docs/about/emulation/uftrace: add info about automatic tracing

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20260210201344.1403613-4-pierrick.bouvier@linaro.org
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

diff --git a/docs/about/emulation.rst b/docs/about/emulation.rst
index e8793b0f9cef91f11e12a8c23562b735ed22fcfc..f547e118eefe617d9b70e68342a13ac588889a54 100644 (file)
--- a/docs/about/emulation.rst
+++ b/docs/about/emulation.rst
@@ -849,7 +849,7 @@ Symbols must be present in ELF binaries.
 It tracks the call stack (based on frame pointer analysis). Thus, your program
 and its dependencies must be compiled using ``-fno-omit-frame-pointer
 -mno-omit-leaf-frame-pointer``. In 2024, `Ubuntu and Fedora enabled it by
-default again on x64
+default again on 64-bit platforms
 <https://www.brendangregg.com/blog/2024-03-17/the-return-of-the-frame-pointers.html>`_.
 On aarch64, this is less of a problem, as they are usually part of the ABI,
 except for leaf functions. That's true for user space applications, but not
@@ -976,7 +976,7 @@ You can follow the exact same instructions for a x64 system, combining edk2,
 Linux, and Ubuntu, simply by switching to
 `x86_64 <https://github.com/pbo-linaro/qemu-linux-stack/tree/x86_64>`_ branch.
 
-To build the system::
+To build and run the system::
 
     # Install dependencies
     $ sudo apt install -y podman qemu-user-static
@@ -988,7 +988,14 @@ To build the system::
     # system can be started using:
     $ ./run.sh /path/to/qemu-system-aarch64
 
-To generate a uftrace for a system boot from that::
+    # generate a uftrace for execution (collect symbols automatically)
+    $ ./trace.sh /path/to/qemu-system-aarch64
+    # show output log to read timestamps
+    $ cat uftrace.data/exec.log
+    # generate final trace (compressed) for perfetto
+    $ ./perfetto.sh <start_timestamp> <end_timestamp> ~/trace.gz
+
+To generate manually the same trace::
 
     # run true and poweroff the system
     $ env INIT=true ./run.sh path/to/qemu-system-aarch64 \