diff mbox series

[v8,04/23] mm/uffd: PTE_MARKER_UFFD_WP

Message ID 20220405014838.14131-1-peterx@redhat.com (mailing list archive)
State New
Headers show
Series userfaultfd-wp: Support shmem and hugetlbfs | expand

Commit Message

Peter Xu April 5, 2022, 1:48 a.m. UTC 
This patch introduces the 1st user of pte marker: the uffd-wp marker.

When the pte marker is installed with the uffd-wp bit set, it means this pte
was wr-protected by uffd.

We will use this special pte to arm the ptes that got either unmapped or
swapped out for a file-backed region that was previously wr-protected.  This
special pte could trigger a page fault just like swap entries.

This idea is greatly inspired by Hugh and Andrea in the discussion, which is
referenced in the links below.

Some helpers are introduced to detect whether a swap pte is uffd wr-protected.
After the pte marker introduced, one swap pte can be wr-protected in two forms:
either it is a normal swap pte and it has _PAGE_SWP_UFFD_WP set, or it's a pte
marker that has PTE_MARKER_UFFD_WP set.

Link: https://lore.kernel.org/lkml/20201126222359.8120-1-peterx@redhat.com/
Link: https://lore.kernel.org/lkml/20201130230603.46187-1-peterx@redhat.com/
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/linux/swapops.h       |  3 ++-
 include/linux/userfaultfd_k.h | 43 +++++++++++++++++++++++++++++++++++
 mm/Kconfig                    |  9 ++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)

Comments

kernel test robot April 6, 2022, 1:41 a.m. UTC | #1 
Hi Peter,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on hnaz-mm/master]
[also build test ERROR on arnd-asm-generic/master linus/master v5.18-rc1 next-20220405]
[cannot apply to linux/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Peter-Xu/userfaultfd-wp-Support-shmem-and-hugetlbfs/20220405-100136
base:   https://github.com/hnaz/linux-mm master
config: ia64-buildonly-randconfig-r005-20220405 (https://download.01.org/0day-ci/archive/20220406/202204060938.eKyGvcev-lkp@intel.com/config)
compiler: ia64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/5baea0f03d347e5b13fff03af297858f1247d51a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Peter-Xu/userfaultfd-wp-Support-shmem-and-hugetlbfs/20220405-100136
        git checkout 5baea0f03d347e5b13fff03af297858f1247d51a
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=ia64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from arch/ia64/include/asm/pgtable.h:153,
                    from include/linux/pgtable.h:6,
                    from arch/ia64/include/asm/uaccess.h:40,
                    from include/linux/uaccess.h:11,
                    from include/linux/sched/task.h:11,
                    from include/linux/sched/signal.h:9,
                    from include/linux/rcuwait.h:6,
                    from include/linux/percpu-rwsem.h:7,
                    from include/linux/fs.h:33,
                    from arch/ia64/kernel/sys_ia64.c:10:
   arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
         |                                                ^~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from arch/ia64/kernel/sys_ia64.c:21:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:243:16: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:14: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:38: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                      ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:244:38: note: each undeclared identifier is reported only once for each function it appears in
   arch/ia64/kernel/sys_ia64.c: At top level:
   arch/ia64/kernel/sys_ia64.c:71:1: warning: no previous prototype for 'ia64_getpriority' [-Wmissing-prototypes]
      71 | ia64_getpriority (int which, int who)
         | ^~~~~~~~~~~~~~~~
   arch/ia64/kernel/sys_ia64.c:85:1: warning: no previous prototype for 'sys_getpagesize' [-Wmissing-prototypes]
      85 | sys_getpagesize (void)
         | ^~~~~~~~~~~~~~~
   arch/ia64/kernel/sys_ia64.c:91:1: warning: no previous prototype for 'ia64_brk' [-Wmissing-prototypes]
      91 | ia64_brk (unsigned long brk)
         | ^~~~~~~~
   arch/ia64/kernel/sys_ia64.c:161:1: warning: no previous prototype for 'ia64_mremap' [-Wmissing-prototypes]
     161 | ia64_mremap (unsigned long addr, unsigned long old_len, unsigned long new_len, unsigned long flags,
         | ^~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from arch/ia64/include/asm/pgtable.h:153,
                    from include/linux/pgtable.h:6,
                    from arch/ia64/include/asm/uaccess.h:40,
                    from include/linux/uaccess.h:11,
                    from include/linux/sched/task.h:11,
                    from kernel/fork.c:23:
   arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
         |                                                ^~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from kernel/fork.c:52:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:243:16: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:14: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:38: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                      ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:244:38: note: each undeclared identifier is reported only once for each function it appears in
   kernel/fork.c: At top level:
   kernel/fork.c:163:13: warning: no previous prototype for 'arch_release_task_struct' [-Wmissing-prototypes]
     163 | void __weak arch_release_task_struct(struct task_struct *tsk)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~
   kernel/fork.c:853:20: warning: no previous prototype for 'arch_task_cache_init' [-Wmissing-prototypes]
     853 | void __init __weak arch_task_cache_init(void) { }
         |                    ^~~~~~~~~~~~~~~~~~~~
   kernel/fork.c:948:12: warning: no previous prototype for 'arch_dup_task_struct' [-Wmissing-prototypes]
     948 | int __weak arch_dup_task_struct(struct task_struct *dst,
         |            ^~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from arch/ia64/include/asm/pgtable.h:153,
                    from include/linux/pgtable.h:6,
                    from include/linux/mm.h:29,
                    from kernel/sysctl.c:23:
   arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
         |                                                ^~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from kernel/sysctl.c:46:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:243:16: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:14: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:38: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                      ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:244:38: note: each undeclared identifier is reported only once for each function it appears in
   cc1: some warnings being treated as errors
--
   In file included from arch/ia64/include/asm/pgtable.h:153,
                    from include/linux/pgtable.h:6,
                    from include/linux/mm.h:29,
                    from mm/vmscan.c:15:
   arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
         |                                                ^~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from include/linux/migrate.h:8,
                    from mm/vmscan.c:44:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:243:16: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:14: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:38: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                      ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:244:38: note: each undeclared identifier is reported only once for each function it appears in
   In file included from mm/vmscan.c:57:
   include/linux/swapops.h: At top level:
>> include/linux/swapops.h:289:20: error: conflicting types for 'is_pte_marker_entry'; have 'bool(swp_entry_t)' {aka '_Bool(swp_entry_t)'}
     289 | static inline bool is_pte_marker_entry(swp_entry_t entry)
         |                    ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from include/linux/migrate.h:8,
                    from mm/vmscan.c:44:
   include/linux/userfaultfd_k.h:243:16: note: previous implicit declaration of 'is_pte_marker_entry' with type 'int()'
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
   In file included from mm/vmscan.c:57:
>> include/linux/swapops.h:294:26: error: conflicting types for 'pte_marker_get'; have 'pte_marker(swp_entry_t)' {aka 'long unsigned int(swp_entry_t)'}
     294 | static inline pte_marker pte_marker_get(swp_entry_t entry)
         |                          ^~~~~~~~~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from include/linux/migrate.h:8,
                    from mm/vmscan.c:44:
   include/linux/userfaultfd_k.h:244:14: note: previous implicit declaration of 'pte_marker_get' with type 'int()'
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from arch/ia64/include/asm/pgtable.h:153,
                    from include/linux/pgtable.h:6,
                    from arch/ia64/include/asm/uaccess.h:40,
                    from include/linux/uaccess.h:11,
                    from include/linux/sched/task.h:11,
                    from include/linux/sched/signal.h:9,
                    from include/linux/rcuwait.h:6,
                    from include/linux/percpu-rwsem.h:7,
                    from include/linux/fs.h:33,
                    from fs/proc/meminfo.c:2:
   arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable 'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
         |                                                ^~~~~~~
   In file included from include/linux/hugetlb.h:14,
                    from fs/proc/meminfo.c:6:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:243:16: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     243 |         return is_pte_marker_entry(entry) &&
         |                ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:14: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |              ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:244:38: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     244 |             (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                      ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:244:38: note: each undeclared identifier is reported only once for each function it appears in
   fs/proc/meminfo.c: At top level:
   fs/proc/meminfo.c:22:28: warning: no previous prototype for 'arch_report_meminfo' [-Wmissing-prototypes]
      22 | void __attribute__((weak)) arch_report_meminfo(struct seq_file *m)
         |                            ^~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/is_pte_marker_entry +243 include/linux/userfaultfd_k.h

