From: Mart Lubbers <mart@martlubbers.net>
Date: Mon, 2 Mar 2015 11:19:11 +0000 (+0100)
Subject: ex4 done
X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=548799acae4e7ed35850357c4ba27c542b912256;p=sws1-1415.git

ex4 done
---

diff --git a/ass3/mart/sws1-assignment3-s4109503-s4202015/exercise1.c b/ass3/mart/sws1-assignment3-s4109503-s4202015/exercise1.c
index 28d6a2c..2baefbc 100644
--- a/ass3/mart/sws1-assignment3-s4109503-s4202015/exercise1.c
+++ b/ass3/mart/sws1-assignment3-s4109503-s4202015/exercise1.c
@@ -1,14 +1,11 @@
 #include <stdio.h>
 #include <stdint.h>
 #include "magicfunction.h"
-
 #define MAX 4194304/sizeof(uint64_t)
-
 uint64_t determine_start()
 {
 	return 0x567856785678;
 }
-
 int main(void)
 {
 	uint64_t filler = 0x123412341234;
@@ -18,19 +15,16 @@ int main(void)
 	/*Fill the stack with a filler value*/
 	for(p = &stack -1; p >= &stack - 1 - MAX; p--)
 		*p = filler;
-
 	/*Find the beginning of the function stack with the function*/
 	determine_start();
 	for(q = &stack -1; q>=&stack-1-MAX; q--)
 		if(*q == 0x567856785678)
 			break;
-	
 	/*Run the function and find the last occurance of non stack filler */
 	magic_function();
 	for(p = &stack - 1 - MAX; p <= q; p++)
 		if(*p != filler)
 			break;
-
 	printf("%td byte stack size used\n", (char*)p-(char*)q);
 	return 0;
 }
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise1.c b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise1.c
index b361d09..2615c75 100644
--- a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise1.c
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise1.c
@@ -8,4 +8,5 @@ int main(void)
 	for(size_t i = 1 << 31; i >= 1; i /= 2, free(b))
 		d = (b = malloc(block += d * i)) == NULL ? -1 : 1;
 	printf("One malloc can allocate at most %zu bytes\n", block);
+	return 0;
 }
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2.c b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2.c
new file mode 100644
index 0000000..4343e61
--- /dev/null
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2.c
@@ -0,0 +1,28 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+void heap_attack(void)
+{
+	char *b = malloc(1);
+	while(memcmp(--b, "s4109503", 8) != 0);
+	b += 8;
+	while(memcmp(b, "s4202015", 8) != 0)
+		*b++ = ' ';
+}
+
+int  main(void)
+{
+	char *s1 = malloc(8);
+	if(s1 == NULL)
+		return -1;
+	char *s2 = malloc(8);
+	if(s2 == NULL)
+		return -1;
+	strcpy(s1, "s4109503");
+	strcpy(s2, "s4202015");
+	heap_attack();
+	printf("student 1: \"%s\"\n", s1);
+	printf("student 2: \"%s\"\n", s2);
+	return 0;
+}
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2c b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2c
new file mode 100644
index 0000000..39e2602
--- /dev/null
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2c
@@ -0,0 +1 @@
+Strings are null terminated, therefore the 8th byte is \0
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2e b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2e
new file mode 100644
index 0000000..b0e6e7a
--- /dev/null
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise2e
@@ -0,0 +1,3 @@
+It will deallocate the space and the next allocation could be not in the
+neighbourhood of the first(that is free'd). It might get overwritten too, and
+therefore you might not be able to find it anymore.
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3.c b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3.c
new file mode 100644
index 0000000..f97359c
--- /dev/null
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3.c
@@ -0,0 +1,42 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void) /* https://www.kernel.org/doc/Documentation/CodingStyle */
+{
+	int i;
+	int j;
+	unsigned long long **m;
+	unsigned long long **mt;
+
+	while(1){
+		m = malloc(1000*sizeof(unsigned long long*));
+		if(m == NULL)
+			return -1;
+		for(i = 0; i<1000; i++){
+			m[i] = malloc(1000*sizeof(unsigned long long));
+			if(m[i] == NULL)
+				return -1;
+		}
+
+		mt = malloc(1000*sizeof(unsigned long long*));
+		if(mt == NULL)
+			return -1;
+		for(i = 0; i<1000; i++){
+			mt[i] = malloc(1000*sizeof(unsigned long long));
+			if(mt[i] == NULL)
+				return -1;
+		}
+
+		for(i = 0; i < 1000; i++)
+			for(j = 0; j < 1000; j++)
+				mt[i][j] = m[j][i];
+		
+		for(i = 0; i<1000; i++){
+			free(m[i]);
+			free(mt[i]);
+		}
+		free(m);
+		free(mt);
+	}
+	return 0;
+}
diff --git a/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3b b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3b
new file mode 100644
index 0000000..4f230d2
--- /dev/null
+++ b/ass4/mart/sws1-assignment4-s4109503-s4202015/exercise3b
@@ -0,0 +1,2 @@
+We run out of space. The matrices are deallocated but the content isn't. It
+leaks memory.