linux-kernel - [PATCH] PCI: rcar-host: Avoid objtool no-cfi warning in rcar_pcie

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Message-Id: <20251013-rcar_pcie_probe-avoid-nocfi-objtool-warning-v1-1-552876b94f04@kernel.org>
Date: Mon, 13 Oct 2025 11:25:49 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Marek Vasut <marek.vasut+renesas@...il.com>, 
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kwilczynski@...nel.org>, 
 Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>, 
 Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, 
 Magnus Damm <magnus.damm@...il.com>, linux-pci@...r.kernel.org, 
 linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
 llvm@...ts.linux.dev, kernel test robot <lkp@...el.com>, 
 Kees Cook <kees@...nel.org>, 
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, 
 Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] PCI: rcar-host: Avoid objtool no-cfi warning in
 rcar_pcie_probe()

After commit 894af4a1cde6 ("objtool: Validate kCFI calls"), compile
testing pcie-rcar-host.c with CONFIG_FINEIBT=y and CONFIG_OF=n results
in a no-cfi objtool warning in rcar_pcie_probe():

  $ cat allno.config
  CONFIG_CFI=y
  CONFIG_COMPILE_TEST=y
  CONFIG_CPU_MITIGATIONS=y
  CONFIG_GENERIC_PHY=y
  CONFIG_MITIGATION_RETPOLINE=y
  CONFIG_MODULES=y
  CONFIG_PCI=y
  CONFIG_PCI_MSI=y
  CONFIG_PCIE_RCAR_HOST=y
  CONFIG_X86_KERNEL_IBT=y

  $ make -skj"$(nproc)" ARCH=x86_64 KCONFIG_ALLCONFIG=1 LLVM=1 clean allnoconfig vmlinux
  vmlinux.o: warning: objtool: rcar_pcie_probe+0x191: no-cfi indirect call!

When CONFIG_OF is unset, of_device_get_match_data() returns NULL, so
LLVM knows this indirect call has no valid destination and drops the
kCFI setup before the call, triggering the objtool check that makes sure
all indirect calls have kCFI setup.

Check that host->phy_init_fn is not NULL before calling it to avoid the
warning.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510092124.O2IX0Jek-lkp@intel.com/
Reviewed-by: Kees Cook <kees@...nel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
Another alternative is to make this driver depend on CONFIG_OF since it
clearly requires it but that would restrict compile testing so I went
with this first.
---
 drivers/pci/controller/pcie-rcar-host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
index 213028052aa5..15514c9c1927 100644
--- a/drivers/pci/controller/pcie-rcar-host.c
+++ b/drivers/pci/controller/pcie-rcar-host.c
@@ -981,7 +981,7 @@ static int rcar_pcie_probe(struct platform_device *pdev)
 		goto err_clk_disable;
 
 	host->phy_init_fn = of_device_get_match_data(dev);
-	err = host->phy_init_fn(host);
+	err = host->phy_init_fn ? host->phy_init_fn(host) : -ENODEV;
 	if (err) {
 		dev_err(dev, "failed to init PCIe PHY\n");
 		goto err_clk_disable;

---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251013-rcar_pcie_probe-avoid-nocfi-objtool-warning-1a975accb6b6

Best regards,
--  
Nathan Chancellor <nathan@...nel.org>