[LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[David Hildenbrand]

Let's provide include/lapi/userfaultfd.h such that we can fix
the dirtyc0w_shmem testcase and cleanup the userfaultfd01 testcase.

Cc: Martin Doucha <mdoucha@suse.cz>
Cc: Cyril Hrubis <chrubis@suse.cz>
Cc: Petr Vorel <pvorel@suse.cz>

David Hildenbrand (3):
  lapi/userfaultfd.h: Preparation for removing compile-time TCONF
    handling from userfaultfd testcases
  security/dirtyc0w_shmem: Fix compile-time absence of
    UFFD_FEATURE_MINOR_SHMEM
  syscalls/userfaultfd01: Remove compile-time TCONF handling

 include/lapi/userfaultfd.h                    | 190 ++++++++++++++++++
 .../dirtyc0w_shmem/dirtyc0w_shmem_child.c     |  12 +-
 .../syscalls/userfaultfd/userfaultfd01.c      |   8 +-
 3 files changed, 192 insertions(+), 18 deletions(-)
 create mode 100644 include/lapi/userfaultfd.h

-- 
2.38.1


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[LTP] [PATCH v1 1/3] lapi/userfaultfd.h: Preparation for removing compile-time TCONF handling from userfaultfd testcases

[David Hildenbrand]

Let's provide a minimal include/lapi/userfaultfd.h that contains the
initial userfaultfd uabi from v4.1, plus selected additions from other
releases relevant for the two testcases we have for now.

We can extend this header later as required, for example, once testcases
want to test userfaultfd-wp support.

Note that some dead code (#ifdef 0) and unnecessary definitions that keep
changing (UFFD_API_IOCTLS) were dropped from the v4.1 version.

Suggested-by: Martin Doucha <mdoucha@suse.cz>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/lapi/userfaultfd.h | 190 +++++++++++++++++++++++++++++++++++++
 1 file changed, 190 insertions(+)
 create mode 100644 include/lapi/userfaultfd.h

diff --git a/include/lapi/userfaultfd.h b/include/lapi/userfaultfd.h
new file mode 100644
index 000000000..4d52b7c4b
--- /dev/null
+++ b/include/lapi/userfaultfd.h
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
+ * Copyright (C) 2015,2022 Red Hat, Inc.
+ *
+ * Mostly copied/adapted from <linux/userfaultfd.h>
+ */
+
+#ifndef LAPI_USERFAULTFD_H__
+#define LAPI_USERFAULTFD_H__
+
+#include <unistd.h>
+#include <sys/types.h>
+#include "lapi/syscalls.h"
+
+#ifdef HAVE_LINUX_USERFAULTFD_H
+#include <linux/userfaultfd.h>
+#endif
+
+/* userfaultfd support was added in v4.1 */
+#ifndef UFFD_API
+#define UFFD_API ((__u64)0xAA)
+
+/*
+ * Valid ioctl command number range with this API is from 0x00 to
+ * 0x3F.  UFFDIO_API is the fixed number, everything else can be
+ * changed by implementing a different UFFD_API. If sticking to the
+ * same UFFD_API more ioctl can be added and userland will be aware of
+ * which ioctl the running kernel implements through the ioctl command
+ * bitmask written by the UFFDIO_API.
+ */
+#define _UFFDIO_REGISTER		(0x00)
+#define _UFFDIO_UNREGISTER		(0x01)
+#define _UFFDIO_WAKE			(0x02)
+#define _UFFDIO_COPY			(0x03)
+#define _UFFDIO_ZEROPAGE		(0x04)
+#define _UFFDIO_API			(0x3F)
+
+/* userfaultfd ioctl ids */
+#define UFFDIO 0xAA
+#define UFFDIO_API		_IOWR(UFFDIO, _UFFDIO_API,	\
+				      struct uffdio_api)
+#define UFFDIO_REGISTER		_IOWR(UFFDIO, _UFFDIO_REGISTER, \
+				      struct uffdio_register)
+#define UFFDIO_UNREGISTER	_IOR(UFFDIO, _UFFDIO_UNREGISTER,	\
+				     struct uffdio_range)
+#define UFFDIO_WAKE		_IOR(UFFDIO, _UFFDIO_WAKE,	\
+				     struct uffdio_range)
+#define UFFDIO_COPY		_IOWR(UFFDIO, _UFFDIO_COPY,	\
+				      struct uffdio_copy)
+#define UFFDIO_ZEROPAGE		_IOWR(UFFDIO, _UFFDIO_ZEROPAGE,	\
+				      struct uffdio_zeropage)
+
+/* read() structure */
+struct uffd_msg {
+	__u8	event;
+
+	__u8	reserved1;
+	__u16	reserved2;
+	__u32	reserved3;
+
+	union {
+		struct {
+			__u64	flags;
+			__u64	address;
+		} pagefault;
+
+		struct {
+			/* unused reserved fields */
+			__u64	reserved1;
+			__u64	reserved2;
+			__u64	reserved3;
+		} reserved;
+	} arg;
+} __packed;
+
+/*
+ * Start at 0x12 and not at 0 to be more strict against bugs.
+ */
+#define UFFD_EVENT_PAGEFAULT	0x12
+
+/* flags for UFFD_EVENT_PAGEFAULT */
+#define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
+#define UFFD_PAGEFAULT_FLAG_WP		(1<<1)	/* If reason is VM_UFFD_WP */
+
+struct uffdio_api {
+	/* userland asks for an API number and the features to enable */
+	__u64 api;
+	/*
+	 * Kernel answers below with the all available features for
+	 * the API, this notifies userland of which events and/or
+	 * which flags for each event are enabled in the current
+	 * kernel.
+	 *
+	 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
+	 * are to be considered implicitly always enabled in all kernels as
+	 * long as the uffdio_api.api requested matches UFFD_API.
+	 */
+	__u64 features;
+
+	__u64 ioctls;
+};
+
+struct uffdio_range {
+	__u64 start;
+	__u64 len;
+};
+
+struct uffdio_register {
+	struct uffdio_range range;
+#define UFFDIO_REGISTER_MODE_MISSING	((__u64)1<<0)
+#define UFFDIO_REGISTER_MODE_WP		((__u64)1<<1)
+	__u64 mode;
+
+	/*
+	 * kernel answers which ioctl commands are available for the
+	 * range, keep at the end as the last 8 bytes aren't read.
+	 */
+	__u64 ioctls;
+};
+
+struct uffdio_copy {
+	__u64 dst;
+	__u64 src;
+	__u64 len;
+	/*
+	 * There will be a wrprotection flag later that allows to map
+	 * pages wrprotected on the fly. And such a flag will be
+	 * available if the wrprotection ioctl are implemented for the
+	 * range according to the uffdio_register.ioctls.
+	 */
+#define UFFDIO_COPY_MODE_DONTWAKE		((__u64)1<<0)
+	__u64 mode;
+
+	/*
+	 * "copy" is written by the ioctl and must be at the end: the
+	 * copy_from_user will not read the last 8 bytes.
+	 */
+	__s64 copy;
+};
+
+struct uffdio_zeropage {
+	struct uffdio_range range;
+#define UFFDIO_ZEROPAGE_MODE_DONTWAKE		((__u64)1<<0)
+	__u64 mode;
+
+	/*
+	 * "zeropage" is written by the ioctl and must be at the end:
+	 * the copy_from_user will not read the last 8 bytes.
+	 */
+	__s64 zeropage;
+};
+#endif /* UFFD_API */
+
+
+/* UFFD_USER_MODE_ONLY was added in v5.11 */
+#ifndef UFFD_USER_MODE_ONLY
+#define UFFD_USER_MODE_ONLY 1
+#endif /* UFFD_USER_MODE_ONLY */
+
+
+/* UFFD_PAGEFAULT_FLAG_MINOR and UFFDIO_CONTINUE were added in v5.13 */
+#ifndef UFFD_PAGEFAULT_FLAG_MINOR
+#define UFFD_FEATURE_MINOR_HUGETLBFS		(1<<9)
+#define UFFDIO_REGISTER_MODE_MINOR	((__u64)1<<2)
+
+#define _UFFDIO_CONTINUE		(0x07)
+#define UFFDIO_CONTINUE		_IOWR(UFFDIO, _UFFDIO_CONTINUE,	\
+				      struct uffdio_continue)
+
+struct uffdio_continue {
+	struct uffdio_range range;
+#define UFFDIO_CONTINUE_MODE_DONTWAKE		((__u64)1<<0)
+	__u64 mode;
+
+	/*
+	 * Fields below here are written by the ioctl and must be at the end:
+	 * the copy_from_user will not read past here.
+	 */
+	__s64 mapped;
+};
+#endif /* UFFD_PAGEFAULT_FLAG_MINOR */
+
+
+/* UFFD_FEATURE_MINOR_SHMEM was added in v5.14 */
+#ifndef UFFD_FEATURE_MINOR_SHMEM
+#define UFFD_FEATURE_MINOR_SHMEM		(1<<10)
+#endif /* UFFD_FEATURE_MINOR_SHMEM */
+
+#endif /* LAPI_USERFAULTFD_H__ */
-- 
2.38.1


