Messages in this thread | | | Date | Mon, 6 Dec 2021 22:10:06 +0800 | Subject | Re: [PATCH] arm64: mm: Make randomization works again in some case | From | Kefeng Wang <> |
| |
Hello, Ard and Catalin, kindly ping...
On 2021/11/4 14:27, Kefeng Wang wrote: > After commit 97d6786e0669 ("arm64: mm: account for hotplug memory when > randomizing the linear region"), the KASLR could not work well in some > case, eg, without memory hotplug and with va=39/pa=44, that is, linear > region size < CPU's addressable PA range, the KASLR fails now but could > work before this commit. Let's calculate pa range by memblock end/start > without CONFIG_RANDOMIZE_BASE. > > Meanwhile, let's add a warning message if linear region size is too small > for randomization. > > Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > --- > Hi Ard, one more question, the parange from mmfr0 register may also too large, > then even with this patch, the randomization still could not work. > > If we know the max physical memory range(including hotplug memory), could we > add a way(maybe cmdline) to set max parange, then we could make randomization > works in more cases, any thought? > > arch/arm64/mm/init.c | 30 +++++++++++++++++++++--------- > 1 file changed, 21 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index a8834434af99..27ec7f2c6fdb 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -284,21 +284,33 @@ void __init arm64_memblock_init(void) > > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { > extern u16 memstart_offset_seed; > - u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); > - int parange = cpuid_feature_extract_unsigned_field( > - mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); > - s64 range = linear_region_size - > - BIT(id_aa64mmfr0_parange_to_phys_shift(parange)); > + s64 range; > + > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) { > + u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1); > + int parange = cpuid_feature_extract_unsigned_field( > + mmfr0, ID_AA64MMFR0_PARANGE_SHIFT); > + range = linear_region_size - > + BIT(id_aa64mmfr0_parange_to_phys_shift(parange)); > + > + } else { > + range = linear_region_size - > + (memblock_end_of_DRAM() - memblock_start_of_DRAM()); > + } > > /* > * If the size of the linear region exceeds, by a sufficient > * margin, the size of the region that the physical memory can > * span, randomize the linear region as well. > */ > - if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) { > - range /= ARM64_MEMSTART_ALIGN; > - memstart_addr -= ARM64_MEMSTART_ALIGN * > - ((range * memstart_offset_seed) >> 16); > + if (memstart_offset_seed > 0) { > + if (range < (s64)ARM64_MEMSTART_ALIGN) { > + pr_warn("linear mappings size is too small for KASLR\n"); > + } else { > + range /= ARM64_MEMSTART_ALIGN; > + memstart_addr -= ARM64_MEMSTART_ALIGN * > + ((range * memstart_offset_seed) >> 16); > + } > } > } >
| |