From: Peter Zijlstra <peterz@infradead.org>
To: David Laight <David.Laight@aculab.com>
Cc: Kees Cook <keescook@chromium.org>,
Sami Tolvanen <samitolvanen@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Joao Moreira <joao@overdrivepizza.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
"linux-hardening@vger.kernel.org"
<linux-hardening@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"llvm@lists.linux.dev" <llvm@lists.linux.dev>
Subject: Re: [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG
Date: Tue, 17 May 2022 11:38:36 +0200 [thread overview]
Message-ID: <YoNtHOm6VH3adwxt@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <ebd0c266697a42c8b7609ff6cbc5f6c9@AcuMS.aculab.com>
On Tue, May 17, 2022 at 08:48:41AM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 17 May 2022 09:41
> ...
> > > If we use %eax instead of %r10d for the hash transfer (as per Joao), and
> > > use int3 instead of ud2, then we can shrink the fineibt sequence to:
> > >
> > > __cfi_\func:
> > > endbr # 4
> > > xorl $0x12345678, %eax # 5
> > > jz 1f # 2
> > > int3 # 1
> > > \func:
> > > ...
> > >
> > > Which is 12 bytes, and needs a larger preamble (up from 9 in the current
> > > proposal).
> >
> > On all that; perhaps it would be good to have a compiler option to
> > specify the preamble size. It can enforce the minimum at 7 to have at
> > least the required:
> >
> > movl $0x12345678, %eax
> > int3
> > int3
> >
> > but any larger number will just increase the preamble with int3 padding
> > at the top.
> >
> > That can go right along with the option to supress endbr when preamble
> > :-)
>
> You also need a compiler option to specify the register.
> While (I think) %eax is usable in kernel, it isn't in userspace.
> It is used in varargs calls to pass (IIRC) the number of fp
> args that are passed in registers.
You're mistaken, the compiler doesn't emit the FineIBT code *at*all*.
That's all patched in later. For kCFI the mov is never executed and is
only there to make it a valid instruction.
next prev parent reply other threads:[~2022-05-17 9:39 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-13 20:21 [RFC PATCH v2 00/21] KCFI support Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 01/21] efi/libstub: Filter out CC_FLAGS_CFI Sami Tolvanen
2022-05-14 21:42 ` Kees Cook
2022-05-16 15:44 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 02/21] arm64/vdso: " Sami Tolvanen
2022-05-14 21:42 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 03/21] kallsyms: Ignore __kcfi_typeid_ Sami Tolvanen
2022-05-14 21:43 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 04/21] cfi: Remove CONFIG_CFI_CLANG_SHADOW Sami Tolvanen
2022-05-14 21:43 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 05/21] cfi: Drop __CFI_ADDRESSABLE Sami Tolvanen
2022-05-14 21:44 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 06/21] cfi: Switch to -fsanitize=kcfi Sami Tolvanen
2022-05-14 21:46 ` Kees Cook
2022-05-15 3:41 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 07/21] cfi: Add type helper macros Sami Tolvanen
2022-05-14 21:49 ` Kees Cook
2022-05-16 12:28 ` Rasmus Villemoes
2022-05-16 16:23 ` Sami Tolvanen
2022-05-16 16:04 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 08/21] psci: Fix the function type for psci_initcall_t Sami Tolvanen
2022-05-14 21:50 ` Kees Cook
2022-05-16 15:44 ` Sami Tolvanen
2022-05-17 8:47 ` Mark Rutland
2022-05-13 20:21 ` [RFC PATCH v2 09/21] arm64: Add types to indirect called assembly functions Sami Tolvanen
2022-05-14 21:50 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 10/21] arm64: Add CFI error handling Sami Tolvanen
2022-05-14 21:51 ` Kees Cook
2022-05-16 16:24 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 11/21] arm64: Drop unneeded __nocfi attributes Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-16 16:28 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 12/21] treewide: Drop function_nocfi Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 13/21] treewide: Drop WARN_ON_FUNCTION_MISMATCH Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 14/21] treewide: Drop __cficanonical Sami Tolvanen
2022-05-14 21:56 ` Kees Cook
2022-05-16 16:32 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 15/21] objtool: Don't warn about __cfi_ preambles falling through Sami Tolvanen
2022-05-14 21:56 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 16/21] x86/tools/relocs: Ignore __kcfi_typeid_ relocations Sami Tolvanen
2022-05-14 21:57 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 17/21] x86: Add types to indirectly called assembly functions Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 18/21] x86/purgatory: Disable CFI Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 19/21] x86/vdso: " Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG Sami Tolvanen
2022-05-14 22:02 ` Kees Cook
2022-05-16 18:57 ` Sami Tolvanen
2022-05-15 3:19 ` Kees Cook
2022-05-16 8:32 ` David Laight
2022-05-16 16:39 ` Sami Tolvanen
2022-05-16 21:32 ` David Laight
2022-05-16 21:44 ` Peter Zijlstra
2022-05-16 22:03 ` Sami Tolvanen
2022-05-17 6:44 ` Peter Zijlstra
2022-05-17 20:36 ` Sami Tolvanen
2022-05-17 7:56 ` David Laight
2022-05-16 9:54 ` Peter Zijlstra
2022-05-16 11:45 ` Peter Zijlstra
2022-05-16 12:58 ` Peter Zijlstra
2022-05-20 13:49 ` Matthew Wilcox
2022-05-16 17:15 ` Sami Tolvanen
2022-05-16 18:30 ` Peter Zijlstra
2022-05-16 19:39 ` Sami Tolvanen
2022-05-16 20:37 ` Peter Zijlstra
2022-05-25 20:02 ` Kees Cook
2022-05-16 22:59 ` Kees Cook
2022-05-17 8:05 ` Peter Zijlstra
2022-05-17 8:32 ` Joao Moreira
2022-05-17 8:40 ` Peter Zijlstra
2022-05-17 8:48 ` David Laight
2022-05-17 9:38 ` Peter Zijlstra [this message]
2022-05-13 20:21 ` [RFC PATCH v2 21/21] init: Drop __nocfi from __init Sami Tolvanen
2022-05-14 22:03 ` Kees Cook
2022-05-16 17:16 ` Sami Tolvanen
[not found] ` <CA+icZUWr+-HjMvY1VZf+nqjTadxSTDciux0Y5Y-+p_j4o7CmXg@mail.gmail.com>
2022-05-16 17:57 ` [RFC PATCH v2 00/21] KCFI support Sami Tolvanen
2022-05-17 7:33 ` Sedat Dilek
2022-05-17 18:49 ` Nathan Chancellor
2022-05-19 9:01 ` Sedat Dilek
2022-05-19 20:26 ` Nathan Chancellor
2022-05-19 20:41 ` Sami Tolvanen
2022-05-17 8:57 ` Peter Zijlstra
2022-05-17 20:25 ` Sami Tolvanen
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