PCI: Fix PREL32 relocations for LTO

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>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-10-samitolvanen@google.com

diff --git a/include/linux/pci.h b/include/linux/pci.h
index b32126d26997e2eae6b53543cf40f9fd97f4db8b..2276e5d001921f9796b6c50171d9aba37deb40c4 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1917,7 +1917,7 @@ enum pci_fixup_pass {
 };
 
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,  \
+#define ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
                                    class_shift, hook)                  \
        __ADDRESSABLE(hook)                                             \
        asm(".section " #sec ", \"a\"                           \n"     \
@@ -1926,10 +1926,33 @@ enum pci_fixup_pass {
            ".long "    #class ", " #class_shift "              \n"     \
            ".long "    #hook " - .                             \n"     \
            ".previous                                          \n");
+
+/*
+ * Clang's LTO may rename static functions in C, but has no way to
+ * handle such renamings when referenced from inline asm. To work
+ * around this, create global C stubs for these cases.
+ */
+#ifdef CONFIG_LTO_CLANG
+#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);                                              \
+       }                                                               \
+       ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,  \
+                                 class_shift, stub)
+#else
+#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)
+#endif
+
 #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,        \