On 2020-07-03 00:40, Scott Cheloha wrote:
On Fri, Jun 26, 2020 at 04:53:14PM +0300, Paul Irofti wrote:
On Wed, Jun 24, 2020 at 11:53:23AM +0200, Robert Nagy wrote:
On 22/06/20 19:12 +0300, Paul Irofti wrote:
New iteration:
- ps_timekeep should not coredump, pointed by deraadt@
- set ps_timekeep to 0 before user uvm_map for randomization
- map timekeep before fixup. confirmed by naddy@ that it fixes NULL init
- initialize va. clarified by kettenis@
How's the magical max skew value research going? Do we have a value yet?
Paul
I think we should pick 100 for now and then we can adjust it later if needed.
Of course this depends on kettenis' lfence diff so that amd ryzen tsc is sane.
I looked at dmesglog and the reported values are indeed small. 99 was
the highest on an Atom. I updated the diff to 100. I think we can adapt
this as we get more reports (if ever).
OK?
One thing...
diff --git lib/libc/arch/amd64/gen/usertc.c lib/libc/arch/amd64/gen/usertc.c
new file mode 100644
index 00000000000..56016c8eca1
--- /dev/null
+++ lib/libc/arch/amd64/gen/usertc.c
@@ -0,0 +1,41 @@
+/* $OpenBSD$ */
+/*
+ * Copyright (c) 2020 Paul Irofti <[email protected]>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <sys/timetc.h>
+
+static inline u_int
+rdtsc(void)
+{
+ uint32_t hi, lo;
+ asm volatile("rdtsc" : "=a"(lo), "=d"(hi));
+ return ((uint64_t)lo)|(((uint64_t)hi)<<32);
+}
We need to lfence this.
In userland too? Why? Anyway. I think this diff should be committed. It
is too long since we have been dancing around it and these sorts of
comments can always be addressed in tree.
Paul
