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/* The MINIX model of memory allocation reserves a fixed amount of memory for
* the combined text, data, and stack segments. The amount used for a child
* process created by FORK is the same as the parent had. If the child does
* an EXEC later, the new size is taken from the header of the file EXEC'ed.
*
* The layout in memory consists of the text segment, followed by the data
* segment, followed by a gap (unused memory), followed by the stack segment.
* The data segment grows upward and the stack grows downward, so each can
* take memory from the gap. If they meet, the process must be killed. The
* procedures in this file deal with the growth of the data and stack segments.
*
* The entry points into this file are:
* do_brk: BRK/SBRK system calls to grow or shrink the data segment
*/
#define _SYSTEM 1
#include <minix/callnr.h>
#include <minix/com.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/ds.h>
#include <minix/endpoint.h>
#include <minix/minlib.h>
#include <minix/type.h>
#include <minix/ipc.h>
#include <minix/sysutil.h>
#include <minix/syslib.h>
#include <minix/bitmap.h>
#include <errno.h>
#include "glo.h"
#include "vm.h"
#include "proto.h"
#include "util.h"
#define DATA_CHANGED 1 /* flag value when data segment size changed */
#define STACK_CHANGED 2 /* flag value when stack size changed */
/*===========================================================================*
* do_brk *
*===========================================================================*/
int do_brk(message *msg)
{
/* Perform the brk(addr) system call.
* The parameter, 'addr' is the new virtual address in D space.
*/
int proc;
if (vm_isokendpt(msg->m_source, &proc) != OK) {
printf("VM: bogus endpoint VM_BRK %d\n", msg->m_source);
return EINVAL;
}
return real_brk(&vmproc[proc], (vir_bytes) msg->m_lc_vm_brk.addr);
}
/*===========================================================================*
* real_brk *
*===========================================================================*/
int real_brk(struct vmproc *vmp, vir_bytes v)
{
if(map_region_extend_upto_v(vmp, v) == OK) {
return OK;
}
return(ENOMEM);
}
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