efi/x86: Preserve %ebx correctly in efi_set_virtual_address_map()

Commit: 59f2a61 ("efi: Add 'runtime' pointer to struct efi") modified the assembler routine called by efi_set_virtual_address_map(), to grab the 'runtime' EFI service pointer while running with paging disabled (which is tricky to do in C code) After the change, register %ebx is not restored correctly, resulting in all kinds of weird behavior, so fix that. Reported-by: Guenter Roeck <[email protected]> Tested-by: Guenter Roeck <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Link: https://lore.kernel.org/r/[email protected] Link: https://lore.kernel.org/r/[email protected]
josf · Mar 8, 2020 · 57648ad · 57648ad
1 parent dd09fad
commit 57648ad
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/arch/x86/platform/efi/efi_stub_32.S b/arch/x86/platform/efi/efi_stub_32.S
@@ -54,7 +54,7 @@ SYM_FUNC_START(efi_call_svam)
 	orl	$0x80000000, %edx
 	movl	%edx, %cr0
 
-	pop	%ebx
+	movl	16(%esp), %ebx
 	leave
 	ret
 SYM_FUNC_END(efi_call_svam)