mprotect(2) [sunos man page]
mprotect(2) System Calls mprotect(2) NAME
mprotect - set protection of memory mapping SYNOPSIS
#include <sys/mman.h> int mprotect(void *addr, size_t len, int prot); DESCRIPTION
The mprotect() function changes the access protections on the mappings specified by the range [addr, addr + len), rounding len up to the next multiple of the page size as returned by sysconf(3C), to be that specified by prot. Legitimate values for prot are the same as those permitted for mmap(2) and are defined in <sys/mman.h> as: PROT_READ /* page can be read */ PROT_WRITE /* page can be written */ PROT_EXEC /* page can be executed */ PROT_NONE /* page can not be accessed */ When mprotect() fails for reasons other than EINVAL, the protections on some of the pages in the range [addr, addr + len) may have been changed. If the error occurs on some page at addr2, then the protections of all whole pages in the range [addr, addr2] will have been modi- fied. RETURN VALUES
Upon successful completion, mprotect() returns 0. Otherwise, it returns -1 and sets errno to indicate the error. ERRORS
The mprotect() function will fail if: EACCES The prot argument specifies a protection that violates the access permission the process has to the underlying memory object. EINVAL The len argument has a value equal to 0, or addr is not a multiple of the page size as returned by sysconf(3C). ENOMEM Addresses in the range [addr, addr + len) are invalid for the address space of a process, or specify one or more pages which are not mapped. The mprotect() function may fail if: EAGAIN The address range [addr, addr + len) includes one or more pages that have been locked in memory and that were mapped MAP_PRIVATE; prot includes PROT_WRITE; and the system has insufficient resources to reserve memory for the private pages that may be created. These private pages may be created by store operations in the now-writable address range. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
mmap(2), plock(3C), mlock(3C), mlockall(3C), sysconf(3C), attributes(5), standards(5) SunOS 5.10 12 Jan 1998 mprotect(2)
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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)