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Subject[PATCH 03/20] efi/x86: re-disable RT services for 32-bit kernels running on 64-bit EFI
Date
Commit a8147dba75b1 ("efi/x86: Rename efi_is_native() to efi_is_mixed()")
renamed and refactored efi_is_native() into efi_is_mixed(), but failed
to take into account that these are not diametrical opposites.

Mixed mode is a construct that permits 64-bit kernels to boot on 32-bit
firmware, but there is another non-native combination which is supported,
i.e., 32-bit kernels booting on 64-bit firmware, but only for boot and not
for runtime services. Also, mixed mode can be disabled in Kconfig, in
which case the 64-bit kernel can still be booted from 32-bit firmware,
but without access to runtime services.

Due to this oversight, efi_runtime_supported() now incorrectly returns
true for such configurations, resulting in crashes at boot. So fix this
by making efi_runtime_supported() aware of this.

As a side effect, some efi_thunk_xxx() stubs have become obsolete, so
remove them as well.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/include/asm/efi.h | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 2d1378f19b74..b35b5d423e9d 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -163,10 +163,10 @@ static inline bool efi_is_mixed(void)

static inline bool efi_runtime_supported(void)
{
- if (!efi_is_mixed())
+ if (IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT))
return true;

- if (!efi_enabled(EFI_OLD_MEMMAP))
+ if (IS_ENABLED(CONFIG_EFI_MIXED) && !efi_enabled(EFI_OLD_MEMMAP))
return true;

return false;
@@ -176,7 +176,6 @@ extern void parse_efi_setup(u64 phys_addr, u32 data_len);

extern void efifb_setup_from_dmi(struct screen_info *si, const char *opt);

-#ifdef CONFIG_EFI_MIXED
extern void efi_thunk_runtime_setup(void);
extern efi_status_t efi_thunk_set_virtual_address_map(
void *phys_set_virtual_address_map,
@@ -184,19 +183,6 @@ extern efi_status_t efi_thunk_set_virtual_address_map(
unsigned long descriptor_size,
u32 descriptor_version,
efi_memory_desc_t *virtual_map);
-#else
-static inline void efi_thunk_runtime_setup(void) {}
-static inline efi_status_t efi_thunk_set_virtual_address_map(
- void *phys_set_virtual_address_map,
- unsigned long memory_map_size,
- unsigned long descriptor_size,
- u32 descriptor_version,
- efi_memory_desc_t *virtual_map)
-{
- return EFI_SUCCESS;
-}
-#endif /* CONFIG_EFI_MIXED */
-

/* arch specific definitions used by the stub code */

--
2.20.1
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