Suppose we are in following code, at line 4.

--What is the entry at the top of kernel stack A (old) ?

--What is the next entry?

--And the next ?

--And the next few entries (their order is not clearly known from the figures) but you can say what they are as a group.

1 # void swtch(struct context **old, struct context *new);

2 #

3 # Save current register context in old

4 # and then load register context from new.

5 .globl swtch

6 swtch:

7 # Save old registers

8 movl 4(%esp), %eax # put old ptr into eax

9 popl 0(%eax) # save the old IP

10 movl %esp, 4(%eax) # and stack

11 movl %ebx, 8(%eax) # and other registers

12 movl %ecx, 12(%eax)

13 movl %edx, 16(%eax)

14 movl %esi, 20(%eax)

15 movl %edi, 24(%eax)

16 movl %ebp, 28(%eax)

17

18 # Load new registers

19 movl 4(%esp), %eax # put new ptr into eax

20 movl 28(%eax), %ebp # restore other registers

21 movl 24(%eax), %edi

22 movl 20(%eax), %esi

23 movl 16(%eax), %edx

24 movl 12(%eax), %ecx

25 movl 8(%eax), %ebx

26 movl 4(%eax), %esp # stack is switched here

27 pushl 0(%eax) # return addr put in place

28 ret # finally return into new ctxt