From: Jakub Jelinek <jakub@redhat.com>
To: Kees Cook <kees@kernel.org>
Cc: Andrea Pinski <andrew.pinski@oss.qualcomm.com>,
Jeffrey Law <jefflaw@qti.qualcomm.com>,
Joseph Myers <josmyers@redhat.com>,
Richard Biener <rguenther@suse.de>,
Martin Uecker <uecker@tugraz.at>,
Peter Zijlstra <peterz@infradead.org>,
Ard Biesheuvel <ardb@kernel.org>, Jan Hubicka <hubicka@ucw.cz>,
Richard Earnshaw <richard.earnshaw@arm.com>,
Richard Sandiford <richard.sandiford@arm.com>,
Marcus Shawcroft <marcus.shawcroft@arm.com>,
Kyrylo Tkachov <kyrylo.tkachov@arm.com>,
Kito Cheng <kito.cheng@gmail.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Andrew Waterman <andrew@sifive.com>,
Jim Wilson <jim.wilson.gcc@gmail.com>,
Dan Li <ashimida.1990@gmail.com>,
Sami Tolvanen <samitolvanen@google.com>,
Ramon de C Valle <rcvalle@google.com>,
Joao Moreira <joao@overdrivepizza.com>,
Nathan Chancellor <nathan@kernel.org>,
Bill Wendling <morbo@google.com>,
Osterlund Sebastian <sebastian.osterlund@intel.com>,
Constable Scott D <scott.d.constable@intel.com>,
gcc-patches@gcc.gnu.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v16 4/7] x86: Add x86_64 Kernel Control Flow Integrity implementation
Date: Mon, 5 Oct 2026 12:51:45 +0200 [thread overview]
Message-ID: <asOBQfGfzUOX4uFq@tucnak> (raw)
In-Reply-To: <20260902164935.1390773-4-kees@kernel.org>
On Wed, Sep 02, 2026 at 09:49:29AM -0700, Kees Cook wrote:
> +** movl \$-?[0-9]+, %r10d
> +** addl -4\((%r[a-z0-9]+)\), %r10d
> +** je .Lkcfi_call([0-9]+)
What is reason to use movl + addl instead of just cmpl?
I mean,
int foo (int *p) { return *p == 0x12345678; }
is compiled into
cmpl $305419896, (%rdi)
so I wonder why you can't just compare -4(%r11) with
a 32-bit immediate.
Are you trying to avoid the immediate to be present in the insn
sequence, so that nothing can do an indirect call to the insn after this
compare?
Jakub
next prev parent reply other threads:[~2026-10-05 10:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-02 16:49 [PATCH v16 0/7] Introduce Kernel Control Flow Integrity ABI [PR107048] Kees Cook
2026-09-02 16:49 ` [PATCH v16 1/7] kcfi: Introduce KCFI typeinfo mangling API Kees Cook
2026-09-02 16:49 ` [PATCH v16 2/7] kcfi: Add core Kernel Control Flow Integrity infrastructure Kees Cook
2026-09-02 16:49 ` [PATCH v16 3/7] kcfi: Add regression test suite Kees Cook
2026-09-02 16:49 ` [PATCH v16 4/7] x86: Add x86_64 Kernel Control Flow Integrity implementation Kees Cook
2026-10-05 10:51 ` Jakub Jelinek [this message]
2026-10-05 22:38 ` Kees Cook
2026-09-02 16:49 ` [PATCH v16 5/7] aarch64: Add AArch64 " Kees Cook
2026-09-02 16:49 ` [PATCH v16 6/7] arm: Add ARM 32-bit " Kees Cook
2026-09-02 16:49 ` [PATCH v16 7/7] riscv: Add RISC-V " Kees Cook
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