With POWER10, architecture is adding new pmem flush and sync instructions.
The kernel should prevent the usage of MAP_SYNC if applications are not using
the new instructions on newer hardware.
This patch adds a prctl option MAP_SYNC_ENABLE that can be used to enable
the usage of MAP_SYNC. The kernel config option is added to allow the user
to control whether MAP_SYNC should be enabled by default or not.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
include/linux/sched/coredump.h | 13 ++++++++++---
include/uapi/linux/prctl.h | 3 +++
kernel/fork.c | 8 +++++++-
kernel/sys.c | 18 ++++++++++++++++++
mm/Kconfig | 3 +++
mm/mmap.c | 4 ++++
6 files changed, 45 insertions(+), 4 deletions(-)
diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
index ecdc6542070f..9ba6b3d5f991 100644
--- a/include/linux/sched/coredump.h
+++ b/include/linux/sched/coredump.h
@@ -72,9 +72,16 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_DISABLE_THP 24 /* disable THP for all VMAs */
#define MMF_OOM_VICTIM 25 /* mm is the oom victim */
#define MMF_OOM_REAP_QUEUED 26 /* mm was queued for oom_reaper */
-#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
+#define MMF_DISABLE_MAP_SYNC 27 /* disable THP for all VMAs */
+#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
+#define MMF_DISABLE_MAP_SYNC_MASK (1 << MMF_DISABLE_MAP_SYNC)
-#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
- MMF_DISABLE_THP_MASK)
+#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK | \
+ MMF_DISABLE_THP_MASK | MMF_DISABLE_MAP_SYNC_MASK)
+
+static inline bool map_sync_enabled(struct mm_struct *mm)
+{
+ return !(mm->flags & MMF_DISABLE_MAP_SYNC_MASK);
+}
#endif /* _LINUX_SCHED_COREDUMP_H */
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 07b4f8131e36..ee4cde32d5cf 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -238,4 +238,7 @@ struct prctl_mm_map {
#define PR_SET_IO_FLUSHER 57
#define PR_GET_IO_FLUSHER 58
+#define PR_SET_MAP_SYNC_ENABLE 59
+#define PR_GET_MAP_SYNC_ENABLE 60
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 8c700f881d92..d5a9a363e81e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -963,6 +963,12 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
+#ifdef CONFIG_ARCH_MAP_SYNC_DISABLE
+unsigned long default_map_sync_mask = MMF_DISABLE_MAP_SYNC_MASK;
+#else
+unsigned long default_map_sync_mask = 0;
+#endif
+
static int __init coredump_filter_setup(char *s)
{
default_dump_filter =
@@ -1039,7 +1045,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm,
struct task_struct *p,
mm->flags = current->mm->flags & MMF_INIT_MASK;
mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
} else {
- mm->flags = default_dump_filter;
+ mm->flags = default_dump_filter | default_map_sync_mask;
mm->def_flags = 0;
}
diff --git a/kernel/sys.c b/kernel/sys.c
index d325f3ab624a..f6127cf4128b 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2450,6 +2450,24 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2,
unsigned long, arg3,
clear_bit(MMF_DISABLE_THP, &me->mm->flags);
up_write(&me->mm->mmap_sem);
break;
+
+ case PR_GET_MAP_SYNC_ENABLE:
+ if (arg2 || arg3 || arg4 || arg5)
+ return -EINVAL;
+ error = !test_bit(MMF_DISABLE_MAP_SYNC, &me->mm->flags);
+ break;
+ case PR_SET_MAP_SYNC_ENABLE:
+ if (arg3 || arg4 || arg5)
+ return -EINVAL;
+ if (down_write_killable(&me->mm->mmap_sem))
+ return -EINTR;
+ if (arg2)
+ clear_bit(MMF_DISABLE_MAP_SYNC, &me->mm->flags);
+ else
+ set_bit(MMF_DISABLE_MAP_SYNC, &me->mm->flags);
+ up_write(&me->mm->mmap_sem);
+ break;
+
case PR_MPX_ENABLE_MANAGEMENT:
case PR_MPX_DISABLE_MANAGEMENT:
/* No longer implemented: */
diff --git a/mm/Kconfig b/mm/Kconfig
index c1acc34c1c35..38fd7cfbfca8 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -867,4 +867,7 @@ config ARCH_HAS_HUGEPD
config MAPPING_DIRTY_HELPERS
bool
+config ARCH_MAP_SYNC_DISABLE
+ bool
+
endmenu
diff --git a/mm/mmap.c b/mm/mmap.c
index f609e9ec4a25..613e5894f178 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1464,6 +1464,10 @@ unsigned long do_mmap(struct file *file, unsigned long
addr,
case MAP_SHARED_VALIDATE:
if (flags & ~flags_mask)
return -EOPNOTSUPP;
+
+ if ((flags & MAP_SYNC) && !map_sync_enabled(mm))
+ return -EOPNOTSUPP;
+
if (prot & PROT_WRITE) {
if (!(file->f_mode & FMODE_WRITE))
return -EACCES;
--
2.26.2
