Commit-ID: b1994304fc399f5d3a5368c81111d713490c4799 Gitweb: http://git.kernel.org/tip/b1994304fc399f5d3a5368c81111d713490c4799 Author: Matt Fleming <matt.fleming@xxxxxxxxx> AuthorDate: Sun, 15 Apr 2012 16:06:04 +0100 Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> CommitDate: Mon, 16 Apr 2012 11:41:44 -0700 x86, efi: Add dedicated EFI stub entry point The method used to work out whether we were booted by EFI firmware or via a boot loader is broken. Because efi_main() is always executed when booting from a boot loader we will dereference invalid pointers either on the stack (CONFIG_X86_32) or contained in %rdx (CONFIG_X86_64) when searching for an EFI System Table signature. Instead of dereferencing these invalid system table pointers, add a new entry point that is only used when booting from EFI firmware, when we know the pointer arguments will be valid. With this change legacy boot loaders will no longer execute efi_main(), but will instead skip EFI stub initialisation completely. [ hpa: Marking this for urgent/stable since it is a regression when the option is enabled; without the option the patch has no effect ] Signed-off-by: Matt Fleming <matt.hfleming@xxxxxxxxx> Link: http://lkml.kernel.org/r/1334584744.26997.14.camel@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Reported-by: Jordan Justen <jordan.l.justen@xxxxxxxxx> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> v3.3 --- arch/x86/boot/compressed/head_32.S | 14 +++++++++++--- arch/x86/boot/compressed/head_64.S | 22 ++++++++++++++++------ arch/x86/boot/tools/build.c | 15 +++++++++++---- 3 files changed, 38 insertions(+), 13 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index a055993..c85e3ac 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -33,6 +33,9 @@ __HEAD ENTRY(startup_32) #ifdef CONFIG_EFI_STUB + jmp preferred_addr + + .balign 0x10 /* * We don't need the return address, so set up the stack so * efi_main() can find its arugments. @@ -41,12 +44,17 @@ ENTRY(startup_32) call efi_main cmpl $0, %eax - je preferred_addr movl %eax, %esi - call 1f + jne 2f 1: + /* EFI init failed, so hang. */ + hlt + jmp 1b +2: + call 3f +3: popl %eax - subl $1b, %eax + subl $3b, %eax subl BP_pref_address(%esi), %eax add BP_code32_start(%esi), %eax leal preferred_addr(%eax), %eax diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 558d76c..87e03a1 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -200,18 +200,28 @@ ENTRY(startup_64) * entire text+data+bss and hopefully all of memory. */ #ifdef CONFIG_EFI_STUB - pushq %rsi + /* + * The entry point for the PE/COFF executable is 0x210, so only + * legacy boot loaders will execute this jmp. + */ + jmp preferred_addr + + .org 0x210 mov %rcx, %rdi mov %rdx, %rsi call efi_main - popq %rsi - cmpq $0,%rax - je preferred_addr movq %rax,%rsi - call 1f + cmpq $0,%rax + jne 2f 1: + /* EFI init failed, so hang. */ + hlt + jmp 1b +2: + call 3f +3: popq %rax - subq $1b, %rax + subq $3b, %rax subq BP_pref_address(%rsi), %rax add BP_code32_start(%esi), %eax leaq preferred_addr(%rax), %rax diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c index ed54976..24443a3 100644 --- a/arch/x86/boot/tools/build.c +++ b/arch/x86/boot/tools/build.c @@ -205,8 +205,13 @@ int main(int argc, char ** argv) put_unaligned_le32(file_sz, &buf[pe_header + 0x50]); #ifdef CONFIG_X86_32 - /* Address of entry point */ - put_unaligned_le32(i, &buf[pe_header + 0x28]); + /* + * Address of entry point. + * + * The EFI stub entry point is +16 bytes from the start of + * the .text section. + */ + put_unaligned_le32(i + 16, &buf[pe_header + 0x28]); /* .text size */ put_unaligned_le32(file_sz, &buf[pe_header + 0xb0]); @@ -217,9 +222,11 @@ int main(int argc, char ** argv) /* * Address of entry point. startup_32 is at the beginning and * the 64-bit entry point (startup_64) is always 512 bytes - * after. + * after. The EFI stub entry point is 16 bytes after that, as + * the first instruction allows legacy loaders to jump over + * the EFI stub initialisation */ - put_unaligned_le32(i + 512, &buf[pe_header + 0x28]); + put_unaligned_le32(i + 528, &buf[pe_header + 0x28]); /* .text size */ put_unaligned_le32(file_sz, &buf[pe_header + 0xc0]); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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