CODEWITHSUNDEEP
clinuxlayoutspacememory-address
MetallicPriest
MetallicPriest

Reputation: 30795

Address Space Layout for a Multithreaded Linux Process

I want to know the full detail of the address space layout of a multithreaded Linux Process for both 64 bit and 32 bit. Link to any article that describes it will be appreciated. And note that I need to know full details, not just an overview, because I will be directly dealing with it. So I need to know for example, where are the thread stacks located, the heap, thread private data etc...

Upvotes: 7

Views: 2176

Answers (1)

osgx
osgx

Reputation: 94345

Thread stacks are allocated with mmap at thread start (or even before - you can set the stack space in pthread_attrs). TLS data is stored in the beginning of thread's stack. Size of thread's stacks is fixed, typically it is from 2 to 8 MB. Stack size of each thread can't be changed while the thread is live. (First thread - running main - is still uses main stack at the end of address space and this stack may grow and shrink.) Heap and code is shared between all threads. Mutexes can be anywhere in data section - it is just a struct.

The mmap of thread's stack is not fixed at any address:

Glibc sources

 mem = mmap (NULL, size, prot,
                  MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);

PS modern GCC allows threads stack to be unlimited with SplitStacks feature

Upvotes: 8

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