On Thu, 2007-07-05 at 16:55 -0500, Scott Wood wrote: > As revealed by the recent "Prevent data exception in kernel space" > patch, versions of glibc prior to 2.4[1] assume that, on powerpc32, they > can execute out of any readable mapping, regardless of whether it is > marked for execution. This happens in the elf_machine_load_address() > function. > > To maintain compatibility with these versions, we could change the test > in do_page_fault() to include VM_READ as well as VM_EXEC on targets that > don't have a separate exec-bit in hardware (are there any powerpc mmus > that do?). However, Segher suggested on IRC that we may want to drop > compatibility with those old versions of glibc, and that I should seek > your input. > > Personally, I'd rather stick the VM_READ in there, partially for selfish > reasons (our root filesystems are based on older glibcs), and because it > seems a little too soon to deprecate glibc 2.3, but also because in the > absence of hardware support, the VM_EXEC check will be nondeterministic, > kicking in only when the first fault for a page is to execute. > > -Scott > > [1] It's possible that there are other instances of this in 2.4 and that > the actual version is newer; I ran into obnoxious cross compilation > issues trying to try it. However, > > <rant> > Glibc already has target-specific code/headers; if you need to know > something that you'd otherwise need a runs-on-the-target autoconf test > for, why not just stick it in such a target-specific header? In this > case, it was trying to figure out the size of "long double". > </rant> > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-dev
Since may be a security problem (non-exec mappings being executed), I really believe we don't want to keep the compatibility. Regards, Rodrigo (BSDaemon). -- Rodrigo Rubira Branco Software Engineer Advanced Linux Response Team (ALRT) / Linux on Power Toolchain IBM Linux Technology Center (IBM/LTC) [EMAIL PROTECTED] GPG KeyID: 1FCEDEA1
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