Somewhat newb question about assy and the heap.

Posted by Eric M on Stack Overflow See other posts from Stack Overflow or by Eric M
Published on 2011-01-09T03:21:25Z Indexed on 2011/01/09 3:54 UTC
Read the original article Hit count: 220

Filed under:

memory-allocation

|

assembler

Ultimately I am just trying to figure out how to dynamically allocate heap memory from within assembly.

If I call Linux sbrk() from assembly code, can I use the address returned as I would use an address of a statically (ie in the .data section of my program listing) declared chunk of memory?

I know Linux uses the hardware MMU if present, so I am not sure if what sbrk returns is a 'raw' pointer to real RAM, or is it a cooked pointer to RAM that may be modified by Linux's VM system?

I read this: How are sbrk/brk implemented in Linux?. I suspect I can not use the return value from sbrk() without worry: the MMU fault on access-non-allocated-address must cause the VM to alter the real location in RAM being addressed. Thus assy, not linked against libc or what-have-you, would not know the address has changed.

Does this make sense, or am I out to lunch?

© Stack Overflow or respective owner

Related posts about memory-allocation

Memory allocation in case of static variables

as seen on Stack Overflow - Search for 'Stack Overflow'
I am always confused about static variables, and the way memory allocation happens for them. For example: int a = 1; const int b = 2; static const int c = 3; int foo(int &arg){ arg++; return arg; } How is the memory allocated for a,b and c? What is the difference (in terms of memory)… >>> More
Java - Memory Allocation for Classes

as seen on Stack Overflow - Search for 'Stack Overflow'
Where is the definition of class stored in memory ? >>> More
Dynamic memory allocation for 3D array

as seen on Stack Overflow - Search for 'Stack Overflow'
How can i allocate 3D arrays using malloc? >>> More
Memory Allocation Profiling in C++

as seen on Stack Overflow - Search for 'Stack Overflow'
I am writing an application and am surprised to see its total memory usage is already too high. I want to profile the dynamic memory usage of my application: How many objects of each kind are there in the heap, and which functions created these objects? Also, how much memory is used by each of the… >>> More
Memory allocation in Xvfb

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I have following this blog in setting Xvfb in my ubuntu environment: http://corpocrat.com/2008/08/19/how-to-install-xvfb-x11-server-in-linux-server/ So I did this: Xvfb :1 -screen 0 800x600x24& My question is does Xvfb only allocate memory during initialization? i.e. just enough for a… >>> More

Related posts about assembler

What Are Some Advantages/Disadvantages of Using C over Assembly?

as seen on Programmers - Search for 'Programmers'
I'm currently studying engineering in Telecommunications and Electronics and we have migrated from assembler to C in microprocessor programming. I have doubts that this is a good idea. What are some advantages and disadvantages of C compared to assembly? The advantages/disadvantages I see are: Advantages: I… >>> More
Using assembler x86 to write to .net

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm a total beginner when it comes to computer languages, and was asked for a code to write .NET with assembler x86, and i'm stuck here at the moment. Any basic code lines would work, still couldn't find any on the web. >>> More
When is assembler faster than C?

as seen on Stack Overflow - Search for 'Stack Overflow'
One of the stated reasons for knowing assembler is that, on occasion, it can be employed to write code that will be more performant than writing that code in a higher-level language, C in particular. However, I've also heard it stated many times that although that's not entirely false, the cases… >>> More
Cheap programmable, portable device

as seen on Programmers - Search for 'Programmers'
Since a long time I have thrived for being able to program something I can take with me - a very small computer like a programmable calculator, gameboy, pocket PC or cellphone. However, I didn't find anything fitting yet! The thing I'm looking at is the price, because I can't afford to spend too… >>> More
Any good, easy to learn from books or tutorials for learning assembly? [on hold]

as seen on Programmers - Search for 'Programmers'
I've been a developer since 2009 and I've learnt a lot of languages since, but I've always wanted to understand and be able to code in the lowest level language so I can directly (or at least very close to directly) speak to machines through my code. There was a point in time when someone showed… >>> More