lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 26 Sep 2022 14:39:21 +0200
From:   Peter Zijlstra <>
To:     Sami Tolvanen <>
Cc:, Kees Cook <>,
        Josh Poimboeuf <>,,
        Catalin Marinas <>,
        Will Deacon <>,
        Mark Rutland <>,
        Nathan Chancellor <>,
        Nick Desaulniers <>,
        Joao Moreira <>,
        Sedat Dilek <>,
        Steven Rostedt <>,,,,
Subject: Re: [PATCH v5 00/22] KCFI support

On Thu, Sep 08, 2022 at 02:54:42PM -0700, Sami Tolvanen wrote:
> KCFI is a forward-edge control-flow integrity scheme in the upcoming
> Clang 16 release, which is more suitable for kernel use than the
> existing CFI scheme used by CONFIG_CFI_CLANG. KCFI doesn't require
> LTO, doesn't alter function references to point to a jump table, and
> won't break function address equality.
> This series replaces the current arm64 CFI implementation with KCFI
> and adds support for x86_64.
> KCFI requires assembly functions that are indirectly called from C
> code to be annotated with type identifiers. As type information is
> only available in C, the compiler emits expected type identifiers
> into the symbol table, so they can be referenced from assembly
> without having to hardcode type hashes. Patch 6 adds helper macros
> for annotating functions, and patches 9 and 20 add annotations.
> In case of a type mismatch, KCFI always traps. To support error
> handling, the compiler generates a .kcfi_traps section for x86_64,
> which contains the locations of each trap, and for arm64, encodes
> the necessary register information to the ESR. Patches 10 and 22 add
> arch-specific error handlers.
> To test this series, you'll need a ToT Clang toolchain. The series
> is also available pn GitHub:

As mentioned at plumbers, my only concern is somewhat excessive use of
CFI_CLANG as oposed to something more compiler neutral. But I suppose
that's something we can cleanup/fix when GCC grows support for this.

Acked-by: Peter Zijlstra (Intel) <>
Tested-by: Peter Zijlstra (Intel) <>

(as in I ran kCFI + call-depth-tracking + FineIBT on a bunch of

HJL, can you look at adding kCFI support to GCC ?

Powered by blists - more mailing lists