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Diffstat (limited to 'man2/mprotect.2')
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diff --git a/man2/mprotect.2 b/man2/mprotect.2 deleted file mode 100644 index 91812f5..0000000 --- a/man2/mprotect.2 +++ /dev/null @@ -1,363 +0,0 @@ -.\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com> -.\" and Copyright (C) 1995 Michael Shields <shields@tembel.org>. -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com> -.\" Modified 1997-05-31 by Andries Brouwer <aeb@cwi.nl> -.\" Modified 2003-08-24 by Andries Brouwer <aeb@cwi.nl> -.\" Modified 2004-08-16 by Andi Kleen <ak@muc.de> -.\" 2007-06-02, mtk: Fairly substantial rewrites and additions, and -.\" a much improved example program. -.\" -.TH mprotect 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -mprotect, pkey_mprotect \- set protection on a region of memory -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <sys/mman.h> -.P -.BI "int mprotect(void " addr [. len "], size_t " len ", int " prot ); -.P -.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */" -.B #include <sys/mman.h> -.P -.BI "int pkey_mprotect(void " addr [. len "], size_t " len ", int " prot ", int " pkey ");" -.fi -.SH DESCRIPTION -.BR mprotect () -changes the access protections for the calling process's memory pages -containing any part of the address range in the -interval [\fIaddr\fP,\ \fIaddr\fP+\fIlen\fP\-1]. -.I addr -must be aligned to a page boundary. -.P -If the calling process tries to access memory in a manner -that violates the protections, then the kernel generates a -.B SIGSEGV -signal for the process. -.P -.I prot -is a combination of the following access flags: -.B PROT_NONE -or a bitwise OR of the other values in the following list: -.TP -.B PROT_NONE -The memory cannot be accessed at all. -.TP -.B PROT_READ -The memory can be read. -.TP -.B PROT_WRITE -The memory can be modified. -.TP -.B PROT_EXEC -The memory can be executed. -.TP -.BR PROT_SEM " (since Linux 2.5.7)" -The memory can be used for atomic operations. -This flag was introduced as part of the -.BR futex (2) -implementation (in order to guarantee the ability to perform atomic -operations required by commands such as -.BR FUTEX_WAIT ), -but is not currently used in on any architecture. -.TP -.BR PROT_SAO " (since Linux 2.6.26)" -.\" commit aba46c5027cb59d98052231b36efcbbde9c77a1d -.\" commit ef3d3246a0d06be622867d21af25f997aeeb105f -The memory should have strong access ordering. -This feature is specific to -the PowerPC architecture -(version 2.06 of the architecture specification adds the SAO CPU feature, -and it is available on POWER 7 or PowerPC A2, for example). -.P -Additionally (since Linux 2.6.0), -.I prot -can have one of the following flags set: -.TP -.\" mm/mmap.c: -.\" vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) | -.\" mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; -.\" And calc_vm_flag_bits converts only GROWSDOWN/DENYWRITE/LOCKED. -.B PROT_GROWSUP -Apply the protection mode up to the end of a mapping -that grows upwards. -(Such mappings are created for the stack area on -architectures\[em]for example, HP-PARISC\[em]that -have an upwardly growing stack.) -.\" The VMA is one that was marked with VM_GROWSUP by the kernel -.\" when the stack was created. Note that (unlike VM_GROWSDOWN), -.\" there is no mmap() flag (analogous to MAP_GROWSDOWN) for -.\" creating a VMA that is marked VM_GROWSUP. -.TP -.B PROT_GROWSDOWN -Apply the protection mode down to the beginning of a mapping -that grows downward -(which should be a stack segment or a segment mapped with the -.B MAP_GROWSDOWN -flag set). -.P -Like -.BR mprotect (), -.BR pkey_mprotect () -changes the protection on the pages specified by -.I addr -and -.IR len . -The -.I pkey -argument specifies the protection key (see -.BR pkeys (7)) -to assign to the memory. -The protection key must be allocated with -.BR pkey_alloc (2) -before it is passed to -.BR pkey_mprotect (). -For an example of the use of this system call, see -.BR pkeys (7). -.SH RETURN VALUE -On success, -.BR mprotect () -and -.BR pkey_mprotect () -return zero. -On error, these system calls return \-1, and -.I errno -is set to indicate the error. -.SH ERRORS -.TP -.B EACCES -The memory cannot be given the specified access. -This can happen, for example, if you -.BR mmap (2) -a file to which you have read-only access, then ask -.BR mprotect () -to mark it -.BR PROT_WRITE . -.TP -.B EINVAL -\fIaddr\fP is not a valid pointer, -or not a multiple of the system page size. -.TP -.B EINVAL -.RB ( pkey_mprotect ()) -\fIpkey\fP has not been allocated with -.BR pkey_alloc (2) -.TP -.B EINVAL -Both -.B PROT_GROWSUP -and -.B PROT_GROWSDOWN -were specified in -.IR prot . -.TP -.B EINVAL -Invalid flags specified in -.IR prot . -.TP -.B EINVAL -(PowerPC architecture) -.B PROT_SAO -was specified in -.IR prot , -but SAO hardware feature is not available. -.TP -.B ENOMEM -Internal kernel structures could not be allocated. -.TP -.B ENOMEM -Addresses in the range -.RI [ addr , -.IR addr + len \-1] -are invalid for the address space of the process, -or specify one or more pages that are not mapped. -(Before Linux 2.4.19, the error -.B EFAULT -was incorrectly produced for these cases.) -.TP -.B ENOMEM -Changing the protection of a memory region would result in the total number of -mappings with distinct attributes (e.g., read versus read/write protection) -exceeding the allowed maximum. -.