1 /* The MINIX model of memory allocation reserves a fixed amount of memory for
2 * the combined text, data, and stack segments. The amount used for a child
3 * process created by FORK is the same as the parent had. If the child does
4 * an EXEC later, the new size is taken from the header of the file EXEC'ed.
5 *
6 * The layout in memory consists of the text segment, followed by the data
7 * segment, followed by a gap (unused memory), followed by the stack segment.
8 * The data segment grows upward and the stack grows downward, so each can
9 * take memory from the gap. If they meet, the process must be killed. The
10 * procedures in this file deal with the growth of the data and stack segments.
11 *
12 * The entry points into this file are:
13 * do_brk: BRK/SBRK system calls to grow or shrink the data segment
14 */
15
16 #define _SYSTEM 1
17
18 #include <minix/callnr.h>
19 #include <minix/com.h>
20 #include <minix/config.h>
21 #include <minix/const.h>
22 #include <minix/ds.h>
23 #include <minix/endpoint.h>
24 #include <minix/minlib.h>
25 #include <minix/type.h>
26 #include <minix/ipc.h>
27 #include <minix/sysutil.h>
28 #include <minix/syslib.h>
29 #include <minix/bitmap.h>
30
31 #include <errno.h>
32
33 #include "glo.h"
34 #include "vm.h"
35 #include "proto.h"
36 #include "util.h"
37
38 #define DATA_CHANGED 1 /* flag value when data segment size changed */
39 #define STACK_CHANGED 2 /* flag value when stack size changed */
40
41 /*===========================================================================*
42 * do_brk *
43 *===========================================================================*/
do_brk(message * msg)44 int do_brk(message *msg)
45 {
46 /* Perform the brk(addr) system call.
47 * The parameter, 'addr' is the new virtual address in D space.
48 */
49 int proc;
50
51 if (vm_isokendpt(msg->m_source, &proc) != OK) {
52 printf("VM: bogus endpoint VM_BRK %d\n", msg->m_source);
53 return EINVAL;
54 }
55
56 return real_brk(&vmproc[proc], (vir_bytes) msg->m_lc_vm_brk.addr);
57 }
58
59 /*===========================================================================*
60 * real_brk *
61 *===========================================================================*/
real_brk(struct vmproc * vmp,vir_bytes v)62 int real_brk(struct vmproc *vmp, vir_bytes v)
63 {
64 if(map_region_extend_upto_v(vmp, v) == OK) {
65 return OK;
66 }
67
68 return(ENOMEM);
69 }
70