x86/build: Build compressed x86 kernels as PIE

2017-04-11T08:57:47+00:00

commit 6d92bc9d483aa1751755a66fee8fb39dffb088c0 upstream. The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X relocation to get the symbol address in PIC. When the compressed x86 kernel isn't built as PIC, the linker optimizes R_386_GOT32X relocations to their fixed symbol addresses. However, when the compressed x86 kernel is loaded at a different address, it leads to the following load failure: Failed to allocate space for phdrs during the decompression stage. If the compressed x86 kernel is relocatable at run-time, it should be compiled with -fPIE, instead of -fPIC, if possible and should be built as Position Independent Executable (PIE) so that linker won't optimize R_386_GOT32X relocation to its fixed symbol address. Older linkers generate R_386_32 relocations against locally defined symbols, _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle R_386_32 relocations when relocating the kernel. To generate R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as hidden in both 32-bit and 64-bit x86 kernels. To build a 64-bit compressed x86 kernel as PIE, we need to disable the relocation overflow check to avoid relocation overflow errors. We do this with a new linker command-line option, -z noreloc-overflow, which got added recently: commit 4c10bbaa0912742322f10d9d5bb630ba4e15dfa7 Author: H.J. Lu Date: Tue Mar 15 11:07:06 2016 -0700 Add -z noreloc-overflow option to x86-64 ld Add -z noreloc-overflow command-line option to the x86-64 ELF linker to disable relocation overflow check. This can be used to avoid relocation overflow check if there will be no dynamic relocation overflow at run-time. The 64-bit compressed x86 kernel is built as PIE only if the linker supports -z noreloc-overflow. So far 64-bit relocatable compressed x86 kernel boots fine even when it is built as a normal executable. Signed-off-by: H.J. Lu Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org [ Edited the changelog and comments. ] Signed-off-by: Ingo Molnar Signed-off-by: Willy Tarreau

efi: fix 32bit kernel boot failed problem using efi

2016-08-26T17:58:54+00:00

Commit 35d5134b7d5a ("x86/efi: Correct EFI boot stub use of code32_start") imported a bug, which will cause 32bit kernel boot failed using efi method. It should use the label's address instead of the value stored in the label to caculate the address of code32_start. Signed-off-by: Fupan Li Reviewed-by: Matt Fleming Signed-off-by: Stefan Guendhoer

first commit

2016-08-15T02:19:42+00:00

xavi/android_kernel_m2note/arch/x86/boot/compressed, branch ng-7.1.2

x86/build: Build compressed x86 kernels as PIE

efi: fix 32bit kernel boot failed problem using efi

first commit