collect configuration of mmio devices

Firecracker pass the configuration of all mmio device by a Linux kernel parameter
This parameter is defined as followd:

virtio_mmio.device=
   [VMMIO] Memory mapped virtio (platform) device.

      <size>@<baseaddr>:<irq>[:<id>]
   where:
      <size>     := size (can use standard suffixes like K, M and G)
      <baseaddr> := physical base address
      <irq>      := interrupt number (as passed to request_irq())
      <id>       := (optional) platform device id
   example:
                 virtio_mmio.device=1K@0x100b0000:48:7
   Can be used multiple times for multiple devices.

This patch parse the command line and store the string
<size>@<baseaddr>:<irq>[:<id>] in a vector, which is part of CLI.

This PR based on preliminary work of @duanyu-yu

src/env.rs

@@ -1,6 +1,6 @@
 //! Central parsing of the command-line parameters.
 
-use alloc::string::String;
+use alloc::string::{String, ToString};
 use alloc::vec::Vec;
 use core::str;
 
@@ -27,6 +27,8 @@ struct Cli {
 	freq: Option<u16>,
 	env_vars: HashMap<String, String, RandomState>,
 	args: Vec<String>,
+	#[allow(dead_code)]
+	mmio: Vec<String>,
 }
 
 /// Whether Hermit is running under the "uhyve" hypervisor.
@@ -43,6 +45,7 @@ impl Default for Cli {
 			RandomState::with_seeds(0, 0, 0, 0),
 		);
 		let mut args = Vec::new();
+		let mut mmio = Vec::new();
 
 		let words = shell_words::split(kernel::args().unwrap_or_default()).unwrap();
 		debug!("cli_words = {words:?}");
@@ -54,6 +57,12 @@ impl Default for Cli {
 			})
 		};
 		while let Some(word) = words.next() {
+			if word.as_str().starts_with("virtio_mmio.device=") {
+				let v: Vec<&str> = word.as_str().split('=').collect();
+				mmio.push(v[1].to_string());
+				continue;
+			}
+
 			match word.as_str() {
 				#[cfg(not(target_arch = "riscv64"))]
 				"-freq" => {
@@ -88,6 +97,8 @@ impl Default for Cli {
 			freq,
 			env_vars,
 			args,
+			#[allow(dead_code)]
+			mmio,
 		}
 	}
 }
@@ -111,3 +122,9 @@ pub fn vars() -> Iter<'static, String, String> {
 pub fn args() -> &'static [String] {
 	CLI.get().unwrap().args.as_slice()
 }
+
+/// Returns the configuration of all mmio devices
+#[allow(dead_code)]
+pub fn mmio() -> &'static [String] {
+	CLI.get().unwrap().mmio.as_slice()
+}