93 lines
1.6 KiB
C
93 lines
1.6 KiB
C
#include <sys/types.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <syscall.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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DEFN_SYSCALL2(shm_obtain, 35, char *, size_t *)
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DEFN_SYSCALL1(shm_release, 36, char *)
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int main_server(volatile char *shm);
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int main_client(volatile char *shm);
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int main (int argc, char ** argv) {
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if (argc < 2) {
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fprintf(stderr, "%s: expected argument\n", argv[0]);
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return 1;
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}
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printf("(This should fork and the child process (but not the parent) should segfault)\n");
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size_t size = 27;
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volatile char * shm = (char *)syscall_shm_obtain(argv[1], &size);
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if (shm == NULL) {
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return 1;
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}
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int pid = getpid();
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uint32_t f = fork();
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if (getpid() != pid) {
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// Child: client
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return main_client(shm);
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} else {
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// Parent: server
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return main_server(shm);
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}
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return 0;
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}
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int main_server(volatile char *shm) {
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char c;
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volatile char *s;
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/*
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* Now put some things into the memory for the
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* other process to read.
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*/
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s = shm;
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for (c = 'a'; c <= 'z'; c++)
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*s++ = c;
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*s = '\0';
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/*
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* Finally, we wait until the other process
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* changes the first character of our memory
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* to '*', indicating that it has read what
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* we put there.
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*/
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while (*shm != '*') {}
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return 0;
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}
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int main_client(volatile char *shm) {
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int shmid;
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volatile char *s;
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/*
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* Now read what the server put in the memory.
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*/
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while (*shm != 'a');
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for (s = shm; *s != '\0'; s++)
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printf("%c", *s);
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printf("\n");
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/*
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* Finally, change the first character of the
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* segment to '*', indicating we have read
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* the segment.
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*/
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*shm = '*';
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return 0;
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}
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