When kernel starts in 64-bit mode we inherit GDT from a bootloader.
It may cause a problem if the GDT doesn't have 32-bit code segment
where we expect it to be.
Load our own GDT with known segments.
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
arch/x86/boot/compressed/head_64.S | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/boot/compressed/head_64.S
b/arch/x86/boot/compressed/head_64.S
index c813cb004056..f0c3a2f7e528 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -313,6 +313,11 @@ ENTRY(startup_64)
* first.
*/
+ /* Make sure we have GDT with 32-bit code segment */
+ leaq gdt(%rip), %rax
+ movq %rax, gdt64+2(%rip)
+ lgdt gdt64(%rip)
+
/*
* paging_prepare() sets up the trampoline and checks if we need to
* enable 5-level paging.
@@ -547,6 +552,11 @@ no_longmode:
#include "../../kernel/verify_cpu.S"
.data
+gdt64:
+ .word gdt_end - gdt
+ .long 0
+ .word 0
+ .quad 0
gdt:
.word gdt_end - gdt
.long gdt
--
2.16.1
