[PATCH] EFI x86: pass firmware call parameters on the stack

["Frédéric Riss" <frederic.riss@gmail.com>]

When calling into an EFI firmware, the parameters need to be passed on
the stack. The recent change to use -mregparm=3 breaks x86 EFI support.
This patch is needed to allow the new Intel-based Macs to suspend to ram
when run in EFI mode (efi.get_time is called during the suspend phase).

Signed-off-by: Frederic Riss <frederic.riss@gmail.com>

---

[As I couldn't find an official maintainer for the linux/efi.h file and
the file header is quite old, I'm Cc:ing the last 2 commiters.]

This patch fixes the issue for x86, but the file is also used by IA64. I
would have used asmlinkage to force arguments on the stack, but it has a
special meaning on IA64, thus I used a raw regparm(0) GCC attribute.
This attribute is documented only for x86, I hope it has no side effect
on other archs.

diff --git a/include/linux/efi.h b/include/linux/efi.h
index df1c918..1db5321 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -157,25 +157,35 @@ typedef struct {
 	unsigned long reset_system;
 } efi_runtime_services_t;
 
-typedef efi_status_t efi_get_time_t (efi_time_t *tm, efi_time_cap_t *tc);
-typedef efi_status_t efi_set_time_t (efi_time_t *tm);
+typedef efi_status_t efi_get_time_t (efi_time_t *tm, efi_time_cap_t *tc)
+			__attribute__((regparm(0)));
+typedef efi_status_t efi_set_time_t (efi_time_t *tm)
+			__attribute__((regparm(0)));
 typedef efi_status_t efi_get_wakeup_time_t (efi_bool_t *enabled, efi_bool_t *pending,
-					    efi_time_t *tm);
-typedef efi_status_t efi_set_wakeup_time_t (efi_bool_t enabled, efi_time_t *tm);
+					    efi_time_t *tm)
+			__attribute__((regparm(0)));
+typedef efi_status_t efi_set_wakeup_time_t (efi_bool_t enabled, efi_time_t *tm)
+			__attribute__((regparm(0)));
 typedef efi_status_t efi_get_variable_t (efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
-					 unsigned long *data_size, void *data);
+					 unsigned long *data_size, void *data)
+			__attribute__((regparm(0)));
 typedef efi_status_t efi_get_next_variable_t (unsigned long *name_size, efi_char16_t *name,
-					      efi_guid_t *vendor);
+					      efi_guid_t *vendor)
+			__attribute__((regparm(0)));
 typedef efi_status_t efi_set_variable_t (efi_char16_t *name, efi_guid_t *vendor, 
 					 unsigned long attr, unsigned long data_size, 
-					 void *data);
-typedef efi_status_t efi_get_next_high_mono_count_t (u32 *count);
+					 void *data)
+			__attribute__((regparm(0)));
+typedef efi_status_t efi_get_next_high_mono_count_t (u32 *count)
+			__attribute__((regparm(0)));
 typedef void efi_reset_system_t (int reset_type, efi_status_t status,
-				 unsigned long data_size, efi_char16_t *data);
+				 unsigned long data_size, efi_char16_t *data)
+			__attribute__((regparm(0)));
 typedef efi_status_t efi_set_virtual_address_map_t (unsigned long memory_map_size,
 						unsigned long descriptor_size,
 						u32 descriptor_version,
-						efi_memory_desc_t *virtual_map);
+						efi_memory_desc_t *virtual_map)
+			__attribute__((regparm(0)));
 
 /*
  *  EFI Configuration Table and GUID definitions