mprotect.2 (2010 09)

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mprotect(2) mprotect(2)

NAME

mprotect() - set or check 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(), to be that

speciﬁed by prot. Legitimate values for prot are the same as those permitted for

mmap() and are deﬁned

<sys/mman.h>:

PROT_READ Page can be read.

PROT_WRITE Page can be written.

PROT_EXEC Page can be executed.

PROT_NONE Page cannot be accessed.

PROT_CHECK Check page effective permissions

PROT_CHECK ﬂag is speciﬁed, mprotect() checks the access protections on the mappings speciﬁed

with the rest of prot value to see if the requested permissions are set.

If the address range being modiﬁed corresponds to a mapped ﬁle that was mapped with

MAP_SHARED,

mprotect() grants write access permission only if the ﬁle descriptor used to map the ﬁle was opened

for writing. If the address range corresponds to a mapped ﬁle that was mapped with the

MAP_PRIVATE

or the MAP_ANONYMOUS ﬂag,

mprotect() grants all requested access permissions.

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.

For example, if an error occurs on some page at an addr2 , then

mprotect()

may have modiﬁed the

protections of all whole pages in the range [addr ,addr2 ].

RETURN VALUE

Upon successful completion,

mprotect() returns 0. Otherwise, it returns − 1 and sets errno to indi-

cate the error.

ERRORS

The

mprotect() function will fail if:

[EACCES] The prot argument speciﬁes a protection that violates, or is different than (in the

case where ﬂag

PROT_CHECK is present), the access permission the process has to

the underlying memory object.

[EINVAL] prot is invalid, or addr is not a multiple of the page size as returned by

sysconf(_SC_PAGE_SIZE).

[EFAULT] The range speciﬁed by [addr, addr+len] (from, and including, addr to, but not

including, addr+len ) is invalid for the address space of a process, or the range

speciﬁes one or more unmapped pages.

[ENOMEM] Addresses in the range [addr, addr +len] are invalid for the address space of a pro-

cess, or specify one or more pages which are not mapped.

[EAGAIN] The prot argument speciﬁes PROT_WRITE over a MAP_PRIVATE mapping and

there are insufﬁcient memory resources to reserve for locking the private page.

AUTHOR

mprotect() was developed by HP, AT&T, and OSF.

Summary of content (2 pages)

PAGE 1
mprotect(2) mprotect(2) NAME mprotect() - set or check protection of memory mapping SYNOPSIS #include 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(), to be that specified by prot . Legitimate values for prot are the same as those permitted for mmap() and are defined in
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mprotect(2) mprotect(2) STANDARDS CONFORMANCE mprotect(): AES, SVID3 A mA 2 Hewlett-Packard Company −2− HP-UX 11i Version 3: September 2010