From: Chih-En Lin <shiyn.lin@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Qi Zheng <zhengqi.arch@bytedance.com>,
David Hildenbrand <david@redhat.com>,
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Dinglan Peng <peng301@purdue.edu>,
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Huichun Feng <foxhoundsk.tw@gmail.com>
Subject: [PATCH v5 02/17] mm: Allow user to control COW PTE via prctl
Date: Fri, 14 Apr 2023 22:23:26 +0800 [thread overview]
Message-ID: <20230414142341.354556-3-shiyn.lin@gmail.com> (raw)
In-Reply-To: <20230414142341.354556-1-shiyn.lin@gmail.com>
Add a new prctl, PR_SET_COW_PTE, to allow the user to enable COW PTE.
Since it has a time gap between using the prctl to enable the COW PTE
and doing the fork, we use two states (MMF_COW_PTE_READY and MMF_COW_PTE)
to determine the task that wants to do COW PTE or already doing it.
The MMF_COW_PTE_READY flag marks the task to do COW PTE in the next time
of fork(). During fork(), if MMF_COW_PTE_READY set, fork() will unset the
flag and set the MMF_COW_PTE flag. After that, fork() might shares PTEs
instead of duplicates it.
Signed-off-by: Chih-En Lin <shiyn.lin@gmail.com>
---
include/linux/sched/coredump.h | 13 ++++++++++++-
include/uapi/linux/prctl.h | 6 ++++++
kernel/sys.c | 11 +++++++++++
3 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
index 0e17ae7fbfd3..dff4b0938c39 100644
--- a/include/linux/sched/coredump.h
+++ b/include/linux/sched/coredump.h
@@ -87,7 +87,18 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
+/*
+ * MMF_COW_PTE_READY: Marking the task to do COW PTE in the next time of
+ * fork(). During fork(), if MMF_COW_PTE_READY set, fork() will unset the
+ * flag and set the MMF_COW_PTE flag. After that, fork() might shares PTEs
+ * rather than duplicates it.
+ */
+#define MMF_COW_PTE_READY 29 /* Share PTE tables in next time of fork() */
+#define MMF_COW_PTE 30 /* PTE tables are shared between processes */
+#define MMF_COW_PTE_MASK (1 << MMF_COW_PTE)
+
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
- MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK)
+ MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK |\
+ MMF_COW_PTE_MASK)
#endif /* _LINUX_SCHED_COREDUMP_H */
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 1312a137f7fb..8fc82ced80b5 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -290,4 +290,10 @@ struct prctl_mm_map {
#define PR_SET_VMA 0x53564d41
# define PR_SET_VMA_ANON_NAME 0
+/*
+ * Set the prepare flag, MMF_COW_PTE_READY, to do the share (copy-on-write)
+ * page table in the next time of fork.
+ */
+#define PR_SET_COW_PTE 65
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 495cd87d9bf4..eb1c38c4bad2 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2377,6 +2377,14 @@ static inline int prctl_get_mdwe(unsigned long arg2, unsigned long arg3,
PR_MDWE_REFUSE_EXEC_GAIN : 0;
}
+static int prctl_set_cow_pte(struct mm_struct *mm)
+{
+ if (test_bit(MMF_COW_PTE, &mm->flags))
+ return -EINVAL;
+ set_bit(MMF_COW_PTE_READY, &mm->flags);
+ return 0;
+}
+
SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
unsigned long, arg4, unsigned long, arg5)
{
@@ -2661,6 +2669,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_SET_VMA:
error = prctl_set_vma(arg2, arg3, arg4, arg5);
break;
+ case PR_SET_COW_PTE:
+ error = prctl_set_cow_pte(me->mm);
+ break;
default:
error = -EINVAL;
break;
--
2.34.1
next prev parent reply other threads:[~2023-04-14 14:24 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-14 14:23 [PATCH v5 00/17] Introduce Copy-On-Write to Page Table Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 01/17] mm: Split out the present cases from zap_pte_range() Chih-En Lin
2023-04-14 14:23 ` Chih-En Lin [this message]
2023-04-14 14:23 ` [PATCH v5 03/17] mm: Add Copy-On-Write PTE to fork() Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 04/17] mm: Add break COW PTE fault and helper functions Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 05/17] mm: Handle COW-ed PTE during zapping Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 06/17] mm/rmap: Break COW PTE in rmap walking Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 07/17] mm/khugepaged: Break COW PTE before scanning pte Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 08/17] mm/ksm: Break COW PTE before modify shared PTE Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 09/17] mm/madvise: Handle COW-ed PTE with madvise() Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 10/17] mm/gup: Trigger break COW PTE before calling follow_pfn_pte() Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 11/17] mm/mprotect: Break COW PTE before changing protection Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 12/17] mm/userfaultfd: Support COW PTE Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 13/17] mm/migrate_device: " Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 14/17] fs/proc: Support COW PTE with clear_refs_write Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 15/17] events/uprobes: Break COW PTE before replacing page Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 16/17] mm: fork: Enable COW PTE to fork system call Chih-En Lin
2023-04-14 14:23 ` [PATCH v5 17/17] mm: Check the unexpected modification of COW-ed PTE Chih-En Lin
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