Implement stack probe for x86

[kubo39]

TODO:

• add some code that is broken without this patch.
• add test case.
• check version LLVM supports stack probe.

[jhass]

Could you provide some reference/motivation for this? :)

[kubo39]

@jhass
Sure :)
The problem is that if a stack frame which is larger than the OS-thread guard page, a function could skip over the guard page and may corrupt the heap or another thread. This patch solves by using LLVM's stackprobe.

According to LLVM LangRef Manual

This attribute indicates that the function will trigger a guard region in the end of the stack. It ensures that accesses to the stack must be no further apart than the size of the guard region to a previous access of the stack. It takes one required string value, the name of the stack probing function that will be called.

• other references/implementations:
  • Rust
  • Zig

[jhass]

Huh, so another thing you would expect LLVM to just handle for you.

[asterite]

Could you provide some code that is broken without this patch? Otherwise, I feel like we'll be merging something without really knowing or understand what this does.