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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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  • Deeper function profiling/emulation

    - by Syntax_Error
    Hello everyone Merry Christmas I need an advice I have the following code: int main() { int k=5000000; int p; int sum=0; for (p=0;p<k;p++) { sum+=p; } return 0; } When I assemble it I get main: pushl %ebp movl %esp, %ebp subl $16, %esp movl $5000000, -4(%ebp) movl $0, -12(%ebp) movl $0, -8(%ebp) jmp .L2 .L3: movl -8(%ebp), %eax addl %eax, -12(%ebp) addl $1, -8(%ebp) .L2: movl -8(%ebp), %eax cmpl -4(%ebp), %eax jl .L3 movl $0, %eax leave ret If I run it through gprof I get that main executed the most, which is quite obvious! Yet I want to go a step further and be able to know if L2, or L3 executed the most. here it is obvious that L3 executed the most. yet is there some kind of profiler, emulator that can give me that data for an entire code?

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  • Within a DLL, how is the function table structured?

    - by Willi Ballenthin
    I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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  • Lua-Objective-C bridge on the iphone

    - by John Smith
    I have partially ported the LuaObjCBridge to the iPhone. Most things work but there are still some issues I have to deal with. There are sections where #defines are defined with-respect-to intel or ppc. Is the ARM chip closer to intel or ppc? Here is the most relevant section where most of the defines are: #if defined(__ppc__)||defined(__PPC__)||defined(__powerpc__) #define LUA_OBJC_METHODCALL_INT_IS_SHORTEST_INTEGRAL_TYPE #define LUA_OBJC_METHODCALL_PASS_FLOATS_IN_MARG_HEADER #define LUA_OBJC_POWER_ALIGNMENT #elif defined(__i386__)||defined(__arm__) #warning LuaObjCBridge is not fully tested for use on Intel chips. #define LUA_OBJC_METHODCALL_RETURN_STRUCTS_DIRECTLY // Use this or the code was crashing for me for structs LUA_OBJC_METHODCALL_RETURN_STRUCTS_DIRECTLY_LIMIT #define LUA_OBJC_METHODCALL_USE_OBJC_MSGSENDV_FPRET #define LUA_OBJC_METHODCALL_RETURN_STRUCTS_DIRECTLY_LIMIT 8 #define LUA_OBJC_INTEL_ALIGNMENT #endif For now I added arm with i386, but I could be wrong

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  • PPC breakpoints

    - by xtophyr
    How is a breakpoint implemented on PPC (On OS X, to be specific)? For example, on x86 it's typically done with the INT 3 instruction (0xCC) -- is there an instruction comparable to this for ppc? Or is there some other way they're set/implemented?

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  • Need complete picture of virtual adress space

    - by claws
    Hello, This image gives a good picture about Virtual Adress space. But it only says half of the story. It only gives complete picture of User Adress space ie.. lower 50% (or 75% in some cases). What about the rest 50% (or 25%) which is occupied by the kernel. I know kernel also has so many different things like kernel modules , device drivers, core kernel itself. There must be some kind of layout right? What is its layout? If you say its Operating System dependent. I would say, there are two major operating systems Windows & Linux. Please give answer for any one these.

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  • What's the purpose of the rotate instructions (ROL, RCL on x86) ?

    - by lgratian
    I always wondered what's the purpose of the rotate instructions some CPUs have (ROL, RCL on x86, for example). What kind of software makes use of these instructions? I first thought they may be used for encryption/computing hash codes, but these libraries are written usually in C, which doesn't have operators that map to these instructions. Has anybody found an use for them? Why where they added to the instructions set?

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  • x86 Instruction Format: "ba 0e 00 00 00" ... "mov $0xe,%edx"

    - by Andrew Tomazos - Fathomling
    I'm getting the following line in the disassembly from objdump -d of an x86 linux program... 4000b0: ba 0e 00 00 00 mov $0xe,%edx I'm trying to understand how the machine code "ba 0e 00 00 00" maps to "mov $0xe,%edx" In the manual move immediate 32-bit is: B8 + rd ... MOV r32, imm32 ie "B8" not "BA" In fact none of the MOV opcodes are "BA". If someone could break down "ba 0e 00 00 00" and explain bit-wise how to get to "mov $0xe,%edx" it would be most helpful.

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  • How is the implicit segment register of a near pointer determined?

    - by Daniel Trebbien
    In section 4.3 of Intel 64® and IA-32 Architectures Software Developer's Manual. Volume 1: Basic Architecture, it says: A near pointer is a 32-bit offset ... within a segment. Near pointers are used for all memory references in a flat memory model or for references in a segmented model where the identity of the segment being accessed is implied. This leads me to wondering: how is the implied segment register determined? I know that (%eip) and displaced (%eip) (e.g. -4(%eip)) addresses use %cs by default, and that (%esp) and displaced (%esp) addresses use %ss, but what about (%eax), (%edx), (%edi), (%ebp) etc., and can the implicit segment register depend also on the instruction that the memory address operand appears in?

