dracut, initcpio: make libgcc_s search universal

Closes: #427.

docs/man/dist/man7/zfsbootmenu.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "ZFSBOOTMENU" "7" "2023-05-21" "" "ZFSBootMenu"
+.TH "ZFSBOOTMENU" "7" "2023-07-17" "" "ZFSBootMenu"
 .SH NAME
 zfsbootmenu \- System Integration
 .SH SYNOPSIS
@@ -436,6 +436,13 @@ kexec \-\-unload
 should be sufficient to return to the main menu. Likewise, the hook may construct and execute its own \fIkexec\fP command to alter boot\-time parameters. This may be useful, for example, to allow ZFSBootMenu to select a boot environment and then restructure the boot process to launch a Xen kernel with the selected environment configured as dom0.
 .UNINDENT
 .UNINDENT
+.sp
+\fBzfsbootmenu_skip_gcc_s=yes\fP
+.INDENT 0.0
+.INDENT 3.5
+The ZFSBootMenu module attempts to detect and install a copy of the library \fBlibgcc_s.so\fP in its initramfs image on glibc systems. Because several executables may have latent dependencies on this library via a \fBdlopen\fP call in glibc itself, a failure to detect and install the library will cause initramfs generation to fail. If the host system has no dependencies on \fBlibgcc_s.so\fP, set \fBzfsbootmenu_skip_gcc_s=yes\fP to avoid this failure. Alternatively, if \fBlibgcc_s.so\fP is present in an undetected location, set this option and configure Dracut to explicitly install the library.
+.UNINDENT
+.UNINDENT
 .SH OPTIONS FOR MKINITCPIO
 .sp
 The \fBdracut\fP options specified above may also be specified in a mkinitcpio configuration file when \fBgenerate\-zbm\fP is configured to create images using \fBmkinitcpio\fP\&. However, whereas the \fB<executable\-list>\fP values in the dracut configuration should be specified as a single, space\-separated string; in the mkinitcpio configuration, each \fB<executable\-list>\fP value must be specified as a Bash array like the standard mkinitcpio arguments.

docs/man/zfsbootmenu.7.rst

@@ -261,6 +261,10 @@ In addition to standard dracut configuration options, the ZFSBootMenu dracut mod
 
   should be sufficient to return to the main menu. Likewise, the hook may construct and execute its own *kexec* command to alter boot-time parameters. This may be useful, for example, to allow ZFSBootMenu to select a boot environment and then restructure the boot process to launch a Xen kernel with the selected environment configured as dom0.
 
+**zfsbootmenu_skip_gcc_s=yes**
+
+  The ZFSBootMenu module attempts to detect and install a copy of the library **libgcc_s.so** in its initramfs image on glibc systems. Because several executables may have latent dependencies on this library via a **dlopen** call in glibc itself, a failure to detect and install the library will cause initramfs generation to fail. If the host system has no dependencies on **libgcc_s.so**, set **zfsbootmenu_skip_gcc_s=yes** to avoid this failure. Alternatively, if **libgcc_s.so** is present in an undetected location, set this option and configure Dracut to explicitly install the library.
+
 .. _zbm-mkinitcpio-options:
 
 Options for mkinitcpio

dracut/module-setup.sh

@@ -68,27 +68,22 @@ install() {
     fi
   done
 
-  # Workaround for zfsonlinux/zfs#4749 by ensuring libgcc_s.so(.1) is included
-  _ret=0
-  # If zpool requires libgcc_s.so*, dracut will track and include it
-  if ! ldd "$( command -v zpool )" | grep -qF 'libgcc_s.so'; then
-    # On systems with gcc-config (Gentoo, Funtoo, etc.), use it to find libgcc_s
-    if command -v gcc-config >/dev/null 2>&1; then
-      dracut_install "/usr/lib/gcc/$(s=$(gcc-config -c); echo "${s%-*}/${s##*-}")/libgcc_s.so.1"
-      _ret=$?
-    # Otherwise, use dracut's library installation function to find the right one
-    elif ! inst_libdir_file "libgcc_s.so*"; then
-      # If all else fails, just try looking for some gcc arch directory
-      dracut_install /usr/lib/gcc/*/*/libgcc_s.so*
-      _ret=$?
-    fi
-  fi
-
-  if [ ${_ret} -ne 0 ]; then
-    dfatal "Unable to install libgcc_s.so"
+  # Add libgcc_s as appropriate
+  local _libgcc_s
+  if ! _libgcc_s="$( find_libgcc_s )"; then
+    dfatal "Unable to locate libgcc_s.so"
     exit 1
   fi
 
