82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* A small program to print out the memory locations of the following:
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* - BSS (via array[])
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* - stack (via first variable in first function)
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* - variable on stack
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* - heap (via malloc)
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* - shared memory (vi shmat)
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*/
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#include <sys/shm.h>
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#include <errno.h>
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#define ARRAY_SIZE 40000
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#define MALLOC_SIZE 100000
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#define SHM_SIZE 100000
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#define SHM_MODE 0600
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char array[ARRAY_SIZE];
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int
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main(int argc, char **argv) {
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int shmid;
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char *ptr, *shmptr;
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char func_array[ARRAY_SIZE];
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printf("array[] from %lx to %lx\n", (unsigned long)&array[0],
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(unsigned long)&array[ARRAY_SIZE]);
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printf("stack around %lx\n", (unsigned long)&shmid);
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printf("func_array[] (on stack) from %lx to %lx\n",
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(unsigned long)&func_array[0],
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(unsigned long)&func_array[ARRAY_SIZE]);
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if ((ptr = malloc(MALLOC_SIZE)) == NULL) {
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fprintf(stderr, "Unable to allocate memory: %s\n",
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strerror(errno));
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exit(1);
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}
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printf("malloced from %lx to %lx\n", (unsigned long)ptr,
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(unsigned long)ptr+MALLOC_SIZE);
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if ((shmid = shmget(IPC_PRIVATE, SHM_SIZE, SHM_MODE)) < 0) {
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fprintf(stderr, "Unable to get shared memory: %s\n",
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strerror(errno));
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exit(1);
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}
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if ((shmptr = shmat(shmid, 0, 0)) == (void *)-1) {
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fprintf(stderr, "Unable to map shared memory: %s\n",
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strerror(errno));
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exit(1);
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}
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printf("shared memory attached from %lx to %lx\n", (unsigned long)shmptr,
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(unsigned long)shmptr+SHM_SIZE);
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if (shmctl(shmid, IPC_RMID, 0) < 0) {
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fprintf(stderr, "shmctl error: %s\n", strerror(errno));
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exit(1);
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}
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return 0;
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}
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