populate SMBIOS system version with Git metadata

Currently, the SMBIOS system (type 1) table has a hard-coded version
field. It would be nice if this was instead populated with details about
the Propolis version, as described in issue #701.

This branch adds a `build.rs`` script that uses [the `vergen` crate][1]
to emit information about the Git revision that Propolis was build from.
Now, we can generate a version string that describes the git branch,
commit hash, and commit depth, as described in [this comment][2]. This
is generated in a `propolis::version()` function, which also includes
the Bhyve API version (detected at runtime). This results in version
strings like:

```
Propolis v0.1.0-658 (0d8efa1) eliza/somebios-version, <unknown Bhyve API version>
```
(on a Linux machine; the Bhyve version would be present on illumos)

In addition to populating the SMBIOS system version, this commit also
sets the Clap version for CLI commands, so that the `--version` flag
will print out the same value that's set in SMBIOS.

[1]: https://docs.rs/vergen
[2]: #701 (comment)

Cargo.toml

@@ -160,3 +160,4 @@ tracing-bunyan-formatter = "0.3.3"
 tracing-subscriber = "0.3.14"
 usdt = { version = "0.5", default-features = false }
 uuid = "1.3.2"
+vergen = { version = "8.0.0", features = ["git", "gitcl"]}

bin/propolis-server/src/main.rs

@@ -19,7 +19,7 @@ use propolis_server::{
 };
 
 #[derive(Debug, Parser)]
-#[clap(about, version)]
+#[clap(about, version = propolis::version())]
 /// An HTTP server providing access to Propolis
 enum Args {
     /// Generates the OpenAPI specification.

bin/propolis-standalone/src/main.rs

@@ -1281,6 +1281,7 @@ fn api_version_checks(log: &slog::Logger) -> std::io::Result<()> {
 }
 
 #[derive(clap::Parser)]
+#[clap(version = propolis::version())]
 /// Propolis command-line frontend for running a VM.
 struct Args {
     /// Either the VM config file or a previously captured snapshot image.

lib/propolis/Cargo.toml

@@ -43,6 +43,10 @@ rand = { workspace = true, optional = true }
 softnpu-lib = { workspace = true, optional = true }
 dlpi = { workspace = true, optional = true }
 
+[build-dependencies]
+anyhow.workspace = true
+vergen.workspace = true
+
 [dev-dependencies]
 crossbeam-channel.workspace = true
 tempfile.workspace = true

lib/propolis/build.rs

@@ -0,0 +1,16 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+fn main() -> anyhow::Result<()> {
+    // Generate Git version information.
+    vergen::EmitBuilder::builder()
+        // Don't emit timestamps and build info.
+        .idempotent()
+        .git_branch()
+        .git_sha(true)
+        .git_commit_count()
+        .emit()?;
+
+    Ok(())
+}

lib/propolis/src/firmware/smbios/table.rs

@@ -351,7 +351,7 @@ pub mod type0 {
         BiosExtCharacteristics => u16,
     }
 }
-#[derive(Default)]
+
 pub struct Type1 {
     pub manufacturer: SmbString,
     pub product_name: SmbString,
@@ -381,6 +381,22 @@ impl Table for Type1 {
     }
 }
 
+impl Default for Type1 {
+    fn default() -> Self {
+        Type1 {
+            manufacturer: SmbString::default(),
+            product_name: SmbString::default(),
+            version: SmbString::try_from(crate::version())
+                .expect("version string should not contain NULs"),
+            serial_number: SmbString::default(),
+            uuid: [0; 16],
+            wake_up_type: type1::WakeUpType::default(),
+            sku_number: SmbString::default(),
+            family: SmbString::default(),
+        }
+    }
+}
+
 pub mod type1 {
     use super::*;
 

lib/propolis/src/lib.rs

@@ -35,3 +35,46 @@ pub mod vmm;
 
 pub use exits::{VmEntry, VmExit};
 pub use vmm::Machine;
+
+pub fn version() -> &'static str {
+    lazy_static::lazy_static! {
+        static ref VERSION: String = {
+            use std::fmt::Write;
+
+            let git = option_env!("VERGEN_GIT_BRANCH")
+                .and_then(|branch| Some((branch, option_env!("VERGEN_GIT_SHA")?)))
+                .and_then(|(branch, sha)| Some((branch, sha, option_env!("VERGEN_GIT_COMMIT_COUNT")?)));
+
+            let mut version = format!("Propolis v{}", env!("CARGO_PKG_VERSION"));
+            if let Some((branch, sha, commit)) = git {
+                write!(version, "-{commit} ({sha}) {branch}, ")
+                    .expect("writing to a string never fails");
+            } else {
+                version.push_str(" <unknown git commit>, ");
+            }
+            match bhyve_api::api_version() {
+                Ok(v) => {
+                    write!(version, "Bhyve API v{v}")
+                        .expect("writing to a string never fails");
+                }
+                Err(_) => {
+                    version.push_str("<unknown Bhyve API version>");
+                }
+            }
+            version
+        };
+    };
+    &VERSION
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn print_version() {
+        let v = version();
+        eprintln!("version: {v}");
+        assert!(v.starts_with("Propolis v"));
+    }
+}