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[LTP] [PATCH v1 2/3] security/dirtyc0w_shmem: Fix compile-time absence of UFFD_FEATURE_MINOR_SHMEM

[David Hildenbrand]

Without UFFD_FEATURE_MINOR_SHMEM, we'd currently let the parent run into
a timeout because we don't make the checkpoint happy, failing the
testcase instead of skipping it as TCONF.

Let's make compilation always work by including include/lapi/userfaultfd.h.

Reported-by: Martin Doucha <mdoucha@suse.cz>
Fixes: a46f8956f ("security/dirtyc0w_shmem: Add new test for CVE-2022-2590")
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 .../security/dirtyc0w_shmem/dirtyc0w_shmem_child.c   | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/testcases/kernel/security/dirtyc0w_shmem/dirtyc0w_shmem_child.c b/testcases/kernel/security/dirtyc0w_shmem/dirtyc0w_shmem_child.c
index 61799a504..9c2b03994 100644
--- a/testcases/kernel/security/dirtyc0w_shmem/dirtyc0w_shmem_child.c
+++ b/testcases/kernel/security/dirtyc0w_shmem/dirtyc0w_shmem_child.c
@@ -20,17 +20,11 @@
 #include <sys/syscall.h>
 #include <sys/ioctl.h>
 
-#ifdef HAVE_LINUX_USERFAULTFD_H
-#include <linux/userfaultfd.h>
-#endif
-
-#ifdef UFFD_FEATURE_MINOR_SHMEM
-
 #define TST_NO_DEFAULT_MAIN
 #include "tst_test.h"
 #include "tst_safe_macros.h"
 #include "tst_safe_pthread.h"
-#include "lapi/syscalls.h"
+#include "lapi/userfaultfd.h"
 
 #define TMP_DIR "tmp_dirtyc0w_shmem"
 #define TEST_FILE TMP_DIR"/testfile"
@@ -238,7 +232,3 @@ int main(void)
 
 	return 0;
 }
-#else /* UFFD_FEATURE_MINOR_SHMEM */
-#include "tst_test.h"
-TST_TEST_TCONF("System does not have userfaultfd minor fault support for shmem");
-#endif /* UFFD_FEATURE_MINOR_SHMEM */
-- 
2.38.1


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[LTP] [PATCH v1 3/3] syscalls/userfaultfd01: Remove compile-time TCONF handling

[David Hildenbrand]

Let's remove the conditional compile-time TCONF handling by including
include/lapi/userfaultfd.h .

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 testcases/kernel/syscalls/userfaultfd/userfaultfd01.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c b/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
index 2dae2ec78..c2c684d2b 100644
--- a/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
+++ b/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
@@ -12,13 +12,11 @@
 #include "config.h"
 #include "tst_test.h"
 
-#ifdef HAVE_LINUX_USERFAULTFD_H
-#include <linux/userfaultfd.h>
 #include <poll.h>
 
 #include "tst_safe_macros.h"
 #include "tst_safe_pthread.h"
-#include "lapi/syscalls.h"
+#include "lapi/userfaultfd.h"
 
 static int page_size;
 static char *page;
@@ -122,7 +120,3 @@ static struct tst_test test = {
 	.test_all = run,
 	.min_kver = "4.3",
 };
-
-#else
-	TST_TEST_TCONF("This system does not provide userfaultfd support");
-#endif
-- 
2.38.1


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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[Petr Vorel]

Hi David,

If I remember correctly the reason for runtime check was ppc64le
missing userfaultfd minor fault support which needs to be check in runtime,
right? [1]. At least this is how I understand Martin's suggestion [2] to replace
compile time check with lapi. I'd state this reason at first commit message as
it's not obvious.

Otherwise whole patchset LGTM.

Kind regards,
Petr

[1] https://lore.kernel.org/ltp/30abc28c-be3c-0f9e-0c2e-6614fdd30e0c@suse.cz/
[2] https://lore.kernel.org/ltp/6ce3a102-f2ec-16be-927d-a32ab46eaf0c@suse.cz/

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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[Martin Doucha]

On 28. 11. 22 12:57, Petr Vorel wrote:
> Hi David,
> 
> If I remember correctly the reason for runtime check was ppc64le
> missing userfaultfd minor fault support which needs to be check in runtime,
> right? [1]. At least this is how I understand Martin's suggestion [2] to replace
> compile time check with lapi. I'd state this reason at first commit message as
> it's not obvious.

