| From 4d3bb00d3d845bf0a46bd17df947cc8b837a52ec Mon Sep 17 00:00:00 2001 |
| From: Arvind Sankar <nivedita@alum.mit.edu> |
| Date: Sun, 8 Mar 2020 09:08:44 +0100 |
| Subject: [PATCH] x86/boot: Use unsigned comparison for addresses |
| |
| commit 81a34892c2c7c809f9c4e22c5ac936ae673fb9a2 upstream. |
| |
| 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: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S |
| index 37380c0d5999..01d628ea3402 100644 |
| --- 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 02ded42e9f66..514f8797a475 100644 |
| --- a/arch/x86/boot/compressed/head_64.S |
| +++ b/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: |
| -- |
| 2.7.4 |
| |
