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authorLudovic Courtès <ludovic.courtes@inria.fr>2020-05-07 22:49:20 +0200
committerLudovic Courtès <ludo@gnu.org>2020-05-14 17:21:27 +0200
commit6456232164890dbf5aa20394ee24637feb4b7b9e (patch)
tree8fbdad7a851dd1762756c7178864d6919a62c00f /gnu/packages/aux-files
parent4449e7c5e4c8b746c786fc9a5ea82eab60f6c846 (diff)
pack: Add relocation via ld.so and fakechroot.
* gnu/packages/aux-files/run-in-namespace.c (HAVE_EXEC_WITH_LOADER): New macro. (bind_mount): Rename to... (mirror_directory): ... this. Add 'firmlink' argument and use it instead of calling mkdir/open/close/mount directly. (bind_mount, make_symlink): New functions. (exec_in_user_namespace): Adjust accordingly. (exec_with_loader) [HAVE_EXEC_WITH_LOADER]: New function. (exec_performance): New function. (engines): Add them. * guix/scripts/pack.scm (wrapped-package)[fakechroot-library] [audit-module]: New procedures. [audit-source]: New variable. [build](elf-interpreter, elf-loader-compile-flags): New procedures. (build-wrapper): Use them. * tests/guix-pack-relocatable.sh: Test with 'GUIX_EXECUTION_ENGINE=fakechroot'. * doc/guix.texi (Invoking guix pack): Document the 'performance' and 'fakechroot' engines. * gnu/packages/aux-files/pack-audit.c: New file. * Makefile.am (AUX_FILES): Add it.
Diffstat (limited to 'gnu/packages/aux-files')
-rw-r--r--gnu/packages/aux-files/pack-audit.c85
-rw-r--r--gnu/packages/aux-files/run-in-namespace.c160
2 files changed, 230 insertions, 15 deletions
diff --git a/gnu/packages/aux-files/pack-audit.c b/gnu/packages/aux-files/pack-audit.c
new file mode 100644
index 0000000000..374787e8b9
--- /dev/null
+++ b/gnu/packages/aux-files/pack-audit.c
@@ -0,0 +1,85 @@
+/* GNU Guix --- Functional package management for GNU
+ Copyright (C) 2020 Ludovic Courtès <ludo@gnu.org>
+
+ This file is part of GNU Guix.
+
+ GNU Guix is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or (at
+ your option) any later version.
+
+ GNU Guix is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with GNU Guix. If not, see <http://www.gnu.org/licenses/>. */
+
+/* This file implements part of the GNU ld.so audit interface. It is used by
+ the "fakechroot" engine of the 'guix pack -RR' wrappers to make sure the
+ loader looks for shared objects under the "fake" root directory. */
+
+#define _GNU_SOURCE 1
+
+#include <link.h>
+
+#include <error.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+/* The pseudo root directory and store that we are relocating to. */
+static const char *root_directory;
+static char *store;
+
+/* The original store, "/gnu/store" by default. */
+static const char original_store[] = "@STORE_DIRECTORY@";
+
+/* Like 'malloc', but abort if 'malloc' returns NULL. */
+static void *
+xmalloc (size_t size)
+{
+ void *result = malloc (size);
+ assert (result != NULL);
+ return result;
+}
+
+unsigned int
+la_version (unsigned int v)
+{
+ if (v != LAV_CURRENT)
+ error (1, 0, "cannot handle interface version %u", v);
+
+ root_directory = getenv ("FAKECHROOT_BASE");
