[RFC PATCH v3 2/4] x86/fault: Attempt to fixup unhandled #PF on ENCLU before signaling

[Sean Christopherson <sean.j.christopherson@intel.com>]

Call fixup_sgx_enclu_exception() in the SIGSEGV and SIGBUS paths of
the page fault handler immediately prior to signaling.  If the fault
is fixed, return cleanly and do not generate a signal.

In the SIGSEGV flow, make sure the error code passed to userspace has
been sanitized.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/mm/fault.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 7e8a7558ca07..d3903965334c 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -28,6 +28,7 @@
 #include <asm/mmu_context.h>		/* vma_pkey()			*/
 #include <asm/efi.h>			/* efi_recover_from_page_fault()*/
 #include <asm/desc.h>			/* store_idt(), ...		*/
+#include <asm/sgx.h>			/* fixup_sgx_enclu_exception()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -928,6 +929,9 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 		if (address >= TASK_SIZE_MAX)
 			error_code |= X86_PF_PROT;
 
+		if (fixup_sgx_enclu_exception(regs, X86_TRAP_PF, error_code, address))
+			return;
+
 		if (likely(show_unhandled_signals))
 			show_signal_msg(regs, error_code, address, tsk);
 
@@ -1045,6 +1049,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 	if (is_prefetch(regs, error_code, address))
 		return;
 
+	if (fixup_sgx_enclu_exception(regs, X86_TRAP_PF, error_code, address))
+		return;
+
 	set_signal_archinfo(address, error_code);
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.19.2