On 6/25/2025 5:51 AM, Kirill A. Shutemov wrote:
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.
In case of FRED, before handling #SS as LASS violation, kernel has to
check if there's a fixup for the exception. It can address #SS due to
invalid user context on ERETU[1]. See 5105e7687ad3 ("x86/fred: Fixup
Forgot to put the link to [1]? Maybe just remove "[1]"?
fault on ERETU by jumping to fred_entrypoint_user") for more details.
Co-developed-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/traps.c | 39 +++++++++++++++++++++++++++++++++------
1 file changed, 33 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index e2ad760b17ea..f1f92e1ba524 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 +860,39 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
cond_local_irq_disable(regs);
}
+#define SSFSTR "stack segment fault"
+
+DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment)
+{
+ if (user_mode(regs))
+ goto error_trap;
+
+ if (cpu_feature_enabled(X86_FEATURE_FRED) &&
+ fixup_exception(regs, X86_TRAP_SS, error_code, 0))
+ return;
+
Thanks for making the change for FRED.
+ if (cpu_feature_enabled(X86_FEATURE_LASS)) {
+ enum kernel_gp_hint hint;
+ unsigned long gp_addr;
+
+ hint = get_kernel_gp_address(regs, &gp_addr);
+ if (hint != GP_NO_HINT) {
+ printk(SSFSTR ", %s 0x%lx", kernel_gp_hint_help[hint],
+ gp_addr);
+ }
+
+ if (hint != GP_NON_CANONICAL)
+ gp_addr = 0;
Nit: GP/gp don't seem fit here, maybe we need a more generic name?
Sorry I don't have a recommendation.
+
+ die_addr(SSFSTR, regs, error_code, gp_addr);
+ return;
+ }
+
+error_trap:
+ do_error_trap(regs, error_code, "stack segment", X86_TRAP_SS, SIGBUS,
+ 0, NULL);
The indentation has changed; I believe the original formatting is
preferable.
+}
+
static bool do_int3(struct pt_regs *regs)
{
int res;
Just minor comments, so
Reviewed-by: Xin Li (Intel) <xin@xxxxxxxxx>
