started porting simple brainfuck interpreter

1 files changed, 85 insertions, 0 deletions

diff --git a/userspace/syscalls.c b/userspace/syscalls.c
new file mode 100644
index 0000000..6547879
--- /dev/null
+++ b/userspace/syscalls.c
@@ -0,0 +1,85 @@
+
+//printf needs following syscalls: sbrk write close fstat isatty lseek read
+//
+
+#include <sys/stat.h>
+
+int close(int file) 
+{
+   return -1;
+}
+
+int fstat(int file, struct stat *st)
+{
+    st->st_mode = S_IFCHR;
+    return 0;
+}
+
+int isatty(int file) {
+    return 1;
+}
+
+int lseek(int file, int ptr, int dir) {
+    return 0;
+}
+
+int read(int file, char *ptr, int len) {
+    return 0;
+}
+    int open(const char *name, int flags, int mode) {
+	            return -1;
+		              }
+
+
+int write(int file, char *ptr, int len) 
+{
+
+    int todo;
+    for (todo = 0; todo < len; todo++) 
+    {
+
+	char byte=(*ptr++);
+        int byt=byte;
+
+	int ebx; // will hold return value;
+	// system call 
+	asm("pusha");
+	asm("mov $61,%eax"); // select syscall)
+
+	asm("mov %0,%%edx"::"m"(byt));
+	//asm("mov $88,%edx");
+
+	asm("int $0x80"); // actual syscall ! interrupt
+        asm("mov %%ebx, %0": "=b" (ebx));
+	asm("popa");
+	//
+	
+    }
+    return len;
+}
+
+caddr_t sbrk(int incr) 
+{
+	    
+//            extern char _end;		/* Defined by the linker */
+	    char _end;
+            static char *heap_end;
+            char *prev_heap_end;
+          
+            if (heap_end == 0) {
+              heap_end = &_end;
+            }
+            prev_heap_end = heap_end;
+	    /*
+            if (heap_end + incr > stack_ptr) {
+              write (1, "Heap and stack collision\n", 25);
+              abort ();
+            }
+	    */
+          
+            heap_end += incr;
+            return (caddr_t) prev_heap_end;
+}
+
+//
+