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