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Date: Sat, 1 Oct 2022 19:52:53 +0200
From: Sedat Dilek <sedat.dilek@...il.com>
To: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
"Moreira, Joao" <joao.moreira@...el.com>
Subject: Re: [GIT PULL] kcfi updates for v6.1-rc1
On Sat, Oct 1, 2022 at 6:36 PM Kees Cook <keescook@...omium.org> wrote:
>
> Hi Linus,
>
> Please pull these Control Flow Integrity updates for v6.1-rc1. As this
> touches treewide things, arm64, and x86, I carried this tree instead of
> it living in -tip, etc. This replaces the more fragile Clang CFI with
> the new Clang KCFI that has been designed specifically for the Linux
> kernel. GCC support is expected[1] in the future.
>
> 3 expected conflicts are minimal:
>
> - arm64: https://lore.kernel.org/linux-next/20220927185911.512737-1-broonie@kernel.org/
>
> - bpf-next: https://lore.kernel.org/linux-next/20220927190811.514527-1-broonie@kernel.org/
> Note that the above fix actually has a typo: the ")) ||" should be
> ") ||", which was later fixed in linux-next.
>
> - arm64-fixes: https://lore.kernel.org/linux-next/20220927190318.513999-1-broonie@kernel.org/
> The conflicting commit in arm64-fixes is needed for a bug in the older
> Clang CFI support. Merging arm64-fixes first may help resolve this
> one in a way that is easier for -stable to consume (i.e. arm64-fixes
> CFI fix lands, then the kcfi tree removes the block entirely), but
> the CFI fix could also just be sent directly to -stable directly if
> anything goes wrong.
>
I checked my long list of logs, journals and selfmade Linux (Debian)
packages in my Clang-CFI / KCFI testing.
My first email to Sami was (in private):
[Clang-ThinLTO][Clang-CFI] "[PATCH] x86/asm: Replace __force_order
with memory clobber"
Aug 25, 2020, 7:30 PM
My first tryouts was with Linux v5.9-rc1 and LLVM-11;
# grep cfi packages_*.txt | egrep 'llvm|clang' | sort | head -10
packages_0612.txt:ii linux-image-5.9.0-rc1-12-amd64-llvm11-cfi
5.9.0~rc1-12~bullseye+dileks1
...
packages_0625.txt:ii linux-image-5.9.0-rc2-4-amd64-llvm11-cfi
5.9.0~rc2-4~bullseye+dileks1
...
# LC_ALL=C ll packages_0612.txt packages_0625.txt
-rw-r--r-- 1 root root 95K Aug 23 2020 packages_0612.txt
-rw-r--r-- 1 root root 96K Aug 26 2020 packages_0625.txt
My first HOORAY was with a selfmade
linux-image-5.9.0-rc2-4-amd64-llvm11-cfi on 26-Aug-2020 - on bare
metal, of course.
Two years ago.
Today, we have Linux v6.0 FINAL and LLVM-15.0.2 coming ([1] has a KCFI
Git for LLVM-15)...
Time goes bye, so quickly...
Thanks to Sami and the LLVM/Clang maintainers and community!
-Sedat-
[1] https://github.com/samitolvanen/llvm-project/commits/15.x/kcfi
> Thanks!
