[PULL,19/49] scripts/kvm/kvm_stat: Fixup syscall error reporting

Commit Message

Paolo Bonzini Jan. 26, 2016, 1:46 p.m. UTC

From: Janosch Frank <[e-mail]>

In 2008 a patch was written that introduced ctypes.get_errno() and
set_errno() as official interfaces to the libc errno variable. Using
them we can avoid accessing private libc variables.
The patch was included in python 2.6.

Also we need to raise the right exception, with the right parameters
and a helpful message.

Signed-off-by: Janosch Frank <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>
---
 scripts/kvm/kvm_stat | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

Patch

diff --git a/scripts/kvm/kvm_stat b/scripts/kvm/kvm_stat
index b5422f8..457624d 100755
--- a/scripts/kvm/kvm_stat
+++ b/scripts/kvm/kvm_stat
@@ -287,10 +287,8 @@  filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
 if EXIT_REASONS:
     filters['kvm_exit'] = ('exit_reason', EXIT_REASONS)
 
-libc = ctypes.CDLL('libc.so.6')
+libc = ctypes.CDLL('libc.so.6', use_errno=True)
 syscall = libc.syscall
-get_errno = libc.__errno_location
-get_errno.restype = ctypes.POINTER(ctypes.c_int)
 
 class perf_event_attr(ctypes.Structure):
     _fields_ = [('type', ctypes.c_uint32),
@@ -351,8 +349,9 @@  class Event(object):
             group_leader = group.events[0].fd
         fd = _perf_event_open(attr, -1, group.cpu, group_leader, 0)
         if fd == -1:
-            err = get_errno()[0]
-            raise Exception('perf_event_open failed, errno = ' + err.__str__())
+            err = ctypes.get_errno()
+            raise OSError(err, os.strerror(err),
+                          'while calling sys_perf_event_open().')
         if tracefilter:
             fcntl.ioctl(fd, IOCTL_NUMBERS['SET_FILTER'], tracefilter)
         self.fd = fd