On 6/20/2025 6:53 AM, Kirill A. Shutemov wrote:
From: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
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
@@ -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;
+ }
Please add the following FRED code:
if (cpu_feature_enabled(X86_FEATURE_FRED) &&
fixup_exception(regs, X86_TRAP_SS, error_code, 0))
return;
Because the following FRED fixup
https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5105e7687ad3dffde77f6e4393b5530e83d672dc
is otherwise skipped, it is interpreted as a LASS #SS before reaching
the FRED fixup (which is indeed a userspace fault but triggered from
a specific kernel IP as described in the commit changelog).
The x86 selftest sigreturn_64 fails w/o the above fix.
+
+ hint = get_kernel_gp_address(regs, &gp_addr);
+ if (hint != GP_NO_HINT) {
+ printk(GPFSTR ", %s 0x%lx", kernel_gp_hint_help[hint],
GPFSTR?
#define GPFSTR "general protection fault"
It is misleading here, you need something like SSFSTR which tells
exactly which exception caused it.
Thanks!
Xin
