I also intend to add another wrapper script generation function for
running executables while changing the root directory.
Signed-off-by: James Le Cuirot <ch...@gentoo.org>
---
eclass/sysroot.eclass | 85 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
create mode 100644 eclass/sysroot.eclass
diff --git a/eclass/sysroot.eclass b/eclass/sysroot.eclass
new file mode 100644
index 0000000000000..14f1d251b773d
--- /dev/null
+++ b/eclass/sysroot.eclass
@@ -0,0 +1,85 @@
+# Copyright 2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: sysroot.eclass
+# @MAINTAINER:
+# cr...@gentoo.org
+# @AUTHOR:
+# James Le Cuirot <ch...@gentoo.org>
+# @SUPPORTED_EAPIS: 7 8
+# @BLURB: Common functions for using a different sysroot (e.g. cross-compiling)
+
+case ${EAPI} in
+ 7|8) ;;
+ *) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+# @FUNCTION: qemu_arch
+# @DESCRIPTION:
+# Return the QEMU architecture name for the given target or CHOST. This name is
+# used in qemu-user binary filenames, e.g. qemu-ppc64le.
+qemu_arch() {
+ local target=${1:-${CHOST}}
+ case ${target} in
+ armeb*) echo armeb ;;
+ arm*) echo arm ;;
+ hppa*) echo hppa ;;
+ i?86*) echo i386 ;;
+ m68*) echo m68k ;;
+ mips64el*-gnuabi64) echo mips64el ;;
+ mips64el*-gnuabin32) echo mipsn32el ;;
+ mips64*-gnuabi64) echo mips64 ;;
+ mips64*-gnuabin32) echo mipsn32 ;;
+ powerpc64le*) echo ppc64le ;;
+ powerpc64*) echo ppc64 ;;
+ powerpc*) echo ppc ;;
+ *) echo "${target%%-*}" ;;
+ esac
+}
+
+# @FUNCTION: sysroot_make_run_prefixed
+# @DESCRIPTION:
+# Create a wrapper script for directly running executables within a sysroot
+# without changing the root directory. The path to that script is returned. If
+# no sysroot has been set, then this function returns unsuccessfully.
+#
+# The script explicitly uses QEMU if this is necessary and it is available in
+# this environment. It may otherwise implicitly use a QEMU outside this
+# environment if binfmt_misc has been used with the F flag. It is not feasible
+# to add a conditional dependency on QEMU.
+sysroot_make_run_prefixed() {
+ [[ -z ${SYSROOT} ]] && return 1
+
+ local SCRIPT="${T}"/sysroot-run-prefixed
+ local QEMU_ARCH=$(qemu_arch)
+
+ # Both methods below might need help to find GCC's libraries. GCC might
not
+ # even be installed in the SYSROOT. Note that Clang supports this flag
too.
+ local LIBGCC=$($(tc-getCC) ${CPPFLAGS} ${CFLAGS} ${LDFLAGS}
-print-libgcc-file-name)
+
+ if [[ ${QEMU_ARCH} == $(qemu_arch "${CBUILD}") ]]; then
+ # glibc: ld.so is a symlink, ldd is a binary.
+ # musl: ld.so doesn't exist, ldd is a symlink.
+ local DYNLINKER=$(find "${ESYSROOT}"/usr/bin/{ld.so,ldd} -type
l -print -quit 2>/dev/null || die "failed to find dynamic linker")
+
+ # musl symlinks ldd to ld-musl.so to libc.so. We want the
ld-musl.so
+ # path, not the libc.so path, so don't resolve the symlinks
entirely.
+ DYNLINKER=$(readlink -ev "${DYNLINKER}" || die "failed to find
dynamic linker")
+
+ # Using LD_LIBRARY_PATH to set the prefix is not perfect, as it
doesn't
+ # adjust RUNPATHs, but it is probably good enough.
+ install -m0755 /dev/stdin "${SCRIPT}" <<-EOF || die
+ #!/bin/sh
+
LD_LIBRARY_PATH="\${LD_LIBRARY_PATH}\${LD_LIBRARY_PATH+:}${LIBGCC%/*}:${ESYSROOT}/$(get_libdir):${ESYSROOT}/usr/$(get_libdir)"
exec "${DYNLINKER}" "\${@}"
+ EOF
+ else
+ # Use QEMU's environment variables rather than its command line
+ # arguments to cover both explicit and implicit QEMU usage.
+ install -m0755 /dev/stdin "${SCRIPT}" <<-EOF || die
+ #!/bin/sh
+
QEMU_SET_ENV="\${QEMU_SET_ENV}\${QEMU_SET_ENV+,}LD_LIBRARY_PATH=\${LD_LIBRARY_PATH}\${LD_LIBRARY_PATH+:}${LIBGCC%/*}"
QEMU_LD_PREFIX="${SYSROOT}" exec $(type -P "qemu-${QEMU_ARCH}") "\${@}"
+ EOF
+ fi
+
+ echo "${SCRIPT}"
+}
--
2.49.0
