[PATCH 2/3] s390/vdso: fix arch_data access for __arch_get_hw_counter()

Heiko Carstens
2021-03-23T21:59:54Z

Li Wang reported that clock_gettime(CLOCK_MONOTONIC_RAW, ...) returns
incorrect values when time is provided via vdso instead of system call:

vdso_ts_nsec = 4484351380985507, vdso_ts.tv_sec = 4484351, vdso_ts.tv_nsec = 380985507
sys_ts_nsec = 1446923235377, sys_ts.tv_sec = 1446, sys_ts.tv_nsec = 923235377

Within the s390 specific vdso function __arch_get_hw_counter() tries
to read tod clock steering values from the arch_data member of the
passed in vdso_data structure.
However only the arch_data member of the first clock source base
(CS_HRES_COARSE) is initialized. For CS_RAW arch_data is not at all
initialized, which explains the incorrect returned values.

It is a bit odd to provide the required tod clock steering parameters
only within the first element of the _vdso_data array. However for
time namespaces even no member of the _timens_data array contains the
required data, which would make fixing __arch_get_hw_counter() quite
complicated.

Therefore simply add an s390 specific vdso data page which contains
the tod clock steering parameters. Everything else seems to be
unnecessary complex.

Reported-by: Li Wang <liwang@redhat.com>
Fixes: 1ba2d6c0fd4e ("s390/vdso: simplify __arch_get_hw_counter()")
Fixes: eeab78b05d20 ("s390/vdso: implement generic vdso time namespace support")
Link: https://lore.kernel.org/linux-s390/YFnxr1ZlMIOIqjfq@osiris
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/Kconfig | 1 -
arch/s390/include/asm/vdso.h | 4 +++-
arch/s390/include/asm/vdso/data.h | 13 ------------
arch/s390/include/asm/vdso/datapage.h | 17 +++++++++++++++
arch/s390/include/asm/vdso/gettimeofday.h | 11 ++++++++--
arch/s390/kernel/time.c | 6 +++---
arch/s390/kernel/vdso.c | 25 ++++++++++++++++++++---
arch/s390/kernel/vdso64/vdso64.lds.S | 3 ++-
8 files changed, 56 insertions(+), 24 deletions(-)
delete mode 100644 arch/s390/include/asm/vdso/data.h
create mode 100644 arch/s390/include/asm/vdso/datapage.h

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index c1ff874e6c2e..532ce0fcc659 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -77,7 +77,6 @@ config S390
select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_SYSCALL_WRAPPER
select ARCH_HAS_UBSAN_SANITIZE_ALL
- select ARCH_HAS_VDSO_DATA
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_INLINE_READ_LOCK
select ARCH_INLINE_READ_LOCK_BH
diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h
index b45e3dddd2c2..0d047f519df6 100644
--- a/arch/s390/include/asm/vdso.h
+++ b/arch/s390/include/asm/vdso.h
@@ -3,17 +3,19 @@
#define __S390_VDSO_H__

#include <vdso/datapage.h>
+#include <asm/vdso/datapage.h>

/* Default link address for the vDSO */
#define VDSO64_LBASE 0

-#define __VVAR_PAGES 2
+#define __VVAR_PAGES 3

#define VDSO_VERSION_STRING LINUX_2.6.29

#ifndef __ASSEMBLY__

extern struct vdso_data *vdso_data;
+extern struct s390_vdso_data *s390_vdso_data;

int vdso_getcpu_init(void);

diff --git a/arch/s390/include/asm/vdso/data.h b/arch/s390/include/asm/vdso/data.h
deleted file mode 100644
index 7b3cdb4a5f48..000000000000
--- a/arch/s390/include/asm/vdso/data.h
+++ /dev/null
@@ -1,13 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __S390_ASM_VDSO_DATA_H
-#define __S390_ASM_VDSO_DATA_H
-
-#include <linux/types.h>
-#include <vdso/datapage.h>
-
-struct arch_vdso_data {
- __u64 tod_steering_delta;
- __u64 tod_steering_end;
-};
-
-#endif /* __S390_ASM_VDSO_DATA_H */
diff --git a/arch/s390/include/asm/vdso/datapage.h b/arch/s390/include/asm/vdso/datapage.h
new file mode 100644
index 000000000000..bfae78d814af
--- /dev/null
+++ b/arch/s390/include/asm/vdso/datapage.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __S390_ASM_VDSO_DATAPAGE_H
+#define __S390_ASM_VDSO_DATAPAGE_H
+
+#include <linux/types.h>
+
+#ifndef __ASSEMBLY__
+
+struct s390_vdso_data {
+ __u64 tod_steering_delta;
+ __u64 tod_steering_end;
+};
+
+extern struct s390_vdso_data _s390_data __attribute__((visibility("hidden")));
+
+#endif /* __ASSEMBLY__ */
+#endif /* __S390_ASM_VDSO_DATAPAGE_H */
diff --git a/arch/s390/include/asm/vdso/gettimeofday.h b/arch/s390/include/asm/vdso/gettimeofday.h
index ed89ef742530..bbd6da6b1651 100644
--- a/arch/s390/include/asm/vdso/gettimeofday.h
+++ b/arch/s390/include/asm/vdso/gettimeofday.h
@@ -9,6 +9,7 @@
#include <asm/timex.h>
#include <asm/unistd.h>
#include <asm/vdso.h>
+#include <asm/vdso/datapage.h>
#include <linux/compiler.h>

