Commit 91ed140d authored Mar 31, 2016 by Borislav Petkov Committed by Ingo Molnar Apr 13, 2016

x86/asm: Make sure verify_cpu() has a good stack



04633df0 ("x86/cpu: Call verify_cpu() after having entered long mode too")
added the call to verify_cpu() for sanitizing CPU configuration.

The latter uses the stack minimally and it can happen that we land in
startup_64() directly from a 64-bit bootloader. Then we want to use our
own, known good stack.

Do that.

APs don't need this as the trampoline sets up a stack for them.

Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1459434062-31055-1-git-send-email-bp@alien8.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 60a0e203

arch/x86/kernel/head_64.S

+8 −0

Original line number	Diff line number	Diff line
		@@ -65,6 +65,14 @@ startup_64:
		* tables and then reload them.
		*/

		/*
		* Setup stack for verify_cpu(). "-8" because stack_start is defined
		* this way, see below. Our best guess is a NULL ptr for stack
		* termination heuristics and we don't want to break anything which
		* might depend on it (kgdb, ...).
		*/
		leaq (__end_init_task - 8)(%rip), %rsp

		/* Sanitize CPU configuration */
		call verify_cpu

include/asm-generic/vmlinux.lds.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -245,7 +245,9 @@

		#define INIT_TASK_DATA(align) \
		. = ALIGN(align); \
		*(.data..init_task)
		VMLINUX_SYMBOL(__start_init_task) = .; \
		*(.data..init_task) \
		VMLINUX_SYMBOL(__end_init_task) = .;

		/*
		* Read only Data