Chapter 7.7, Problem 7.5PP

Explanation of Solution

Computing the value of the relocated reference to swap in the “callq” instruction:

From the given question, the function “swap” in object file “m.o” is

9: e8 00 00 00 00callqe<main+oxe>

Based on the relocates PC-relative references,

• $\text{ADDR(s)}=\text{ADDR(}\text{.text)}=\text{0x4004d0}$
  • Here “ADDR” means run-time addresses for each section.
• $\text{ADDR(r}\text{.symbol)}\text{=}\text{ADDR(swap)}\text{=}\text{0x4004e8}$

Compute the run time address of the references using the formula of “refaddr = ADDR(s) + r.offset”

$\begin{array}{c}\text{refaddr}\text{=}\text{ADDR(s)}\text{+}\text{r}\text{.offset}\\ \text{=}\text{0x4004d0}\text{+}\text{0xa}\\ \text{=}\text{0x4004da}\end{array}$

Then updates the reference by using the below formula

$\begin{array}{c}\text{*refptr}\text{=}\text{(usnsigned)}\text{(ADDR(}\end{array}$