After the EFI stub has done its business, it jumps into the kernel by branching to offset #0 of the loaded Image, which is where it expects to find the header containing a 'branch to stext' instruction.
However, the UEFI spec 2.1.1 states the following regarding PE/COFF image loading: "A UEFI image is loaded into memory through the LoadImage() Boot Service. This service loads an image with a PE32+ format into memory. This PE32+ loader is required to load all sections of the PE32+ image into memory." In other words, it is /not/ required to load parts of the image that are not covered by a PE/COFF section, so it may not have loaded the header at the expected offset, as it is not covered by any PE/COFF section. So instead, jump to 'stext' directly, which is at the base of the PE/COFF .text section, by supplying a symbol 'stext_offset' to efi-entry.o which contains the relative offset of stext into the Image. Also replace other open coded calculations of the same value with a reference to 'stext_offset' Signed-off-by: Ard Biesheuvel <[email protected]> --- Changes since v2: - rebased onto 3.17+ - added spec reference to commit message Changes since v1: - drop :lo12: relocation against stext_offset in favor of using a literal '=stext_offset' which is safer arch/arm64/kernel/efi-entry.S | 3 ++- arch/arm64/kernel/head.S | 10 ++++++---- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S index 619b1dd7bcde..a0016d3a17da 100644 --- a/arch/arm64/kernel/efi-entry.S +++ b/arch/arm64/kernel/efi-entry.S @@ -61,7 +61,8 @@ ENTRY(efi_stub_entry) */ mov x20, x0 // DTB address ldr x0, [sp, #16] // relocated _text address - mov x21, x0 + ldr x21, =stext_offset + add x21, x0, x21 /* * Flush dcache covering current runtime addresses diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 0a6e4f924df8..8c06c9d269d2 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -132,6 +132,8 @@ efi_head: #endif #ifdef CONFIG_EFI + .globl stext_offset + .set stext_offset, stext - efi_head .align 3 pe_header: .ascii "PE" @@ -155,7 +157,7 @@ optional_header: .long 0 // SizeOfInitializedData .long 0 // SizeOfUninitializedData .long efi_stub_entry - efi_head // AddressOfEntryPoint - .long stext - efi_head // BaseOfCode + .long stext_offset // BaseOfCode extra_header_fields: .quad 0 // ImageBase @@ -172,7 +174,7 @@ extra_header_fields: .long _end - efi_head // SizeOfImage // Everything before the kernel image is considered part of the header - .long stext - efi_head // SizeOfHeaders + .long stext_offset // SizeOfHeaders .long 0 // CheckSum .short 0xa // Subsystem (EFI application) .short 0 // DllCharacteristics @@ -217,9 +219,9 @@ section_table: .byte 0 .byte 0 // end of 0 padding of section name .long _end - stext // VirtualSize - .long stext - efi_head // VirtualAddress + .long stext_offset // VirtualAddress .long _edata - stext // SizeOfRawData - .long stext - efi_head // PointerToRawData + .long stext_offset // PointerToRawData .long 0 // PointerToRelocations (0 for executables) .long 0 // PointerToLineNumbers (0 for executables) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