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  • would there be such case of jumping, if yes how?

    - by Pooria
    I have an issue in the mind and that is since the jump instruction changes EIP register by adding signed offsets to it(if I'm not making a mistake here), on IA-32 architecture how would going upward in memory from location 0x7FFFFFFF(biggest positive number in signed logic) to 0x80000000(least negative number in signed logic) be possible? or maybe there shouldn't be such jump due to the nature of signed logic?

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  • Nested loop traversing arrays

    - by alecco
    There are 2 very big series of elements, the second 100 times bigger than the first. For each element of the first series, there are 0 or more elements on the second series. This can be traversed and processed with 2 nested loops. But the unpredictability of the amount of matching elements for each member of the first array makes things very, very slow. The actual processing of the 2nd series of elements involves logical and (&) and a population count. I couldn't find good optimizations using C but I am considering doing inline asm, doing rep* mov* or similar for each element of the first series and then doing the batch processing of the matching bytes of the second series, perhaps in buffers of 1MB or something. But the code would be get quite messy. Does anybody know of a better way? C preferred but x86 ASM OK too. Many thanks! Sample/demo code with simplified problem, first series are "people" and second series are "events", for clarity's sake. (the original problem is actually 100m and 10,000m entries!) #include <stdio.h> #include <stdint.h> #define PEOPLE 1000000 // 1m struct Person { uint8_t age; // Filtering condition uint8_t cnt; // Number of events for this person in E } P[PEOPLE]; // Each has 0 or more bytes with bit flags #define EVENTS 100000000 // 100m uint8_t P1[EVENTS]; // Property 1 flags uint8_t P2[EVENTS]; // Property 2 flags void init_arrays() { for (int i = 0; i < PEOPLE; i++) { // just some stuff P[i].age = i & 0x07; P[i].cnt = i % 220; // assert( sum < EVENTS ); } for (int i = 0; i < EVENTS; i++) { P1[i] = i % 7; // just some stuff P2[i] = i % 9; // just some other stuff } } int main(int argc, char *argv[]) { uint64_t sum = 0, fcur = 0; int age_filter = 7; // just some init_arrays(); // Init P, P1, P2 for (int64_t p = 0; p < PEOPLE ; p++) if (P[p].age < age_filter) for (int64_t e = 0; e < P[p].cnt ; e++, fcur++) sum += __builtin_popcount( P1[fcur] & P2[fcur] ); else fcur += P[p].cnt; // skip this person's events printf("(dummy %ld %ld)\n", sum, fcur ); return 0; } gcc -O5 -march=native -std=c99 test.c -o test

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  • Interrupt ?13 (ah=48) - not working

    - by GLeBaTi
    I want fetch the parameters of my hard disk. Using the technique described here. This is code showing normal parameters of floppy disk: mov dl,00h mov ah,08h int 13h This is code, showing not valid parameters of hard disk (may be, my hard disk space is big (LBA)): mov dl,80h mov ah,08h int 13h And I've written this code: mov dl,80h mov ah,48h int 13h The code is giving cf = 1(error). How do I fix it?

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  • Metamorphic generator

    - by user222094
    I am trying to find references about different designs of metamorphic generators can someone point me to the right direction. I have gone through some papers in ACM but couldn't find what I am looking for.

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  • jQuery sequence and function call problem

