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From f703950fc461d87b9833246be8721593aa5ec460 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Nikola=20Forr=C3=B3?= <nforro@redhat.com>
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Date: Thu, 8 Aug 2019 16:59:54 +0200
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Subject: [PATCH 2/6] mmap.2: fix EINVAL conditions
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---
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man-pages/man2/mmap.2 | 60 +++++++++++++++++++++++++++++++++++++------
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1 file changed, 52 insertions(+), 8 deletions(-)
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diff --git a/man-pages/man2/mmap.2 b/man-pages/man2/mmap.2
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index 798e0dd..6a9248c 100644
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--- a/man-pages/man2/mmap.2
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+++ b/man-pages/man2/mmap.2
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@@ -126,6 +126,23 @@ or
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.BR munmap ()
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is called.
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.TP
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+.BR MAP_SHARED_VALIDATE " (since Linux 4.15)"
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+This flag provides the same behavior as
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+.B MAP_SHARED
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+except that
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+.B MAP_SHARED
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+mappings ignore unknown flags in
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+.IR flags .
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+By contrast, when creating a mapping using
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+.BR MAP_SHARED_VALIDATE ,
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+the kernel verifies all passed flags are known and fails the
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+mapping with the error
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+.BR EOPNOTSUPP
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+for unknown flags.
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+This mapping type is also required to be able to use some mapping flags
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+(e.g.,
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+.BR MAP_SYNC ).
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+.TP
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.B MAP_PRIVATE
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Create a private copy-on-write mapping.
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Updates to the mapping are not visible to other processes
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@@ -135,8 +152,14 @@ It is unspecified whether changes made to the file after the
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.BR mmap ()
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call are visible in the mapped region.
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.LP
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-Both of these flags are described in POSIX.1-2001.
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-
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+Both
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+.B MAP_SHARED
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+and
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+.B MAP_PRIVATE
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+are described in POSIX.1-2001 and POSIX.1-2008.
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+.B MAP_SHARED_VALIDATE
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+is a Linux extension.
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+.LP
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In addition, zero or more of the following values can be ORed in
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.IR flags :
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.TP
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@@ -290,6 +313,27 @@ support can later be transparently implemented for glibc.
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.\" "pthread_create() slow for many threads; also time to revisit 64b
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.\" context switch optimization?"
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.TP
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+.BR MAP_SYNC " (since Linux 4.15)"
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+This flag is available only with the
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+.B MAP_SHARED_VALIDATE
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+mapping type;
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+mappings of type
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+.B MAP_SHARED
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+will silently ignore this flag.
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+This flag is supported only for files supporting DAX
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+(direct mapping of persistent memory).
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+For other files, creating a mapping with this flag results in an
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+.B EOPNOTSUPP
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+error.
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+.IP
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+Shared file mappings with this flag provide the guarantee that while
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+some memory is writably mapped in the address space of the process,
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+it will be visible in the same file at the same offset even after
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+the system crashes or is rebooted.
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+In conjunction with the use of appropriate CPU instructions,
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+this provides users of such mappings with a more efficient way
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+of making data modifications persistent.
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+.TP
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.BR MAP_UNINITIALIZED " (since Linux 2.6.33)"
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Don't clear anonymous pages.
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This flag is intended to improve performance on embedded devices.
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@@ -302,7 +346,7 @@ that option is normally enabled only on embedded devices
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.LP
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Of the above flags, only
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.B MAP_FIXED
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-is specified in POSIX.1-2001.
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+is specified in POSIX.1-2001 and POSIX.1-2008.
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However, most systems also support
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.B MAP_ANONYMOUS
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(or its synonym
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@@ -436,11 +480,11 @@ was 0.
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.TP
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.B EINVAL
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.I flags
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-contained neither
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-.B MAP_PRIVATE
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+contained none of
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+.BR MAP_PRIVATE ,
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+.B MAP_SHARED
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or
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-.BR MAP_SHARED ,
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-or contained both of these values.
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+.BR MAP_SHARED_VALIDATE .
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.TP
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.B ENFILE
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.\" This is for shared anonymous segments
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@@ -495,7 +539,7 @@ Attempted access to a portion of the buffer that does not correspond
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to the file (for example, beyond the end of the file, including the
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case where another process has truncated the file).
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.SH CONFORMING TO
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-SVr4, 4.4BSD, POSIX.1-2001.
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+POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD.
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.\" SVr4 documents additional error codes ENXIO and ENODEV.
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.\" SUSv2 documents additional error codes EMFILE and EOVERFLOW.
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.SH AVAILABILITY
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--
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2.21.0
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