more comments

1 files changed, 22 insertions, 5 deletions

diff --git a/setjmp.S b/setjmp.S
index aee5590..64c587a 100644
--- a/setjmp.S
+++ b/setjmp.S
@@ -1,3 +1,20 @@
+#   int  setjmp(struct jmpbuf *jmp);
+#   void longjmp(struct jmpbuf *jmp);
+# 
+# Setjmp saves its stack environment in jmp
+# for later use by longjmp.  It returns 0.
+# 
+# Longjmp restores the environment saved by
+# the last call of setjmp. It then causes 
+# execution to continue as if the call of setjmp
+# had just returned 1.
+# 
+# The caller of setjmp must not itself have
+# returned in the interim.  All accessible data
+# have values as of the time longjmp was called.
+#
+#    [Description, but not code, borrowed from Plan 9.]
+
 .globl setjmp
 setjmp:
   movl 4(%esp), %eax
@@ -9,10 +26,10 @@ setjmp:
   movl %edi, 16(%eax)
   movl %esp, 20(%eax)
   movl %ebp, 24(%eax)
-  pushl 0(%esp)   /* %eip */
+  pushl 0(%esp)   # %eip
   popl 28(%eax)
 
-  movl $0, %eax   /* return value */
+  movl $0, %eax   # return value
   ret
 
 .globl longjmp
@@ -27,8 +44,8 @@ longjmp:
   movl 20(%eax), %esp
   movl 24(%eax), %ebp
 
-  addl $4, %esp   /* pop %eip into thin air */
-  pushl 28(%eax)  /* push new %eip */
+  addl $4, %esp   # pop and discard %eip
+  pushl 28(%eax)  # push new %eip
 
-  movl $1, %eax   /* return value (appears to come from setjmp!) */
+  movl $1, %eax   # return value (appears to come from setjmp!)
   ret