mmap anonymous

userland/linux/brk.c

@@ -0,0 +1,24 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#brk */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <unistd.h>
+
+int main(void) {
+    void *b = sbrk(0);
+    int *p = (int *)b;
+
+    /* Move it 2 ints forward */
+    brk(p + 2);
+
+    /* Use the ints. */
+    *p = 1;
+    *(p + 1) = 2;
+    assert(*p == 1);
+    assert(*(p + 1) == 2);
+
+    /* Deallocate back. */
+    brk(b);
+
+    return 0;
+}

userland/linux/mmap_anonymous.c

@@ -0,0 +1,40 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#mmap-map-anonymous */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+int main(void) {
+    int *is;
+    size_t nbytes = 2 * sizeof(*is);
+
+    /* Allocate 2 ints. */
+    is = mmap(
+        NULL,
+        nbytes,
+        PROT_READ | PROT_WRITE,
+        MAP_SHARED | MAP_ANONYMOUS,
+        -1,
+        0
+    );
+
+    /* This can happen for example if we ask for too much memory. */
+    if (is == NULL) {
+        perror("mmap");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Write to and read from the allocated memory. */
+    is[0] = 1;
+    is[1] = 2;
+    assert(is[0] == 1);
+    assert(is[1] == 2);
+
+    /* Free the allocated memory. */
+    munmap(is, nbytes);
+
+    return EXIT_SUCCESS;
+}