(address . guix-patches@gnu.org)(name . Ludovic Courtès)(address . ludovic.courtes@inria.fr)
20190314161026.15696-1-ludo@gnu.org
From: Ludovic Courtès <ludovic.courtes@inria.fr>
* gnu/packages/aux-files/run-in-namespace.c (exec_with_proot): New
function.
(main): When 'clone' fails, call 'rm_rf'.
[PROOT_PROGRAM]: When 'clone' fails, call 'exec_with_proot'.
* guix/scripts/pack.scm (wrapped-package): Add #:proot?.
[proot]: New procedure.
[build]: Compile with -DPROOT_PROGRAM when PROOT? is true.
* guix/scripts/pack.scm (%options): Set the 'relocatable?' value to
'proot when "-R" is passed several times.
(guix-pack): Pass #:proot? to 'wrapped-package'.
* tests/guix-pack-relocatable.sh: Use "-RR" on Intel systems that lack
user namespace support.
* doc/guix.texi (Invoking guix pack): Document -RR.
---
doc/guix.texi | 39 ++++++++++++++-----
gnu/packages/aux-files/run-in-namespace.c | 47 ++++++++++++++++++++++-
guix/scripts/pack.scm | 33 +++++++++++++---
tests/guix-pack-relocatable.sh | 21 +++++++---
4 files changed, 119 insertions(+), 21 deletions(-)
Toggle diff (258 lines)
diff --git a/doc/guix.texi b/doc/guix.texi
index 043aad1b65..3a6a35b9c6 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4760,14 +4760,24 @@ symlinks, as well as empty mount points for virtual file systems like
procfs.
@end table
+@cindex relocatable binaries
@item --relocatable
@itemx -R
Produce @dfn{relocatable binaries}---i.e., binaries that can be placed
-anywhere in the file system hierarchy and run from there. For example,
-if you create a pack containing Bash with:
+anywhere in the file system hierarchy and run from there.
+
+When this option is passed once, the resulting binaries require support for
+@dfn{user namespaces} in the kernel Linux; when passed
+@emph{twice}@footnote{Here's a trick to memorize it: @code{-RR}, which adds
+PRoot support, can be thought of as the abbreviation of ``Really
+Relocatable''. Neat, isn't it?}, relocatable binaries fall to back to PRoot
+if user namespaces are unavailable, and essentially work anywhere---see below
+for the implications.
+
+For example, if you create a pack containing Bash with:
@example
-guix pack -R -S /mybin=bin bash
+guix pack -RR -S /mybin=bin bash
@end example
@noindent
@@ -4786,12 +4796,23 @@ In that shell, if you type @code{ls /gnu/store}, you'll notice that
altogether! That is probably the simplest way to deploy Guix-built
software on a non-Guix machine.
-There's a gotcha though: this technique relies on the @dfn{user
-namespace} feature of the kernel Linux, which allows unprivileged users
-to mount or change root. Old versions of Linux did not support it, and
-some GNU/Linux distributions turn it off; on these systems, programs
-from the pack @emph{will fail to run}, unless they are unpacked in the
-root file system.
+@quotation Note
+By default, relocatable binaries rely on the @dfn{user namespace} feature of
+the kernel Linux, which allows unprivileged users to mount or change root.
+Old versions of Linux did not support it, and some GNU/Linux distributions
+turn it off.
+
+To produce relocatable binaries that work even in the absence of user
+namespaces, pass @option{--relocatable} or @option{-R} @emph{twice}. In that
+case, binaries will try user namespace support and fall back to PRoot if user
+namespaces are not supported.
+
+The @uref{https://proot-me.github.io/, PRoot} program provides the necessary
+support for file system virtualization. It achieves that by using the
+@code{ptrace} system call on the running program. This approach has the
+advantage to work without requiring special kernel support, but it incurs
+run-time overhead every time a system call is made.
