This series adds the ability to use the entire PE image space for decompression, provides the preferred address to the PE loader via the header, and finally restricts efi_relocate_kernel to cases where we really need it rather than whenever we were loaded at something other than preferred address. Based on tip:efi/core + the cleanup series [1] [1] https://lore.kernel.org/linux-efi/20200301230436.2246909-1-nivedita@xxxxxxxxxxxx/ Changes from v1 - clarify a few comments - cleanups to code formatting Arvind Sankar (5): x86/boot/compressed/32: Save the output address instead of recalculating it efi/x86: Decompress at start of PE image load address efi/x86: Add kernel preferred address to PE header efi/x86: Remove extra headroom for setup block efi/x86: Don't relocate the kernel unless necessary arch/x86/boot/compressed/head_32.S | 42 +++++++++++++++------- arch/x86/boot/compressed/head_64.S | 42 ++++++++++++++++++++-- arch/x86/boot/header.S | 6 ++-- arch/x86/boot/tools/build.c | 44 ++++++++++++++++------- drivers/firmware/efi/libstub/x86-stub.c | 48 ++++++++++++++++++++++--- 5 files changed, 147 insertions(+), 35 deletions(-) Range-diff against v1: 1: 0cdb6bf27a24 ! 1: 2ecbf60b9ecd x86/boot/compressed/32: Save the output address instead of recalculating it @@ Metadata ## Commit message ## x86/boot/compressed/32: Save the output address instead of recalculating it - In preparation for being able to decompress starting at a different - address than startup_32, save the calculated output address instead of - recalculating it later. + In preparation for being able to decompress into a buffer starting at a + different address than startup_32, save the calculated output address + instead of recalculating it later. We now keep track of three addresses: %edx: startup_32 as we were loaded by bootloader 2: d4df840752ac ! 2: e2bdbe6cb692 efi/x86: Decompress at start of PE image load address @@ arch/x86/boot/compressed/head_64.S: SYM_FUNC_START(efi32_pe_entry) movl -4(%ebp), %esi // loaded_image movl LI32_image_base(%esi), %esi // loaded_image->image_base movl %ebx, %ebp // startup_32 for efi32_pe_stub_entry ++ /* ++ * We need to set the image_offset variable here since startup_32 will ++ * use it before we get to the 64-bit efi_pe_entry in C code. ++ */ + subl %esi, %ebx + movl %ebx, image_offset(%ebp) // save image_offset jmp efi32_pe_stub_entry @@ drivers/firmware/efi/libstub/x86-stub.c: unsigned long efi_main(efi_handle_t han efi_printk("efi_relocate_kernel() failed!\n"); goto fail; } ++ /* ++ * Now that we've copied the kernel elsewhere, we no longer ++ * have a setup block before startup_32, so reset image_offset ++ * to zero in case it was set earlier. ++ */ + image_offset = 0; } 3: 4bae68f25b90 ! 3: ea840f78f138 efi/x86: Add kernel preferred address to PE header @@ arch/x86/boot/header.S: optional_header: extra_header_fields: + # PE specification requires ImageBase to be 64k-aligned -+ .set ImageBase, (LOAD_PHYSICAL_ADDR+0xffff) & ~0xffff ++ .set image_base, (LOAD_PHYSICAL_ADDR + 0xffff) & ~0xffff #ifdef CONFIG_X86_32 - .long 0 # ImageBase -+ .long ImageBase # ImageBase ++ .long image_base # ImageBase #else - .quad 0 # ImageBase -+ .quad ImageBase # ImageBase ++ .quad image_base # ImageBase #endif .long 0x20 # SectionAlignment .long 0x20 # FileAlignment 4: 2330a25c6b0f ! 4: c25a9b507d6d efi/x86: Remove extra headroom for setup block @@ Commit message account for setup block") added headroom to the PE image to account for the setup block, which wasn't used for the decompression buffer. - Now that we decompress from the start of the image, this is no longer - required. + Now that the decompression buffer is located at the start of the image, + and includes the setup block, this is no longer required. Add a check to make sure that the head section of the compressed kernel won't overwrite itself while relocating. This is only for 5: 2081f91cbe75 ! 5: d3dc3af1c7b8 efi/x86: Don't relocate the kernel unless necessary @@ arch/x86/boot/tools/build.c: static void update_pecoff_text(unsigned int text_st * Size of code: Subtract the size of the first sector (512 bytes) ## drivers/firmware/efi/libstub/x86-stub.c ## +@@ + + #include "efistub.h" + ++/* Maximum physical address for 64-bit kernel with 4-level paging */ ++#define MAXMEM_X86_64_4LEVEL (1ull << 46) ++ + static efi_system_table_t *sys_table; + extern const bool efi_is64; + extern u32 image_offset; @@ drivers/firmware/efi/libstub/x86-stub.c: unsigned long efi_main(efi_handle_t handle, struct boot_params *boot_params) { @@ drivers/firmware/efi/libstub/x86-stub.c: unsigned long efi_main(efi_handle_t han - * address, relocate it. + * If the kernel isn't already loaded at a suitable address, + * relocate it. ++ * + * It must be loaded above LOAD_PHYSICAL_ADDR. -+ * The maximum address for 64-bit is 1 << 46 for 4-level paging. ++ * ++ * The maximum address for 64-bit is 1 << 46 for 4-level paging. This ++ * is defined as the macro MAXMEM, but unfortunately that is not a ++ * compile-time constant if 5-level paging is configured, so we instead ++ * define our own macro for use here. ++ * + * For 32-bit, the maximum address is complicated to figure out, for + * now use KERNEL_IMAGE_SIZE, which will be 512MiB, the same as what + * KASLR uses. ++ * + * Also relocate it if image_offset is zero, i.e. we weren't loaded by + * LoadImage, but we are not aligned correctly. */ - if (bzimage_addr - image_offset != hdr->pref_address) { ++ + buffer_start = ALIGN(bzimage_addr - image_offset, + hdr->kernel_alignment); + buffer_end = buffer_start + hdr->init_size; + -+ if (buffer_start < LOAD_PHYSICAL_ADDR -+ || IS_ENABLED(CONFIG_X86_32) && buffer_end > KERNEL_IMAGE_SIZE -+ || IS_ENABLED(CONFIG_X86_64) && buffer_end > 1ull << 46 -+ || image_offset == 0 && !IS_ALIGNED(bzimage_addr, -+ hdr->kernel_alignment)) { ++ if ((buffer_start < LOAD_PHYSICAL_ADDR) || ++ (IS_ENABLED(CONFIG_X86_32) && buffer_end > KERNEL_IMAGE_SIZE) || ++ (IS_ENABLED(CONFIG_X86_64) && buffer_end > MAXMEM_X86_64_4LEVEL) || ++ (image_offset == 0 && !IS_ALIGNED(bzimage_addr, ++ hdr->kernel_alignment))) { status = efi_relocate_kernel(&bzimage_addr, hdr->init_size, hdr->init_size, hdr->pref_address, -- 2.24.1
