swtch saves callee-saved registers

swtch idles on per-CPU stack, not on calling process's stack
fix pipe bugs
usertest.c tests pipes, fork, exit, close

1 files changed, 14 insertions, 0 deletions

diff --git a/ulib.c b/ulib.c
index 694501e..d99acdd 100644
--- a/ulib.c
+++ b/ulib.c
@@ -5,6 +5,13 @@ fork()
   asm("int $48");
 }
 
+int
+exit()
+{
+  asm("mov $2, %eax");
+  asm("int $48");
+}
+
 void
 cons_putc(int c)
 {
@@ -42,3 +49,10 @@ write(int fd, char *buf, int n)
   asm("mov $6, %eax");
   asm("int $48");
 }
+
+int
+close(int fd)
+{
+  asm("mov $8, %eax");
+  asm("int $48");
+}