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Subject[tip: x86/seves] x86/boot/compressed/64: Reload CS in startup_32
The following commit has been merged into the x86/seves branch of tip:

Commit-ID: 0c289ff81c24033777fab23019039f11e1449ba4
Gitweb: https://git.kernel.org/tip/0c289ff81c24033777fab23019039f11e1449ba4
Author: Joerg Roedel <jroedel@suse.de>
AuthorDate: Wed, 10 Mar 2021 09:43:20 +01:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Thu, 18 Mar 2021 16:44:43 +01:00

x86/boot/compressed/64: Reload CS in startup_32

Exception handling in the startup_32 boot path requires the CS
selector to be correctly set up. Reload it from the current GDT.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210312123824.306-4-joro@8bytes.org
---
arch/x86/boot/compressed/head_64.S | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index e94874f..c59c80c 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -107,9 +107,16 @@ SYM_FUNC_START(startup_32)
movl %eax, %gs
movl %eax, %ss

-/* setup a stack and make sure cpu supports long mode. */
+ /* Setup a stack and load CS from current GDT */
leal rva(boot_stack_end)(%ebp), %esp

+ pushl $__KERNEL32_CS
+ leal rva(1f)(%ebp), %eax
+ pushl %eax
+ lretl
+1:
+
+ /* Make sure cpu supports long mode. */
call verify_cpu
testl %eax, %eax
jnz .Lno_longmode
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