[−][src]Trait context_coroutine::stacks::Stack

pub trait Stack {
    fn top(&self) -> StackPointer;

    fn size(&self) -> usize;
}

Organisation of the stack in x86 (and nearly all other modern CPUs).

  • The bottom (origin) of the stack is a high address.
  • The top of the stack is a low address.
  • The stack grows downwards.
  • Thus pushing onto the stack subtracts from the top address, making it lower (smaller).
  • Thus popping from the stack adds to the top address, making it higher (larger).
  • Eli Bendersky explains this well.

A diagram:-

eg 0x1006  +---+ Top (origin): High Address
           | S |
           | T |
           | A |
           | C |
           | K |
eg 0x1000  +---+ Bottom: Low Address

Pushing a 2 byte value, X, grows the stack thus:-

eg 0x1006  +---+ Top (origin): High Address
           | S |
           | T |
           | A |
           | C |
           | K |
eg 0x1000  |···| Former Bottom
           | X |
eg  0x998  +---+ Bottom: Low Address

Stacks can have a 'guard' page below the Bottom which can be mprotected'd as PROT_NONE; any reads or write will cause a SIGSEGV.

eg 0x1006  +---+ Top (origin): High Address
           | S |
           | T |
           | A | Regular Pages (mprotect: PROT_READ + PROT_WRITE)
           | C |
           | K |
eg 0x1000  +---+ Bottom: Low Address
           |   |
           |   | Guard Page (mprotect: PROT_NONE)
           |   |
           +---+ Bottom of Guard Page

A 'guard' page is 4,096 bytes on x86-64.

Required methods

fn top(&self) -> StackPointer

Top.

This must be page aligned.

fn size(&self) -> usize

Size, excluding any guard page at the bottom.

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Implementors

impl Stack for ProtectedStack[src]

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