esp \\1000:00403515 54 push ebx \\1000:00403516 53 jz 40355fh \\1000:00403517 657445 outsb \\1000:0040351a 6e jnz 40358ah \\1000:0040351b 756d push esi \\1000:0040351d 56 xrefs first: 1000:004034b7 number : 1 \\; popad \\1000:0040351e 61 insb \\1000:0040351f 6c jnz 403587h \\1000:00403520 7565 add [esi+45h], cl \\1000:00403522 004e45 push esp \\1000:00403525 54 inc edi \\1000:00403526 47 db 65 ;'e' \\1000:00403527 65 xrefs first: 1000:004034be number : 1 \\; db 74 ;'t' \\1000:00403528 74 db 50 ;'p' \\1000:00403529 50 db 72 ;'r' \\1000:0040352a 72 db 6f ;'o' \\1000:0040352b 6f db 70 ;'p' \\1000:0040352c 70 db 65 ;'e' \\1000:0040352d 65 db 72 ;'r' \\1000:0040352e 72 db 74 ;'t' \\1000:0040352f 74 db 79 ;'y' \\1000:00403530 79 db 00 \\1000:00403531 00 db 4e ;'n' \\1000:00403532 4e db 45 ;'e' \\1000:00403533 45 db 54 ;'t' \\1000:00403534 54 db 47 ;'g' \\1000:00403535 47 db 65 ;'e' \\1000:00403536 65 db 74 ;'t' \\1000:00403537 74 db 46 ;'f' \\1000:00403538 46 db 69 ;'i' \\1000:00403539 69 db 65 ;'e' \\1000:0040353a 65 db 6c ;'l' \\1000:0040353b 6c db 64 ;'d' \\1000:0040353c 64 db 00 \\1000:0040353d 00 could not fit the rest in because of Stack overflow limitions

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• x86_64 assembler: only one call per subroutine?

  - by zneak

  Hello everyone, I decided yesterday to start doing assembler. Most of it is okay (well, as okay as assembler can be), but I'm getting some problems with gas. It seems that I can call functions only once. After that, any subsequent call opcode with the same function name will fail. I must be doing something terribly wrong, though I can't see what. Take this small C function for instance: void path_free(path_t path) { if (path == NULL) return; free(((point_list_t*)path)->points); free(path); } I "translated" it to assembler like that: .globl _path_free _path_free: push rbp mov rbp, rsp cmp rdi, 0 jz byebye push rdi mov rdi, qword ptr [rdi] call _free pop rdi sub rsp, 8 call _free byebye: leave ret This triggers the following error for the second call _free: suffix or operands invalid for ``call''. And if I change it to something else, like free2, everything works (until link time, that is). Assembler code gcc -S gave me looks very similar to what I've done (except it's in AT&T syntax), so I'm kind of lost. I'm doing this on Mac OS X under the x86_64 architecture.

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• A way to edit content by altering one file?

  - by Chris

  Hi, I have a contact css tab on my left side on my website, I have more then 30 pages and I don't wantto manually alter all those pages later when data had changed. Does anyone knows a sollution so I only have to alter 1 file to have all pages edited? Perhaps in javascript? The code below is for the tab <div class="slide-out-div"> <a class="handle" href="http://link-for-non-js-users">Content</a> <h3>Onze contact gegevens</h3> <p>Adres: van Ostadestraat 55<br /> Postcode: 8932 JZ<br /> Plaats: Leeuwarden<br /> Tel: 058 844 66 28<br /> Mob: 0629594595 <br /> E-mail: <a href="mailto:[email protected]">[email protected]</a><br /><br /> </p> <p>Mocht u vragen hebben dan kunt u gerust bij ons terecht voor meer informatie.</p>

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• x86 Assembly: Before Making a System Call on Linux Should You Save All Registers?

  - by mudge

  I have the below code that opens up a file, reads it into a buffer and then closes the file. The close file system call requires that the file descriptor number be in the ebx register. The ebx register gets the file descriptor number before the read system call is made. My question is should I save the ebx register on the stack or somewhere before I make the read system call, (could int 80h trash the ebx register?). And then restore the ebx register for the close system call? Or is the code I have below fine and safe? I have run the below code and it works, I'm just not sure if it is generally considered good assembly practice or not because I don't save the ebx register before the int 80h read call. ;; open up the input file mov eax,5 ; open file system call number mov ebx,[esp+8] ; null terminated string file name, first command line parameter mov ecx,0o ; access type: O_RDONLY int 80h ; file handle or negative error number put in eax test eax,eax js Error ; test sign flag (SF) for negative number which signals error ;; read in the full input file mov ebx,eax ; assign input file descripter mov eax,3 ; read system call number mov ecx,InputBuff ; buffer to read into mov edx,INPUT_BUFF_LEN ; total bytes to read int 80h test eax,eax js Error ; if eax is negative then error jz Error ; if no bytes were read then error add eax,InputBuff ; add size of input to the begining of InputBuff location mov [InputEnd],eax ; assign address of end of input ;; close the input file ;; file descripter is already in ebx mov eax,6 ; close file system call number int 80h

