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Re: seg-fault in unexelf.c
Re: seg-fault in unexelf.c
Sun, 23 Jul 2006 00:50:22 +1200
Chip Coldwell writes:
> On Sat, 22 Jul 2006, Nick Roberts wrote:
> > I regularly build on FC5 without optimization and don't have any problems
> > (although I haven't done "make bootstrap for a while, the final build uses
> > "./temacs -l loadup -batch dump").
> Which version?
> If you mean 21.4 (the one that ships with FC5), then all
> this means is that, for whatever reason, your kernel is aways setting up
> the temacs process with a contiguous address space. The fact that the
> Linux kernel could set up a process virtual address space with holes in it
> has to be dealt with anyway.
Isn't this related to items in the PROBLEMS file (some of which I thought had
*** Linux: Segfault during `make bootstrap' under certain recent versions of
the Linux kernel.
With certain recent Linux kernels (like the one of Redhat Fedora Core 1 and
newer), the new "Exec-shield" functionality is enabled by default, which
creates a different memory layout that breaks the emacs dumper. Emacs tries
to handle this at build time, but if the workaround used fails, these
instructions can be useful. The work-around explained here is not enough on
Fedora Core 4 (and possible newer). Read the next item.
Configure can overcome the problem of exec-shield if the architecture is x86
and the program setarch is present. On other architectures no workaround is
You can check the Exec-shield state like this:
It returns non-zero when Exec-shield is enabled, 0 otherwise. Please read
your system documentation for more details on Exec-shield and associated
commands. Exec-shield can be turned off with this command:
echo "0" > /proc/sys/kernel/exec-shield
When Exec-shield is enabled, building Emacs will segfault during the
execution of this command:
./temacs --batch --load loadup [dump|bootstrap]
To work around this problem, it is necessary to temporarily disable
Exec-shield while building Emacs, or, on x86, by using the `setarch'
command when running temacs like this:
setarch i386 ./temacs --batch --load loadup [dump|bootstrap]
*** Fedora Core 4 GNU/Linux: Segfault during dumping.
In addition to exec-shield explained above "Linux: Segfault during `make
bootstrap' under certain recent versions of the Linux kernel" item, Linux
kernel shipped with Fedora Core 4 randomizes the virtual address space of a
process. As the result dumping may fail even if you turn off exec-shield. In
this case, use the -R option to the setarch command:
setarch i386 -R ./temacs --batch --load loadup [dump|bootstrap]
setarch i386 -R make bootstrap