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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 05:58:48 +0000 (07:58 +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 fd0b6a272dd5bf252b4aad12be6b961789cc2404..7532f6f536774a8d496c7808d7d59c2d0dfec65b 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -170,7 +170,7 @@ preferred_addr:
        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 9e3a183561a9abe95f8b8e1f6e9747308ec7fd6b..3fac2d133e4eccae9d1a3a213c5fd223c5d0ee14 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -104,7 +104,7 @@ ENTRY(startup_32)
        notl    %eax
        andl    %eax, %ebx
        cmpl    $LOAD_PHYSICAL_ADDR, %ebx
-       jge     1f
+       jae     1f
 #endif
        movl    $LOAD_PHYSICAL_ADDR, %ebx
 1:
@@ -339,7 +339,7 @@ preferred_addr:
        notq    %rax
        andq    %rax, %rbp
        cmpq    $LOAD_PHYSICAL_ADDR, %rbp
-       jge     1f
+       jae     1f
 #endif
        movq    $LOAD_PHYSICAL_ADDR, %rbp
 1: