x86/boot: Use unsigned comparison for addresses

[ Upstream commit 81a3489 ]

The load address is compared with LOAD_PHYSICAL_ADDR using a signed
comparison currently (using jge instruction).

When loading a 64-bit kernel using the new efi32_pe_entry() point added by:

  97aa276 ("efi/x86: Add true mixed mode entry point into .compat section")

using Qemu with -m 3072, the firmware actually loads us above 2Gb,
resulting in a very early crash.

Use the JAE instruction to perform a unsigned comparison instead, as physical
addresses should be considered unsigned.

Signed-off-by: Arvind Sankar <[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]
Signed-off-by: Sasha Levin <[email protected]>

Author: nivedita76

arch/x86/boot/compressed/head_32.S

@@ -106,7 +106,7 @@ ENTRY(startup_32)
 	notl	%eax
 	andl    %eax, %ebx
 	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
-	jge	1f
+	jae	1f
 #endif
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 1:

arch/x86/boot/compressed/head_64.S

@@ -106,7 +106,7 @@ ENTRY(startup_32)
 	notl	%eax
 	andl	%eax, %ebx
 	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
-	jge	1f
+	jae	1f
 #endif
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 1:
@@ -297,7 +297,7 @@ ENTRY(startup_64)
 	notq	%rax
 	andq	%rax, %rbp
 	cmpq	$LOAD_PHYSICAL_ADDR, %rbp
-	jge	1f
+	jae	1f
 #endif
 	movq	$LOAD_PHYSICAL_ADDR, %rbp
 1: