treewide: use read_to_string directly

Signed-off-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>

Author: KarlK90

src/cmdline.rs

@@ -1,8 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+use std::fs::read_to_string;
+
 use nix::mount::MsFlags;
 
-use crate::{read_file, Result};
+use crate::Result;
 
 pub struct CmdlineOptions {
     pub root: Option<String>,
@@ -67,7 +69,7 @@ fn parse_nfsroot(options: &mut CmdlineOptions) -> Result<()> {
     };
     rootflags.push_str(",addr=");
     if !nfsroot.contains(':') {
-        let pnp = read_file("/proc/net/pnp")?;
+        let pnp = read_to_string("/proc/net/pnp")?;
         for line in pnp.lines() {
             match line.split_once(' ') {
                 None => continue,

src/dmverity.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
 use std::fs::OpenOptions;
+use std::fs::{read_to_string, OpenOptions};
 use std::mem::size_of;
 use std::os::fd::IntoRawFd;
 use std::path::Path;
@@ -12,7 +13,7 @@ use nix::libc::dev_t;
 use nix::sys::stat::minor;
 
 use crate::cmdline::CmdlineOptions;
-use crate::{read_file, Result};
+use crate::Result;
 
 const DM_VERSION_MAJOR: u32 = 4;
 
@@ -132,7 +133,7 @@ pub fn prepare_dmverity(options: &mut CmdlineOptions) -> Result<bool> {
     let mut salt = "";
     let mut root_hash = "";
 
-    let params = read_file("/verity-params")?;
+    let params = read_to_string("/verity-params")?;
     for line in params.lines() {
         match line.split_once('=') {
             None => continue,

src/main.rs

@@ -46,10 +46,6 @@ pub fn mkdir(dir: &str) -> Result<()> {
     Ok(())
 }
 
-fn read_file(filename: &str) -> std::result::Result<String, String> {
-    read_to_string(filename).map_err(|e| format!("Failed to read {filename}: {e}"))
-}
-
 /*
  * Setup stdout/stderr. The kernel will create /dev/console in the
  * initramfs, so we can use that.
@@ -152,7 +148,7 @@ fn init() -> Result<()> {
 
     setup_log()?;
 
-    let cmdline = read_file("/proc/cmdline")?;
+    let cmdline = read_to_string("/proc/cmdline")?;
     let mut options = CmdlineOptions {
         ..Default::default()
     };