| Message ID | 1459352589-28721-3-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | 546c8c44f092b2f23291fe499c221efc8cabbb67 |
| Headers | show |
Hi Ard, On Wed, Mar 30, 2016 at 05:43:07PM +0200, Ard Biesheuvel wrote: > Apart from the arm64/linux and EFI header data structures, there is nothing > in the .head.text section that must reside at the beginning of the Image. > So let's move it to the .init section where it belongs. > > Note that this involves some minor tweaking of the EFI header, primarily > because the address of 'stext' no longer coincides with the start of the > .text section. It also requires a couple of relocated symbol references > to be slightly rewritten or their definition moved to the linker script. [...] > ENTRY(stext) > bl preserve_boot_args > bl el2_setup // Drop to EL1, w20=cpu_boot_mode > @@ -223,12 +224,12 @@ ENTRY(stext) > * the TCR will have been set. > */ > ldr x27, 0f // address to jump to after > - // MMU has been enabled > + neg x27, x27 // MMU has been enabled > adr_l lr, __enable_mmu // return (PIC) address > b __cpu_setup // initialise processor > ENDPROC(stext) > .align 3 > -0: .quad __mmap_switched - (_head - TEXT_OFFSET) + KIMAGE_VADDR > +0: .quad (_text - TEXT_OFFSET) - __mmap_switched - KIMAGE_VADDR I'm struggling to understand why you need to change this. Furthermore, it looks like the gas docs for expressions require that addition/subtraction can only be performed on arguments that are in the same section, so this feels pretty rickety. What's the problem you're solving here? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 14 April 2016 at 18:32, Will Deacon <will.deacon@arm.com> wrote: > Hi Ard, > > On Wed, Mar 30, 2016 at 05:43:07PM +0200, Ard Biesheuvel wrote: >> Apart from the arm64/linux and EFI header data structures, there is nothing >> in the .head.text section that must reside at the beginning of the Image. >> So let's move it to the .init section where it belongs. >> >> Note that this involves some minor tweaking of the EFI header, primarily >> because the address of 'stext' no longer coincides with the start of the >> .text section. It also requires a couple of relocated symbol references >> to be slightly rewritten or their definition moved to the linker script. > > [...] > >> ENTRY(stext) >> bl preserve_boot_args >> bl el2_setup // Drop to EL1, w20=cpu_boot_mode >> @@ -223,12 +224,12 @@ ENTRY(stext) >> * the TCR will have been set. >> */ >> ldr x27, 0f // address to jump to after >> - // MMU has been enabled >> + neg x27, x27 // MMU has been enabled >> adr_l lr, __enable_mmu // return (PIC) address >> b __cpu_setup // initialise processor >> ENDPROC(stext) >> .align 3 >> -0: .quad __mmap_switched - (_head - TEXT_OFFSET) + KIMAGE_VADDR >> +0: .quad (_text - TEXT_OFFSET) - __mmap_switched - KIMAGE_VADDR > > I'm struggling to understand why you need to change this. Furthermore, > it looks like the gas docs for expressions require that addition/subtraction > can only be performed on arguments that are in the same section, so > this feels pretty rickety. > > What's the problem you're solving here? > The problem is that this function is no longer in the same section as _head aka _text, so the latter can only appear in the reloc expression as a positive term, and the remaining ones will all be combined into the addend. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S index cae3112f7791..e88c064b845c 100644 --- a/arch/arm64/kernel/efi-entry.S +++ b/arch/arm64/kernel/efi-entry.S @@ -62,7 +62,7 @@ ENTRY(entry) */ mov x20, x0 // DTB address ldr x0, [sp, #16] // relocated _text address - movz x21, #:abs_g0:stext_offset + ldr w21, =stext_offset add x21, x0, x21 /* diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 4203d5f257bc..b43417618847 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -102,8 +102,6 @@ _head: #endif #ifdef CONFIG_EFI - .globl __efistub_stext_offset - .set __efistub_stext_offset, stext - _head .align 3 pe_header: .ascii "PE" @@ -123,11 +121,11 @@ optional_header: .short 0x20b // PE32+ format .byte 0x02 // MajorLinkerVersion .byte 0x14 // MinorLinkerVersion - .long _end - stext // SizeOfCode + .long _end - efi_header_end // SizeOfCode .long 0 // SizeOfInitializedData .long 0 // SizeOfUninitializedData .long __efistub_entry - _head // AddressOfEntryPoint - .long __efistub_stext_offset // BaseOfCode + .long efi_header_end - _head // BaseOfCode extra_header_fields: .quad 0 // ImageBase @@ -144,7 +142,7 @@ extra_header_fields: .long _end - _head // SizeOfImage // Everything before the kernel image is considered part of the header - .long __efistub_stext_offset // SizeOfHeaders + .long efi_header_end - _head // SizeOfHeaders .long 0 // CheckSum .short 0xa // Subsystem (EFI application) .short 0 // DllCharacteristics @@ -188,10 +186,10 @@ section_table: .byte 0 .byte 0 .byte 0 // end of 0 padding of section name - .long _end - stext // VirtualSize - .long __efistub_stext_offset // VirtualAddress - .long _edata - stext // SizeOfRawData - .long __efistub_stext_offset // PointerToRawData + .long _end - efi_header_end // VirtualSize + .long efi_header_end - _head // VirtualAddress + .long _edata - efi_header_end // SizeOfRawData + .long efi_header_end - _head // PointerToRawData .long 0 // PointerToRelocations (0 for executables) .long 0 // PointerToLineNumbers (0 for executables) @@ -200,15 +198,18 @@ section_table: .long 0xe0500020 // Characteristics (section flags) /* - * EFI will load stext onwards at the 4k section alignment + * EFI will load .text onwards at the 4k section alignment * described in the PE/COFF header. To ensure that instruction * sequences using an adrp and a :lo12: immediate will function - * correctly at this alignment, we must ensure that stext is + * correctly at this alignment, we must ensure that .text is * placed at a 4k boundary in the Image to begin with. */ .align 12 +efi_header_end: #endif + __INIT + ENTRY(stext) bl preserve_boot_args bl el2_setup // Drop to EL1, w20=cpu_boot_mode @@ -223,12 +224,12 @@ ENTRY(stext) * the TCR will have been set. */ ldr x27, 0f // address to jump to after - // MMU has been enabled + neg x27, x27 // MMU has been enabled adr_l lr, __enable_mmu // return (PIC) address b __cpu_setup // initialise processor ENDPROC(stext) .align 3 -0: .quad __mmap_switched - (_head - TEXT_OFFSET) + KIMAGE_VADDR +0: .quad (_text - TEXT_OFFSET) - __mmap_switched - KIMAGE_VADDR /* * Preserve the arguments passed by the bootloader in x0 .. x3 @@ -397,7 +398,7 @@ __create_page_tables: ldr x5, =KIMAGE_VADDR add x5, x5, x23 // add KASLR displacement create_pgd_entry x0, x5, x3, x6 - ldr w6, kernel_img_size + ldr w6, =kernel_img_size add x6, x6, x5 mov x3, x24 // phys offset create_block_map x0, x7, x3, x5, x6 @@ -414,9 +415,6 @@ __create_page_tables: ret x28 ENDPROC(__create_page_tables) - -kernel_img_size: - .long _end - (_head - TEXT_OFFSET) .ltorg /* diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h index 5e360ce88f10..4fd72da646a3 100644 --- a/arch/arm64/kernel/image.h +++ b/arch/arm64/kernel/image.h @@ -71,8 +71,12 @@ DEFINE_IMAGE_LE64(_kernel_offset_le, TEXT_OFFSET); \ DEFINE_IMAGE_LE64(_kernel_flags_le, __HEAD_FLAGS); +kernel_img_size = _end - (_text - TEXT_OFFSET); + #ifdef CONFIG_EFI +__efistub_stext_offset = stext - _text; + /* * Prevent the symbol aliases below from being emitted into the kallsyms * table, by forcing them to be absolute symbols (which are conveniently
Apart from the arm64/linux and EFI header data structures, there is nothing in the .head.text section that must reside at the beginning of the Image. So let's move it to the .init section where it belongs. Note that this involves some minor tweaking of the EFI header, primarily because the address of 'stext' no longer coincides with the start of the .text section. It also requires a couple of relocated symbol references to be slightly rewritten or their definition moved to the linker script. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/efi-entry.S | 2 +- arch/arm64/kernel/head.S | 32 +++++++++----------- arch/arm64/kernel/image.h | 4 +++ 3 files changed, 20 insertions(+), 18 deletions(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel