x86: make traps on entry code be debuggable in user space, 64-bit
Unify the x86-64 behavior for 32-bit processes that set
bogus %cs/%ss values (the only ones that can fault in iret)
match what the native i386 behavior is. (do not kill the task
via do_exit but generate a SIGSEGV signal)
[ tglx@linutronix.de: build fix ]
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index bea8474..e518928 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -593,13 +593,22 @@
.quad native_iret, bad_iret
.previous
.section .fixup,"ax"
- /* force a signal here? this matches i386 behaviour */
- /* running with kernel gs */
bad_iret:
- movq $11,%rdi /* SIGSEGV */
- TRACE_IRQS_ON
- ENABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
- jmp do_exit
+ /*
+ * The iret traps when the %cs or %ss being restored is bogus.
+ * We've lost the original trap vector and error code.
+ * #GPF is the most likely one to get for an invalid selector.
+ * So pretend we completed the iret and took the #GPF in user mode.
+ *
+ * We are now running with the kernel GS after exception recovery.
+ * But error_entry expects us to have user GS to match the user %cs,
+ * so swap back.
+ */
+ pushq $0
+
+ SWAPGS
+ jmp general_protection
+
.previous
/* edi: workmask, edx: work */