+@end quotation
@item --expression=@var{expr}
@itemx -e @var{expr}
diff --git a/gnu/packages/aux-files/run-in-namespace.c b/gnu/packages/aux-files/run-in-namespace.c
index f0cff88552..551f4db88a 100644
--- a/gnu/packages/aux-files/run-in-namespace.c
+++ b/gnu/packages/aux-files/run-in-namespace.c
@@ -1,5 +1,5 @@
/* GNU Guix --- Functional package management for GNU
- Copyright (C) 2018 Ludovic Courtès <ludo@gnu.org>
+ Copyright (C) 2018, 2019 Ludovic Courtès <ludo@gnu.org>
This file is part of GNU Guix.
@@ -212,6 +212,46 @@ disallow_setgroups (pid_t pid)
}
+#ifdef PROOT_PROGRAM
+
+/* Execute the wrapped program with PRoot, passing it ARGC and ARGV, and
+ "bind-mounting" STORE in the right place. */
+static void
+exec_with_proot (const char *store, int argc, char *argv[])
+{
+ int proot_specific_argc = 4;
+ int proot_argc = argc + proot_specific_argc;
+ char *proot_argv[proot_argc], *proot;
+ char bind_spec[strlen (store) + 1 + sizeof "@STORE_DIRECTORY@"];
+
+ strcpy (bind_spec, store);
+ strcat (bind_spec, ":");
+ strcat (bind_spec, "@STORE_DIRECTORY@");
+
+ proot = concat (store, PROOT_PROGRAM);
+
+ proot_argv[0] = proot;
+ proot_argv[1] = "-b";
+ proot_argv[2] = bind_spec;
+ proot_argv[3] = "@WRAPPED_PROGRAM@";
+
+ for (int i = 0; i < argc; i++)
+ proot_argv[i + proot_specific_argc] = argv[i + 1];
+
+ proot_argv[proot_argc] = NULL;
+
+ /* Seccomp support seems to invariably lead to segfaults; disable it by
+ default. */
+ setenv ("PROOT_NO_SECCOMP", "1", 0);
+
+ int err = execv (proot, proot_argv);
+ if (err < 0)
+ assert_perror (errno);
+}
+
+#endif
+
+
int
main (int argc, char *argv[])
{
@@ -274,6 +314,10 @@ main (int argc, char *argv[])
break;
case -1:
+ rm_rf (new_root);
+#ifdef PROOT_PROGRAM
+ exec_with_proot (store, argc, argv);
+#else
fprintf (stderr, "%s: error: 'clone' failed: %m\n", argv[0]);
fprintf (stderr, "\
This may be because \"user namespaces\" are not supported on this system.\n\
@@ -281,6 +325,7 @@ Consequently, we cannot run '@WRAPPED_PROGRAM@',\n\
unless you move it to the '@STORE_DIRECTORY@' directory.\n\
\n\
Please refer to the 'guix pack' documentation for more information.\n");
+#endif
return EXIT_FAILURE;
default:
diff --git a/guix/scripts/pack.scm b/guix/scripts/pack.scm
index e2ecddfbfc..bfb8b85356 100644
--- a/guix/scripts/pack.scm
+++ b/guix/scripts/pack.scm
@@ -517,10 +517,14 @@ please email '~a'~%")
;;;
(define* (wrapped-package package
- #:optional (compiler (c-compiler)))
+ #:optional (compiler (c-compiler))
+ #:key proot?)
(define runner
(local-file (search-auxiliary-file "run-in-namespace.c")))
+ (define (proot)
+ (specification->package "proot-static"))
+
(define build
(with-imported-modules (source-module-closure
'((guix build utils)
@@ -550,10 +554,19 @@ please email '~a'~%")
(("@STORE_DIRECTORY@") (%store-directory)))
(let* ((base (strip-store-prefix program))
- (result (string-append #$output "/" base)))
+ (result (string-append #$output "/" base))
+ (proot #$(and proot?
