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[bug#41189] [PATCH 3/3] pack: Add relocation via ld.so and fakechroot.
From: |
Ludovic Courtès |
Subject: |
[bug#41189] [PATCH 3/3] pack: Add relocation via ld.so and fakechroot. |
Date: |
Mon, 11 May 2020 19:11:35 +0200 |
From: Ludovic Courtès <address@hidden>
* 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]: New
procedures.
[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.
---
doc/guix.texi | 13 ++
gnu/packages/aux-files/run-in-namespace.c | 174 ++++++++++++++++++++--
guix/scripts/pack.scm | 65 +++++++-
tests/guix-pack-relocatable.sh | 6 +
4 files changed, 237 insertions(+), 21 deletions(-)
diff --git a/doc/guix.texi b/doc/guix.texi
index 958ed9ceec..a70a058afb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5228,6 +5228,10 @@ following execution engines are supported:
Try user namespaces and fall back to PRoot if user namespaces are not
supported (see below).
+@item performance
+Try user namespaces and fall back to Fakechroot if user namespaces are
+not supported (see below).
+
@item userns
Run the program through user namespaces and abort if they are not
supported.
@@ -5239,6 +5243,15 @@ 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.
+
+@item fakechroot
+Run through Fakechroot. @uref{https://github.com/dex4er/fakechroot/,
+Fakechroot} virtualizes file system accesses by intercepting calls to C
+library functions such as @code{open}, @code{stat}, @code{exec}, and so
+on. Unlike PRoot, it incurs very little overhead. However, it does not
+always work: for example, some file system accesses made from within the
+C library are not intercepted, and file system accesses made @i{via}
+direct syscalls are not intercepted either, leading to erratic behavior.
@end table
@vindex GUIX_EXECUTION_ENGINE
diff --git a/gnu/packages/aux-files/run-in-namespace.c
b/gnu/packages/aux-files/run-in-namespace.c
index 6beac7fd53..ed72a169f2 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 PROGRAM_RUNPATH)
+
+
/* Like 'malloc', but abort if 'malloc' returns NULL. */
static void *
xmalloc (size_t size)
@@ -113,9 +118,42 @@ 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);
@@ -150,17 +188,7 @@ 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.
@@ -244,7 +272,7 @@ 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);
@@ -336,6 +364,106 @@ exec_with_proot (const char *store, int argc, char
*argv[])
#endif
+
+#if HAVE_EXEC_WITH_LOADER
+
+static void
+exec_with_loader (const char *store, int argc, char *argv[])
+{
+ static const char *runpath[] = PROGRAM_RUNPATH;
+ char *library_path;
+ size_t size = 0;
+
+ for (size_t i = 0; runpath[i] != NULL; i++)
+ size += strlen (store) + strlen (runpath[i]) + 1; /* upper bound */
+
+ library_path = xmalloc (size + 1);
+ library_path[0] = '\0';
+
+ for (size_t i = 0; runpath[i] != NULL; i++)
+ {
+ if (strncmp (runpath[i], "@STORE_DIRECTORY@",
+ sizeof "@STORE_DIRECTORY@" - 1) == 0)
+ {
+ strcat (library_path, store);
+ strcat (library_path, runpath[i] + sizeof "@STORE_DIRECTORY@");
+ }
+ else
+ strcat (library_path, runpath[i]); /* possibly $ORIGIN */
+
+ strcat (library_path, ":");
+ }
+
+ library_path[strlen (library_path) - 1] = '\0'; /* Remove trailing colon. */
+
+ char *loader = concat (store,
+ PROGRAM_INTERPRETER + sizeof "@STORE_DIRECTORY@");
+ 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] = "--library-path";
+ loader_argv[2] = library_path;
+ loader_argv[3] = "--preload";
+ loader_argv[4] = concat (store,
+ FAKECHROOT_LIBRARY + sizeof "@STORE_DIRECTORY@");
+ loader_argv[5] = concat (store,
+ "@WRAPPED_PROGRAM@" + sizeof "@STORE_DIRECTORY@");
+
+ 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, "@STORE_DIRECTORY@");
+ char *new_store_parent = dirname (strdup (new_store));
+ mkdir_p (new_store_parent);
+ symlink (store, new_store);
+
+ 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. */
@@ -352,7 +480,7 @@ 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[])
{
@@ -366,13 +494,29 @@ 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 }
};
diff --git a/guix/scripts/pack.scm b/guix/scripts/pack.scm
index 580f696b41..3b72496a34 100644
--- a/guix/scripts/pack.scm
+++ b/guix/scripts/pack.scm
@@ -684,15 +684,26 @@ last resort for relocation."
(define (proot)
(specification->package "proot-static"))
+ (define (fakechroot-library)
+ (file-append (specification->package "fakechroot")
+ "/lib/fakechroot/libfakechroot.so"))
+
(define build
(with-imported-modules (source-module-closure
'((guix build utils)
- (guix build union)))
+ (guix build union)
+ (guix build gremlin)
+ (guix elf)))
#~(begin
(use-modules (guix build utils)
((guix build union) #:select (relative-file-name))
+ (guix build gremlin)
+ (guix elf)
+ (ice-9 binary-ports)
(ice-9 ftw)
- (ice-9 match))
+ (ice-9 match)
+ (srfi srfi-1)
+ (rnrs bytevectors))
(define input
;; The OUTPUT* output of PACKAGE.
