commit 63f9bea765da7b25ca12d14cb4e30b9f2fab06df
parent 5bb82b0d0d6e7769bfbddeac3b7ad89728d9f856
Author: dwrz <dwrz@dwrz.net>
Date: Fri, 13 Nov 2020 17:14:52 +0000
Document x86 assembly examples
Diffstat:
2 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/x86-assembly/src/exit/exit.s b/x86-assembly/src/exit/exit.s
@@ -3,10 +3,14 @@
_start:
# Store system call 1 in the EAX register.
+ # mov = instruction
+ # $1, %eax = operands
+ # %eax = register
mov $1, %eax
# Store the exit code 0 in the EBX register.
mov $0, %ebx
# Call interrupt handler 0x80 (128) -- on Linux, this is the kernel.
+ # Kernel will take over and see 1 in %eax, 0 in %ebx.
int $0x80
diff --git a/x86-assembly/src/func/func.s b/x86-assembly/src/func/func.s
@@ -29,3 +29,13 @@ square:
pop %rbp
# ret pops and return to address on stack.
ret
+
+# |----------------+-----------+----------------|
+# | Address | Data | Stack Pointers |
+# |----------------+-----------+----------------|
+# | 0x7fffffffe8f8 | | |
+# | 0x7fffffffe900 | 0x0 (rbp) | |
+# | 0x7fffffffe908 | 0x401002 | |
+# | 0x7fffffffe910 | 3 | ←rsp |
+# |----------------+-----------+----------------|
+# ←rbp
