add some practice problems from 4HEADmaster

1 files changed, 26 insertions, 0 deletions

diff --git a/4/practice_problem_4_7_and_8_ambiguities.c b/4/practice_problem_4_7_and_8_ambiguities.c
new file mode 100644
index 0000000..043a692
--- /dev/null
+++ b/4/practice_problem_4_7_and_8_ambiguities.c
@@ -0,0 +1,26 @@
+/*
+pushtest:
+	movq %rsp, %rax 	Copy stack pointer
+	pushq %rsp		Push stack pointer, original or after incrementing
+	popq %rdx		Pop the value back
+	subq %rdx, %rax		Always 0 on this machine
+
+It must first push the original rsp decremented address and then decrement rsp itself, otherwise a difference is expected after pushing and popping.
+*/
+
+/*
+poptest:
+	movq %rsp, %rdi		Save the original sp
+	pushq $0xabcd		Push test value
+	popq %rsp		Pop test value to rsp
+	movq %rsp, %rax 	Set popped value as return value
+	movq %rdi, %rsp
+	ret
+
+Rsp gets set the value in memory at rsp.
+
+From solutions:
+mrmovq (%rsp), %rsp
+
+I guess it just reads the stack value and overwrites it into rsp
+*/