1 files changed, 145 insertions, 0 deletions
diff --git a/miniany/libc-freestanding.c b/miniany/libc-freestanding.c
new file mode 100644
index 0000000..b4e48f8
--- /dev/null
+++ b/miniany/libc-freestanding.c
@@ -0,0 +1,145 @@
+/*
+ * minimal freestanding C library
+ * 
+ * works for IA-32 and Linux, uses old INT 80h software interrupts
+ * for system calls.
+ * 
+ */
+
+int strlen( char *s )
+{
+	char *p;
+	
+	p = s;
+	while( *p != '\0' ) {
+		p++;
+	}
+	
+	return p - s;
+}
+
+enum {
+	EXIT_SUCCESS = 0,
+	EXIT_FAILURE = 1
+};
+
+enum {
+	SYSCALL_EXIT = 1,
+	SYSCALL_READ = 3,
+	SYSCALL_WRITE = 4
+};
+
+int errno;
+
+static __attribute__((noinline)) int syscall1( int id, int arg0 )
+{
+	int retval;
+   
+	__asm__ volatile( "\
+		push %%ebx\n\
+		mov %1, %%eax\n\
+		mov %2, %%ebx\n\
+		int $0x80\n\
+		mov %%eax, %0\n\
+		pop %%ebx\n" : "=m"( retval ) : "m"( id ), "m"( arg0 )
+		: "eax", "ebx" );
+
+	if( retval < 0 ) {
+		errno = -retval;
+		return -1;
+	}
+
+	return retval;
+}
+
+static __attribute__((noinline)) int syscall3( int id, int arg0, int arg1, int arg2 )
+{
+	int retval;
+   
+	__asm__ volatile( "\
+		push %%ebx\n\
+		push %%ecx\n\
+		push %%edx\n\
+		mov %1, %%eax\n\
+		mov %2, %%ebx\n\
+		mov %3, %%ecx\n\
+		mov %4, %%edx\n\
+		int $0x80\n\
+		mov %%eax, %0\n\
+		pop %%edx\n\
+		pop %%ecx\n\
+		pop %%ebx\n" : "=m"( retval ) : "m"( id ), "m"( arg0 ), "m"( arg1 ), "m"( arg2 )
+		: "eax", "ebx", "ecx", "edx" );		
+
+	if( retval < 0 ) {
+		errno = -retval;
+		return -1;
+	}
+	
+	return retval;
+}
+
+enum {
+	STDIN_FILENO = 0,
+	STDOUT_FILENO = 1,
+	STDERR_FILENO = 2
+};
+
+static void print_char( int fd, int c )
+{
+	char s[1];
+	s[0] = c;
+	syscall3( SYSCALL_WRITE, fd, (int)s, 1 );
+}
+
+static void print_string( char *s )
+{
+	syscall3( SYSCALL_WRITE, STDOUT_FILENO, (int)s, strlen( s ) );
+}
+
+static void print_newline( void )
+{
+	print_char( STDOUT_FILENO, '\n' );
+}
+
+static int read_string( int fd, char *buf, int size )
+{
+	return syscall3( SYSCALL_READ, fd, (int)buf, size );
+}
+
+enum {
+	EOF = -1
+};
+
+int puts( char *s )
+{
+	print_string( s );
+	print_newline( );
+	
+	return 1;
+}
+
+int getchar( )
+{
+	int res;
+	char buf[1];
+	
+	res = read_string( STDIN_FILENO, buf, 1 );
+	if( res == 0 ) {
+		return EOF;
+	}
+	
+	return buf[0];
+}
+
+int putchar( int c )
+{
+	print_char( STDOUT_FILENO, c );
+	
+	return c;
+}
+
+void exit( int status )
+{
+	syscall1( SYSCALL_EXIT, status );
+}