vm_map_protect(9) manual page

Manual Pages — VM_MAP_PROTECT

NAME

vm_map_protect – apply protection bits to a virtual memory region

SYNOPSIS

#include <sys/param.h>

#include <vm/vm.h>

#include <vm/vm_map.h>

int
vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end, vm_prot_t new_prot, vm_prot_t new_maxprot, int flags);

DESCRIPTION

The vm_map_protect() function sets the protection bits and maximum protection bits of the address region bounded by start and end within the map map.

If the flags argument has the VM_MAP_PROTECT_SET_PROT bit set, then the effective protection is set to new_prot.

If the flags argument has the VM_MAP_PROTECT_SET_MAXPROT bit set, then the maximum protection is set to new_maxprot. Protection bits not included into new_maxprot will be cleared from existing entries.

The values specified by new_prot and new_maxprot are not allowed to include any protection bits that are not set in existing max_protection on every entry within the range. The operation will fail if this condition is violated. For instance, this prevents upgrading a shared mapping of a read-only file from read-only to read-write.

The specified range must not contain sub-maps.

IMPLEMENTATION NOTES

The function acquires a lock on the map for the duration, by calling vm_map_lock(9). Also, any in-progress wiring operation on the map affecting the specified range will cause vm_map_protect to sleep, waiting for completion.

RETURN VALUES

`KERN_SUCCESS`	The specified protection bits were set successfully.
`KERN_INVALID_ARGUMENT`	A sub-map entry was encountered in the range,
`KERN_PROTECTION_FAILURE`	The value of new_prot or new_maxprot exceed max_protection for an entry within the range.
`KERN_PROTECTION_FAILURE`	The map does not allow simultaneous setting of write and execute permissions, but new_prot has both `VM_PROT_WRITE` and `VM_PROT_EXECUTE` set.
`KERN_RESOURCE_SHORTAGE`	A copy-on-write mapping is transitioned from read-only to read-write, and not enough swap space is available to back the copied pages.
`KERN_OUT_OF_BOUNDS`	Both new protection and new maximum protection updates were requested, but the specified new_prot is not a subset of new_maxprot.

AUTHORS

This manual page was written by Bruce M Simpson <Mt bms@spc.org>.

VM_MAP_PROTECT (9)

January 23, 2021

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