The following commit has been merged into the x86/seves branch of tip: Commit-ID: 3add38cb96a1ae7d152db69ab4329e809c2af2d4 Gitweb: https://git.kernel.org/tip/3add38cb96a1ae7d152db69ab4329e809c2af2d4 Author: Joerg Roedel <jroedel@xxxxxxx> AuthorDate: Mon, 07 Sep 2020 15:15:33 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 07 Sep 2020 21:44:01 +02:00 x86/head/64: Switch to initial stack earlier 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@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200907131613.12703-33-joro@xxxxxxxxxx --- arch/x86/kernel/head_64.S | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index f402087..83050c9 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -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
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