+ #~(string-drop
+ #$(file-append (proot) "/bin/proot")
+ (+ (string-length (%store-directory))
+ 1)))))
(mkdir-p (dirname result))
- (invoke #$compiler "-std=gnu99" "-static" "-Os" "-g0" "-Wall"
- "run.c" "-o" result)
+ (apply invoke #$compiler "-std=gnu99" "-static" "-Os" "-g0" "-Wall"
+ "run.c" "-o" result
+ (if proot
+ (list (string-append "-DPROOT_PROGRAM=\""
+ proot "\""))
+ '()))
(delete-file "run.c")))
(setvbuf (current-output-port) 'line)
@@ -646,7 +659,12 @@ please email '~a'~%")
(exit 0)))
(option '(#\R "relocatable") #f #f
(lambda (opt name arg result)
- (alist-cons 'relocatable? #t result)))
+ (match (assq-ref result 'relocatable?)
+ (#f
+ (alist-cons 'relocatable? #t result))
+ (_
+ (alist-cons 'relocatable? 'proot
+ (alist-delete 'relocatable? result))))))
(option '(#\e "expression") #t #f
(lambda (opt name arg result)
(alist-cons 'expression arg result)))
@@ -821,11 +839,14 @@ Create a bundle of PACKAGE.\n"))
#:graft? (assoc-ref opts 'graft?))))
(let* ((dry-run? (assoc-ref opts 'dry-run?))
(relocatable? (assoc-ref opts 'relocatable?))
+ (proot? (eq? relocatable? 'proot))
(manifest (let ((manifest (manifest-from-args store opts)))
;; Note: We cannot honor '--bootstrap' here because
;; 'glibc-bootstrap' lacks 'libc.a'.
(if relocatable?
- (map-manifest-entries wrapped-package manifest)
+ (map-manifest-entries
+ (cut wrapped-package <> #:proot? proot?)
+ manifest)
manifest)))
(pack-format (assoc-ref opts 'format))
(name (string-append (symbol->string pack-format)
diff --git a/tests/guix-pack-relocatable.sh b/tests/guix-pack-relocatable.sh
index 554416627b..38dcf1e485 100644
--- a/tests/guix-pack-relocatable.sh
+++ b/tests/guix-pack-relocatable.sh
@@ -1,5 +1,5 @@
# GNU Guix --- Functional package management for GNU
-# Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
+# Copyright © 2018, 2019 Ludovic Courtès <ludo@gnu.org>
#
# This file is part of GNU Guix.
#
@@ -41,17 +41,28 @@ STORE_PARENT="`dirname $NIX_STORE_DIR`"
export STORE_PARENT
if test "$STORE_PARENT" = "/"; then exit 77; fi
-# This test requires user namespaces and associated command-line tools.
-if ! unshare -mrf sh -c 'mount -t tmpfs none "$STORE_PARENT"'
+if unshare -mrf sh -c 'mount -t tmpfs none "$STORE_PARENT"'
then
- exit 77
+ # Test the wrapper that relies on user namespaces.
+ relocatable_option="-R"
+else
+ case "`uname -m`" in
+ x86_64|i?86)
+ # Test the wrapper that falls back to PRoot.
+ relocatable_option="-RR";;
+ *)
+ # XXX: Our 'proot' package currently fails tests on non-Intel
+ # architectures, so skip this by default.
+ exit 77;;
+ esac
fi
test_directory="`mktemp -d`"
export test_directory
trap 'chmod -Rf +w "$test_directory"; rm -rf "$test_directory"' EXIT
-tarball="`guix pack -R -S /Bin=bin sed`"
+export relocatable_option
+tarball="`guix pack $relocatable_option -S /Bin=bin sed`"
(cd "$test_directory"; tar xvf "$tarball")
# Run that relocatable 'sed' in a user namespace where we "erase" the store by
--
2.21.0