@@ -711,6 +722,47 @@ last resort for relocation."
(#f base)
(index (string-drop base index)))))
+ (define (elf-interpreter elf)
+ ;; Return the interpreter of ELF as a string, or #f if ELF has no
+ ;; interpreter segment.
+ (match (find (lambda (segment)
+ (= (elf-segment-type segment) PT_INTERP))
+ (elf-segments elf))
+ (#f #f) ;maybe a .so
+ (segment
+ (let ((bv (make-bytevector (- (elf-segment-memsz segment) 1))))
+ (bytevector-copy! (elf-bytes elf)
+ (elf-segment-offset segment)
+ bv 0 (bytevector-length bv))
+ (utf8->string bv)))))
+
+ (define (elf-loader-compile-flags program)
+ ;; Return the cpp flags defining macros for the ld.so/fakechroot
+ ;; wrapper of PROGRAM.
+
+ ;; TODO: Handle scripts by wrapping their interpreter.
+ (if (elf-file? program)
+ (let* ((bv (call-with-input-file program get-bytevector-all))
+ (elf (parse-elf bv)))
+ (match (elf-dynamic-info elf)
+ (#f '())
+ (dyninfo
+ (let ((runpath (elf-dynamic-info-runpath dyninfo))
+ (interp (elf-interpreter elf)))
+ (if interp
+ (list (string-append "-DPROGRAM_INTERPRETER=\""
+ interp "\"")
+ (string-append "-DPROGRAM_RUNPATH={ "
+ (string-join
+ (map object->string
+ runpath)
+ ", ")
+ ", NULL }")
+ (string-append "-DFAKECHROOT_LIBRARY=\""
+ #$(fakechroot-library) "\""))
+ '())))))
+ '()))
+
(define (build-wrapper program)
;; Build a user-namespace wrapper for PROGRAM.
(format #t "building wrapper for '~a'...~%" program)
@@ -730,10 +782,11 @@ last resort for relocation."
(mkdir-p (dirname result))
(apply invoke #$compiler "-std=gnu99" "-static" "-Os" "-g0"
"-Wall"
"run.c" "-o" result
- (if proot
- (list (string-append "-DPROOT_PROGRAM=\""
- proot "\""))
- '()))
+ (append (if proot
+ (list (string-append "-DPROOT_PROGRAM=\""
+ proot "\""))
+ '())
+ (elf-loader-compile-flags program)))
(delete-file "run.c")))
(setvbuf (current-output-port) 'line)
diff --git a/tests/guix-pack-relocatable.sh b/tests/guix-pack-relocatable.sh
index cb56815fed..358cac5b26 100644
--- a/tests/guix-pack-relocatable.sh
+++ b/tests/guix-pack-relocatable.sh
@@ -94,6 +94,12 @@ case "`uname -m`" in
export GUIX_EXECUTION_ENGINE
"$test_directory/Bin/sed" --version > "$test_directory/output"
grep 'GNU sed' "$test_directory/output"
+
+ # Now with fakechroot.
+ GUIX_EXECUTION_ENGINE="fakechroot"
+ "$test_directory/Bin/sed" --version > "$test_directory/output"
+ grep 'GNU sed' "$test_directory/output"
+
chmod -Rf +w "$test_directory"; rm -rf "$test_directory"/*
;;
*)
--
2.26.2
- [bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR', Ludovic Courtès, 2020/05/11
- [bug#41189] [PATCH 1/3] pack: Wrapper honors 'GUIX_EXECUTION_ENGINE' environment variable., Ludovic Courtès, 2020/05/11
- [bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR', Carlos O'Donell, 2020/05/12
- [bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR', Ludovic Courtès, 2020/05/12
- [bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR', Carlos O'Donell, 2020/05/12
- [bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR', Ludovic Courtès, 2020/05/12
- [bug#41189] [PATCH v2 0/4] Add Fakechroot engine for 'guix pack -RR', Ludovic Courtès, 2020/05/13
- [bug#41189] [PATCH v2 1/4] pack: Wrapper honors 'GUIX_EXECUTION_ENGINE' environment variable., Ludovic Courtès, 2020/05/13
- [bug#41189] [PATCH v2 3/4] gnu: Add fakechroot., Ludovic Courtès, 2020/05/13
- [bug#41189] [PATCH v2 4/4] pack: Add relocation via ld.so and fakechroot., Ludovic Courtès, 2020/05/13
- [bug#41189] [PATCH v2 2/4] pack: Factorize store references in wrapper., Ludovic Courtès, 2020/05/13
- bug#41189: [PATCH v2 0/4] Add Fakechroot engine for 'guix pack -RR', Ludovic Courtès, 2020/05/14