From: Greg Kroah-Hartman Date: Fri, 29 Jan 2021 10:49:41 +0000 (+0100) Subject: 4.9-stable patches X-Git-Tag: v4.4.254~3 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4d1112604a16c12832d564bfd5ae00dfef86a3cb;p=thirdparty%2Fkernel%2Fstable-queue.git 4.9-stable patches added patches: x86-boot-compressed-disable-relocation-relaxation.patch --- diff --git a/queue-4.9/series b/queue-4.9/series index d41ec4ee90c..a8a96bbf205 100644 --- a/queue-4.9/series +++ b/queue-4.9/series @@ -27,3 +27,4 @@ net_sched-avoid-shift-out-of-bounds-in-tcindex_set_parms.patch net-dsa-b53-fix-an-off-by-one-in-checking-vlan-vid.patch revert-mm-slub-fix-a-memory-leak-in-sysfs_slab_add.patch tracing-fix-race-in-trace_open-and-buffer-resize-call.patch +x86-boot-compressed-disable-relocation-relaxation.patch diff --git a/queue-4.9/x86-boot-compressed-disable-relocation-relaxation.patch b/queue-4.9/x86-boot-compressed-disable-relocation-relaxation.patch new file mode 100644 index 00000000000..817fd2dbfe5 --- /dev/null +++ b/queue-4.9/x86-boot-compressed-disable-relocation-relaxation.patch @@ -0,0 +1,90 @@ +From foo@baz Fri Jan 29 11:33:40 AM CET 2021 +From: Arvind Sankar +Date: Tue, 11 Aug 2020 20:43:08 -0400 +Subject: x86/boot/compressed: Disable relocation relaxation + +From: Arvind Sankar + +commit 09e43968db40c33a73e9ddbfd937f46d5c334924 upstream. + +The x86-64 psABI [0] specifies special relocation types +(R_X86_64_[REX_]GOTPCRELX) for indirection through the Global Offset +Table, semantically equivalent to R_X86_64_GOTPCREL, which the linker +can take advantage of for optimization (relaxation) at link time. This +is supported by LLD and binutils versions 2.26 onwards. + +The compressed kernel is position-independent code, however, when using +LLD or binutils versions before 2.27, it must be linked without the -pie +option. In this case, the linker may optimize certain instructions into +a non-position-independent form, by converting foo@GOTPCREL(%rip) to $foo. + +This potential issue has been present with LLD and binutils-2.26 for a +long time, but it has never manifested itself before now: + +- LLD and binutils-2.26 only relax + movq foo@GOTPCREL(%rip), %reg + to + leaq foo(%rip), %reg + which is still position-independent, rather than + mov $foo, %reg + which is permitted by the psABI when -pie is not enabled. + +- GCC happens to only generate GOTPCREL relocations on mov instructions. + +- CLang does generate GOTPCREL relocations on non-mov instructions, but + when building the compressed kernel, it uses its integrated assembler + (due to the redefinition of KBUILD_CFLAGS dropping -no-integrated-as), + which has so far defaulted to not generating the GOTPCRELX + relocations. + +Nick Desaulniers reports [1,2]: + + "A recent change [3] to a default value of configuration variable + (ENABLE_X86_RELAX_RELOCATIONS OFF -> ON) in LLVM now causes Clang's + integrated assembler to emit R_X86_64_GOTPCRELX/R_X86_64_REX_GOTPCRELX + relocations. LLD will relax instructions with these relocations based + on whether the image is being linked as position independent or not. + When not, then LLD will relax these instructions to use absolute + addressing mode (R_RELAX_GOT_PC_NOPIC). This causes kernels built with + Clang and linked with LLD to fail to boot." + +Patch series [4] is a solution to allow the compressed kernel to be +linked with -pie unconditionally, but even if merged is unlikely to be +backported. As a simple solution that can be applied to stable as well, +prevent the assembler from generating the relaxed relocation types using +the -mrelax-relocations=no option. For ease of backporting, do this +unconditionally. + +[0] https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/linker-optimization.tex#L65 +[1] https://lore.kernel.org/lkml/20200807194100.3570838-1-ndesaulniers@google.com/ +[2] https://github.com/ClangBuiltLinux/linux/issues/1121 +[3] https://reviews.llvm.org/rGc41a18cf61790fc898dcda1055c3efbf442c14c0 +[4] https://lore.kernel.org/lkml/20200731202738.2577854-1-nivedita@alum.mit.edu/ + +Reported-by: Nick Desaulniers +Signed-off-by: Arvind Sankar +Signed-off-by: Ingo Molnar +Tested-by: Nick Desaulniers +Tested-by: Sedat Dilek +Acked-by: Ard Biesheuvel +Reviewed-by: Nick Desaulniers +Cc: stable@vger.kernel.org +Link: https://lore.kernel.org/r/20200812004308.1448603-1-nivedita@alum.mit.edu +[nc: Backport to 4.9] +Signed-off-by: Nathan Chancellor +Signed-off-by: Greg Kroah-Hartman +--- + arch/x86/boot/compressed/Makefile | 2 ++ + 1 file changed, 2 insertions(+) + +--- a/arch/x86/boot/compressed/Makefile ++++ b/arch/x86/boot/compressed/Makefile +@@ -35,6 +35,8 @@ KBUILD_CFLAGS += -mno-mmx -mno-sse + KBUILD_CFLAGS += $(call cc-option,-ffreestanding) + KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector) + KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) ++# Disable relocation relaxation in case the link is not PIE. ++KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no) + + KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ + GCOV_PROFILE := n