+  local _lib
+  while read -r _lib ; do
+    [ -n "${_lib}" ] || continue
+    if ! dracut_install "${_lib}"; then
+      dfatal "Failed to install '${_lib}'"
+      exit 1
+    fi
+  done <<< "${_libgcc_s}"
+
   # shellcheck disable=SC2154
   while read -r doc ; do
     relative="${doc//${zfsbootmenu_module_root}\//}"

initcpio/install/zfsbootmenu

@@ -138,6 +138,22 @@ build() {
     # Binaries required for ZBM operation
     add_zbm_binaries
 
+    # Add libgcc_s as appropriate
+    local _libgcc_s
+    if ! _libgcc_s="$( find_libgcc_s )"; then
+        error "unable to locate libgcc_s.so"
+        exit 1
+    fi
+
+    local _lib
+    while read -r _lib ; do
+        [ -n "${_lib}" ] || continue
+        if ! add_binary "${_lib}"; then
+            error "Failed to install '${_lib}'"
+            exit 1
+        fi
+    done <<< "${_libgcc_s}"
+
     # On-line documentation
     while read -r doc; do
         relative="${doc#"${zfsbootmenu_module_root}/"}"

zfsbootmenu/install-helpers.sh

@@ -184,3 +184,73 @@ create_zbm_traceconf() {
 	export zfsbootmenu_trace_baud=${zfsbootmenu_trace_baud}
 	EOF
 }
+
+find_libgcc_s() {
+  local f libdirs libbase ldir zlibs matched
+
+  # Skip detection if desired
+  # shellcheck disable=SC2154
+  case "${zfsbootmenu_skip_gcc_s,,}" in
+    yes|on|1) return 0 ;;
+  esac
+
+  # This is only required on glibc systems due to a dlopen in pthread_cancel
+  # https://github.com/openzfs/zfs/commit/24554082bd93cb90400c4cb751275debda229009
+  ldconfig -p 2>/dev/null | grep -qF 'libc.so.6' || return 0
+
+  # Build a list of libraries linked by zpool
+  zlibs="$( ldd "$( command -v zpool 2>/dev/null )" )" || zlibs=
+
+  # If zpool links libgcc_s overtly, there is no need for further action
+  if grep -qF 'libgcc_s.so' <<< "${zlibs}"; then
+    return 0
+  fi
+
+  # Query gcc-config for a current runtime profile if possible
+  if command -v gcc-config >/dev/null 2>&1; then
+    local gver
+    if gver="$( gcc-config -c )"; then
+      for f in "/usr/lib/gcc/${gver%-*}/${gver##*-}"/libgcc_s.so*; do
+        [ -e "${f}" ] || continue
+        echo "${f}"
+        matched="yes"
+      done
+      [ -n "${matched}" ] && return 0
+    fi
+  fi
+
+  # Try walking library paths to find libgcc_s
+
+  # Search the system cache (adapted from dracut)
+  libdirs="$( ldconfig -pN 2>/dev/null \
+              | grep -E -v '/(lib|lib64|usr/lib|usr/lib64)/[^/]*$' \
+              | sed -n 's,.* => \(.*\)/.*,\1,p' | sort | uniq )" || libdirs=""
+
+  # Search zpool dependencies to figure out system libdirs
+  if [[ "${zlibs}" == */lib64/* ]]; then
+    libbase="lib64"
+  else
+    libbase="lib"
+  fi
+
+  # Look in all possible system library directories
+  libdirs="/${libbase} /usr/${libbase} ${libdirs}"
+  for ldir in ${libdirs}; do
+    for f in "${ldir}"/libgcc_s.so*; do
+      [ -e "${f}" ] || continue
+      echo "${f}"
+      matched="yes"
+    done
+  done
+  [ -n "${matched}" ] && return 0
+
+  # As a final fallback, just try to grab *any* libgcc_s from GCC
+  for f in /usr/lib/gcc/*/*/libgcc_s.so*; do
+    [ -f "${f}" ] || continue
+    echo "${f}"
+    matched="yes"
+  done
+
+  [ -n "${matched}" ] && return 0
+  return 1
+}