Re: [PATCH 1/1] efi/libstub: Fix mixed mode boot issue after macro refactor

[Arvind Sankar <nivedita@alum.mit.edu>]

On Mon, May 04, 2020 at 04:15:59PM +0200, Ard Biesheuvel wrote:
> On Mon, 4 May 2020 at 16:02, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> >
> > On Mon, May 04, 2020 at 10:05:23AM +0200, Ard Biesheuvel wrote:
> > > On Mon, 4 May 2020 at 02:38, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > > >
> > > > Commit
> > > >   22090f84bc3f ("efi/libstub: unify EFI call wrappers for non-x86")
> > > >
> > > > refactored the macros that are used to provide wrappers for mixed-mode
> > > > calls on x86, allowing us to boot a 64-bit kernel on 32-bit firmware.
> > > >
> > > > Unfortunately, this broke mixed mode boot due to the fact that
> > > > efi_is_native() is not a macro on x86.
> > > >
> > > > Fix this by conditioning the generic macro definitions on
> > > > CONFIG_EFI_MIXED, and removing the wrapper definitions on x86 if
> > > > CONFIG_EFI_MIXED is not enabled.
> > > >
> > > > Reported-by: Guenter Roeck <linux@roeck-us.net>
> > > > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> > >
> > > Thanks Arvind.
> > >
> > > Currently, CONFIG_EFI_MIXED is never referenced outside of arch/x86,
> > > and I prefer to keep it that way.
> >
> > All these macros go together though -- they should either all be defined
> > or none, so it makes sense to put them under a single #if.
> 
> True.
> 
> > If you think
> > it's possible that a future architecture might need the wrappers but not
> > be mixed, we could maybe add an ARCH_NEEDS_EFISTUB_WRAPPERS?
> >
> 
> Well, remember that x86 used wrappers for native invocations only two
> releases ago, but that was mainly because of the SysV vs MS ABI issue,
> so the issue could emerge again, but it is unlikely.
> 

Yep.

Would the below be more palatable?

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index cd0c3fbf6156..6b9ab0d8b2a7 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -225,13 +225,15 @@ efi_status_t efi_set_virtual_address_map(unsigned long memory_map_size,
 
 /* arch specific definitions used by the stub code */
 
-extern const bool efi_is64;
+#ifdef CONFIG_EFI_MIXED
+
+#define ARCH_HAS_EFISTUB_WRAPPERS
 
 static inline bool efi_is_64bit(void)
 {
-	if (IS_ENABLED(CONFIG_EFI_MIXED))
-		return efi_is64;
-	return IS_ENABLED(CONFIG_X86_64);
+	extern const bool efi_is64;
+
+	return efi_is64;
 }
 
 static inline bool efi_is_native(void)
@@ -356,6 +358,15 @@ static inline u32 efi64_convert_status(efi_status_t status)
 						   runtime),		\
 				    func, __VA_ARGS__))
 
+#else /* CONFIG_EFI_MIXED */
+
+static inline bool efi_is_64bit(void)
+{
+	return IS_ENABLED(CONFIG_X86_64);
+}
+
+#endif /* CONFIG_EFI_MIXED */
+
 extern bool efi_reboot_required(void);
 extern bool efi_is_table_address(unsigned long phys_addr);
 
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 874233cf8820..4f10a09563f3 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -33,20 +33,14 @@ extern bool efi_novamap;
 
 extern const efi_system_table_t *efi_system_table;
 
-#ifndef efi_bs_call
+#ifndef ARCH_HAS_EFISTUB_WRAPPERS
+
+#define efi_is_native()		(true)
 #define efi_bs_call(func, ...)	efi_system_table->boottime->func(__VA_ARGS__)
-#endif
-#ifndef efi_rt_call
 #define efi_rt_call(func, ...)	efi_system_table->runtime->func(__VA_ARGS__)
-#endif
-#ifndef efi_is_native
-#define efi_is_native()		(true)
-#endif
-#ifndef efi_table_attr
 #define efi_table_attr(inst, attr)	(inst->attr)
-#endif
-#ifndef efi_call_proto
 #define efi_call_proto(inst, func, ...) inst->func(inst, ##__VA_ARGS__)
+
 #endif
 
 #define efi_info(msg)		do {			\