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Full Discussion: Mmap source
Operating Systems BSD Mmap source Post 302858477 by dcicc on Monday 30th of September 2013 01:43:25 PM
Old 09-30-2013
Mmap source

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?

Code:
map_pages(size_t pages)
{
struct pdinfo *pi, *spi;
struct pginfo **pd;
u_long pidx,lidx;
void *result, *tail;
u_long index;

pages <<=malloc_pageshift;
result = MMAP(pages + malloc_guard);

For the life of me, I can't track down source code for mmap(). I know that this is a kernel system call, but where is that source? In particular, I'm interested to see how mmap() now returns a randomized location in memory.

Last edited by Scott; 09-30-2013 at 05:26 PM.. Reason: Code tags
 

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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 5.11 27 Jun 2000 getpagesize(3C)
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