From: Peter Zijlstra <peterz@infradead.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>,
Marek Vasut <marek.vasut+renesas@gmail.com>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Krzysztof Wilczy??ski <kwilczynski@kernel.org>,
Manivannan Sadhasivam <mani@kernel.org>,
Rob Herring <robh@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Magnus Damm <magnus.damm@gmail.com>, Kees Cook <kees@kernel.org>,
linux-pci@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v2] PCI: rcar-host: Add OF Kconfig dependency to avoid objtool no-cfi warning
Date: Tue, 14 Oct 2025 21:47:28 +0200 [thread overview]
Message-ID: <20251014194728.GD1206438@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20251014191330.GA899677@bhelgaas>
On Tue, Oct 14, 2025 at 02:13:30PM -0500, Bjorn Helgaas wrote:
> Ugh. This might be the best solution, but it's a bit problematic
> without a hint about why "depends on OF" is here. Theoretically there
> are stubs for everything to make COMPILE_TEST work, so I think we're
> about to drop all the dependencies on OF.
Its those stubs are exactly the problem.
> This dependency to avoid a no-cfi warning looks like the kind of thing
> that could someday go away if the tools get smarter. Maybe we can add
> a Kconfig comment here, but I don't really know enough to write one.
> Something like this?
Its not a CFI warning per-se, the compiler is hitting known UB
(unconditional NULL deref) and is currently emitting a NULL pointer
indirect call, but given how aggressive clang has been on encountering
UB it might just stop code-gen entirely and generate fall-through
warnings (been there done that).
Smarter compiler here is only going to make this worse.
next prev parent reply other threads:[~2025-10-14 19:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-14 18:20 [PATCH v2] PCI: rcar-host: Add OF Kconfig dependency to avoid objtool no-cfi warning Nathan Chancellor
2025-10-14 19:13 ` Bjorn Helgaas
2025-10-14 19:47 ` Peter Zijlstra [this message]
2025-10-14 22:25 ` Nathan Chancellor
2025-10-27 12:26 ` Manivannan Sadhasivam
2025-12-18 5:23 ` Manivannan Sadhasivam
2025-12-26 23:46 ` Bjorn Helgaas
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