mvalid(2) System Calls Manual mvalid(2)NAME
mvalid - Checks memory region for validity
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int mvalid ( caddr_t addr, size_t len, int prot );
PARAMETERS
Specifies the address of the region whose validity is to be checked. Specifies length in bytes of the region specified by the addr parame-
ter. Specifies the desired access protection for the region.
DESCRIPTION
The mvalid() function checks the validity of a memory region. A region is considered to be valid if accesses of the requested type are
allowed to all addresses in the region.
The sys/mman.h header file defines the following access options: The mapped region can be read. The mapped region can be written. The
mapped region can be executed.
The prot parameter can be any combination of PROT_READ, PROT_WRITE, and PROT_EXEC ORed together.
RETURN VALUES
The mvalid() function returns 0 (zero) if accesses requiring the specified protection are allowed to all addresses within the specified
range of addresses. Otherwise, the mvalid() function returns -1 and sets errno to indicate the error.
ERRORS
If the mvalid() function fails, errno may be set to one of the following values: The range specified by [addr, addr + len) is invalid for
the process' address space, or the range specifies one or more unmapped pages, or one or more pages of the range disallows accesses of the
specified protection. The prot parameter is invalid, or the addr parameter is not a multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE).
RELATED INFORMATION
Functions: mmap(2), mprotect(2), sysconf(3) delim off
mvalid(2)
Check Out this Related Man Page
mprotect(2) System Calls Manual mprotect(2)NAME
mprotect - Modifies access protections of memory mapping
SYNOPSIS
#include <sys/mman.h>
int mprotect ( void *addr, size_t len, int prot );
The following definitions of the addr parameter do not conform to current standards and are supported only for backward compatibility:
caddr_t addr const void addr
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
mprotect(): XSH4.2
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Points to the address of the region to be modified. Specifies the length in bytes of the region to be modified. Specifies access permis-
sions as PROT_NONE or any combination of PROT_READ, PROT_WRITE, and PROT_EXEC ORed together.
DESCRIPTION
The mprotect() function modifies the access protection of a mapped file or shared memory region. The addr and len parameters specify the
address and length in bytes of the region to be modified. The len parameter must be a multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE). If len is not a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE), the length of the region will be
rounded up to the next multiple of the page size.
The prot parameter specifies the new access protection for the region. The sys/mman.h header file defines the following access options:
The mapped region can be read. The mapped region can be written. The mapped region can be executed. The mapped region cannot be
accessed.
The prot parameter can be PROT_NONE or any combination of PROT_READ, PROT_WRITE, and PROT_EXEC ORed together. If PROT_NONE is not speci-
fied, access permissions may be granted to the region in addition to those explicitly requested, except that write access will not be
granted unless PROT_WRITE is specified.
If the region is a mapped file which was mapped with MAP_SHARED, the mprotect() function grants read or execute access permission only if
the file descriptor used to map the file is open for reading, and grants write access permission only if the file descriptor used to map
the file is open for writing. If the region is a mapped file which was mapped with MAP_PRIVATE, the mprotect() function grants read,
write, or execute access permission only if the file descriptor used to map the file is open for reading. If the region is a shared memory
region which was mapped with MAP_ANONYMOUS, the mprotect() function grants all requested access permissions.
The mprotect() function does not modify the access permission of any region which lies outside of the specified region, except that the
effect on addresses between the end of the region and the end of the page containing the end of the region is unspecified.
If the mprotect() function fails under a condition other than that specified by [EINVAL], the access protection of some of the pages in the
range [addr, addr + len) may have been changed. For example, if the error occurs on some page at an addr2, mprotect() may have modified
the protections of all whole pages in the range [addr, addr2).
RETURN VALUES
Upon successful completion, the mprotect() function returns 0 (zero). Otherwise, mprotect() returns -1 and sets errno to indicate the
error.
ERRORS
The mprotect() function sets errno to the specified values for the following conditions:
The prot parameter specifies a protection that conflicts with the access permission set for the underlying file. The prot parameter speci-
fies PROT_WRITE over a MAP_PRIVATE mapping and there are insufficient memory resources to reserve for locking the private page. [Tru64
UNIX] Some or all of the addresses in the range starting at addr and continuing for len bytes are locked. [Tru64 UNIX] The range [addr,
addr + len) includes an invalid address. The prot parameter is invalid, or the addr parameter is not a multiple of the page size as
returned by sysconf(_SC_PAGE_SIZE). [Tru64 UNIX] Addresses in the range [addr, addr + len) are invalid for the address space of a
process, or specify one or more unmapped pages.
[Tru64 UNIX] A system resource was exhausted or a system limit was exceeded. The most common case occurs when the calling process
exceeds the kernel configuration parameter VPAGEMAX. This limit specifies the maximum number of pages per process that can reside
in regions of contiguous virtual address space which have mixed page protections. The system administrator can override the default
VPAGEMAX value by setting the vpagemax nnn option in the system configuration file, then reconfiguring the kernel, and finally
rebooting the system.
RELATED INFORMATION
Functions: getpagesize(2), mmap(2), msync(2), sysconf(3)
Standards: standards(5) delim off
mprotect(2)