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x86/boot: Use unsigned comparison for addresses

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[ Upstream commit 81a34892c2 ]

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:

  97aa276579 ("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>
This commit is contained in:
Arvind Sankar
2020-03-08 09:08:44 +01:00
committed by Chris
parent 34284255b9
commit bf8bd073da
2 changed files with 3 additions and 3 deletions
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2
arch/x86/boot/compressed/head_32.S
View File

@@ -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:

4
arch/x86/boot/compressed/head_64.S
View File

@@ -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: