Hi
I want to lock or prevent a portion of memory which I allocated. So I tried MLOCK, MPROTECT and some like this. But all these functions works only on page border. Can I know why that so.
Because that's how virtual memory works.
All those permissions take memory too, and have to be stored somewhere. Imagine how much memory would be required to remember access permissions for each individual byte of memory on your system! They had to simplify it somewhere, and pages is how they did that. Cut memory into larger, more manageable chunks.
If you need to individually protect parts, why not keep pointers to pages in your structure?
Quote:
Is that possible to protect a portion of memory which is in middle of the page.
No.
By the way: It's against the rules to spam multiple topics of the same question rephrased across different forums. If you're not answered immediately, wait -- we're not "on call".
P.S. It's possible to cause a bus error in the middle of a page by mapping in a file that's shorter than a page, but you only get errors trying to read/write past EOF, nowhere else.
Last edited by Corona688; 03-24-2011 at 11:26 AM..
Hello. I'm writing some random access i/o software on Solaris 8 using mmap64 to memory map large files (my test file is ~25 GB).
The abbreviated code fragment is:
fd = open(cbuf,O_RDONLY|O_LARGEFILE);
struct stat statbuf;
fstat(fd,&statbuf);
off_t len =... (0 Replies)
We recently have been seeing the following type of error on our development server. Being somewhat new to HP-UX I was hoping to get some insight. Here is what I have found.
I have been doing some research.
/usr/lib/dld.sl: Call to mmap() failed - TEXT /u07/mdev/lib/libCLEND.sl... (2 Replies)
I'm using select() to monitor multiple file descriptors (inet sockets) in application. But this application must also collaborate with other applications on the same host via shared memory (mmap'ed file) due to performance reasons. How can I become notification that mmaped memory is changed or... (1 Reply)
Dear Experts,
i have a problem related to mmap(), when i run my program on sun for 64 bit which is throwing SIGBUS when it encounters mmap() function, what is the reason how to resolve this one, because it is working for 32 bit.
with regards,
vidya. (2 Replies)
Descriptions:
Develop a program that uses mmap() to map a file to memory space. Prepare such a file by yourself and do the follows.
<LI class=MsoNormal>Display the content of the file after mapping; <LI class=MsoNormal>Output how many digits included in the file; <LI class=MsoNormal>Replace... (1 Reply)
I want to know whether this is possile or ever been tried out.
I want to obtain a chuck of memory using mmap()
I do it so :
n = mmap(0, 8000, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
And hold on to that memory, when a process requests for memory, some memory is... (2 Replies)
I'm new to kernels and C, and I am tinkering around trying to understand OpenBSD's secure memory management. I'm stumped on a couple points.
I've read up on malloc() which was apparently modified years ago to allocate memory using mmap. First question, that would be this here, right?
... (4 Replies)
Discussion started by: dcicc
4 Replies
LEARN ABOUT OPENDARWIN
getpagesize
getpagesize(3C) Standard C Library Functions getpagesize(3C)NAME
getpagesize - get system page size
SYNOPSIS
#include <unistd.h>
int getpagesize(void);
DESCRIPTION
The getpagesize() function returns the number of bytes in a page. Page granularity is the granularity of many of the memory management
calls.
The page size is a system page size and need not be the same as the underlying hardware page size.
The getpagesize() function is equivalent to sysconf(_SC_PAGE_SIZE) and sysconf(_SC_PAGESIZE). See sysconf(3C).
RETURN VALUES
The getpagesize() function returns the current page size.
ERRORS
No errors are defined.
USAGE
The value returned by getpagesize() need not be the minimum value that malloc(3C) can allocate. Moreover, the application cannot assume
that an object of this size can be allocated with malloc().
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO pagesize(1), brk(2), getrlimit(2), mmap(2), mprotect(2), munmap(2), malloc(3C), msync(3C), sysconf(3C), attributes(5)SunOS 5.10 27 Jun 2000 getpagesize(3C)