From b8ff87a6158886771677e6dc8139bac6e3cba717 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 10 Jan 2014 15:54:31 +0000 Subject: [PATCH] x86/efi: Firmware agnostic handover entry points The EFI handover code only works if the "bitness" of the firmware and the kernel match, i.e. 64-bit firmware and 64-bit kernel - it is not possible to mix the two. This goes against the tradition that a 32-bit kernel can be loaded on a 64-bit BIOS platform without having to do anything special in the boot loader. Linux distributions, for one thing, regularly run only 32-bit kernels on their live media. Despite having only one 'handover_offset' field in the kernel header, EFI boot loaders use two separate entry points to enter the kernel based on the architecture the boot loader was compiled for, (1) 32-bit loader: handover_offset (2) 64-bit loader: handover_offset + 512 Since we already have two entry points, we can leverage them to infer the bitness of the firmware we're running on, without requiring any boot loader modifications, by making (1) and (2) valid entry points for both CONFIG_X86_32 and CONFIG_X86_64 kernels. To be clear, a 32-bit boot loader will always use (1) and a 64-bit boot loader will always use (2). It's just that, if a single kernel image supports (1) and (2) that image can be used with both 32-bit and 64-bit boot loaders, and hence both 32-bit and 64-bit EFI. (1) and (2) must be 512 bytes apart at all times, but that is already part of the boot ABI and we could never change that delta without breaking existing boot loaders anyhow. Signed-off-by: Matt Fleming --- arch/x86/boot/Makefile | 2 +- arch/x86/boot/compressed/eboot.c | 9 +++-- arch/x86/boot/compressed/head_32.S | 2 +- arch/x86/boot/compressed/head_64.S | 62 ++++++++++++++++++++++++++---- arch/x86/boot/tools/build.c | 22 +++++++---- arch/x86/include/asm/efi.h | 6 +-- 6 files changed, 80 insertions(+), 23 deletions(-) diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index 878df7e88cd4..abb9eba61b50 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -80,7 +80,7 @@ targets += voffset.h $(obj)/voffset.h: vmlinux FORCE $(call if_changed,voffset) -sed-zoffset := -e 's/^\([0-9a-fA-F]*\) . \(startup_32\|startup_64\|efi_pe_entry\|efi_stub_entry\|input_data\|_end\|z_.*\)$$/\#define ZO_\2 0x\1/p' +sed-zoffset := -e 's/^\([0-9a-fA-F]*\) . \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|z_.*\)$$/\#define ZO_\2 0x\1/p' quiet_cmd_zoffset = ZOFFSET $@ cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@ diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index ab1f3a2f1e1e..5e1ba4fa3f79 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -1256,12 +1256,13 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext, } static efi_status_t exit_boot(struct boot_params *boot_params, - void *handle) + void *handle, bool is64) { struct efi_info *efi = &boot_params->efi_info; unsigned long map_sz, key, desc_size; efi_memory_desc_t *mem_map; struct setup_data *e820ext; + const char *signature; __u32 e820ext_size; __u32 nr_desc, prev_nr_desc; efi_status_t status; @@ -1295,7 +1296,9 @@ get_map: goto get_map; /* Allocated memory, get map again */ } - memcpy(&efi->efi_loader_signature, EFI_LOADER_SIGNATURE, sizeof(__u32)); + signature = is64 ? EFI64_LOADER_SIGNATURE : EFI32_LOADER_SIGNATURE; + memcpy(&efi->efi_loader_signature, signature, sizeof(__u32)); + efi->efi_systab = (unsigned long)sys_table; efi->efi_memdesc_size = desc_size; efi->efi_memdesc_version = desc_version; @@ -1408,7 +1411,7 @@ struct boot_params *efi_main(struct efi_config *c, hdr->code32_start = bzimage_addr; } - status = exit_boot(boot_params, handle); + status = exit_boot(boot_params, handle, is64); if (status != EFI_SUCCESS) goto fail; diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index eed23c087d6c..cccc05f0681c 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -64,7 +64,7 @@ ENTRY(efi_pe_entry) pushl %ecx jmp 2f /* Skip efi_config initialization */ -ENTRY(efi_stub_entry) +ENTRY(efi32_stub_entry) add $0x4, %esp popl %ecx popl %edx diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 