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• Problem with bootstrap loader and kernel

  - by dboarman-FissureStudios

  We are working on a project to learn how to write a kernel and learn the ins and outs. We have a bootstrap loader written and it appears to work. However we are having a problem with the kernel loading. I'll start with the first part: bootloader.asm: [BITS 16] [ORG 0x0000] ; ; all the stuff in between ; ; the bottom of the bootstrap loader datasector dw 0x0000 cluster dw 0x0000 ImageName db "KERNEL SYS" msgLoading db 0x0D, 0x0A, "Loading Kernel Shell", 0x0D, 0x0A, 0x00 msgCRLF db 0x0D, 0x0A, 0x00 msgProgress db ".", 0x00 msgFailure db 0x0D, 0x0A, "ERROR : Press key to reboot", 0x00 TIMES 510-($-$$) DB 0 DW 0xAA55 ;************************************************************************* The bootloader.asm is too long for the editor without causing it to chug and choke. In addition, the bootloader and kernel do work within bochs as we do get the message "Welcome to our OS". Anyway, the following is what we have for a kernel at this point. kernel.asm: [BITS 16] [ORG 0x0000] [SEGMENT .text] ; code segment mov ax, 0x0100 ; location where kernel is loaded mov ds, ax mov es, ax cli mov ss, ax ; stack segment mov sp, 0xFFFF ; stack pointer at 64k limit sti mov si, strWelcomeMsg ; load message call _disp_str mov ah, 0x00 int 0x16 ; interrupt: await keypress int 0x19 ; interrupt: reboot _disp_str: lodsb ; load next character or al, al ; test for NUL character jz .DONE mov ah, 0x0E ; BIOS teletype mov bh, 0x00 ; display page 0 mov bl, 0x07 ; text attribute int 0x10 ; interrupt: invoke BIOS jmp _disp_str .DONE: ret [SEGMENT .data] ; initialized data segment strWelcomeMsg db "Welcome to our OS", 0x00 [SEGMENT .bss] ; uninitialized data segment Using nasm 2.06rc2 I compile as such: nasm bootloader.asm -o bootloader.bin -f bin nasm kernel.asm -o kernel.sys -f bin We write bootloader.bin to the floppy as such: dd if=bootloader.bin bs=512 count=1 of/dev/fd0 We write kernel.sys to the floppy as such: cp kernel.sys /dev/fd0 As I stated, this works in bochs. But booting from the floppy we get output like so: Loading Kernel Shell ........... ERROR : Press key to reboot Other specifics: OpenSUSE 11.2, GNOME desktop, AMD x64 Any other information I may have missed, feel free to ask. I tried to get everything in here that would be needed. If I need to, I can find a way to get the entire bootloader.asm posted somewhere. We are not really interested in using GRUB either for several reasons. This could change, but we want to see this boot successful before we really consider GRUB.

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• MBR Booting from DOS

  - by eflukx

  For a project I would like to invoke the MBR on the first harddisk directly from DOS. I've written a small assembler program that loads the MBR in memory at 0:7c00h an does a far jump to it. I've put my util on a bootable floppy. The disk (HD0, 0x80) i'm trying to boot has a TrueCrypt boot loader on it. It shows up the TrueCrypt screen, but after typing in the password it crashes the system. When I run my little utlility (w00t.com) on a normal WinXP machine it seams to crash immedealty. Apparently I'm forgetting some crucial stuff the BIOS normally does, my guess is it's something trivial. Can someone with better bare-metal DOS and BIOS experience help me out? Heres my code: .MODEL tiny .386 _TEXT SEGMENT USE16 INCLUDE BootDefs.i ORG 100h start: ; http://vxheavens.com/lib/vbw05.html ; Before DOS has booted the BIOS stores the amount of usable lower memory ; in a word located at 0:413h in memory. We going to erase this value because ; we have booted dos before loading the bootsector, and dos is fat (and ugly). ; fake free memory ;push ds ;push 0 ;pop ds ;mov ax, TC_BOOT_LOADER_SEGMENT / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED ;mov word ptr ds:[413h], ax ;ax = memory in K ;pop ds ;lea si, memory_patched_msg ;call print ;mov ax, cs mov ax, 0 mov es, ax ; read first sector to es:7c00h (== cs:7c00) mov dl, 80h mov cl, 1 mov al, 1 mov bx, 7c00h ;load sector to es:bx call read_sectors lea si, mbr_loaded_msg call print lea si, jmp_to_mbr_msg call print ;Set BIOS default values in environment cli mov dl, 80h ;(drive C) xor ax, ax mov ds, ax mov es, ax mov ss, ax mov sp, 0ffffh sti push es push 7c00h retf ;Jump to MBR code at 0:7c00h ; Print string print: xor bx, bx mov ah, 0eh cld @@: lodsb test al, al jz print_end int 10h jmp @B print_end: ret ; Read sectors of the first cylinder read_sectors: mov ch, 0 ; Cylinder mov dh, 0 ; Head ; DL = drive number passed from BIOS mov ah, 2 int 13h jnc read_ok lea si, disk_error_msg call print read_ok: ret memory_patched_msg db 'Memory patched', 13, 10, 7, 0 mbr_loaded_msg db 'MBR loaded', 13, 10, 7, 0 jmp_to_mbr_msg db 'Jumping to MBR code', 13, 10, 7, 0 disk_error_msg db 'Disk error', 13, 10, 7, 0 _TEXT ENDS END start

