kernel.git/arch/arm64/Makefile, branch linux-4.14.y

arm64: link with -z norelro regardless of CONFIG_RELOCATABLE

2020-11-05T10:06:51Z

commit 3b92fa7485eba16b05166fddf38ab42f2ff6ab95 upstream. With CONFIG_EXPERT=y, CONFIG_KASAN=y, CONFIG_RANDOMIZE_BASE=n, CONFIG_RELOCATABLE=n, we observe the following failure when trying to link the kernel image with LD=ld.lld: error: section: .exit.data is not contiguous with other relro sections ld.lld defaults to -z relro while ld.bfd defaults to -z norelro. This was previously fixed, but only for CONFIG_RELOCATABLE=y. Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options") Signed-off-by: Nick Desaulniers Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201016175339.2429280-1-ndesaulniers@google.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: makefile fix build of .i file in external module case

2019-12-01T08:13:59Z

[ Upstream commit 98356eb0ae499c63e78073ccedd9a5fc5c563288 ] After 'a66649dab350 arm64: fix vdso-offsets.h dependency' if one will try to build .i file in case of external kernel module, build fails complaining that prepare0 target is missing. This issue came up with SystemTap when it tries to build variety of .i files for its own generated kernel modules trying to figure given kernel features/capabilities. The issue is that prepare0 is defined in top level Makefile only if KBUILD_EXTMOD is not defined. .i file rule depends on prepare and in case KBUILD_EXTMOD defined top level Makefile contains empty rule for prepare. But after mentioned commit arch/arm64/Makefile would introduce dependency on prepare0 through its own prepare target. Fix it to put proper ifdef KBUILD_EXTMOD around code introduced by mentioned commit. It matches what top level Makefile does. Acked-by: Kevin Brodsky Signed-off-by: Victor Kamensky Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin

arm64: relocatable: fix inconsistencies in linker script and options

2019-01-13T09:01:06Z

commit 3bbd3db86470c701091fb1d67f1fab6621debf50 upstream. readelf complains about the section layout of vmlinux when building with CONFIG_RELOCATABLE=y (for KASLR): readelf: Warning: [21]: Link field (0) should index a symtab section. readelf: Warning: [21]: Info field (0) should index a relocatable section. Also, it seems that our use of '-pie -shared' is contradictory, and thus ambiguous. In general, the way KASLR is wired up at the moment is highly tailored to how ld.bfd happens to implement (and conflate) PIE executables and shared libraries, so given the current effort to support other toolchains, let's fix some of these issues as well. - Drop the -pie linker argument and just leave -shared. In ld.bfd, the differences between them are unclear (except for the ELF type of the produced image [0]) but lld chokes on seeing both at the same time. - Rename the .rela output section to .rela.dyn, as is customary for shared libraries and PIE executables, so that it is not misidentified by readelf as a static relocation section (producing the warnings above). - Pass the -z notext and -z norelro options to explicitly instruct the linker to permit text relocations, and to omit the RELRO program header (which requires a certain section layout that we don't adhere to in the kernel). These are the defaults for current versions of ld.bfd. - Discard .eh_frame and .gnu.hash sections to avoid them from being emitted between .head.text and .text, screwing up the section layout. These changes only affect the ELF image, and produce the same binary image. [0] b9dce7f1ba01 ("arm64: kernel: force ET_DYN ELF type for ...") Cc: Nick Desaulniers Cc: Peter Smith Tested-by: Nick Desaulniers Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: remove no-op -p linker flag

