mirror of https://github.com/mkerrisk/man-pages
mmap.2: Minor tweaks to Jan Kara's patch
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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man2/mmap.2
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man2/mmap.2
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@ -127,19 +127,21 @@ to the underlying file requires the use of
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.BR msync (2).)
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.TP
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.BR MAP_SHARED_VALIDATE " (since Linux 4.15)"
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The same as
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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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In contrast when creating mapping of
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.B MAP_SHARED_VALIDATE
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mapping type, the kernel verifies all passed flags are known and fails the
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mapping with
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By contrast, when creating a mapping using
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.B 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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otherwise.
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This mapping type is also required to be able to use some mapping flags.
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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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@ -155,6 +157,8 @@ Both
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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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.PP
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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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@ -432,19 +436,20 @@ support can later be transparently implemented for glibc.
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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 flags is available only with
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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
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mapping type;
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mappings of type
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.B MAP_SHARED
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type will silently ignore this flag.
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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 mapping with this flag results in
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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 writeably mapped in the address space of the process,
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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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This allows users of such mappings to make data modifications
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