From 724d077860e103631605f09a7de35e3ad8796f56 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Sun, 5 Feb 2023 18:35:26 +0100
Subject: qemu: cheap insn trace example

---
 src/tools/qemu-src/Makefile |  9 +++++++++
 src/tools/qemu-src/test.s   | 16 ++++++++++++++++
 src/tools/qemu.md           |  8 ++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 src/tools/qemu-src/Makefile
 create mode 100644 src/tools/qemu-src/test.s

(limited to 'src/tools')

diff --git a/src/tools/qemu-src/Makefile b/src/tools/qemu-src/Makefile
new file mode 100644
index 0000000..1d21811
--- /dev/null
+++ b/src/tools/qemu-src/Makefile
@@ -0,0 +1,9 @@
+test: test.s
+	as -o test.o test.s
+	ld -o test test.o testc.o
+
+trace: test
+	qemu-x86_64 -singlestep -d nochain,cpu ./test 2>&1 | awk '/RIP/ { print $$1; }'
+
+clean:
+	$(RM) test test-bin test.o
diff --git a/src/tools/qemu-src/test.s b/src/tools/qemu-src/test.s
new file mode 100644
index 0000000..562b2ec
--- /dev/null
+++ b/src/tools/qemu-src/test.s
@@ -0,0 +1,16 @@
+.section .text, "ax"
+
+.global _start
+_start:
+    xor %rax, %rax
+    mov $0x8, %rax
+1:
+    cmp $0, %rax
+    je 2f
+    dec %rax
+    jmp 1b
+2:
+    # x86-64 exit(2) syscall
+    mov $0, %rdi
+    mov $60, %rax
+    syscall
diff --git a/src/tools/qemu.md b/src/tools/qemu.md
index 2a833e4..4351435 100644
--- a/src/tools/qemu.md
+++ b/src/tools/qemu.md
@@ -269,6 +269,14 @@ qemu-system-x86_64                                                     \
 ```
 Instructions to build a minimal [`Kernel` and `initrd`][blog-qemu-dbg].
 
+## Appendix: Cheap instruction tracer
+```make
+{{ #include qemu-src/Makefile }}
+```
+```x86asm
+{{ #include qemu-src/test.s }}
+```
+
 ## References
 
 - [QEMU USB][doc-qemu-usb]
-- 
cgit v1.2.3