Once again RPL checks have been introduced which don't account for a
32-bit kernel living in ring 1 when running in a PV Xen domain. The
case in FIXUP_FRAME has been preventing boot; adjust BUG_IF_WRONG_CR3
as well just in case.
Fixes: 3c88c692c287 ("x86/stackframe/32: Provide consistent pt_regs")
Signed-off-by: Jan Beulich <jbeul...@suse.com>
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -48,6 +48,17 @@
#include "calling.h"
+#ifndef CONFIG_XEN_PV
+# define USER_SEGMENT_RPL_MASK SEGMENT_RPL_MASK
+#else
+/*
+ * When running paravirtualized on Xen the kernel runs in ring 1, and hence
+ * simple mask based tests (i.e. ones not comparing against USER_RPL) have to
+ * ignore bit 0. See also the C-level get_kernel_rpl().
+ */
+# define USER_SEGMENT_RPL_MASK (SEGMENT_RPL_MASK & ~1)
+#endif
+
.section .entry.text, "ax"
/*
@@ -172,7 +183,7 @@
ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
.if \no_user_check == 0
/* coming from usermode? */
- testl $SEGMENT_RPL_MASK, PT_CS(%esp)
+ testl $USER_SEGMENT_RPL_MASK, PT_CS(%esp)
jz .Lend_\@
.endif
/* On user-cr3? */
@@ -217,7 +228,7 @@
testl $X86_EFLAGS_VM, 4*4(%esp)
jnz .Lfrom_usermode_no_fixup_\@
#endif
- testl $SEGMENT_RPL_MASK, 3*4(%esp)
+ testl $USER_SEGMENT_RPL_MASK, 3*4(%esp)
jnz .Lfrom_usermode_no_fixup_\@
orl $CS_FROM_KERNEL, 3*4(%esp)
