tree-wide: actually pretty-print error messages

We setup pretty-printing with all the thiserror-based Error structs, but
then only bubble the error up to the main, where it just gets printed
with the `Debug` trait.

This "catches" the error in the main and performs pretty printing using
the `Display` trait.

Before:

    Error: FailedCreatingListener(SocketError(Os { code: 98, kind:
        AddrInUse, message: "Address already in use" }))

After:

    [2023-07-06T17:20:47Z ERROR vhost_device_scsi] Failed creating
        listener: socket error: Address already in use (os error 98)

vhost-device-vsock is a bit special since it does not let error messages
bubble up to the main. It also does .unwrap() in most places, but it
_does_  pretty print errors during the main request handling part.

Had to slightly adjust the coverage since we have no tests for the main
functions.

Signed-off-by: Erik Schilling <erik.schilling@linaro.org>

coverage_config_x86_64.json

@@ -1,5 +1,5 @@
 {
-  "coverage_score": 69.6,
+  "coverage_score": 69.0,
   "exclude_path": "",
   "crate_features": ""
 }

crates/gpio/src/backend.rs

@@ -5,8 +5,9 @@
 //
 // SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
 
-use log::{info, warn};
+use log::{error, info, warn};
 use std::num::ParseIntError;
+use std::process::exit;
 use std::sync::{Arc, RwLock};
 use std::thread::spawn;
 
@@ -184,10 +185,13 @@ fn start_backend<D: 'static + GpioDevice + Send + Sync>(args: GpioArgs) -> Resul
     Ok(())
 }
 
-pub(crate) fn gpio_init() -> Result<()> {
+pub(crate) fn gpio_init() {
     env_logger::init();
 
-    start_backend::<PhysDevice>(GpioArgs::parse())
+    if let Err(e) = start_backend::<PhysDevice>(GpioArgs::parse()) {
+        error!("{e}");
+        exit(1);
+    }
 }
 
 #[cfg(test)]

crates/gpio/src/main.rs

@@ -13,7 +13,7 @@ mod gpio;
 mod vhu_gpio;
 
 #[cfg(target_env = "gnu")]
-fn main() -> backend::Result<()> {
+fn main() {
     backend::gpio_init()
 }
 

crates/i2c/src/main.rs

@@ -8,8 +8,9 @@
 mod i2c;
 mod vhu_i2c;
 
-use log::{info, warn};
+use log::{error, info, warn};
 use std::num::ParseIntError;
+use std::process::exit;
 use std::sync::{Arc, RwLock};
 use std::thread::spawn;
 
@@ -233,10 +234,13 @@ fn start_backend<D: 'static + I2cDevice + Send + Sync>(args: I2cArgs) -> Result<
     Ok(())
 }
 
-fn main() -> Result<()> {
+fn main() {
     env_logger::init();
 
-    start_backend::<PhysDevice>(I2cArgs::parse())
+    if let Err(e) = start_backend::<PhysDevice>(I2cArgs::parse()) {
+        error!("{e}");
+        exit(1);
+    }
 }
 
 #[cfg(test)]

crates/rng/src/main.rs

@@ -5,8 +5,9 @@
 // SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
 mod vhu_rng;
 
-use log::{info, warn};
+use log::{error, info, warn};
 use std::fs::File;
+use std::process::exit;
 use std::sync::{Arc, Mutex, RwLock};
 use std::thread;
 
@@ -161,10 +162,13 @@ pub(crate) fn start_backend(config: VuRngConfig) -> Result<()> {
     Ok(())
 }
 
-fn main() -> Result<()> {
+fn main() {
     env_logger::init();
 
-    start_backend(VuRngConfig::try_from(RngArgs::parse()).unwrap())
+    if let Err(e) = start_backend(VuRngConfig::try_from(RngArgs::parse()).unwrap()) {
+        error!("{e}");
+        exit(1);
+    }
 }
 
 #[cfg(test)]

crates/scsi/src/main.rs

@@ -7,6 +7,7 @@ mod virtio;
 use std::{
     fs::File,
     path::PathBuf,
+    process::exit,
     sync::{Arc, RwLock},
 };
 
@@ -126,11 +127,20 @@ fn start_backend(backend: VhostUserScsiBackend, args: ScsiArgs) -> Result<()> {
     Ok(())
 }
 
-fn main() -> Result<()> {
+fn run() -> Result<()> {
     env_logger::init();
     let args = ScsiArgs::parse();
     let backend = create_backend(&args)?;
-    start_backend(backend, args)
+    start_backend(backend, args)?;
+
+    Ok(())
+}
+
+fn main() {
+    if let Err(e) = run() {
+        error!("{e}");
+        exit(1);
+    }
 }
 
 #[cfg(test)]