1bc206fa4bd0..37c741b0d2ac 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -178,6 +178,13 @@ ENTRY(startup_32) */ pushl $__KERNEL_CS leal startup_64(%ebp), %eax +#ifdef CONFIG_EFI_MIXED + movl efi32_config(%ebp), %ebx + cmp $0, %ebx + jz 1f + leal handover_entry(%ebp), %eax +1: +#endif pushl %eax /* Enter paged protected Mode, activating Long Mode */ @@ -188,6 +195,30 @@ ENTRY(startup_32) lret ENDPROC(startup_32) +#ifdef CONFIG_EFI_MIXED + .org 0x190 +ENTRY(efi32_stub_entry) + add $0x4, %esp /* Discard return address */ + popl %ecx + popl %edx + popl %esi + + leal (BP_scratch+4)(%esi), %esp + call 1f +1: pop %ebp + subl $1b, %ebp + + movl %ecx, efi32_config(%ebp) + movl %edx, efi32_config+8(%ebp) + sgdtl efi32_boot_gdt(%ebp) + + leal efi32_config(%ebp), %eax + movl %eax, efi_config(%ebp) + + jmp startup_32 +ENDPROC(efi32_stub_entry) +#endif + .code64 .org 0x200 ENTRY(startup_64) @@ -231,13 +262,7 @@ ENTRY(efi_pe_entry) mov %rax, %rsi jmp 2f /* Skip the relocation */ -ENTRY(efi_stub_entry) - movq %rdi, efi64_config(%rip) /* Handle */ - movq %rsi, efi64_config+8(%rip) /* EFI System table pointer */ - - leaq efi64_config(%rip), %rax - movq %rax, efi_config(%rip) - +handover_entry: call 1f 1: popq %rbp subq $1b, %rbp @@ -247,7 +272,6 @@ ENTRY(efi_stub_entry) */ movq efi_config(%rip), %rax addq %rbp, 88(%rax) - movq %rdx, %rsi 2: movq efi_config(%rip), %rdi call efi_main @@ -336,6 +360,20 @@ preferred_addr: leaq relocated(%rbx), %rax jmp *%rax +#ifdef CONFIG_EFI_STUB + .org 0x390 +ENTRY(efi64_stub_entry) + movq %rdi, efi64_config(%rip) /* Handle */ + movq %rsi, efi64_config+8(%rip) /* EFI System table pointer */ + + leaq efi64_config(%rip), %rax + movq %rax, efi_config(%rip) + + movq %rdx, %rsi + jmp handover_entry +ENDPROC(efi64_stub_entry) +#endif + .text relocated: @@ -404,6 +442,14 @@ gdt_end: efi_config: .quad 0 +#ifdef CONFIG_EFI_MIXED + .global efi32_config +efi32_config: + .fill 11,8,0 + .quad efi64_thunk + .byte 0 +#endif + .global efi64_config efi64_config: .fill 11,8,0 diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c index bf262077ec92..4f07df5ac5d9 100644 --- a/arch/x86/boot/tools/build.c +++ b/arch/x86/boot/tools/build.c @@ -53,7 +53,8 @@ int is_big_kernel; #define PECOFF_RELOC_RESERVE 0x20 -unsigned long efi_stub_entry; +unsigned long efi32_stub_entry; +unsigned long efi64_stub_entry; unsigned long efi_pe_entry; unsigned long startup_64; @@ -231,20 +232,26 @@ static void efi_stub_defaults(void) /* Defaults for old kernel */ #ifdef CONFIG_X86_32 efi_pe_entry = 0x10; - efi_stub_entry = 0x30; #else efi_pe_entry = 0x210; - efi_stub_entry = 0x230; startup_64 = 0x200; #endif } static void efi_stub_entry_update(void) { -#ifdef CONFIG_X86_64 /* Yes, this is really how we defined it :( */ - efi_stub_entry -= 0x200; + unsigned long addr = efi32_stub_entry; + +#ifdef CONFIG_X86_64 + /* Yes, this is really how we defined it :( */ + addr = efi64_stub_entry - 0x200; +#endif + +#ifdef CONFIG_EFI_MIXED + if (efi32_stub_entry != addr) + die("32-bit and 64-bit EFI entry points do not match\n"); #endif - put_unaligned_le32(efi_stub_entry, &buf[0x264]); + put_unaligned_le32(addr, &buf[0x264]); } #else @@ -289,7 +296,8 @@ static void parse_zoffset(char *fname) p = (char *)buf; while (p && *p) { - PARSE_ZOFS(p, efi_stub_entry); + PARSE_ZOFS(p, efi32_stub_entry); + PARSE_ZOFS(p, efi64_stub_entry); PARSE_ZOFS(p, efi_pe_entry); PARSE_ZOFS(p, startup_64); diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index 3d6b9f81cc68..85856868507b 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -19,9 +19,11 @@ */ #define EFI_OLD_MEMMAP EFI_ARCH_1 +#define EFI32_LOADER_SIGNATURE "EL32" +#define EFI64_LOADER_SIGNATURE "EL64" + #ifdef CONFIG_X86_32 -#define EFI_LOADER_SIGNATURE "EL32" extern unsigned long asmlinkage efi_call_phys(void *, ...); @@ -57,8 +59,6 @@ extern unsigned long asmlinkage efi_call_phys(void *, ...); #else /* !CONFIG_X86_32 */ -#define EFI_LOADER_SIGNATURE "EL64" - extern u64 efi_call0(void *fp); extern u64 efi_call1(void *fp, u64 arg1); extern u64 efi_call2(void *fp, u64 arg1, u64 arg2); -- 2.34.1