+ if (root_directory == NULL)
+ error (1, 0, "'FAKECHROOT_BASE' is not set");
+
+ store = xmalloc (strlen (root_directory) + sizeof original_store);
+ strcpy (store, root_directory);
+ strcat (store, original_store);
+
+ return v;
+}
+
+/* Return NAME, a shared object file name, relocated under STORE. This
+ function is called by the loader whenever it looks for a shared object. */
+char *
+la_objsearch (const char *name, uintptr_t *cookie, unsigned int flag)
+{
+ char *result;
+
+ if (strncmp (name, original_store,
+ sizeof original_store - 1) == 0)
+ {
+ size_t len = strlen (name) - sizeof original_store
+ + strlen (store) + 1;
+ result = xmalloc (len);
+ strcpy (result, store);
+ strcat (result, name + sizeof original_store - 1);
+ }
+ else
+ result = strdup (name);
+
+ return result;
+}
diff --git a/gnu/packages/aux-files/run-in-namespace.c b/gnu/packages/aux-files/run-in-namespace.c
index 6e97359078..5a6b932b87 100644
--- a/gnu/packages/aux-files/run-in-namespace.c
+++ b/gnu/packages/aux-files/run-in-namespace.c
@@ -42,6 +42,11 @@
#include <dirent.h>
#include <sys/syscall.h>
+/* Whether we're building the ld.so/libfakechroot wrapper. */
+#define HAVE_EXEC_WITH_LOADER \
+ (defined PROGRAM_INTERPRETER) && (defined LOADER_AUDIT_MODULE) \
+ && (defined FAKECHROOT_LIBRARY)
+
/* The original store, "/gnu/store" by default. */
static const char original_store[] = "@STORE_DIRECTORY@";
@@ -117,9 +122,42 @@ rm_rf (const char *directory)
assert_perror (errno);
}
-/* Bind mount all the top-level entries in SOURCE to TARGET. */
+/* Make TARGET a bind-mount of SOURCE. Take into account ENTRY's type, which
+ corresponds to SOURCE. */
+static int
+bind_mount (const char *source, const struct dirent *entry,
+ const char *target)
+{
+ if (entry->d_type == DT_DIR)
+ {
+ int err = mkdir (target, 0700);
+ if (err != 0)
+ return err;
+ }
+ else
+ close (open (target, O_WRONLY | O_CREAT));
+
+ return mount (source, target, "none",
+ MS_BIND | MS_REC | MS_RDONLY, NULL);
+}
+
+#if HAVE_EXEC_WITH_LOADER
+
+/* Make TARGET a symlink to SOURCE. */
+static int
+make_symlink (const char *source, const struct dirent *entry,
+ const char *target)
+{
+ return symlink (source, target);
+}
+
+#endif
+
+/* Mirror with FIRMLINK all the top-level entries in SOURCE to TARGET. */
static void
-bind_mount (const char *source, const char *target)
+mirror_directory (const char *source, const char *target,
+ int (* firmlink) (const char *, const struct dirent *,
+ const char *))
{
DIR *stream = opendir (source);
@@ -154,17 +192,7 @@ bind_mount (const char *source, const char *target)
else
{
/* Create the mount point. */
- if (entry->d_type == DT_DIR)
- {
- int err = mkdir (new_entry, 0700);
- if (err != 0)
- assert_perror (errno);
- }
- else
- close (open (new_entry, O_WRONLY | O_CREAT));
-
- int err = mount (abs_source, new_entry, "none",
- MS_BIND | MS_REC | MS_RDONLY, NULL);
+ int err = firmlink (abs_source, entry, new_entry);
/* It used to be that only directories could be bind-mounted. Thus,
keep going if we fail to bind-mount a non-directory entry.
@@ -248,7 +276,7 @@ exec_in_user_namespace (const char *store, int argc, char *argv[])
/* Note: Due to <https://bugzilla.kernel.org/show_bug.cgi?id=183461>
we cannot make NEW_ROOT a tmpfs (which would have saved the need
for 'rm_rf'.) */
- bind_mount ("/", new_root);
+ mirror_directory ("/", new_root, bind_mount);
mkdir_p (new_store);
err = mount (store, new_store, "none", MS_BIND | MS_REC | MS_RDONLY,
NULL);
@@ -341,6 +369,92 @@ exec_with_proot (const char *store, int argc, char *argv[])
#endif
+#if HAVE_EXEC_WITH_LOADER
+
+/* Execute the wrapped program by invoking the loader (ld.so) directly,
+ passing it the audit module and preloading libfakechroot.so. */
+static void
+exec_with_loader (const char *store, int argc, char *argv[])
+{
+ char *loader = concat (store,
+ PROGRAM_INTERPRETER + sizeof original_store);
+ size_t loader_specific_argc = 6;
+ size_t loader_argc = argc + loader_specific_argc;
+ char *loader_argv[loader_argc + 1];
+ loader_argv[0] = argv[0];
+ loader_argv[1] = "--audit";
+ loader_argv[2] = concat (store,
+ LOADER_AUDIT_MODULE + sizeof original_store);
+ loader_argv[3] = "--preload";
+ loader_argv[4] = concat (store,
+ FAKECHROOT_LIBRARY + sizeof original_store);
+ loader_argv[5] = concat (store,
+ "@WRAPPED_PROGRAM@" + sizeof original_store);
+
+ for (size_t i = 0; i < argc; i++)
+ loader_argv[i + loader_specific_argc] = argv[i + 1];
+
+ loader_argv[loader_argc] = NULL;
+
+ /* Set up the root directory. */
+ int err;
+ char *new_root = mkdtemp (strdup ("/tmp/guix-exec-XXXXXX"));
+ mirror_directory ("/", new_root, make_symlink);
+
+ char *new_store = concat (new_root, original_store);
+ char *new_store_parent = dirname (strdup (new_store));
+ mkdir_p (new_store_parent);
+ symlink (store, new_store);
+
+#ifdef GCONV_DIRECTORY
+ /* Tell libc where to find its gconv modules. This is necessary because
+ gconv uses non-interposable 'open' calls. */
+ char *gconv_path = concat (store,
+ GCONV_DIRECTORY + sizeof original_store);
+ setenv ("GCONV_PATH", gconv_path, 1);
+ free (gconv_path);
+#endif
+
+ setenv ("FAKECHROOT_BASE", new_root, 1);
+
+ pid_t child = fork ();
+ switch (child)
+ {
+ case 0:
+ err = execv (loader, loader_argv);
+ if (err < 0)
+ assert_perror (errno);
+ exit (EXIT_FAILURE);
+ break;
+
+ case -1:
+ assert_perror (errno);
+ exit (EXIT_FAILURE);
+ break;
+
+ default:
+ {
+ int status;
+ waitpid (child, &status, 0);
+ chdir ("/"); /* avoid EBUSY */
+ rm_rf (new_root);
+ free (new_root);
+
+ close (2); /* flushing stderr should be silent */
+
+ if (WIFEXITED (status))
+ exit (WEXITSTATUS (status));
+ else
+ /* Abnormal termination cannot really be reproduced, so exit
+ with 255. */
+ exit (255);
+ }
+ }
+}
+
+#endif
+
+
/* Execution engines. */
struct engine
@@ -356,7 +470,7 @@ buffer_stderr (void)
setvbuf (stderr, stderr_buffer, _IOFBF, sizeof stderr_buffer);
}
-/* The default engine. */
+/* The default engine: choose a robust method. */
static void
exec_default (const char *store, int argc, char *argv[])
{
@@ -370,14 +484,30 @@ exec_default (const char *store, int argc, char *argv[])
#endif
}
+/* The "performance" engine: choose performance over robustness. */
+static void
+exec_performance (const char *store, int argc, char *argv[])
+{
+ buffer_stderr ();
+
+ exec_in_user_namespace (store, argc, argv);
+#if HAVE_EXEC_WITH_LOADER
+ exec_with_loader (store, argc, argv);
+#endif
+}
+
/* List of supported engines. */
static const struct engine engines[] =
{
{ "default", exec_default },
+ { "performance", exec_performance },
{ "userns", exec_in_user_namespace },
#ifdef PROOT_PROGRAM
{ "proot", exec_with_proot },
#endif
+#if HAVE_EXEC_WITH_LOADER
+ { "fakechroot", exec_with_loader },
+#endif
{ NULL, NULL }
};