[Qemu-commits] [qemu/qemu] fc3d1b: oslib-posix: Use MAP_STACK in qemu_alloc_stack() o...

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/qemu/qemu
  Commit: fc3d1bad1edf08871275cf469a64e12dae4eba96
      
https://github.com/qemu/qemu/commit/fc3d1bad1edf08871275cf469a64e12dae4eba96
  Author: Brad Smith <address@hidden>
  Date:   2018-11-06 (Tue, 06 Nov 2018)

  Changed paths:
    M util/oslib-posix.c

  Log Message:
  -----------
  oslib-posix: Use MAP_STACK in qemu_alloc_stack() on OpenBSD

Use MAP_STACK in qemu_alloc_stack() on OpenBSD.

Added to our 6.4 release.

MAP_STACK      Indicate that the mapping is used as a stack.  This
         flag must be used in combination with MAP_ANON and
         MAP_PRIVATE.

Implement MAP_STACK option for mmap().  Synchronous faults (pagefault and
syscall) confirm the stack register points at MAP_STACK memory, otherwise
SIGSEGV is delivered. sigaltstack() and pthread_attr_setstack() are modified
to create a MAP_STACK sub-region which satisfies alignment requirements.
Observe that MAP_STACK can only be set/cleared by mmap(), which zeroes the
contents of the region -- there is no mprotect() equivalent operation, so
there is no MAP_STACK-adding gadget.

Signed-off-by: Brad Smith <address@hidden>
Reviewed-by: Kamil Rytarowski <address@hidden>
Reviewed-by: Peter Maydell <address@hidden>
Message-id: address@hidden
Signed-off-by: Peter Maydell <address@hidden>



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