   240	
   241	static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
   242	{
 > 243		return is_pte_marker_entry(entry) &&
 > 244		    (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
   245	}
   246
diff mbox series

Patch

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 7a00627845f0..fffbba0036f6 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -276,7 +276,8 @@  static inline int is_readable_migration_entry(swp_entry_t entry)
 
 typedef unsigned long pte_marker;
 
-#define  PTE_MARKER_MASK     (0)
+#define  PTE_MARKER_UFFD_WP  BIT(0)
+#define  PTE_MARKER_MASK     (PTE_MARKER_UFFD_WP)
 
 #ifdef CONFIG_PTE_MARKER
 
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 33cea484d1ad..bd09c3c89b59 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -15,6 +15,8 @@ 
 
 #include <linux/fcntl.h>
 #include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 #include <asm-generic/pgtable_uffd.h>
 
 /* The set of all possible UFFD-related VM flags. */
@@ -236,4 +238,45 @@  static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
 
 #endif /* CONFIG_USERFAULTFD */
 
+static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
+{
+	return is_pte_marker_entry(entry) &&
+	    (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
+}
+
+static inline bool pte_marker_uffd_wp(pte_t pte)
+{
+#ifdef CONFIG_PTE_MARKER_UFFD_WP
+	swp_entry_t entry;
+
+	if (!is_swap_pte(pte))
+		return false;
+
+	entry = pte_to_swp_entry(pte);
+
+	return pte_marker_entry_uffd_wp(entry);
+#else
+	return false;
+#endif
+}
+
+/*
+ * Returns true if this is a swap pte and was uffd-wp wr-protected in either
+ * forms (pte marker or a normal swap pte), false otherwise.
+ */
+static inline bool pte_swp_uffd_wp_any(pte_t pte)
+{
+#ifdef CONFIG_PTE_MARKER_UFFD_WP
+	if (!is_swap_pte(pte))
+		return false;
+
+	if (pte_swp_uffd_wp(pte))
+		return true;
+
+	if (pte_marker_uffd_wp(pte))
+		return true;
+#endif
+	return false;
+}
+
 #endif /* _LINUX_USERFAULTFD_K_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index a1688b9314b2..6e7c2d59fa96 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -915,6 +915,15 @@  config PTE_MARKER
 	help
 	  Allows to create marker PTEs for file-backed memory.
 
+config PTE_MARKER_UFFD_WP
+	bool "Marker PTEs support for userfaultfd write protection"
+	depends on PTE_MARKER && HAVE_ARCH_USERFAULTFD_WP
+
+	help
+	  Allows to create marker PTEs for userfaultfd write protection
+	  purposes.  It is required to enable userfaultfd write protection on
+	  file-backed memory types like shmem and hugetlbfs.
+
 source "mm/damon/Kconfig"
 
 endmenu