The reason for runtime check is that the presence of the header file 
does not guarantee that the kernel supports UFFD API. The reason for 
LAPI is that we only care about actual kernel support, not build-time 
header files.

-- 
Martin Doucha   mdoucha@suse.cz
QA Engineer for Software Maintenance
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic


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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[David Hildenbrand]

On 28.11.22 13:29, Martin Doucha wrote:
> On 28. 11. 22 12:57, Petr Vorel wrote:
>> Hi David,
>>
>> If I remember correctly the reason for runtime check was ppc64le
>> missing userfaultfd minor fault support which needs to be check in runtime,
>> right? [1]. At least this is how I understand Martin's suggestion [2] to replace
>> compile time check with lapi. I'd state this reason at first commit message as
>> it's not obvious.
> 
> The reason for runtime check is that the presence of the header file
> does not guarantee that the kernel supports UFFD API. The reason for
> LAPI is that we only care about actual kernel support, not build-time
> header files.
> 

Right. Petr, do you still want a commit message state?

-- 
Thanks,

David / dhildenb


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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[Petr Vorel]

> On 28.11.22 13:29, Martin Doucha wrote:
> > On 28. 11. 22 12:57, Petr Vorel wrote:
> > > Hi David,

> > > If I remember correctly the reason for runtime check was ppc64le
> > > missing userfaultfd minor fault support which needs to be check in runtime,
> > > right? [1]. At least this is how I understand Martin's suggestion [2] to replace
> > > compile time check with lapi. I'd state this reason at first commit message as
> > > it's not obvious.

> > The reason for runtime check is that the presence of the header file
> > does not guarantee that the kernel supports UFFD API. The reason for
> > LAPI is that we only care about actual kernel support, not build-time
> > header files.
Thx, agree. BTW I was thinking about compile time check #ifdef
UFFD_FEATURE_MINOR_SHMEM, but that's the same as ifdef HAVE_LINUX_USERFAULTFD_H.


> Right. Petr, do you still want a commit message state?

I can just add to commit message of the first commit the reason Martin reported:
ppc64le on kernel 5.14 does not seem to support userfaultfd minor fault.

(no need to resent new version).

Kind regards,
Petr


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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[Petr Vorel]

> > On 28.11.22 13:29, Martin Doucha wrote:
> > > On 28. 11. 22 12:57, Petr Vorel wrote:
> > > > Hi David,

> > > > If I remember correctly the reason for runtime check was ppc64le
> > > > missing userfaultfd minor fault support which needs to be check in runtime,
> > > > right? [1]. At least this is how I understand Martin's suggestion [2] to replace
> > > > compile time check with lapi. I'd state this reason at first commit message as
> > > > it's not obvious.

> > > The reason for runtime check is that the presence of the header file
> > > does not guarantee that the kernel supports UFFD API. The reason for
> > > LAPI is that we only care about actual kernel support, not build-time
> > > header files.
Also hope that people compile LTP with relevant headers (including LTP distro
package), but of course it's better to cover the case when kernel headers are
missing or for different kernel version.

> Thx, agree. BTW I was thinking about compile time check #ifdef
> UFFD_FEATURE_MINOR_SHMEM, but that's the same as ifdef HAVE_LINUX_USERFAULTFD_H.

> > Right. Petr, do you still want a commit message state?

> I can just add to commit message of the first commit the reason Martin reported:
> ppc64le on kernel 5.14 does not seem to support userfaultfd minor fault.

In the end I merged without any change in commit message. You described the
reason (runtime check) enough in the second commit. I was wrongly looking at
fist commit, sorry for bothering you.

Thank you both!

Kind regards,
Petr

> (no need to resent new version).

> Kind regards,
> Petr


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Re: [LTP] [PATCH v1 0/3] userfaultfd: Fix and remove compile-time TCONF handling

[David Hildenbrand]

>> I can just add to commit message of the first commit the reason Martin reported:
>> ppc64le on kernel 5.14 does not seem to support userfaultfd minor fault.
> 
> In the end I merged without any change in commit message. You described the
> reason (runtime check) enough in the second commit. I was wrongly looking at
> fist commit, sorry for bothering you.
> 
> Thank you both!

Thanks all!

-- 
Thanks,

David / dhildenb


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