#define vdso_calc_delta __arch_vdso_calc_delta
@@ -22,14 +23,20 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
return _vdso_data;
}

+static __always_inline const struct s390_vdso_data *__get_s390_vdso_data(void)
+{
+ return &_s390_data;
+}
+
static inline u64 __arch_get_hw_counter(s32 clock_mode, const struct vdso_data *vd)
{
+ const struct s390_vdso_data *svd = __get_s390_vdso_data();
u64 adj, now;

now = get_tod_clock();
- adj = vd->arch_data.tod_steering_end - now;
+ adj = svd->tod_steering_end - now;
if (unlikely((s64) adj > 0))
- now += (vd->arch_data.tod_steering_delta < 0) ? (adj >> 15) : -(adj >> 15);
+ now += (svd->tod_steering_delta < 0) ? (adj >> 15) : -(adj >> 15);
return now;
}

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index e37285a5101b..ec5c12e541aa 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -83,7 +83,7 @@ void __init time_early_init(void)

/* Initialize TOD steering parameters */
tod_steering_end = tod_clock_base.tod;
- vdso_data->arch_data.tod_steering_end = tod_steering_end;
+ s390_vdso_data->tod_steering_end = tod_steering_end;

if (!test_facility(28))
return;
@@ -381,8 +381,8 @@ static void clock_sync_global(unsigned long delta)
panic("TOD clock sync offset %li is too large to drift\n",
tod_steering_delta);
tod_steering_end = now + (abs(tod_steering_delta) << 15);
- vdso_data->arch_data.tod_steering_end = tod_steering_end;
- vdso_data->arch_data.tod_steering_delta = tod_steering_delta;
+ s390_vdso_data->tod_steering_end = tod_steering_end;
+ s390_vdso_data->tod_steering_delta = tod_steering_delta;

/* Update LPAR offset. */
if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 8c4e07d533c8..4f1dba52b240 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -29,9 +29,16 @@ static union {
u8 page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;

+static union {
+ struct s390_vdso_data data;
+ u8 page[PAGE_SIZE];
+} s390_vdso_page __page_aligned_data;
+
struct vdso_data *vdso_data = vdso_data_store.data;
+struct s390_vdso_data *s390_vdso_data = &s390_vdso_page.data;

enum vvar_pages {
+ VVAR_S390_PAGE_OFFSET,
VVAR_DATA_PAGE_OFFSET,
VVAR_TIMENS_PAGE_OFFSET,
VVAR_NR_PAGES,
@@ -109,14 +116,26 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
vm_fault_t err;

switch (vmf->pgoff) {
+ case VVAR_S390_PAGE_OFFSET:
+ pfn = virt_to_pfn(s390_vdso_data);
+ break;
case VVAR_DATA_PAGE_OFFSET:
+ /*
+ * Fault in VVAR s390 page too, since it will be
+ * accessed to get tod clock steering data anyway.
+ */
+ addr = vma->vm_start + VVAR_S390_PAGE_OFFSET * PAGE_SIZE;
+ pfn = virt_to_pfn(s390_vdso_data);
+ err = vmf_insert_pfn(vma, addr, pfn);
+ if (unlikely(err & VM_FAULT_ERROR))
+ return err;
+ addr = vma->vm_start + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
pfn = virt_to_pfn(vdso_data);
if (timens_page) {
/*
- * Fault in VVAR page too, since it will be accessed
- * to get clock data anyway.
+ * Fault in VVAR data page too, since it will be
+ * accessed to get clock data anyway.
*/
- addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
err = vmf_insert_pfn(vma, addr, pfn);
if (unlikely(err & VM_FAULT_ERROR))
return err;
diff --git a/arch/s390/kernel/vdso64/vdso64.lds.S b/arch/s390/kernel/vdso64/vdso64.lds.S
index 518f1ea405f4..d38e5475df65 100644
--- a/arch/s390/kernel/vdso64/vdso64.lds.S
+++ b/arch/s390/kernel/vdso64/vdso64.lds.S
@@ -13,7 +13,8 @@ ENTRY(_start)

SECTIONS
{
- PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+ PROVIDE(_s390_data = . - __VVAR_PAGES * PAGE_SIZE);
+ PROVIDE(_vdso_data = _s390_data + PAGE_SIZE);
#ifdef CONFIG_TIME_NS
PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
#endif
--
2.25.1