    - by Jonas
    Hi everyone, I'm very new to jquery and programming in general but I'm still trying to achieve something here. I use Fullcalendar to allow the users of my web application to insert an event in the database. The click on a day, view changes to agendaDay, then on a time of the day, and a dialog popup opens with a form. I am trying to combine validate (pre-jquery.1.4), jquery.form to post the form without page refresh The script calendar.php, included in several pages, defines the fullcalendar object and displays it in a div: $(document).ready(function() { function EventLoad() { $("#addEvent").validate({ rules: { calendar_title: "required", calendar_url: { required: false, maxlength: 100, url: true } }, messages: { calendar_title: "Title required", calendar_url: "Invalid URL format" }, success: function() { $('#addEvent').submit(function() { var options = { success: function() { $('#eventDialog').dialog('close'); $('#calendar').fullCalendar( 'refetchEvents' ); } }; // submit the form $(this).ajaxSubmit(options); // return false to prevent normal browser submit and page navigation return false; }); } }); } $('#calendar').fullCalendar({ header: { left: 'prev,next today', center: 'title', right: 'month,agendaWeek,agendaDay' }, theme: true, firstDay: 1, editable: false, events: "json-events.php?list=1&<?php echo $events_list; ?>", <?php if($_GET['page'] == 'home') echo "defaultView: 'agendaWeek',"; ?> eventClick: function(event) { if (event.url) { window.open(event.url); return false; } }, dayClick: function(date, allDay, jsEvent, view) { if (view.name == 'month') { $('#calendar').fullCalendar( 'changeView', 'agendaDay').fullCalendar( 'gotoDate', date ); }else{ if(allDay) { var timeStamp = $.fullCalendar.formatDate( date, 'dddd+dd+MMMM_u'); var $eventDialog = $('<div/>').load("json-events.php?<?php echo $events_list; ?>&new=1&all_day=1&timestamp=" + timeStamp, null, EventLoad).dialog({autoOpen:false,draggable: false, width: 675, modal:true, position:['center',202], resizable: false, title:'Add an Event'}); $eventDialog.dialog('open').attr('id','eventDialog'); } else { var timeStamp = $.fullCalendar.formatDate( date, 'dddd+dd+MMMM_u'); var $eventDialog = $('<div/>').load("json-events.php?<?php echo $events_list; ?>&new=1&all_day=0&timestamp=" + timeStamp, null, EventLoad).dialog({autoOpen:false,draggable: false, width: 675, modal:true, position:['center',202], resizable: false, title:'Add an Event'}); $eventDialog.dialog('open').attr('id','eventDialog');; } } } }); }); The script json-events.php contains the form and also the code to process the data from the submitted form. What happens when I test the whole thing: - first user click on a day, then time of day. Popup opens with time and date indicated on the form. When user submits the form, dialog closes and calendar refreshes its events.... and the event added by the user appears several times (from 4 to up to 11 times!). The form has been processed several times by the receiving php script?! - second user click, the popup opens, user submit empty form. Form is submitted (validate function not triggered) and user redirected to empty page json-events.php (ajaxForm not triggered either) Obviously, my code is wrong (and dirty as well, sorry). Why is the submitted form, submitted several time to receiving script and why is the javascript function EventLoad triggered only once ? Thank you very much for you help. This problem is killing me !

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  • How to have a soft-real-time process in presense of heavily swapping IO-intensive background load?

    - by Vi
    schedtool: PID 32301: PRIO 4, POLICY R: SCHED_RR , NICE -20, AFFINITY 0xf ionice: realtime: prio 4 But the music is stumbling anyway. Background load is low prio (SCHED_IDLEPRIO, idle ionice), but uses a lot of memory (more than is physically available) and does a lot of IO and calculations. Latencytop shows about 1500ms for: Following symlink Writing buffer to disk (sync) Page fault Writing a page to disk both for the bg load and for unrelated processes. Load average is 10 and counting. Why cannot it allocate, for example, 200MHZ of one of the cores and 32M of memory and not less than once per second opportunity for IO for mplayer to make it happy while continuing calculations on the background? Or: why it cannot leave background task and swap loving each other but keeping the rest of the system as if there were no background load? How to have RT processes AND heavy bg load simultaneously (without of virtual machines)?

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  • How do I fix the error: CS1548: Cryptographic failure while signing assembly ?

    - by Paula DiTallo
    The full error in Microsoft Visual Studio on a compile looks like this: error CS1548: Cryptographic failure while signing assembly 'C:\Program Files\Microsoft SQL Server\100\Samples\Analysis Services\Programmability\AMO\AMOAdventureWorks\CS\StoredProcedures\obj\Debug\StoredProcedures.dll' This is likely due to a missing strong key pair value file. The easiest way to solve this problem is to create a new one. Navigate to:  Microsoft Visual Studio 2010>Visual Studio Tools>Visual Studio x64 Win64 Command Prompt (2010)  [if you aren't on an x64 box, pick another command prompt option that fits] Once the MS-Dos window displays, type in this statement: sn -k c:\SampleKey.snk Then copy the output *.snk file to project directory, or the *referenced directory. Remove the old reference to the *.snk file from the project. Add the paired key back to the project as an existing item. When you add back the *.snk file to the project, you will see that the *.snk file is no longer missing.   Our work is done!   *referenced directory: Pay attention to the original error message on compile. The *.snk file that is referenced may be in a directory path you aren't expecting--so you will still get the error unless you change the directory path or write the file to the directory the program is expecting to find the *.snk file.

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  • MySQL to AppEngine

    - by Daniel Naito
    Hi Nick! How are you? I'm from Brazil and study at FATEC (college located in Brazil). I'm trying to learn about AppEngine. Now, I'm trying to load a large database from MySQL to AppEngine to perform some queries, but I don't know how i can do it. I did some testing with CSV files,but is there any way to perform the direct import from MySQL? This database is from Pentaho BI Server (www.pentaho.com). Thank you for your attention. Regards, Daniel Naito

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