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Bug 221281

Summary: app-editors/emacs-{18.59-r4,21.4-r15}: temacs segfaults in dump-emacs w/ kernel 2.6.25
Product: Gentoo Linux Reporter: Ulrich Müller <ulm>
Component: Current packagesAssignee: Emacs project <emacs>
Severity: major    
Priority: High    
Version: 2007.0   
Hardware: x86   
OS: Linux   
Package list:
Runtime testing required: ---
Bug Depends on: 221197    
Bug Blocks: 218127    
Attachments: Stack trace
Kernel config
emerge --info
Patch for 21.4: 17_all_bss-heap-gap.patch
Patch for 18.59: 05_all_bss-heap-gap.patch

Description Ulrich Müller gentoo-dev 2008-05-10 23:00:31 UTC
Building of app-editors/emacs-21.4-r15 (also 18.59-r4) fails with a segmentation fault in dump-emacs / unexec. This is with the system running gentoo-sources-2.6.25-r2. The problem does not show up with 2.6.24-r7.

LC_ALL=C ./temacs -batch -l loadup dump
Finding pointers to doc strings...
Finding pointers to doc strings...done
Wrote /var/tmp/portage/app-editors/emacs-21.4-r15/work/emacs-21.4/lib-src/fns-21.4.1.el
Dumping under names emacs and emacs-21.4.1
make[1]: *** [emacs] Segmentation fault
make[1]: *** Deleting file `emacs'
make[1]: Leaving directory `/var/tmp/portage/app-editors/emacs-21.4-r15/work/emacs-21.4/src'
make: *** [src] Error 2
Comment 1 Ulrich Müller gentoo-dev 2008-05-10 23:02:35 UTC
Created attachment 152785 [details]
Stack trace
Comment 2 Ulrich Müller gentoo-dev 2008-05-10 23:04:03 UTC
Created attachment 152787 [details]
Kernel config
Comment 3 Ulrich Müller gentoo-dev 2008-05-10 23:05:01 UTC
Created attachment 152789 [details]
emerge --info
Comment 4 Ulrich Müller gentoo-dev 2008-05-10 23:18:45 UTC
Created attachment 152791 [details, diff]
Patch for 21.4: 17_all_bss-heap-gap.patch

Patch for Emacs 21.4, backported from Emacs 22.

(A patch for Emacs 18.59 will follow later.)
Comment 5 Ulrich Müller gentoo-dev 2008-05-11 00:36:17 UTC
Created attachment 152799 [details, diff]
Patch for 18.59: 05_all_bss-heap-gap.patch
Comment 6 Ulrich Müller gentoo-dev 2008-05-11 01:23:05 UTC
The breakage is caused by the "randomize brk()" patch.
See the LKML, <>:

| This is known to break older versions of some emacs variants, whose
| dumper code assumed that the last variable declared in the program is
| equal to the start of the dynamically allocated memory region.

The corresponding kernel parameter is accessible via /proc/sys/kernel/randomize_va_space, the breakage occurs if its value is 2.
Comment 7 Ulrich Müller gentoo-dev 2008-05-11 21:52:02 UTC
Fixed in emacs-18.59-r5 and emacs-21.4-r16. Leave this bug open until the fixed versions are marked stable (wrt tracker bug 218127).
Comment 8 Ulrich Müller gentoo-dev 2008-05-13 06:18:46 UTC
Stabilisation of emacs-21.4-r17 is handled in bug 221197.
Comment 9 Ulrich Müller gentoo-dev 2008-05-29 16:50:21 UTC
@x86: Please stabilise emacs-18.59-r5.
Preferably it should be tested with kernel 2.6.25.
Comment 10 Christian Faulhammer (RETIRED) gentoo-dev 2008-05-31 13:40:12 UTC
x86 stable, closing