2018-12-01T08:42:55Z

(commit 1a381d4a0a9a0f999a13faaba22bf6b3fc80dcb9 upstream) Linking the ARM64 defconfig kernel with LLVM lld fails with the error: ld.lld: error: unknown argument: -p Makefile:1015: recipe for target 'vmlinux' failed Without this flag, the ARM64 defconfig kernel successfully links with lld and boots on Dragonboard 410c. After digging through binutils source and changelogs, it turns out that -p is only relevant to ancient binutils installations targeting 32-bit ARM. binutils accepts -p for AArch64 too, but it's always been undocumented and silently ignored. A comment in ld/emultempl/aarch64elf.em explains that it's "Only here for backwards compatibility". Since this flag is a no-op on ARM64, we can safely drop it. Acked-by: Will Deacon Reviewed-by: Nick Desaulniers Signed-off-by: Greg Hackmann Signed-off-by: Catalin Marinas Signed-off-by: Nick Desaulniers Signed-off-by: Sasha Levin

arm64: prevent regressions in compressed kernel image size when upgrading to binutils 2.27

2017-12-20T09:10:29Z

[ Upstream commit fd9dde6abcb9bfe6c6bee48834e157999f113971 ] Upon upgrading to binutils 2.27, we found that our lz4 and gzip compressed kernel images were significantly larger, resulting is 10ms boot time regressions. As noted by Rahul: "aarch64 binaries uses RELA relocations, where each relocation entry includes an addend value. This is similar to x86_64. On x86_64, the addend values are also stored at the relocation offset for relative relocations. This is an optimization: in the case where code does not need to be relocated, the loader can simply skip processing relative relocations. In binutils-2.25, both bfd and gold linkers did this for x86_64, but only the gold linker did this for aarch64. The kernel build here is using the bfd linker, which stored zeroes at the relocation offsets for relative relocations. Since a set of zeroes compresses better than a set of non-zero addend values, this behavior was resulting in much better lz4 compression. The bfd linker in binutils-2.27 is now storing the actual addend values at the relocation offsets. The behavior is now consistent with what it does for x86_64 and what gold linker does for both architectures. The change happened in this upstream commit: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=1f56df9d0d5ad89806c24e71f296576d82344613 Since a bunch of zeroes got replaced by non-zero addend values, we see the side effect of lz4 compressed image being a bit bigger. To get the old behavior from the bfd linker, "--no-apply-dynamic-relocs" flag can be used: $ LDFLAGS="--no-apply-dynamic-relocs" make With this flag, the compressed image size is back to what it was with binutils-2.25. If the kernel is using ASLR, there aren't additional runtime costs to --no-apply-dynamic-relocs, as the relocations will need to be applied again anyway after the kernel is relocated to a random address. If the kernel is not using ASLR, then presumably the current default behavior of the linker is better. Since the static linker performed the dynamic relocs, and the kernel is not moved to a different address at load time, it can skip applying the relocations all over again." Some measurements: $ ld -v GNU ld (binutils-2.25-f3d35cf6) 2.25.51.20141117 ^ $ ls -l vmlinux -rwxr-x--- 1 ndesaulniers eng 300652760 Oct 26 11:57 vmlinux $ ls -l Image.lz4-dtb -rw-r----- 1 ndesaulniers eng 16932627 Oct 26 11:57 Image.lz4-dtb $ ld -v GNU ld (binutils-2.27-53dd00a1) 2.27.0.20170315 ^ pre patch: $ ls -l vmlinux -rwxr-x--- 1 ndesaulniers eng 300376208 Oct 26 11:43 vmlinux $ ls -l Image.lz4-dtb -rw-r----- 1 ndesaulniers eng 18159474 Oct 26 11:43 Image.lz4-dtb post patch: $ ls -l vmlinux -rwxr-x--- 1 ndesaulniers eng 300376208 Oct 26 12:06 vmlinux $ ls -l Image.lz4-dtb -rw-r----- 1 ndesaulniers eng 16932466 Oct 26 12:06 Image.lz4-dtb By Siqi's measurement w/ gzip: binutils 2.27 with this patch (with --no-apply-dynamic-relocs): Image 41535488 Image.gz 13404067 binutils 2.27 without this patch (without --no-apply-dynamic-relocs): Image 41535488 Image.gz 14125516 Any compression scheme should be able to get better results from the longer runs of zeros, not just GZIP and LZ4. 10ms boot time savings isn't anything to get excited about, but users of arm64+compression+bfd-2.27 should not have to pay a penalty for no runtime improvement. Reported-by: Gopinath Elanchezhian Reported-by: Sindhuri Pentyala Reported-by: Wei Wang Suggested-by: Ard Biesheuvel Suggested-by: Rahul Chaudhry Suggested-by: Siqi Lin Suggested-by: Stephen Hines Signed-off-by: Nick Desaulniers Reviewed-by: Ard Biesheuvel [will: added comment to Makefile] Signed-off-by: Will Deacon Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

