x86/boot: Use unsigned comparison for addresses

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:

  97aa276579b2 ("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 <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-6-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-14-ardb@kernel.org

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index e013bdc..46bbe7a 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -105,7 +105,7 @@ SYM_FUNC_START(startup_32)
        notl    %eax
        andl    %eax, %ebx
        cmpl    $LOAD_PHYSICAL_ADDR, %ebx
-       jge     1f
+       jae     1f
 #endif
        movl    $LOAD_PHYSICAL_ADDR, %ebx
 1:

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 6a4ff91..5d8338a 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -105,7 +105,7 @@ SYM_FUNC_START(startup_32)
        notl    %eax
        andl    %eax, %ebx
        cmpl    $LOAD_PHYSICAL_ADDR, %ebx
-       jge     1f
+       jae     1f
 #endif
        movl    $LOAD_PHYSICAL_ADDR, %ebx
 1:
@@ -305,7 +305,7 @@ SYM_CODE_START(startup_64)
        notq    %rax
        andq    %rax, %rbp
        cmpq    $LOAD_PHYSICAL_ADDR, %rbp
-       jge     1f
+       jae     1f
 #endif
        movq    $LOAD_PHYSICAL_ADDR, %rbp
 1: