linux - Find the absolute size of an array/buffer on the stack -

-

I hope the title is not too much missile (I am quite new in the assembly) I play around with gdb debugger And some assembly code that goes as follows: 

  0x00000000004005d7 & lt; + 0>: push% RBP 0x00000000004005d8 & lt; + 1>: mov% rp,% rbp 0x000000004005db & lt; + 4>: $ 0xffffffffff80,% rsp 0x00000000004005df & lt; + 8>: mov% rdi, -0x78 (% rbp) 0x00000000004005e3 & lt; + 12>: mov -0x78 (% RBP),% rdx 0x00000000004005e7 & lt; + 16>: Lea AX, [APB-101] 0x00000000004005eb : mov% rdx,% rsi 0x00000000004005ee & lt; + 23>: mov% rax,% rdi 0x00000000004005f1 & lt; +6>: callq 0x400480 & lt; Strcpy @ plt & gt; 0x000000004005f6 & lt; + 31>: leaveq 0x00000000004005f7 & lt; + 32>: retq

The thing I want to store is to find out the buffer size "[EPB-120]". The thing I have tryed was to set up a breakpoint: 0x00000000004005e7 and if the code runs, then I did the same and said that value to 0x120 decrease the price of EPB to inspect ... but that is the result Is that the full size of the buffer? Or is there a better way to find the size of that indicator? Thank you in advance

First of all, the size of an indicator is always the same.

I'm assuming that you want to know how big a buffer is on the stack strcpy () .

. Buffer Can you tell that he is as follows 

  0x00000000004005d7 & Lt; + 0>: push% RBP 0x00000000004005d8 & lt; + 1>: mov% rp,% rbp 0x00000000004005db & lt; 4>: StackPointer has been reduced by introduction 128 (0xffffffffffffff80 = -128) after the function $ 0 Xffffffffffff80,% rsp

adding. . That's why we have space for 128 bits of local variables 

  0x00000000004005e7 & lt; + 16>: Li eax, [EPB-120] 0x00000000004005eb & LT; + 20>: mov% RDX,% RSI 0x00000000004005ee & LT; + 23>: mov% rax,% RDI 0x00000000004005f1 & lt; + 26>: callq 0x400480 & lt; Strcpy @ plt & gt;

Now, the address of % ebp-120 before strcpy () will be loaded in % eax > Which is carried on % rdi , which is used to call strcpy () .

% ebp-120 tells us that the buffer starts at 120 bytes below % ebp . So if there is no other variable between % ebp and ebp-120 , we can assume that buffer size is 120 bytes.

Please comment it is not clear and I will try to improve clarification.


Comments

Post a Comment

Popular posts from this blog

Pass DB Connection parameters to a Kettle a.k.a PDI table Input step dynamically from Excel -

-
Image
I have a requirement whenever I run my own kettle, dynamically took database connection parameters from an excel source Every run should go. I have an Excel column names: hostname, username, database, password. I want to pass these connection parameters to my table input stage dynamically whenever it runs the job. This is what I was trying to do. You can get it Connection parameters from the DB reading source (for example Excel or a CSV file in my example) < / Li> Store the parameters in the variable Using the variable in your connection's settings. Setting Variables Create another conversion for (you can not do it in the same conversion Uses): set variables element variable: The element that reads / writes your data creates a new connection and sets the connection parameter using $ {variable name_} Note that you will need to type in the field field in the field $ {password} Also keep in mind that this can be a security problem as the
Read more

multithreading - PhantomJS-Node in a for Loop -

-
I am trying to implement a screen-scraps application that opens a URL in which a parameter changes as it is for a loop: var data = [ '100', '101', '102', '103', '104']; (Var indexA = 0; indexA & lt; data.length; indexA ++) for {Phantom Generation ({'port': freeport}, function (pH) {ph.create page (function (page) {page.open ("http: //...++ data [index B] +" ... " , Status {console.log ("open site:" + data [index B], position); / * OLD * / indexB ++; page evaluation (function () {// page scrape and an object Return}, function {console.log (result.dataRequest); // here is the problem}); / * new and fixed * / indexB ++} first console Logs it: Open Site: 100 Success Opens Site: 101 Success B Ola Site: 102 Success Opening Site: 103 Success Opened Site: 104 Success Which is good. Data is verified in scrap HTML and from index to array Matches. So in page 101 I scrap '101 and retrieve' and pu
Read more

c++ - MATLAB .m file to .mex file using Matlab Compiler -

-
I know that it can speak as a very famous topic, but something that helps me with it Not found This scenario is: I have my functions function, no matter what's inside, it's a generic function that may depend on other toolboxes. Does. Has input and output; I want to generate the same myFun.mex function; : Lib myFun This way I get some new files: libmyfun.c libmyfun.dll Libmyfun.exp libmyfun.exports libmyfun .h libmyfun.lib Reading around and I think that Creating a myfun.cpp that is very famous is included: / * gateway function * / zero max function (ent NLHS, MXARRA * PLS [], int NRHS, CONST M Xeray * PHS []) Here is the Variable Deals * / / * code here * /} I have tried to do this and are called Regular of Max Generation: Max ('- v', 'myfun.cpp') But I get many errors, and I should say that my myfun.cpp copy / Paste Function is where I have a lot of doubts ... especially on input / output management. My q
Read more