Some UEFI implementations protect lower 1M memory regions and memory regions allocated by libstub from being executable, which prevents Linux kernel from booting. Disable paging after returning from efi_main() before jumping to potentially relocated code to prevent page fault from happening. Signed-off-by: Baskov Evgeniy <baskov@xxxxxxxxx> --- arch/x86/boot/compressed/head_32.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 659fad53ca82..c66fccaa90a2 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -156,6 +156,18 @@ SYM_FUNC_START_ALIAS(efi_stub_entry) add $0x4, %esp movl 8(%esp), %esi /* save boot_params pointer */ call efi_main + +#ifdef CONFIG_EFI_STRICT_PGTABLE + /* + * Disable paging before jumping to relocated address to prevent + * page faulting on EFI firmware versions that enforces restricted + * permissions on identity page tables + */ + movl %cr0, %ecx + btrl $31, %ecx + movl %ecx, %cr0 +#endif + /* efi_main returns the possibly relocated address of startup_32 */ jmp *%eax SYM_FUNC_END(efi32_stub_entry) -- 2.33.1
