From mboxrd@z Thu Jan 1 00:00:00 1970 From: mawupeng Date: Thu, 19 May 2022 11:09:18 +0000 Subject: Re: [PATCH 0/2] Add support to relocate kernel image to mirrored region Message-Id: <7058b8d8-c0cb-108e-0db9-2fdf5fb154cf@huawei.com> List-Id: References: <20220419070150.254377-1-mawupeng1@huawei.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: ardb@kernel.org Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, dvhart@infradead.org, andy@infradead.org, rppt@kernel.org, paulmck@kernel.org, peterz@infradead.org, jroedel@suse.de, songmuchun@bytedance.com, macro@orcam.me.uk, frederic@kernel.org, W_Armin@gmx.de, john.garry@huawei.com, seanjc@google.com, tsbogend@alpha.franken.de, anshuman.khandual@arm.com, chenhuacai@kernel.org, david@redhat.com, gpiccoli@igalia.com, mark.rutland@arm.com, wangkefeng.wang@huawei.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, linux-ia64@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-mm@kvack.org, mawupeng1@huawei.com 在 2022/5/7 17:28, mawupeng 写道: > > > 在 2022/5/3 17:58, Ard Biesheuvel 写道: >> On Tue, 19 Apr 2022 at 08:43, Wupeng Ma wrote: >>> >>> From: Ma Wupeng >>> >>> Now system image will perfer to be located to mirrored regions both KASLR >>> on and off. >>> >> >> Hello Ma Wupeng, >> >> I wonder if we could simplify this as follows: >> - ignore the non-KASLR case for now, and rely on the bootloader  > load the image into mirrored memory if it exists; > > In grub, memory for static image is allocated via the following path: > > grub_cmd_linux >   kernel = grub_malloc(filelen) >   kernel_alloc_addr = grub_efi_allocate_any_pages (kernel_alloc_pages) >   grub_memcpy (kernel_addr, kernel, grub_min(filelen, kernel_size)) >    grub_loader_set (grub_linux_boot, grub_linux_unload, 0) > > Can we get memory from mirrored region by the following steps: > 1. get memory map by calling grub_efi_get_memory_map() > 2. iter all memory map to find a suitable mirrored memory area > 3. locate kernel image to this area > > So, if kaslr is not enabled >  - grub will load kernel into mirrored region > else >  - arm64-stub.c will relocate kernel image to mirrored region > > Is this feasible? Is this a feasible proposal to relocate the static kernel image itself into more reliable memory? > >> - simplify the KASLR case to the below. > > Yes, we can certainly do this. I will remove my code and use yours. > >> >> I think this is reasonable, because it means we take mirrored memory >> into account when we decide to move the image anyway, but expect the >> boot chain to take care of this if there is no need to move the image. >> >> -------------8<------------------ >> --- a/drivers/firmware/efi/libstub/randomalloc.c >> +++ b/drivers/firmware/efi/libstub/randomalloc.c >> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size, >>                                unsigned long random_seed) >>   { >>          unsigned long map_size, desc_size, total_slots = 0, target_slot; >> +       unsigned long total_mirrored_slots = 0; >>          unsigned long buff_size; >>          efi_status_t status; >>          efi_memory_desc_t *memory_map; >> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size, >>                  slots = get_entry_num_slots(md, size, ilog2(align)); >>                  MD_NUM_SLOTS(md) = slots; >>                  total_slots += slots; >> +               if (md->attribute & EFI_MEMORY_MORE_RELIABLE) >> +                       total_mirrored_slots += slots; >>          } >> >> +       /* only consider mirrored slots for randomization if any exist */ >> +       if (total_mirrored_slots > 0) >> +               total_slots = total_mirrored_slots; >> + >>          /* find a random number between 0 and total_slots */ >>          target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32; >> >> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size, >>                  efi_physical_addr_t target; >>                  unsigned long pages; >> >> +               if (total_mirrored_slots > 0 && >> +                   !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) >> +                       continue; >> + >>                  if (target_slot >= MD_NUM_SLOTS(md)) { >>                          target_slot -= MD_NUM_SLOTS(md); >>                          continue; >> .