vm_map_protect.9: update after code changes
Reviewed by: brooks, markj Discussed with: emaste Sponsored by: The FreeBSD Foundation MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D28311
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Konstantin Belousov
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.\"
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.\" Copyright (c) 2003 Bruce M Simpson <bms@spc.org>
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.\" Copyright (c) 2021 The FreeBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" Parts of this documentation were written by
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.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
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.\" from the FreeBSD Foundation.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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@ -25,7 +30,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 20, 2019
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.Dd January 23, 2021
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.Dt VM_MAP_PROTECT 9
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.Os
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.Sh NAME
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@ -37,70 +42,95 @@
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.In vm/vm_map.h
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.Ft int
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.Fo vm_map_protect
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.Fa "vm_map_t map" "vm_offset_t start" "vm_offset_t end" "vm_prot_t new_prot"
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.Fa "boolean_t set_max"
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.Fa "vm_map_t map"
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.Fa "vm_offset_t start"
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.Fa "vm_offset_t end"
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.Fa "vm_prot_t new_prot"
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.Fa "vm_prot_t new_maxprot"
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.Fa "int flags"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn vm_map_protect
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function sets the protection bits of the address region bounded by
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function sets the protection bits and maximum protection bits of the address
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region bounded by
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.Fa start
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and
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.Fa end
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within the map
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.Fa map
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to
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.Fa map .
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.Pp
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If the
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.Fa flags
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argument has the
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.Dv VM_MAP_PROTECT_SET_PROT
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bit set, then the effective protection is set to
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.Fa new_prot .
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The value specified by
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.Pp
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If the
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.Fa flags
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argument has the
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.Dv VM_MAP_PROTECT_SET_MAXPROT
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bit set, then the maximum protection is set to
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.Fa new_maxprot .
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Protection bits not included into
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.Fa new_maxprot
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will be cleared from existing entries.
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.Pp
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The values specified by
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.Fa new_prot
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may not include any protection bits that are not set in
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and
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.Fa new_maxprot
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are not allowed to include any protection bits that are not set in existing
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.Va max_protection
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on every entry within the range.
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The operation will fail if this condition is violated.
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For instance, this prevents upgrading a shared mapping of a read-only file
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from read-only to read-write.
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.Pp
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If
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.Fa set_max
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is TRUE,
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.Fa new_prot
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is treated as the new
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.Va max_protection
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setting for each underlying entry.
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Protection bits not included
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.Fa new_prot
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will be cleared from existing entries.
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If
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.Fa set_max
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is FALSE only the
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.Va protection
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field is affected.
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.Pp
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The range MUST be contiguous, and MUST NOT contain sub-maps.
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The specified range must not contain sub-maps.
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.Sh IMPLEMENTATION NOTES
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The function acquires a lock on the
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.Fa map
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for the duration, by calling
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.Xr vm_map_lock 9 .
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Also, any in-progress wiring operation on the map affecting the specified
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range will cause
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.Nm
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to sleep, waiting for completion.
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.Sh RETURN VALUES
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The
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.Fn vm_map_protect
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function returns
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.Dv KERN_SUCCESS
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if the protection bits could be set successfully.
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.Pp
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If a sub-map entry was encountered in the range,
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.Dv KERN_INVALID_ARGUMENT
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is returned.
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If the value of
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.Bl -tag -width "Dv KERN_PROTECTION_FAILURE"
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.It Dv KERN_SUCCESS
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The specified protection bits were set successfully.
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.It Dv KERN_INVALID_ARGUMENT
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A sub-map entry was encountered in the range,
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.It Dv KERN_PROTECTION_FAILURE
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The value of
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.Fa new_prot
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would exceed
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or
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.Fa new_maxprot
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exceed
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.Va max_protection
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for an entry within the range,
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.Dv KERN_PROTECTION_FAILURE
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is returned.
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If a copy-on-write mapping is transitioned from read-only to
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read-write, and too little swap space is available for backing the
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copied pages,
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.Dv KERN_RESOURCE_SHORTAGE
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is returned.
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for an entry within the range.
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.It Dv KERN_PROTECTION_FAILURE
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The map does not allow simultaneous setting of write and execute permissions,
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but
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.Fa new_prot
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has both
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.Dv VM_PROT_WRITE
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and
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.Dv VM_PROT_EXECUTE
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set.
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.It Dv KERN_RESOURCE_SHORTAGE
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A copy-on-write mapping is transitioned from read-only to
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read-write, and not enough swap space is available to back the
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copied pages.
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.It Dv KERN_OUT_OF_BOUNDS
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Both new protection and new maximum protection updates were requested,
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but the specified
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.Fa new_prot
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is not a subset of
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.Fa new_maxprot .
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.Sh SEE ALSO
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.Xr vm_map 9
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.Sh AUTHORS
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