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UVM_MAP(9) Kernel Developer's Manual UVM_MAP(9)

uvm_map, uvm_map_pageable, uvm_map_pageable_all, uvm_map_checkprot, uvm_map_protect, uvmspace_alloc, uvmspace_exec, uvmspace_fork, uvmspace_free, uvmspace_share, uvm_uarea_alloc, uvm_uarea_free, UVM_MAPFLAGvirtual address space management interface

#include <sys/param.h>
#include <uvm/uvm.h>

uvm_map(vm_map_t map, vaddr_t *startp, vsize_t size, struct uvm_object *uobj, voff_t uoffset, vsize_t alignment, unsigned int flags);

uvm_map_pageable(vm_map_t map, vaddr_t start, vaddr_t end, boolean_t new_pageable, int lockflags);

uvm_map_pageable_all(vm_map_t map, int flags, vsize_t limit);

uvm_map_checkprot(vm_map_t map, vaddr_t start, vaddr_t end, vm_prot_t protection);

uvm_map_protect(vm_map_t map, vaddr_t start, vaddr_t end, vm_prot_t new_prot, int et, boolean_t set_max, boolean_t checkimmutable);

struct vmspace *
uvmspace_alloc(vaddr_t min, vaddr_t max, boolean_t pageable, boolean_t remove_holes);

uvmspace_exec(struct proc *p, vaddr_t start, vaddr_t end);

struct vmspace *
uvmspace_fork(struct process *pr);

uvmspace_free(struct vmspace *vm);

struct vmspace *
uvmspace_share(struct process *pr);


uvm_uarea_free(struct proc *p);

unsigned int
UVM_MAPFLAG(vm_prot_t prot, vm_prot_t maxprot, vm_inherit_t inh, int advice, int flags);

The () function establishes a valid mapping in map map, which must be unlocked. The new mapping has size size, which must be in PAGE_SIZE units. If alignment is non-zero, it describes the required alignment of the list, in power-of-two notation. The uobj and uoffset arguments can have four meanings. When uobj is NULL and uoffset is UVM_UNKNOWN_OFFSET, uvm_map() does not use the machine-dependent PMAP_PREFER function. If uoffset is any other value, it is used as the hint to PMAP_PREFER. When uobj is not NULL and uoffset is UVM_UNKNOWN_OFFSET, uvm_map() finds the offset based upon the virtual address, passed as startp. If uoffset is any other value, we are doing a normal mapping at this offset. The start address of the map will be returned in startp.

flags passed to () are typically created using the () macro, which uses the following values. The prot and maxprot can take a mix of the following values:

#define PROT_MASK   0x07    /* protection mask */
#define PROT_NONE   0x00    /* protection none */
#define PROT_READ   0x01    /* read */
#define PROT_WRITE  0x02    /* write */
#define PROT_EXEC   0x04    /* exec */

The values that inh can take are:

#define MAP_INHERIT_MASK    0x30    /* inherit mask */
#define MAP_INHERIT_SHARE   0x00    /* "share" */
#define MAP_INHERIT_COPY    0x10    /* "copy" */
#define MAP_INHERIT_NONE    0x20    /* "none" */
#define MAP_INHERIT_ZERO    0x30    /* "zero" */

The values that advice can take are:

#define MADV_NORMAL  0x0     /* 'normal' */
#define MADV_RANDOM  0x1     /* 'random' */
#define MADV_SEQUENTIAL 0x2  /* 'sequential' */
#define MADV_MASK    0x7     /* mask */

The values that flags can take are:

#define UVM_FLAG_FIXED   0x0010000 /* find space */
#define UVM_FLAG_OVERLAY 0x0020000 /* establish overlay */
#define UVM_FLAG_NOMERGE 0x0040000 /* don't merge map entries */
#define UVM_FLAG_COPYONW 0x0080000 /* set copy_on_write flag */
#define UVM_FLAG_TRYLOCK 0x0100000 /* fail if we can not lock map */
#define UVM_FLAG_HOLE    0x0200000 /* no backend */
#define UVM_FLAG_QUERY   0x0400000 /* do everything,
                                      except actual execution */
#define UVM_FLAG_NOFAULT 0x0800000 /* don't fault */
#define UVM_FLAG_UNMAP   0x1000000 /* unmap to make space */
#define UVM_FLAG_STACK   0x2000000 /* page may contain a stack */

The UVM_MAPFLAG macro arguments can be combined with an or operator. There are also some additional macros to extract bits from the flags. The UVM_PROTECTION, UVM_INHERIT, UVM_MAXPROTECTION and UVM_ADVICE macros return the protection, inheritance, maximum protection and advice, respectively. () returns a standard errno.

The () function changes the pageability of the pages in the range from start to end in map map to new_pageable. The () function changes the pageability of all mapped regions. If limit is non-zero and () is implemented, ENOMEM is returned if the amount of wired pages exceed limit. The map is locked on entry if lockflags contain UVM_LK_ENTER, and locked on exit if lockflags contain UVM_LK_EXIT. uvm_map_pageable() and uvm_map_pageable_all() return a standard errno.

The () function checks the protection of the range from start to end in map map against protection. This returns either TRUE or FALSE.

The () function changes the protection start to end in map map to new_prot, also setting the maximum protection to the region to new_prot if set_max is non-zero. The et parameter should be 0, unless a PROT_READ | PROT_WRITE mapping is being changed to extend the stack limit, then it may be UVM_ET_STACK. This function returns a standard errno.

The () function allocates and returns a new address space, with ranges from min to max, setting the pageability of the address space to pageable. If remove_holes is non-zero, hardware ‘holes’ in the virtual address space will be removed from the newly allocated address space.

The () function either reuses the address space of process p if there are no other references to it, or creates a new one with uvmspace_alloc(). The range of valid addresses in the address space is reset to start through end.

The () function creates and returns a new address space based upon the address space of process pr and is typically used when allocating an address space for a child process.

The () function lowers the reference count on the address space vm, freeing the data structures if there are no other references.

The () function returns a reference to the address space of process pr, increasing its reference count.

The () function allocates a thread's ‘uarea’, the memory where its kernel stack and PCB are stored. The () function frees the uarea for thread p, which must no longer be running.


December 9, 2022 OpenBSD-current