github.com/mvdan/u-root-coreutils@v0.0.0-20230122170626-c2eef2898555/pkg/boot/bootcmd/bootcmd.go (about)

     1  // Copyright 2020 the u-root Authors. All rights reserved
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package bootcmd handles common cleanup functions and flags that all boot
     6  // commands should support.
     7  package bootcmd
     8  
     9  import (
    10  	"log"
    11  	"os"
    12  
    13  	"github.com/mvdan/u-root-coreutils/pkg/boot/menu"
    14  	"github.com/mvdan/u-root-coreutils/pkg/mount"
    15  )
    16  
    17  // ShowMenuAndBoot handles common cleanup functions and flags that all boot
    18  // commands should support.
    19  //
    20  // mountPool is unmounted before kexecing. noLoad prints the list of entries
    21  // and exits. If noLoad is false, a boot menu is shown to the user. The
    22  // user-chosen boot entry will be kexec'd unless noExec is true.
    23  func ShowMenuAndBoot(entries []menu.Entry, mountPool *mount.Pool, noLoad, noExec bool) {
    24  	if noLoad {
    25  		log.Print("Not loading menu or kernel. Options:")
    26  		for i, entry := range entries {
    27  			log.Printf("%d. %s", i+1, entry.Label())
    28  			log.Printf("=> %s", entry)
    29  		}
    30  		os.Exit(0)
    31  	}
    32  
    33  	loadedEntry := menu.ShowMenuAndLoad(true, entries...)
    34  
    35  	// Clean up.
    36  	if mountPool != nil {
    37  		if err := mountPool.UnmountAll(mount.MNT_DETACH); err != nil {
    38  			log.Printf("Failed in UnmountAll: %v", err)
    39  		}
    40  	}
    41  	if loadedEntry == nil {
    42  		log.Fatalf("Nothing to boot.")
    43  	}
    44  	if noExec {
    45  		log.Printf("Chosen menu entry: %s", loadedEntry)
    46  		os.Exit(0)
    47  	}
    48  	// Exec should either return an error or not return at all.
    49  	if err := loadedEntry.Exec(); err != nil {
    50  		log.Fatalf("Failed to exec %s: %v", loadedEntry, err)
    51  	}
    52  
    53  	// Kexec should either return an error or not return.
    54  	log.Fatalf("Kexec should have returned an error or not returned at all.")
    55  }