Re: [PATCH v6 17/25] PCI: Fix PREL32 relocations for LTO

Kees Cook
2020-10-15T01:24:58Z

On Mon, Oct 12, 2020 at 05:31:55PM -0700, Sami Tolvanen wrote:
> With Clang's Link Time Optimization (LTO), the compiler can rename
> static functions to avoid global naming collisions. As PCI fixup
> functions are typically static, renaming can break references
> to them in inline assembly. This change adds a global stub to
> DECLARE_PCI_FIXUP_SECTION to fix the issue when PREL32 relocations
> are used.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Another independent patch! :) Bjorn, since you've already Acked this
patch, would be be willing to pick it up for your tree?

-Kees

> ---
> include/linux/pci.h | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 835530605c0d..4e64421981c7 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1909,19 +1909,28 @@ enum pci_fixup_pass {
> };
>
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
> -#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> - class_shift, hook) \
> - __ADDRESSABLE(hook) \
> +#define ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> + class_shift, hook, stub) \
> + void stub(struct pci_dev *dev); \
> + void stub(struct pci_dev *dev) \
> + { \
> + hook(dev); \
> + } \
> asm(".section " #sec ", \"a\" \n" \
> ".balign 16 \n" \
> ".short " #vendor ", " #device " \n" \
> ".long " #class ", " #class_shift " \n" \
> - ".long " #hook " - . \n" \
> + ".long " #stub " - . \n" \
> ".previous \n");
> +
> +#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> + class_shift, hook, stub) \
> + ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> + class_shift, hook, stub)
> #define DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> class_shift, hook) \
> __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> - class_shift, hook)
> + class_shift, hook, __UNIQUE_ID(hook))
> #else
> /* Anonymous variables would be nice... */
> #define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class, \
> --
> 2.28.0.1011.ga647a8990f-goog
>

--
Kees Cook