>
> -Kees
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107048
>
> The following changes since commit 7e18e42e4b280c85b76967a9106a13ca61c16179:
>
> Linux 6.0-rc4 (2022-09-04 13:10:01 -0700)
>
> are available in the Git repository at:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git tags/kcfi-v6.1-rc1
>
> for you to fetch changes up to 3c516f89e17e56b4738f05588e51267e295b5e63:
>
> x86: Add support for CONFIG_CFI_CLANG (2022-09-26 10:13:16 -0700)
>
> ----------------------------------------------------------------
> kcfi updates for v6.1-rc1
>
> This replaces the prior support for Clang's standard Control Flow
> Integrity (CFI) instrumentation, which has required a lot of special
> conditions (e.g. LTO) and work-arounds. The current implementation
> ("Kernel CFI") is specific to C, directly designed for the Linux kernel,
> and takes advantage of architectural features like x86's IBT. This
> series retains arm64 support and adds x86 support. Additional "generic"
> architectural support is expected soon:
> https://github.com/samitolvanen/llvm-project/commits/kcfi_generic
>
> - treewide: Remove old CFI support details
>
> - arm64: Replace Clang CFI support with Clang KCFI support
>
> - x86: Introduce Clang KCFI support
>
> ----------------------------------------------------------------
> Sami Tolvanen (22):
> treewide: Filter out CC_FLAGS_CFI
> scripts/kallsyms: Ignore __kcfi_typeid_
> cfi: Remove CONFIG_CFI_CLANG_SHADOW
> cfi: Drop __CFI_ADDRESSABLE
> cfi: Switch to -fsanitize=kcfi
> cfi: Add type helper macros
> lkdtm: Emit an indirect call for CFI tests
> psci: Fix the function type for psci_initcall_t
> arm64: Add types to indirect called assembly functions
> arm64: Add CFI error handling
> arm64: Drop unneeded __nocfi attributes
> init: Drop __nocfi from __init
> treewide: Drop function_nocfi
> treewide: Drop WARN_ON_FUNCTION_MISMATCH
> treewide: Drop __cficanonical
> objtool: Preserve special st_shndx indexes in elf_update_symbol
> objtool: Disable CFI warnings
> kallsyms: Drop CONFIG_CFI_CLANG workarounds
> x86/tools/relocs: Ignore __kcfi_typeid_ relocations
> x86: Add types to indirectly called assembly functions
> x86/purgatory: Disable CFI
> x86: Add support for CONFIG_CFI_CLANG
>
> Makefile | 13 +-
> arch/Kconfig | 18 +-
> arch/arm64/crypto/ghash-ce-core.S | 5 +-
> arch/arm64/crypto/sm3-ce-core.S | 3 +-
> arch/arm64/include/asm/brk-imm.h | 6 +
> arch/arm64/include/asm/ftrace.h | 2 +-
> arch/arm64/include/asm/linkage.h | 4 +
> arch/arm64/include/asm/mmu_context.h | 4 +-
> arch/arm64/kernel/acpi_parking_protocol.c | 2 +-
> arch/arm64/kernel/alternative.c | 2 +-
> arch/arm64/kernel/cpu-reset.S | 5 +-
> arch/arm64/kernel/cpufeature.c | 4 +-
> arch/arm64/kernel/ftrace.c | 2 +-
> arch/arm64/kernel/machine_kexec.c | 2 +-
> arch/arm64/kernel/psci.c | 2 +-
> arch/arm64/kernel/smp_spin_table.c | 2 +-
> arch/arm64/kernel/traps.c | 47 +++-
> arch/arm64/kernel/vdso/Makefile | 3 +-
> arch/arm64/mm/proc.S | 5 +-
> arch/x86/Kconfig | 2 +
> arch/x86/crypto/blowfish-x86_64-asm_64.S | 5 +-
> arch/x86/entry/vdso/Makefile | 3 +-
> arch/x86/include/asm/cfi.h | 22 ++
> arch/x86/include/asm/linkage.h | 12 +
> arch/x86/kernel/Makefile | 2 +
> arch/x86/kernel/cfi.c | 86 ++++++++
> arch/x86/kernel/traps.c | 4 +-
> arch/x86/lib/memcpy_64.S | 3 +-
> arch/x86/purgatory/Makefile | 4 +
> arch/x86/tools/relocs.c | 1 +
> drivers/firmware/efi/libstub/Makefile | 2 +
> drivers/firmware/psci/psci.c | 12 +-
> drivers/misc/lkdtm/cfi.c | 15 +-
> drivers/misc/lkdtm/usercopy.c | 2 +-
> include/asm-generic/bug.h | 16 --
> include/asm-generic/vmlinux.lds.h | 37 ++--
> include/linux/cfi.h | 59 ++---
> include/linux/cfi_types.h | 45 ++++
> include/linux/compiler-clang.h | 14 +-
> include/linux/compiler.h | 16 +-
> include/linux/compiler_types.h | 4 -
> include/linux/init.h | 6 +-
> include/linux/module.h | 10 +-
> include/linux/pci.h | 4 +-
> kernel/cfi.c | 352 +++++-------------------------
> kernel/kallsyms.c | 17 --
> kernel/kthread.c | 3 +-
> kernel/module/main.c | 50 +----
> kernel/workqueue.c | 2 +-
> scripts/kallsyms.c | 1 +
> scripts/module.lds.S | 23 +-
> tools/objtool/check.c | 7 +-
> tools/objtool/elf.c | 7 +-
> 53 files changed, 425 insertions(+), 554 deletions(-)
> create mode 100644 arch/x86/include/asm/cfi.h
> create mode 100644 arch/x86/kernel/cfi.c
> create mode 100644 include/linux/cfi_types.h
>
> --
> Kees Cook
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