@@ -13,6 +13,7 @@
import curses
import sys, os, time, optparse, ctypes
+from ctypes import *
class DebugfsProvider(object):
def __init__(self):
@@ -239,6 +240,9 @@ import struct, array
libc = ctypes.CDLL('libc.so.6')
syscall = libc.syscall
+get_errno = libc.__errno_location
+get_errno.restype = POINTER(c_int)
+
class perf_event_attr(ctypes.Structure):
_fields_ = [('type', ctypes.c_uint32),
('size', ctypes.c_uint32),
@@ -322,7 +326,8 @@ class Event(object):
group_leader = group.events[0].fd
fd = _perf_event_open(attr, -1, group.cpu, group_leader, 0)
if fd == -1:
- raise Exception('perf_event_open failed')
+ err = get_errno()[0]
+ raise Exception('perf_event_open failed, errno = ' + err.__str__())
if filter:
import fcntl
fcntl.ioctl(fd, ioctl_numbers['SET_FILTER'], filter)
kvm_stat uses syscall() to call perf_event_open(). If this function call fails, the returned value is -1, which doesn't tell the details of the failure (i.e. ENOSYS or EINVAL). This patch retrieves errno and prints it when syscall() fails. The error message will look like "Exception: perf_event_open failed, errno = 38". Signed-off-by: Wei Huang <wei@redhat.com> --- scripts/kvm/kvm_stat | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)