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[Qemu-devel] [Bug 1163034] Re: gnutls28 fails to build from source in ar


From: Peter Maydell
Subject: [Qemu-devel] [Bug 1163034] Re: gnutls28 fails to build from source in armhf
Date: Tue, 09 Apr 2013 22:11:19 -0000

Actually, assuming the guest ARM glibc doesn't have the printf() bug the
code is testing for, we shouldn't take the SIGSEGV anyway, so that's a
red herring. The actual problem here is the setrlimit().

The conftest.c test case works by using rlimit to limit the address
space. This generally doesn't work on QEMU because we just pass the
rlimit syscall through to the host, and end up limiting not just the
guest program but also QEMU itself.  QEMU doesn't expect its own
allocations to fail and typically dies in confusing ways as a result.
(Sometimes we do check allocations and call abort(), which then under
linux-user doesn't work properly because we treat the resulting signal
as if it were caused by the guest and not by QEMU's own code; IIRC we
end up hanging in that situation.) In this particular instance we
segfault in tb_alloc_page() because it doesn't check that
page_find_alloc() didn't return NULL.

[Confirmed by running qemu-arm under gdb.]

Fixing this would require us to implement the address space rlimits
entirely in QEMU by keeping track of how much memory we've handed the
guest so we can fail mmap() etc. That is probably relatively speaking
fairly tractable, though it's not a five minute job.

Unsupported syscall bugs are usually easy fixes, incidentally (though
occasionally they are nasty); also often QEMU will warn but things will
continue OK because the guest libc/userspace supports fallback code for
when a native kernel hasn't yet implemented the new syscall.

-- 
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https://bugs.launchpad.net/bugs/1163034

Title:
  gnutls28 fails to build from source in armhf

Status in QEMU:
  New
Status in “qemu” package in Ubuntu:
  Confirmed

Bug description:
  Please look at
  
https://code.launchpad.net/~costamagnagianfranco/+archive/costamagnagianfranco-ppa/+packages
  and
  
https://code.launchpad.net/~costamagnagianfranco/+archive/costamagnagianfranco-ppa/+build/4457434

  I cannot make gnutls28 build on armhf, I suspect a builder problem

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