[RFC 11/14] x86: add support for Dynamic Kernel Stacks

[Pasha Tatashin]

Add dynamic_stack_fault() calls to the kernel faults, and also declare
HAVE_ARCH_DYNAMIC_STACK = y, so that dynamic kernel stacks can be
enabled on x86 architecture.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 arch/x86/Kconfig        | 1 +
 arch/x86/kernel/traps.c | 3 +++
 arch/x86/mm/fault.c     | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5edec175b9bf..9bb0da3110fa 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -197,6 +197,7 @@ config X86
 	select HAVE_ARCH_USERFAULTFD_WP         if X86_64 && USERFAULTFD
 	select HAVE_ARCH_USERFAULTFD_MINOR	if X86_64 && USERFAULTFD
 	select HAVE_ARCH_VMAP_STACK		if X86_64
+	select HAVE_ARCH_DYNAMIC_STACK		if X86_64
 	select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	select HAVE_ARCH_WITHIN_STACK_FRAMES
 	select HAVE_ASM_MODVERSIONS
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c3b2f863acf0..cc05401e729f 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -413,6 +413,9 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 	}
 #endif
 
+	if (dynamic_stack_fault(current, address))
+		return;
+
 	irqentry_nmi_enter(regs);
 	instrumentation_begin();
 	notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d6375b3c633b..651c558b10eb 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1198,6 +1198,9 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
 	if (is_f00f_bug(regs, hw_error_code, address))
 		return;
 
+	if (dynamic_stack_fault(current, address))
+		return;
+
 	/* Was the fault spurious, caused by lazy TLB invalidation? */
 	if (spurious_kernel_fault(hw_error_code, address))
 		return;
-- 
2.44.0.278.ge034bb2e1d-goog