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
