On Fri, 2019-08-09 at 18:07 +0800, Jason Yan wrote: > This series implements KASLR for powerpc/fsl_booke/32, as a security > feature that deters exploit attempts relying on knowledge of the location > of kernel internals. > > Since CONFIG_RELOCATABLE has already supported, what we need to do is > map or copy kernel to a proper place and relocate. Have you tested this with a kernel that was loaded at a non-zero address? I tried loading a kernel at 0x04000000 (by changing the address in the uImage, and setting bootm_low to 04000000 in U-Boot), and it works without CONFIG_RANDOMIZE and fails with. > Freescale Book-E > parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1 > entries are not suitable to map the kernel directly in a randomized > region, so we chose to copy the kernel to a proper place and restart to > relocate. > > Entropy is derived from the banner and timer base, which will change every > build and boot. This not so much safe so additionally the bootloader may > pass entropy via the /chosen/kaslr-seed node in device tree. How complicated would it be to directly access the HW RNG (if present) that early in the boot? It'd be nice if a U-Boot update weren't required (and particularly concerning that KASLR would appear to work without a U-Boot update, but without decent entropy). -Scott