arm64: ftrace: emit ftrace-mod.o contents through code

2017-12-05T10:26:31Z

commit be0f272bfc83797f70d44faca86954df62e2bbc0 upstream. When building the arm64 kernel with both CONFIG_ARM64_MODULE_PLTS and CONFIG_DYNAMIC_FTRACE enabled, the ftrace-mod.o object file is built with the kernel and contains a trampoline that is linked into each module, so that modules can be loaded far away from the kernel and still reach the ftrace entry point in the core kernel with an ordinary relative branch, as is emitted by the compiler instrumentation code dynamic ftrace relies on. In order to be able to build out of tree modules, this object file needs to be included into the linux-headers or linux-devel packages, which is undesirable, as it makes arm64 a special case (although a precedent does exist for 32-bit PPC). Given that the trampoline essentially consists of a PLT entry, let's not bother with a source or object file for it, and simply patch it in whenever the trampoline is being populated, using the existing PLT support routines. Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: ensure the kernel is compiled for LP64

2017-09-18T10:20:20Z

The kernel needs to be compiled as a LP64 binary for ARM64, even when using a compiler that defaults to code-generation for the ILP32 ABI. Consequently, we need to explicitly pass '-mabi=lp64' (supported on gcc-4.9 and newer). Signed-off-by: Andrew Pinski Signed-off-by: Philipp Tomsich Signed-off-by: Christoph Muellner Signed-off-by: Yury Norov Reviewed-by: David Daney Signed-off-by: Catalin Marinas

arm64: pass endianness info to sparse

2017-06-26T09:15:06Z

ARM64 depends on the macro __AARCH64EB__ being defined or not to correctly select or define endian-specific macros, structures or pieces of code. This macro is predefined by the compiler but sparse knows nothing about it and thus may pre-process files differently from what gcc would. Fix this by passing '-D__AARCH64EL__' or '-D__AARCH64EB__' to sparse depending of the endianness of the kernel, like defined by GCC. Note: In most case it won't change anything since most arm64 use little-endian (but an allyesconfig would use big-endian!). CC: Catalin Marinas CC: Will Deacon CC: linux-arm-kernel@lists.infradead.org Signed-off-by: Luc Van Oostenryck Signed-off-by: Will Deacon

arm64: pass machine size to sparse

2017-06-20T15:47:16Z

When using sparse on the arm64 tree we get many thousands of warnings like 'constant ... is so big it is unsigned long long' or 'shift too big (32) for type unsigned long'. This happens because by default sparse considers the machine as 32bit and defines the size of the types accordingly. Fix this by passing the '-m64' flag to sparse so that sparse can correctly define longs as being 64bit. CC: Catalin Marinas CC: Will Deacon CC: linux-arm-kernel@lists.infradead.org Signed-off-by: Luc Van Oostenryck Signed-off-by: Will Deacon

arm64: ftrace: add support for far branches to dynamic ftrace

2017-06-07T10:52:02Z

Currently, dynamic ftrace support in the arm64 kernel assumes that all core kernel code is within range of ordinary branch instructions that occur in module code, which is usually the case, but is no longer guaranteed now that we have support for module PLTs and address space randomization. Since on arm64, all patching of branch instructions involves function calls to the same entry point [ftrace_caller()], we can emit the modules with a trampoline that has unlimited range, and patch both the trampoline itself and the branch instruction to redirect the call via the trampoline. Signed-off-by: Ard Biesheuvel [will: minor clarification to smp_wmb() comment] Signed-off-by: Will Deacon