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• Subroutine & GoTo design

  - by sub

  I have a strange question concerning subroutines: As I'm creating a minimal language and I don't want to add high-level loops like while or for I was planning on just adding gotos to keep it Turing-Complete. Now I thought, eww - gotos - I wouldn't want to program in that language if I had to use gotos so often. So I thought about adding subroutines instead. I see the difference as the following: gotos Go to (captain obvious) a previously defined point and continue executing the program from there. Leads to hardly understandable and buggy code, I think that's a fact. subroutines Similiar: You define their starting point somewhere, as you call them the program jumps there - but the subroutine can go back to the point it was called from with return. Okay. Why didn't I just add the more function-like, nice looking subroutines? Because: In order to make return work if I call subroutines from within subroutines from within other subroutines, I'd have to use a stack containing the point where the currently running subroutine came from at top. That would then mean that I would, if I create loops using the subroutines, end up with an extremely memory-eating, overflowing stack with return locations. Not good. Don't think of my subroutines as functions. They are just gotos that return to the point they were called from, they don't actually give back values like the return x; statement in nearly all today's languages. Now to my actual questions: How can I solve the above problem with the stack overflow on loops with subroutines? Do I have to add a separate goto language construct without the return option? Assembler doesn't have loops but as I have seen myJumpPoint:, jnz, jz, retn. That means to me that there must also be a stack containing all the return locations. Am I right with that? What about long running loops then? Don't they overflow the stack/eat memory then? Am I getting the retn symbol in assembler totally wrong? If yes, please explain it to me.

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• FASM vc MASM trasnlation problem in mov si, offset msg

  - by Ruben Trancoso

  hi folks, just did my first test with MASM and FASM with the same code (almos) and I falled in trouble. The only difference is that to produce just the 104 bytes I need to write to MBR in FASM I put org 7c00h and in MASM 0h. The problem is on the mov si, offset msg that in the first case transletes it to 44 7C (7c44h) and with masm translates to 44 00 (0044h)! but just when I change org 7c00h to org 0h in MASM. Otherwise it will produce the entire segment from 0 to 7dff. how do I solve it? or in short, how to make MASM produce a binary that begins at 7c00h as it first byte and subsequent jumps remain relative to 7c00h? .model TINY .code org 7c00h ; Boot entry point. Address 07c0:0000 on the computer memory xor ax, ax ; Zero out ax mov ds, ax ; Set data segment to base of RAM jmp start ; Jump to the first byte after DOS boot record data ; ---------------------------------------------------------------------- ; DOS boot record data ; ---------------------------------------------------------------------- brINT13Flag db 90h ; 0002h - 0EH for INT13 AH=42 READ brOEM db 'MSDOS5.0' ; 0003h - OEM name & DOS version (8 chars) brBPS dw 512 ; 000Bh - Bytes/sector brSPC db 1 ; 000Dh - Sectors/cluster brResCount dw 1 ; 000Eh - Reserved (boot) sectors brFATs db 2 ; 0010h - FAT copies brRootEntries dw 0E0h ; 0011h - Root directory entries brSectorCount dw 2880 ; 0013h - Sectors in volume, < 32MB brMedia db 240 ; 0015h - Media descriptor brSPF dw 9 ; 0016h - Sectors per FAT brSPH dw 18 ; 0018h - Sectors per track brHPC dw 2 ; 001Ah - Number of Heads brHidden dd 0 ; 001Ch - Hidden sectors brSectors dd 0 ; 0020h - Total number of sectors db 0 ; 0024h - Physical drive no. db 0 ; 0025h - Reserved (FAT32) db 29h ; 0026h - Extended boot record sig brSerialNum dd 404418EAh ; 0027h - Volume serial number (random) brLabel db 'OSAdventure' ; 002Bh - Volume label (11 chars) brFSID db 'FAT12 ' ; 0036h - File System ID (8 chars) ;------------------------------------------------------------------------ ; Boot code ; ---------------------------------------------------------------------- start: mov si, offset msg call showmsg hang: jmp hang msg db 'Loading...',0 showmsg: lodsb cmp al, 0 jz showmsgd push si mov bx, 0007 mov ah, 0eh int 10h pop si jmp showmsg showmsgd: retn ; ---------------------------------------------------------------------- ; Boot record signature ; ---------------------------------------------------------------------- dw 0AA55h ; Boot record signature END

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