On 08/14/17 at 10:54pm, Baoquan He wrote: > Currently KASLR will parse all e820 entries of RAM type and add all > candidate position into slots array. Then we will choose one slot > randomly as the new position which kernel will be decompressed into > and run at. > > On system with EFI enabled, e820 memory regions are coming from EFI > memory regions by combining adjacent regions. While these EFI memory > regions have more attributes to mark their different use. Mirror > attribute is such kind. The physical memory region whose descriptors > in EFI memory map has EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are > mirrored. The address range mirroring feature of kernel arranges such > mirror region into normal zone and other region into movable zone. And > with mirroring feature enabled, the code and date of kernel can only be > located in more reliable mirror region. However, the current KASLR code > doesn't check EFI memory entries, and could choose new position in > non-mirrored region. This will break the functionality of the address > range mirroring feature.
Thanks a lot for helping improving the patch log, Ingo! Will pay more attention to the description in words and paragraph partition of log. > > So if EFI is detected, iterate EFI memory map and pick the mirror region > to process for adding candidate of randomization slot. If EFI is disabled > or no mirror region found, still process e820 memory map. > > Signed-off-by: Baoquan He <[email protected]> > --- > arch/x86/boot/compressed/kaslr.c | 68 > ++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 66 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/boot/compressed/kaslr.c > b/arch/x86/boot/compressed/kaslr.c > index 99c7194f7ea6..7de23bb279ce 100644 > --- a/arch/x86/boot/compressed/kaslr.c > +++ b/arch/x86/boot/compressed/kaslr.c > @@ -37,7 +37,9 @@ > #include <linux/uts.h> > #include <linux/utsname.h> > #include <linux/ctype.h> > +#include <linux/efi.h> > #include <generated/utsrelease.h> > +#include <asm/efi.h> > > /* Macros used by the included decompressor code below. */ > #define STATIC > @@ -558,6 +560,65 @@ static void process_mem_region(struct mem_vector *entry, > } > } > > +#ifdef CONFIG_EFI > +/* > + * Returns true if mirror region found (and must have been processed > + * for slots adding) > + */ > +static bool > +process_efi_entries(unsigned long minimum, unsigned long image_size) > +{ > + struct efi_info *e = &boot_params->efi_info; > + bool efi_mirror_found = false; > + struct mem_vector region; > + efi_memory_desc_t *md; > + unsigned long pmap; > + char *signature; > + u32 nr_desc; > + int i; > + > + signature = (char *)&e->efi_loader_signature; > + if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && > + strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) > + return false; > + > +#ifdef CONFIG_X86_32 > + /* Can't handle data above 4GB at this time */ > + if (e->efi_memmap_hi) { > + warn("EFI memmap is above 4GB, can't be handled now on x86_32. > EFI should be disabled.\n"); > + return false; > + } > + pmap = e->efi_memmap; > +#else > + pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32)); > +#endif > + > + nr_desc = e->efi_memmap_size / e->efi_memdesc_size; > + for (i = 0; i < nr_desc; i++) { > + md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i); > + if (md->attribute & EFI_MEMORY_MORE_RELIABLE) { > + region.start = md->phys_addr; > + region.size = md->num_pages << EFI_PAGE_SHIFT; > + process_mem_region(®ion, minimum, image_size); > + efi_mirror_found = true; > + > + if (slot_area_index == MAX_SLOT_AREA) { > + debug_putstr("Aborted EFI scan (slot_areas > full)!\n"); > + break; > + } > + } > + } > + > + return efi_mirror_found; > +} > +#else > +static inline bool > +process_efi_entries(unsigned long minimum, unsigned long image_size) > +{ > + return false; > +} > +#endif > + > static void process_e820_entries(unsigned long minimum, > unsigned long image_size) > { > @@ -586,13 +647,16 @@ static unsigned long find_random_phys_addr(unsigned > long minimum, > { > /* Check if we had too many memmaps. */ > if (memmap_too_large) { > - debug_putstr("Aborted e820 scan (more than 4 memmap= args)!\n"); > + debug_putstr("Aborted memory entries scan (more than 4 memmap= > args)!\n"); > return 0; > } > > /* Make sure minimum is aligned. */ > minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); > > + if (process_efi_entries(minimum, image_size)) > + return slots_fetch_random(); > + > process_e820_entries(minimum, image_size); > return slots_fetch_random(); > } > @@ -652,7 +716,7 @@ void choose_random_location(unsigned long input, > */ > min_addr = min(*output, 512UL << 20); > > - /* Walk e820 and find a random address. */ > + /* Walk available memory entries to find a random address. */ > random_addr = find_random_phys_addr(min_addr, output_size); > if (!random_addr) { > warn("Physical KASLR disabled: no suitable memory region!"); > -- > 2.5.5 >
