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oslib-posix: Ignore fcntl("/dev/null", F_SETFL, O_NONBLOCK) failure

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Previous to OpenBSD 6.3 [1], fcntl(F_SETFL) is not permitted on
memory devices.
Trying this call sets errno to ENODEV ("not a memory device"):

  19 ENODEV Operation not supported by device.
    An attempt was made to apply an inappropriate function to a device,
    for example, trying to read a write-only device such as a printer.

Do not assert fcntl failures in this specific case (errno set to ENODEV)
on OpenBSD. This fixes:

  $ lm32-softmmu/qemu-system-lm32
  assertion "f != -1" failed: file "util/oslib-posix.c", line 247, function "qemu_set_nonblock"
  Abort trap (core dumped)

[1] The fix seems c2a35b387f
  "fcntl(F_SETFL) invokes the FIONBIO and FIOASYNC ioctls internally, so
  the memory devices (/dev/null, /dev/zero, etc) need to permit them."

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190307142822.8531-2-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Philippe Mathieu-Daudé 2019-03-07 15:28:21 +01:00 • committed by Paolo Bonzini
parent b0c214ce41
commit 02cdcc96be
1 changed files with 12 additions and 0 deletions
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12
util/oslib-posix.c
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@ -244,7 +244,19 @@ void qemu_set_nonblock(int fd)
f = fcntl(fd, F_GETFL);
assert(f != -1);
f = fcntl(fd, F_SETFL, f | O_NONBLOCK);
#ifdef __OpenBSD__
if (f == -1) {
/*
* Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on
* memory devices and sets errno to ENODEV.
* It's OK if we fail to set O_NONBLOCK on devices like /dev/null,
* because they will never block anyway.
*/
assert(errno == ENODEV);
}
#else
assert(f != -1);
#endif
}
int socket_set_fast_reuse(int fd)