Add a (bad)free in userspace

core/syscall.c

@@ -22,8 +22,8 @@ int syscallExecute(int syscallId, const struct cpu_state *userCtx)
             assert(0);
             break;
         }
-        case SYSCALL_ID_YOLO:
-            ret = printf("YOLO FROM USERSPACE\n");
+        case SYSCALL_ID_HELO:
+            ret = printf("HELLO FROM USERSPACE\n");
             break;
         case SYSCALL_ID_PUTC: {
             unsigned int c;

core/syscall.h

@@ -4,7 +4,7 @@
 #endif
 
 #define SYSCALL_ID_EXIT 1
-#define SYSCALL_ID_YOLO 2
+#define SYSCALL_ID_HELO 2
 #define SYSCALL_ID_PUTC 3
 #define SYSCALL_ID_READ 4
 #define SYSCALL_ID_TEST 5

tests/test.c

@@ -399,7 +399,7 @@ static void userProgramm()
                  "int  %5\n"
                  "movl %%eax, %0"
                  : "=g"(ret)
-                 : "g"(SYSCALL_ID_YOLO), "g"(0), "g"(0), "g"(0), "i"(SYSCALL_INTR_NB)
+                 : "g"(SYSCALL_ID_HELO), "g"(0), "g"(0), "g"(0), "i"(SYSCALL_INTR_NB)
                  : "eax", "ebx", "ecx", "edx");
     asm volatile("movl %1,%%eax \n"
                  "movl %2,%%ebx \n"

userspace/kernel/syscall.h

@@ -4,7 +4,7 @@
 #endif
 
 #define SYSCALL_ID_EXIT 1
-#define SYSCALL_ID_YOLO 2
+#define SYSCALL_ID_HELO 2
 #define SYSCALL_ID_PUTC 3
 #define SYSCALL_ID_READ 4
 #define SYSCALL_ID_TEST 5

userspace/libc.c

@@ -443,25 +443,28 @@ int vasprintf(char **strp, const char *fmt, va_list ap)
 {
     int n       = 0;
     size_t size = 0;
-    char *p = malloc(256);
+    char *p     = malloc(256);
 
     /* Determine required size */
 
     n = vsnprintf(p, size, fmt, ap);
 
-    if (n < 0)
+    if (n < 0){
+        free(p);
         return -1;
+    }
 
     /* One extra byte for '\0' */
 
-    size = min(256U,(size_t)n + 1);
+    size = min(256U, (size_t)n + 1);
 
     n = vsnprintf(p, size, fmt, ap);
 
     if (n < 0) {
+        free(p);
         return -1;
     }
-	*strp = p;
+    *strp = p;
 
     return size;
 }
@@ -521,9 +524,9 @@ int putc(const int c){
     return syscall1(SYSCALL_ID_PUTC, c);
 }
 
-void yolo()
+void helo()
 {
-    syscall0(SYSCALL_ID_YOLO);
+    syscall0(SYSCALL_ID_HELO);
 }
 
 int testSycall5(uint arg1, uint arg2, uint arg3, uint arg4, uint arg5)
@@ -571,23 +574,38 @@ void *brk(void *addr)
     return (void *)syscall1(SYSCALL_ID_BRK, (unsigned int)addr);
 }
 
+static char *heapTop   = 0;
+static char *heapFree  = 0;
+static char *lastAlloc = 0;
+
 void *malloc(size_t size)
 {
-    void *heapTop     = 0;
-    static void *free = 0;
-
     if (heapTop == 0) {
-        heapTop = brk(0);
-        free    = heapTop;
+        heapTop = heapFree = brk(0);
     } else {
         heapTop = brk(0);
     }
 
-    if (free + size > heapTop) {
-        if (brk(heapTop + size))
+    if (heapFree + size + sizeof(size) > heapTop) {
+        if (brk(heapTop + size + sizeof(size)))
             return NULL;
     }
 
-    free += size;
-    return (free - size);
+    *((size_t *)heapFree) = size;
+    heapFree += sizeof(size);
+    lastAlloc = heapFree;
+    heapFree += size;
+    return lastAlloc;
+}
+
+void free(void *ptr)
+{
+    void *size_addr = ((char *)ptr - sizeof(size_t));
+    size_t size     = *(size_t *)size_addr;
+    if (heapFree - size == ptr) {
+        heapFree = size_addr;
+    }
+    //TODO ELSE
+
+    return;
 }

userspace/libc.h

@@ -28,7 +28,6 @@ int vsnprintf(char *str, size_t size, const char *format, va_list ap) __attribut
 int vprintf(const char *format, va_list ap) __attribute__ ((__format__ (printf, 1, 0)));
 int printf(const char *format, ...) __attribute__ ((__format__ (printf, 1, 2)));
 
-// Could be used after malloc is available
 int asprintf(char **strp, const char *fmt, ...) __attribute__ ((__format__ (printf, 2, 3)));
 int vasprintf(char **strp, const char *fmt, va_list ap) __attribute__ ((__format__ (printf, 2, 0)));
 
@@ -42,10 +41,11 @@ int syscall1(int id, unsigned int arg1);
 int syscall0(int id);
 
 void _exit(int status);
-void yolo();
+void helo();
 int testSycall5(uint arg1, uint arg2, uint arg3, uint arg4, uint arg5);
 char readc();
 char getchar();
 int readline(char *buf, int size);
 void *brk(void *addr);
 void *malloc(size_t size);
+void free(void *ptr);