Commit 09a4e4d9 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Kees Cook
Browse files

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: default avatarSami Tolvanen <samitolvanen@google.com>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-10-samitolvanen@google.com
parent 3578ad11

include/linux/pci.h

+25 −2
Original line number Diff line number Diff line
@@ -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,	\