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x86/head/64: Switch to initial stack earlier

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Make sure there is a stack once the kernel runs from virtual addresses.
At this stage any secondary CPU which boots will have lost its stack
because the kernel switched to a new page-table which does not map the
real-mode stack anymore.

This is needed for handling early #VC exceptions caused by instructions
like CPUID.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-33-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2020-09-07 15:15:33 +02:00 committed by Borislav Petkov
parent 7b99819dfb
commit 3add38cb96
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kernel/head_64.S
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@ -192,6 +192,12 @@ SYM_CODE_START(secondary_startup_64)
movl initial_gs+4(%rip),%edx
wrmsr
/*
* Setup a boot time stack - Any secondary CPU will have lost its stack
* by now because the cr3-switch above unmaps the real-mode stack
*/
movq initial_stack(%rip), %rsp
/* Check if nx is implemented */
movl $0x80000001, %eax
cpuid
@ -212,9 +218,6 @@ SYM_CODE_START(secondary_startup_64)
/* Make changes effective */
movq %rax, %cr0
/* Setup a boot time stack */
movq initial_stack(%rip), %rsp
/* zero EFLAGS after setting rsp */
pushq $0
popfq