Add vmsa show command

Prints an existing VMSA binary file as json.

Using json for output lets us use existing json processing tools
for any diff or analysis or reformatting. The downside is the json
pretty printer is not too pretty with our big reserved* arrays.

The json field names match the internal Vmsa stuct field names, so
any change there will change the `show` output. I think this is fine,
since the kernel Vmsa structure can change on us anyways, so `vmsa show`
may not be stable across sevctl versions anyways.

Signed-off-by: Cole Robinson <crobinso@redhat.com>

README.md

@@ -119,4 +119,12 @@ Update an existing VMSA binary file in place, with the passed options.
 $ sevctl vmsa build EXISTING-VMSA0.bin --userspace qemu --family 25 --stepping 1 --model 1 --firmware /path/to/OVMF.amdsev.fd --cpu 0
 ```
 
+### vmsa show
+
+Print an existing VMSA binary file as JSON
+
+```console
+$ sevctl vmsa show EXISTING-VMSA0.bin
+```
+
 License: Apache-2.0

src/main.rs

@@ -113,6 +113,14 @@
 //! ```console
 //! $ sevctl vmsa build EXISTING-VMSA0.bin --userspace qemu --family 25 --stepping 1 --model 1 --firmware /path/to/OVMF.amdsev.fd --cpu 0
 //! ```
+//!
+//! ## vmsa show
+//!
+//! Print an existing VMSA binary file as JSON
+//!
+//! ```console
+//! $ sevctl vmsa show EXISTING-VMSA0.bin
+//! ```
 
 #![deny(clippy::all)]
 #![deny(missing_docs)]
@@ -345,6 +353,7 @@ fn main() {
         SevctlCmd::Verify { sev, oca, ca } => verify::cmd(sevctl.quiet, sev, oca, ca),
         SevctlCmd::Vmsa(option) => match option {
             VmsaCmd::Build(args) => vmsa::build::cmd(args),
+            VmsaCmd::Show(args) => vmsa::show::cmd(args),
             VmsaCmd::Update(args) => vmsa::update::cmd(args),
         },
     };

src/vmsa/mod.rs

@@ -5,6 +5,7 @@
 #![allow(dead_code)]
 
 pub mod build;
+pub mod show;
 pub mod update;
 
 use super::*;
@@ -25,9 +26,16 @@ use uuid::{uuid, Uuid};
 #[derive(StructOpt)]
 pub enum VmsaCmd {
     Build(BuildUpdateCmdArgs),
+    Show(VmsaShowCmdArgs),
     Update(BuildUpdateCmdArgs),
 }
 
+#[derive(StructOpt, Debug)]
+pub struct VmsaShowCmdArgs {
+    #[structopt(help = "VMSA binary file to print as JSON")]
+    pub filename: String,
+}
+
 // cmdline arguments for the "build" and "update" subcommands.
 #[derive(StructOpt, fmt::Debug)]
 pub struct BuildUpdateCmdArgs {

src/vmsa/show.rs

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::{Vmsa, VmsaShowCmdArgs};
+
+pub fn cmd(args: VmsaShowCmdArgs) -> super::Result<()> {
+    let vmsa = Vmsa::from_file(&args.filename)?;
+
+    println!("{}", serde_json::to_string_pretty(&vmsa).unwrap());
+
+    Ok(())
+}