[PATCH v2 5/6] drivers: pci: add support for relative addressing in quirk tables

[Ard Biesheuvel]

Allow the PCI quirk tables to be emitted in a way that avoids absolute
references to the hook functions. This reduces the size of the entries,
and, more importantly, makes them invariant under runtime relocation
(e.g., for KASLR)

Cc: Bjorn Helgaas <bhelg...@google.com>
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
 drivers/pci/quirks.c |  6 ++--
 include/linux/pci.h  | 32 ++++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 6967c6b4cf6b..0a7ba8c7f1f6 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3547,9 +3547,9 @@ static void pci_do_fixups(struct pci_dev *dev, struct 
pci_fixup *f,
                     f->vendor == (u16) PCI_ANY_ID) &&
                    (f->device == dev->device ||
                     f->device == (u16) PCI_ANY_ID)) {
-                       calltime = fixup_debug_start(dev, f->hook);
-                       f->hook(dev);
-                       fixup_debug_report(dev, calltime, f->hook);
+                       calltime = fixup_debug_start(dev, pci_fixup_hook(f));
+                       pci_fixup_hook(f)(dev);
+                       fixup_debug_report(dev, calltime, pci_fixup_hook(f));
                }
 }
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a75c13673852..58eb4e7a15c3 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1735,7 +1735,11 @@ struct pci_fixup {
        u16 device;             /* You can use PCI_ANY_ID here of course */
        u32 class;              /* You can use PCI_ANY_ID here too */
        unsigned int class_shift;       /* should be 0, 8, 16 */
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+       int hook_offset;
+#else
        void (*hook)(struct pci_dev *dev);
+#endif
 };
 
 enum pci_fixup_pass {
@@ -1749,6 +1753,27 @@ enum pci_fixup_pass {
        pci_fixup_suspend_late, /* pci_device_suspend_late() */
 };
 
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,  \
+                                   class_shift, hook)                  \
+       __ADDRESSABLE(hook)                                             \
+       asm(".section " #sec ", \"a\"\n"                                \
+           ".balign    16\n"                                           \
+           ".short "   #vendor ", " #device "\n"                       \
+           ".long "    #class ", " #class_shift "\n"                   \
+           ".long "    VMLINUX_SYMBOL_STR(hook) " - .\n"               \
+           ".previous\n")
+#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)
+
+static inline
+void (*pci_fixup_hook(const struct pci_fixup *f))(struct pci_dev *)
+{
+       return (void *)((unsigned long)&f->hook_offset + f->hook_offset);
+}
+#else
 /* Anonymous variables would be nice... */
 #define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class,        
\
                                  class_shift, hook)                    \
@@ -1756,6 +1781,13 @@ enum pci_fixup_pass {
        __attribute__((__section__(#section), aligned((sizeof(void *)))))    \
                = { vendor, device, class, class_shift, hook };
 
+static inline
+void (*pci_fixup_hook(const struct pci_fixup *f))(struct pci_dev *)
+{
+       return f->hook;
+}
+#endif
+
 #define DECLARE_PCI_FIXUP_CLASS_EARLY(vendor, device, class,           \
                                         class_shift, hook)             \
        DECLARE_PCI_FIXUP_SECTION(.pci_fixup_early,                     \
-- 
2.11.0