\" I.e., the number of VMAs would exceed the 64 kB maximum -(For example, making the protection of a range -.B PROT_READ -in the middle of a region currently protected as -.B PROT_READ|PROT_WRITE -would result in three mappings: -two read/write mappings at each end and a read-only mapping in the middle.) -.SH VERSIONS -.\" SVr4 defines an additional error -.\" code EAGAIN. The SVr4 error conditions don't map neatly onto Linux's. -POSIX says that the behavior of -.BR mprotect () -is unspecified if it is applied to a region of memory that -was not obtained via -.BR mmap (2). -.P -On Linux, it is always permissible to call -.BR mprotect () -on any address in a process's address space (except for the -kernel vsyscall area). -In particular, it can be used -to change existing code mappings to be writable. -.P -Whether -.B PROT_EXEC -has any effect different from -.B PROT_READ -depends on processor architecture, kernel version, and process state. -If -.B READ_IMPLIES_EXEC -is set in the process's personality flags (see -.BR personality (2)), -specifying -.B PROT_READ -will implicitly add -.BR PROT_EXEC . -.P -On some hardware architectures (e.g., i386), -.B PROT_WRITE -implies -.BR PROT_READ . -.P -POSIX.1 says that an implementation may permit access -other than that specified in -.IR prot , -but at a minimum can allow write access only if -.B PROT_WRITE -has been set, and must not allow any access if -.B PROT_NONE -has been set. -.P -Applications should be careful when mixing use of -.BR mprotect () -and -.BR pkey_mprotect (). -On x86, when -.BR mprotect () -is used with -.I prot -set to -.B PROT_EXEC -a pkey may be allocated and set on the memory implicitly -by the kernel, but only when the pkey was 0 previously. -.P -On systems that do not support protection keys in hardware, -.BR pkey_mprotect () -may still be used, but -.I pkey -must be set to \-1. -When called this way, the operation of -.BR pkey_mprotect () -is equivalent to -.BR mprotect (). -.SH STANDARDS -.TP -.BR mprotect () -POSIX.1-2008. -.TP -.BR pkey_mprotect () -Linux. -.SH HISTORY -.TP -.BR mprotect () -POSIX.1-2001, SVr4. -.TP -.BR pkey_mprotect () -Linux 4.9, -glibc 2.27. -.SH NOTES -.SH EXAMPLES -.\" sigaction.2 refers to this example -The program below demonstrates the use of -.BR mprotect (). -The program allocates four pages of memory, makes the third -of these pages read-only, and then executes a loop that walks upward -through the allocated region modifying bytes. -.P -An example of what we might see when running the program is the -following: -.P -.in +4n -.EX -.RB "$" " ./a.out" -Start of region: 0x804c000 -Got SIGSEGV at address: 0x804e000 -.EE -.in -.SS Program source -\& -.\" SRC BEGIN (mprotect.c) -.EX -#include <malloc.h> -#include <signal.h> -#include <stdio.h> -#include <stdlib.h> -#include <sys/mman.h> -#include <unistd.h> -\& -#define handle_error(msg) \e - do { perror(msg); exit(EXIT_FAILURE); } while (0) -\& -static char *buffer; -\& -static void -handler(int sig, siginfo_t *si, void *unused) -{ - /* Note: calling printf() from a signal handler is not safe - (and should not be done in production programs), since - printf() is not async\-signal\-safe; see signal\-safety(7). - Nevertheless, we use printf() here as a simple way of - showing that the handler was called. */ -\& - printf("Got SIGSEGV at address: %p\en", si\->si_addr); - exit(EXIT_FAILURE); -} -\& -int -main(void) -{ - int pagesize; - struct sigaction sa; -\& - sa.sa_flags = SA_SIGINFO; - sigemptyset(&sa.sa_mask); - sa.sa_sigaction = handler; - if (sigaction(SIGSEGV, &sa, NULL) == \-1) - handle_error("sigaction"); -\& - pagesize = sysconf(_SC_PAGE_SIZE); - if (pagesize == \-1) - handle_error("sysconf"); -\& - /* Allocate a buffer aligned on a page boundary; - initial protection is PROT_READ | PROT_WRITE. */ -\& - buffer = memalign(pagesize, 4 * pagesize); - if (buffer == NULL) - handle_error("memalign"); -\& - printf("Start of region: %p\en", buffer); -\& - if (mprotect(buffer + pagesize * 2, pagesize, - PROT_READ) == \-1) - handle_error("mprotect"); -\& - for (char *p = buffer ; ; ) - *(p++) = \[aq]a\[aq]; -\& - printf("Loop completed\en"); /* Should never happen */ - exit(EXIT_SUCCESS); -} -.EE -.\" SRC END -.SH SEE ALSO -.BR mmap (2), -.BR sysconf (3), -.BR pkeys (7) |