virpcimock: Mock __open_2()

Hold on to your hat, this is going to be a wild ride. As nearly
nothing in glibc, nor open() is a real function. Just look into
bits/fcntl2.h and you'll see that open() is actually a thin
wrapper that calls either __open_alias() or __open_2(). Now,
before 801ebb5e the open() done in
virPCIDeviceConfigOpenInternal() had a constant oflags (we were
opening the pci config with O_RDWR). And since we were not
passing any mode nor O_CREAT the wrapper decided to call
__open_alias() which was open() provided by our mock. So far so
good. But after the referenced commit, the oflags is no longer
compile time constant and therefore the wrapper calls __open_2()
which we don't mock and thus the real __open_2() from glibc was
called and thus we did try to open real path from host's /sys.
This of course fails with variety of errors.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

tests/virpcimock.c

@@ -32,6 +32,7 @@
 
 static int (*real_access)(const char *path, int mode);
 static int (*real_open)(const char *path, int flags, ...);
+static int (*real___open_2)(const char *path, int flags);
 static int (*real_close)(int fd);
 static DIR * (*real_opendir)(const char *name);
 static char *(*real_virFileCanonicalizePath)(const char *path);
@@ -805,6 +806,7 @@ init_syms(void)
 
     VIR_MOCK_REAL_INIT(access);
     VIR_MOCK_REAL_INIT(open);
+    VIR_MOCK_REAL_INIT(__open_2);
     VIR_MOCK_REAL_INIT(close);
     VIR_MOCK_REAL_INIT(opendir);
     VIR_MOCK_REAL_INIT(virFileCanonicalizePath);
@@ -932,6 +934,33 @@ open(const char *path, int flags, ...)
     return ret;
 }
 
+
+int
+__open_2(const char *path, int flags)
+{
+    VIR_AUTOFREE(char *) newpath = NULL;
+    int ret;
+
+    init_syms();
+
+    if (STRPREFIX(path, SYSFS_PCI_PREFIX) &&
+        getrealpath(&newpath, path) < 0)
+        return -1;
+
+    ret = real___open_2(newpath ? newpath : path, flags);
+
+    /* Catch both: /sys/bus/pci/drivers/... and
+     * /sys/bus/pci/device/.../driver/... */
+    if (ret >= 0 && STRPREFIX(path, SYSFS_PCI_PREFIX) &&
+        strstr(path, "driver") && add_fd(ret, path) < 0) {
+        real_close(ret);
+        ret = -1;
+    }
+
+    return ret;
+}
+
+
 DIR *
 opendir(const char *path)
 {