From 1887c9b653f99577c0f8ec413b0921a32b6129e2 Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Sun, 8 Mar 2020 09:08:47 +0100 Subject: [PATCH] efi/x86: Decompress at start of PE image load address When booted via PE loader, define image_offset to hold the offset of startup_32() from the start of the PE image, and use it as the start of the decompression buffer. [ mingo: Fixed the grammar in the comments. ] Signed-off-by: Arvind Sankar Signed-off-by: Ard Biesheuvel Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200303221205.4048668-3-nivedita@alum.mit.edu Link: https://lore.kernel.org/r/20200308080859.21568-17-ardb@kernel.org --- arch/x86/boot/compressed/head_32.S | 17 +++++++++++++ arch/x86/boot/compressed/head_64.S | 42 ++++++++++++++++++++++++++++++--- drivers/firmware/efi/libstub/x86-stub.c | 17 ++++++++++--- 3 files changed, 70 insertions(+), 6 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 8941825..ab33070 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -100,6 +100,19 @@ SYM_FUNC_START(startup_32) #ifdef CONFIG_RELOCATABLE movl %edx, %ebx + +#ifdef CONFIG_EFI_STUB +/* + * If we were loaded via the EFI LoadImage service, startup_32() will be at an + * offset to the start of the space allocated for the image. efi_pe_entry() will + * set up image_offset to tell us where the image actually starts, so that we + * can use the full available buffer. + * image_offset = startup_32 - image_base + * Otherwise image_offset will be zero and has no effect on the calculations. + */ + subl image_offset(%edx), %ebx +#endif + movl BP_kernel_alignment(%esi), %eax decl %eax addl %eax, %ebx @@ -226,6 +239,10 @@ SYM_DATA_START_LOCAL(gdt) .quad 0x00cf92000000ffff /* __KERNEL_DS */ SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) +#ifdef CONFIG_EFI_STUB +SYM_DATA(image_offset, .long 0) +#endif + /* * Stack and heap for uncompression */ diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 5d8338a6..d4657d3 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -99,6 +99,19 @@ SYM_FUNC_START(startup_32) #ifdef CONFIG_RELOCATABLE movl %ebp, %ebx + +#ifdef CONFIG_EFI_STUB +/* + * If we were loaded via the EFI LoadImage service, startup_32 will be at an + * offset to the start of the space allocated for the image. efi_pe_entry will + * set up image_offset to tell us where the image actually starts, so that we + * can use the full available buffer. + * image_offset = startup_32 - image_base + * Otherwise image_offset will be zero and has no effect on the calculations. + */ + subl image_offset(%ebp), %ebx +#endif + movl BP_kernel_alignment(%esi), %eax decl %eax addl %eax, %ebx @@ -111,9 +124,8 @@ SYM_FUNC_START(startup_32) 1: /* Target address to relocate to for decompression */ - movl BP_init_size(%esi), %eax - subl $_end, %eax - addl %eax, %ebx + addl BP_init_size(%esi), %ebx + subl $_end, %ebx /* * Prepare for entering 64 bit mode @@ -299,6 +311,20 @@ SYM_CODE_START(startup_64) /* Start with the delta to where the kernel will run at. */ #ifdef CONFIG_RELOCATABLE leaq startup_32(%rip) /* - $startup_32 */, %rbp + +#ifdef CONFIG_EFI_STUB +/* + * If we were loaded via the EFI LoadImage service, startup_32 will be at an + * offset to the start of the space allocated for the image. efi_pe_entry will + * set up image_offset to tell us where the image actually starts, so that we + * can use the full available buffer. + * image_offset = startup_32 - image_base + * Otherwise image_offset will be zero and has no effect on the calculations. + */ + movl image_offset(%rip), %eax + subq %rax, %rbp +#endif + movl BP_kernel_alignment(%rsi), %eax decl %eax addq %rax, %rbp @@ -647,6 +673,10 @@ SYM_DATA_START_LOCAL(gdt) .quad 0x0000000000000000 /* TS continued */ SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) +#ifdef CONFIG_EFI_STUB +SYM_DATA(image_offset, .long 0) +#endif + #ifdef CONFIG_EFI_MIXED SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0) SYM_DATA(efi_is64, .byte 1) @@ -712,6 +742,12 @@ 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 2: popl %edi // restore callee-save registers diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index 69a942f..3e1bc8a 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -19,6 +19,7 @@ static efi_system_table_t *sys_table; extern const bool efi_is64; +extern u32 image_offset; __pure efi_system_table_t *efi_system_table(void) { @@ -365,6 +366,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, struct boot_params *boot_params; struct setup_header *hdr; efi_loaded_image_t *image; + void *image_base; efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID; int options_size = 0; efi_status_t status; @@ -385,7 +387,10 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, efi_exit(handle, status); } - hdr = &((struct boot_params *)efi_table_attr(image, image_base))->hdr; + image_base = efi_table_attr(image, image_base); + image_offset = (void *)startup_32 - image_base; + + hdr = &((struct boot_params *)image_base)->hdr; above4g = hdr->xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G; status = efi_allocate_pages(0x4000, (unsigned long *)&boot_params, @@ -400,7 +405,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, hdr = &boot_params->hdr; /* Copy the second sector to boot_params */ - memcpy(&hdr->jump, efi_table_attr(image, image_base) + 512, 512); + memcpy(&hdr->jump, image_base + 512, 512); /* * Fill out some of the header fields ourselves because the @@ -727,7 +732,7 @@ unsigned long efi_main(efi_handle_t handle, * If the kernel isn't already loaded at the preferred load * address, relocate it. */ - if (bzimage_addr != hdr->pref_address) { + if (bzimage_addr - image_offset != hdr->pref_address) { status = efi_relocate_kernel(&bzimage_addr, hdr->init_size, hdr->init_size, hdr->pref_address, @@ -737,6 +742,12 @@ unsigned long efi_main(efi_handle_t handle, efi_printk("efi_relocate_kernel() failed!\n"); goto fail; } + /* + * Now that we've copied the kernel elsewhere, we no longer + * have a set up block before startup_32(), so reset image_offset + * to zero in case it was set earlier. + */ + image_offset = 0; } /* -- 2.7.4