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x86/boot: Use unsigned comparison for addresses
authorArvind Sankar <nivedita@alum.mit.edu>
Sun, 8 Mar 2020 08:08:44 +0000 (09:08 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 24 Apr 2020 06:00:28 +0000 (08:00 +0200)
[ Upstream commit 81a34892c2c7c809f9c4e22c5ac936ae673fb9a2 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
arch/x86/boot/compressed/head_32.S patch | blob | blame | history
arch/x86/boot/compressed/head_64.S patch | blob | blame | history

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 37380c0d59996b8ed688d0e350111343e5dca0ae..01d628ea34024c1a88192a2a19e12920bceaf196 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/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:
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 39fdede523f216042af652ce8098078b2706cec2..a25127916e67973faa03b06ed4f869beb86e4a68 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -105,7 +105,7 @@ ENTRY(startup_32)
        notl    %eax
        andl    %eax, %ebx
        cmpl    $LOAD_PHYSICAL_ADDR, %ebx
-       jge     1f
+       jae     1f
 #endif
        movl    $LOAD_PHYSICAL_ADDR, %ebx
 1:
@@ -280,7 +280,7 @@ ENTRY(startup_64)
        notq    %rax
        andq    %rax, %rbp
        cmpq    $LOAD_PHYSICAL_ADDR, %rbp
-       jge     1f
+       jae     1f
 #endif
        movq    $LOAD_PHYSICAL_ADDR, %rbp
 1: