[PATCHv6 13/16] x86/traps: Handle LASS thrown #SS

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

LASS throws a #GP for any violations except for stack register accesses,
in which case it throws a #SS instead. Handle this similarly to how other
LASS violations are handled.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/kernel/traps.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 0f558d3369a3..bd8f7e72b238 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -418,12 +418,6 @@ DEFINE_IDTENTRY_ERRORCODE(exc_segment_not_present)
 		      SIGBUS, 0, NULL);
 }
 
-DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment)
-{
-	do_error_trap(regs, error_code, "stack segment", X86_TRAP_SS, SIGBUS,
-		      0, NULL);
-}
-
 DEFINE_IDTENTRY_ERRORCODE(exc_alignment_check)
 {
 	char *str = "alignment check";
@@ -866,6 +860,34 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
 	cond_local_irq_disable(regs);
 }
 
+DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment)
+{
+	if (cpu_feature_enabled(X86_FEATURE_LASS)) {
+		enum kernel_gp_hint hint = GP_NO_HINT;
+		unsigned long gp_addr;
+
+		if (user_mode(regs)) {
+			gp_user_force_sig_segv(regs, X86_TRAP_GP, error_code, GPFSTR);
+			return;
+		}
+
+		hint = get_kernel_gp_address(regs, &gp_addr);
+		if (hint != GP_NO_HINT) {
+			printk(GPFSTR ", %s 0x%lx", kernel_gp_hint_help[hint],
+			       gp_addr);
+		}
+
+		if (hint != GP_NON_CANONICAL)
+			gp_addr = 0;
+
+		die_addr(GPFSTR, regs, error_code, gp_addr);
+		return;
+	}
+
+	do_error_trap(regs, error_code, "stack segment", X86_TRAP_SS, SIGBUS,
+		0, NULL);
+}
+
 static bool do_int3(struct pt_regs *regs)
 {
 	int res;
-- 
2.47.2