From 193fd71a50b8d59b23cff19e2671f6de65715653 Mon Sep 17 00:00:00 2001
From: Daniel Samson <12231216+daniel-samson@users.noreply.github.com>
Date: Fri, 10 Jul 2026 14:12:05 +0100
Subject: [PATCH] Keep the QEMU serial log in qemu-test, not the FHS boot
 volume

The serial capture is a dev/host artifact, so it lands in the qemu-test scratch
area rather than inside zig-out (which we mount as the boot volume). /var/log/system
stays reserved for the kernel's own logging system later.
---
 build.zig | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/build.zig b/build.zig
index b9ee50b..f2bb3be 100644
--- a/build.zig
+++ b/build.zig
@@ -372,18 +372,19 @@ pub fn build(b: *std.Build) void {
         "-device",
         "VGA,edid=on,xres=1280,yres=720",
     });
-    // Capture the guest's serial0 (danos's machine-readable log) to the FHS log
-    // location, /var/log/system — a stand-in for the kernel's own logging system,
-    // which will one day write here itself. One timestamped file per run.
-    const log_dir = b.fmt("{s}/var/log/system", .{b.install_path});
+    // Capture the guest's serial0 (danos's machine-readable log) to the qemu-test
+    // scratch area — a dev/host artifact, kept out of the FHS boot volume we mount.
+    // (/var/log/system is reserved for the kernel's own logging system later.) One
+    // timestamped file per run.
+    const log_dir = b.fmt("{s}/qemu-test", .{b.install_path});
     const make_log_dir = b.addSystemCommand(&.{ "mkdir", "-p", log_dir });
-    const serial_log = b.fmt("{s}/serial0-{s}.log", .{ log_dir, timestamp(b) });
+    const serial_log = b.fmt("{s}/run-x86-64-serial0-{s}.log", .{ log_dir, timestamp(b) });
     run_efi.addArgs(&.{ "-serial", b.fmt("file:{s}", .{serial_log}) });
-    // The whole FHS zig-out must be installed (and the log dir created) before we mount it.
+    // The whole FHS zig-out must be installed (and the scratch dir created) before we mount it.
     run_efi.step.dependOn(b.getInstallStep());
     run_efi.step.dependOn(&make_log_dir.step);
 
-    const run_efi_step = b.step("run-x86-64", "Boot the x86-64 kernel in QEMU (UEFI/OVMF); serial0 is logged to zig-out/var/log/system/serial0-<timestamp>.log");
+    const run_efi_step = b.step("run-x86-64", "Boot the x86-64 kernel in QEMU (UEFI/OVMF); serial0 is logged to zig-out/qemu-test/run-x86-64-serial0-<timestamp>.log");
     run_efi_step.dependOn(&run_efi.step);
 
     // const run_cmd = b.addRunArtifact(exe);