zfsbootmenu/bin/reboot: add reboot-to-uefi functionality

fixes #423

docs/online/recovery-shell.rst

@@ -63,3 +63,7 @@ Common Commands
 **reboot**
 
   Reboot the system using a SysRq magic invocation.
+
+**firmware-setup**
+
+  Reboot the system into the UEFI Firmware Setup interface (if available).

zfsbootmenu/bin/firmware-setup

@@ -0,0 +1 @@
+reboot

zfsbootmenu/bin/reboot

@@ -4,6 +4,7 @@
 # shellcheck disable=SC1091
 sources=(
   /lib/kmsg-log-lib.sh
+  /lib/efi-firmware-lib.sh
   /lib/zfsbootmenu-core.sh
 )
 
@@ -24,6 +25,13 @@ case "${0##*/}" in
   shutdown|poweroff)
     trigger="o"
     ;;
+  firmware-setup)
+    if ! check_fw_setup || ! set_fw_setup; then
+      echo -e "\033[0;31mWARNING: Reboot to UEFI firmware UI unsupported; unable to proceed\033[0m"
+      exit 1
+    fi
+    trigger="b"
+    ;;
   *)
     exit
     ;;
@@ -34,7 +42,7 @@ while read -r _pool; do
 done <<<"$( zpool list -H -o name )"
 
 sysrq="/proc/sysrq-trigger"
-if [ -e  "${sysrq}" ] && [ -w "${sysrq}" ]; then
+if [ -e "${sysrq}" ] && [ -w "${sysrq}" ]; then
   echo "${trigger}" > /proc/sysrq-trigger
 else
   echo "${sysrq} does not exist, hard reset system"

zfsbootmenu/lib/efi-firmware-lib.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+# vim: softtabstop=2 shiftwidth=2 expandtab
+
+source /lib/kmsg-log-lib.sh >/dev/null 2>&1 || exit 1
+source /lib/zfsbootmenu-core.sh >/dev/null 2>&1 || exit 1
+
+check_fw_setup() {
+  local osind_path="/sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c"
+  local osind_supp_path="/sys/firmware/efi/efivars/OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c"
+  if ! is_efi_system; then
+    zdebug "efivarfs unsupported"
+    return 1
+  elif [ ! -r "${osind_supp_path}" ]; then
+    zdebug "OsIndicationsSupported unsupported"
+    return 1
+  elif [ ! -r "${osind_path}" ]; then
+    zdebug "OsIndications unsupported"
+    return 1
+  fi
+
+  # Check if the EFI_OS_INDICATIONS_BOOT_TO_FW_UI = 0x01 bit is set
+  if ! (( $(od -An -t u1 -j4 -N1 "${osind_supp_path}" | tr -dc '0-9') & 1 )); then
+    zdebug "EFI reboot to firmware setup unsupported"
+    return 1
+  fi
+}
+
+set_fw_setup() {
+  local bytes osind_path="/sys/firmware/efi/efivars/OsIndications-8be4df61-93ca-11d2-aa0d-00e098032b8c"
+  local -a osindications
+
+  mount_efivarfs rw
+  if [ ! -w "${osind_path}" ]; then
+    zdebug "OsIndications not writable"
+    return 1
+  fi
+
+  mapfile -t osindications < <(od -An -t x1 -v -w1 "${osind_path}" | tr -dc '[:alnum:]\n')
+
+  # Set the EFI_OS_INDICATIONS_BOOT_TO_FW_UI = 0x01 bit if not already set
+  if ! (( "${osindications[4]}" & 0x01 )); then
+    printf -v osindications[4] '%02x' $(( 0x"${osindications[4]}" | 0x01 ))
+
+    printf -v bytes '\\x%02x' "${osindications[@]}"
+    printf '%b' "$bytes" > "${osind_path}"
+  fi
+}