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01/01: gnu: glibc-final: Catch all cases of a glibc user not requesting
From: |
guix-commits |
Subject: |
01/01: gnu: glibc-final: Catch all cases of a glibc user not requesting 64-bit offsets and then using readdir regardless. |
Date: |
Sun, 27 Sep 2020 18:20:01 -0400 (EDT) |
dannym pushed a commit to branch wip-file-offset-bits-64
in repository guix.
commit 51d13466bbaf862fdd9938f50c58805936c0d185
Author: Danny Milosavljevic <dannym@scratchpost.org>
AuthorDate: Mon Sep 21 17:17:05 2020 +0200
gnu: glibc-final: Catch all cases of a glibc user not requesting 64-bit
offsets and then using readdir regardless.
* gnu/packages/commencement.scm (glibc-final): Catch all cases of a glibc
user not
requesting 64-bit offsets and then using readdir.
---
gnu/packages/commencement.scm | 68 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 67 insertions(+), 1 deletion(-)
diff --git a/gnu/packages/commencement.scm b/gnu/packages/commencement.scm
index e5a4caa..284fa65 100644
--- a/gnu/packages/commencement.scm
+++ b/gnu/packages/commencement.scm
@@ -3462,7 +3462,73 @@ exec ~a/bin/~a-~a -B~a/lib -Wl,-dynamic-linker -Wl,~a/~a
\"$@\"~%"
,hurd-headers-boot0)
'())
,@(package-outputs glibc-final-with-bootstrap-bash))
- ,@(package-arguments glibc-final-with-bootstrap-bash)))))
+ ,@(substitute-keyword-arguments
+ (package-arguments glibc-final-with-bootstrap-bash)
+ ((#:phases phases)
+ `(modify-phases ,phases
+ (add-after 'unpack 'patch-dirent
+ (lambda* (#:key outputs #:allow-other-keys)
+ ;; Linux kernel file offsets are always 64 bits.
+ ;; But userspace can be built to use 32 bit offsets.
+ ;;
+ ;; "struct dirent", returned by readdir, uses d_off to store
+ ;; such an "offset" that it got from the Linux kernel.
+ ;; In the case of ext4 that "offset" is actually a 64 bit
+ ;; hash value.
+ ;;
+ ;; Therefore, there are cases where such an offset that it got
+ ;; from the Linux kernel does not fit in the "struct dirent"
+ ;; field "d_off".
+ ;;
+ ;; If the guest system's glibc is 32 bit AND uses 32 bit
+ ;; file offsets it is going to be very confused.
+ ;; It does check whether d_off fits into the structure
+ ;; it gives back to the user--and it doesn't fit. Hence
readdir
+ ;; fails, with errno == EOVERFLOW (which is undocumented and
thus
+ ;; an API error).
+ ;; This manifests itself in simple directory reads not working
+ ;; anymore in parts of cmake, for example.
+ ;;
+ ;; This manifested in Guix when building stuff for
+ ;; ARMHF on a x86_64 build host using QEMU transparent
emulation.
+ ;;
+ ;; There is a very simple and complete way to avoid this
problem:
+ ;; Just always use 64 bit offsets in user space programs (also
+ ;; on 32 bit machines). The Linux kernel does that already
+ ;; anyway.
+ ;;
+ ;; Note: We might want to avoid using 64 bit when
bootstrapping
+ ;; using mescc (since mescc doesn't directly support 64 bit
+ ;; values)--but then bootstrapping has to be done on a
+ ;; file system other than ext4, or on ext4 with the feature
+ ;; "dir_index" disabled.
+ ;;
+ ;; The change below does not affect 64 bit users.
+ ;;
+ ;; See <https://issues.guix.gnu.org/43513>.
+ (let ((port (open-file "dirent/dirent.h" "a")))
+ (display "
+#ifndef _LIBC
+#if __SIZEOF_LONG__ < 8
+#ifndef __USE_FILE_OFFSET64
+#if defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 32
+#warning \"Using -D_FILE_OFFSET_BITS=32 and using readdir is a bad idea, see
<https://bugzilla.kernel.org/show_bug.cgi?id=205957>\"
+#else
+#undef readdir
+#define readdir @READDIR_WITHOUT_FILE_OFFSET64_IS_A_REALLY_BAD_IDEA@
+#endif
+#endif
+#endif
+#endif
+" port)
+ (close-port port))
+ ;; This file includes <dirent.h> and thus checks sanity
already.
+ ;; TODO: Check dirent/scandir-tail.c, dirent/scandir64-tail.c.
+ (substitute* "posix/glob.c"
+ (("(#[ ]*define[ ][ ]*readdir)") "
+#undef readdir
+#define readdir"))
+ #t)))))))))
(define/system-dependent gcc-boot0-wrapped
;; Make the cross-tools GCC-BOOT0 and BINUTILS-BOOT0 available under the