On Wed, Feb 1, 2017 at 9:42 PM, Bhupesh Sharma <bhsha...@redhat.com> wrote: > This RFC patchset tries to make the powerpc ASLR elf randomness > implementation similar to other ARCHs (like x86). > > The 1st patch introduces the support of ARCH_MMAP_RND_BITS in powerpc > mmap implementation to allow a sane balance between increased randomness > in the mmap address of ASLR elfs and increased address space > fragmentation. > > The 2nd patch increases the ELF_ET_DYN_BASE value from the current > hardcoded value of 0x2000_0000 to something more practical, > i.e. TASK_SIZE - PAGE_SHIFT (which makes sense especially for > 64-bit platforms which would like to utilize more randomization > in the load address of a PIE elf).
I don't think you want this second patch. Moving ELF_ET_DYN_BASE to the top of TASK_SIZE means you'll be constantly colliding with stack and mmap randomization. 0x20000000 is way better since it randomizes up from there towards the mmap area. Is there a reason to avoid the 32-bit memory range for the ELF addresses? -Kees -- Kees Cook Pixel Security