The patch titled
Subject: userfaultfd: update the uffd_msg structure to be the same on 32/64bit
has been added to the -mm tree. Its filename is
userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: update the uffd_msg structure to be the same on 32/64bit
Avoiding to using packed allowed the code to be nicer and it avoided
the reserved1/2/3 but the structure must be the same for 32bit and
64bit archs so x86 applications built with the 32bit ABI can run on
the 64bit kernel without requiring translation of the data read
through the read syscall.
$ gcc -m64 p.c && ./a.out
32
0
16
8
8
16
24
$ gcc -m32 p.c && ./a.out
32
0
16
8
8
16
24
int main()
{
printf("%lu\n", sizeof(struct uffd_msg));
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->event);
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->arg.pagefault.address);
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->arg.pagefault.flags);
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->arg.reserved.reserved1);
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->arg.reserved.reserved2);
printf("%lu\n", (unsigned long) &((struct uffd_msg *) 0)->arg.reserved.reserved3);
}
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/userfaultfd.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff -puN include/uapi/linux/userfaultfd.h~userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2 include/uapi/linux/userfaultfd.h
--- a/include/uapi/linux/userfaultfd.h~userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2
+++ a/include/uapi/linux/userfaultfd.h
@@ -51,9 +51,13 @@
struct uffd_msg {
__u8 event;
+ __u8 reserved1;
+ __u16 reserved2;
+ __u32 reserved3;
+
union {
struct {
- __u32 flags;
+ __u64 flags;
__u64 address;
} pagefault;
@@ -64,7 +68,7 @@ struct uffd_msg {
__u64 reserved3;
} reserved;
} arg;
-};
+} __attribute__((packed));
/*
* Start at 0x12 and not at 0 to be more strict against bugs.
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
thp-cleanup-how-khugepaged-enters-freezer.patch
mm-drop-bogus-vm_bug_on_page-assert-in-put_page-codepath.patch
mm-avoid-tail-page-refcounting-on-non-thp-compound-pages.patch
userfaultfd-linux-documentation-vm-userfaultfdtxt.patch
userfaultfd-linux-documentation-vm-userfaultfdtxt-fix.patch
userfaultfd-waitqueue-add-nr-wake-parameter-to-__wake_up_locked_key.patch
userfaultfd-uapi.patch
userfaultfd-linux-userfaultfd_kh.patch
userfaultfd-add-vm_userfaultfd_ctx-to-the-vm_area_struct.patch
userfaultfd-add-vm_uffd_missing-and-vm_uffd_wp.patch
userfaultfd-call-handle_userfault-for-userfaultfd_missing-faults.patch
userfaultfd-teach-vma_merge-to-merge-across-vma-vm_userfaultfd_ctx.patch
userfaultfd-prevent-khugepaged-to-merge-if-userfaultfd-is-armed.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization-fix.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix.patch
userfaultfd-add-new-syscall-to-provide-memory-externalization-fix-fix-fix.patch
userfaultfd-rename-uffd_apibits-into-features.patch
userfaultfd-rename-uffd_apibits-into-features-fixup.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix.patch
userfaultfd-change-the-read-api-to-return-a-uffd_msg-fix-2.patch
userfaultfd-wake-pending-userfaults.patch
userfaultfd-optimize-read-and-poll-to-be-o1.patch
userfaultfd-optimize-read-and-poll-to-be-o1-fix.patch
userfaultfd-allocate-the-userfaultfd_ctx-cacheline-aligned.patch
userfaultfd-solve-the-race-between-uffdio_copyzeropage-and-read.patch
userfaultfd-buildsystem-activation.patch
userfaultfd-activate-syscall.patch
userfaultfd-activate-syscall-fix.patch
userfaultfd-uffdio_copyuffdio_zeropage-uapi.patch
userfaultfd-mcopy_atomicmfill_zeropage-uffdio_copyuffdio_zeropage-preparation.patch
userfaultfd-avoid-mmap_sem-read-recursion-in-mcopy_atomic.patch
userfaultfd-avoid-mmap_sem-read-recursion-in-mcopy_atomic-fix.patch
userfaultfd-uffdio_copy-and-uffdio_zeropage.patch
fs-userfaultfdc-work-around-i386-build-error.patch
mm-oom_kill-remove-unnecessary-locking-in-oom_enable.patch
mm-oom_kill-clean-up-victim-marking-and-exiting-interfaces.patch
mm-oom_kill-switch-test-and-clear-of-known-tif_memdie-to-clear.patch
mm-oom_kill-generalize-oom-progress-waitqueue.patch
mm-oom_kill-remove-unnecessary-locking-in-exit_oom_victim.patch
mm-oom_kill-simplify-oom-killer-locking.patch
mm-page_alloc-inline-should_alloc_retry.patch
mm-thp-split-out-pmd-collpase-flush-into-a-separate-functions.patch
powerpc-mm-use-generic-version-of-pmdp_clear_flush.patch
mm-clarify-that-the-function-operates-on-hugepage-pte.patch
page-flags-trivial-cleanup-for-pagetrans-helpers.patch
page-flags-introduce-page-flags-policies-wrt-compound-pages.patch
page-flags-define-pg_locked-behavior-on-compound-pages.patch
page-flags-define-behavior-of-fs-io-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-lru-related-flags-on-compound-pages.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-xen-related-flags-on-compound-pages.patch
page-flags-define-pg_reserved-behavior-on-compound-pages.patch
page-flags-define-pg_swapbacked-behavior-on-compound-pages.patch
page-flags-define-pg_swapcache-behavior-on-compound-pages.patch
page-flags-define-pg_mlocked-behavior-on-compound-pages.patch
page-flags-define-pg_uncached-behavior-on-compound-pages.patch
page-flags-define-pg_uptodate-behavior-on-compound-pages.patch
page-flags-look-on-head-page-if-the-flag-is-encoded-in-page-mapping.patch
mm-sanitize-page-mapping-for-tail-pages.patch
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