Add ftrace support to DebugService
This allows us to do ad-hoc kernel-level tracing on a running Metropolis node.
Useful for tracking down complex bugs.
Example: `bazel run //metropolis/cli/dbg -- trace -function_graph_filter blkdev_* function_graph`
Test Plan: Debug utility, manually tested
X-Origin-Diff: phab/D748
GitOrigin-RevId: 924eb795250412a73eb30c0eef4a8c1cc726e5fd
diff --git a/metropolis/node/core/mounts.go b/metropolis/node/core/mounts.go
index c6a626f..7a15c30 100644
--- a/metropolis/node/core/mounts.go
+++ b/metropolis/node/core/mounts.go
@@ -37,6 +37,7 @@
flags uintptr
}{
{"/sys", "sysfs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
+ {"/sys/kernel/tracing", "tracefs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
{"/proc", "proc", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
{"/dev", "devtmpfs", unix.MS_NOEXEC | unix.MS_NOSUID},
{"/dev/pts", "devpts", unix.MS_NOEXEC | unix.MS_NOSUID},