From: Arvind Sankar <nivedita@alum.mit.edu>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 5/5] x86/boot: Use unsigned comparison for addresses
Date: Sun, 1 Mar 2020 18:04:36 -0500 [thread overview]
Message-ID: <20200301230436.2246909-6-nivedita@alum.mit.edu> (raw)
In-Reply-To: <20200301230436.2246909-1-nivedita@alum.mit.edu>
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
commit 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 jae instruction to perform unsigned comparison instead, as physical
addresses should be considered as unsigned.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
arch/x86/boot/compressed/head_32.S | 2 +-
arch/x86/boot/compressed/head_64.S | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index e013bdc1237b..46bbe7ab4adf 100644
--- 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 6a4ff919008c..5d8338a693ce 100644
--- 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:
--
2.24.1
next prev parent reply other threads:[~2020-03-01 23:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 23:04 [PATCH 0/5] efi/x86 cleanups and one bugfix Arvind Sankar
2020-03-01 23:04 ` [PATCH 1/5] efi/x86: Annotate the LOADED_IMAGE_PROTOCOL_GUID with SYM_DATA Arvind Sankar
2020-03-01 23:04 ` [PATCH 2/5] efi/x86: Respect 32-bit ABI in efi32_pe_entry Arvind Sankar
2020-03-01 23:04 ` [PATCH 3/5] efi/x86: Make efi32_pe_entry more readable Arvind Sankar
2020-03-02 7:49 ` Ard Biesheuvel
2020-03-02 16:54 ` Arvind Sankar
2020-03-02 16:57 ` Ard Biesheuvel
2020-03-02 17:02 ` Arvind Sankar
2020-03-02 17:09 ` Ard Biesheuvel
2020-03-01 23:04 ` [PATCH 4/5] efi/x86: Avoid using code32_start Arvind Sankar
2020-03-01 23:04 ` Arvind Sankar [this message]
2020-03-02 7:50 ` [PATCH 0/5] efi/x86 cleanups and one bugfix Ard Biesheuvel
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