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Subject[PATCH 4/5] drivers: pci: add support for relative addressing in quirk tables
Date
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 <bhelgaas@google.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
drivers/pci/quirks.c | 13 ++++++++++---
include/linux/pci.h | 20 ++++++++++++++++++++
2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 6967c6b4cf6b..10126612e342 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3547,9 +3547,16 @@ 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);
+ void (*hook)(struct pci_dev *dev);
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+ hook = (void *)((unsigned long)&f->hook_offset +
+ f->hook_offset);
+#else
+ hook = f->hook;
+#endif
+ calltime = fixup_debug_start(dev, hook);
+ hook(dev);
+ fixup_debug_report(dev, calltime, hook);
}
}

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 4869e66dd659..203544f33345 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1734,7 +1734,11 @@ 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
+ signed int hook_offset;
+#else
void (*hook)(struct pci_dev *dev);
+#endif
};

enum pci_fixup_pass {
@@ -1748,12 +1752,28 @@ 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)
+#else
/* Anonymous variables would be nice... */
#define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class, \
class_shift, hook) \
static const struct pci_fixup __PASTE(__pci_fixup_##name,__LINE__) __used \
__attribute__((__section__(#section), aligned((sizeof(void *))))) \
= { vendor, device, class, class_shift, hook };
+#endif

#define DECLARE_PCI_FIXUP_CLASS_EARLY(vendor, device, class, \
class_shift, hook) \
--
2.11.0
\
 
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