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

Kirill A. Shutemov
2025-06-20T13:53:53Z

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