[PATCH] i386: paravirt unhandled fallthrough

The current code simply calls "start_kernel" directly if we're under a
hypervisor and no paravirt_ops backend wants us, because paravirt.c
registers that as a backend.

This was always a vain hope; start_kernel won't get far without setup.
It's also impossible for paravirt_ops backends which don't sit in the
arch/i386/kernel directory: they can't link before paravirt.o anyway.

Keep it simple: if we pass all the registered paravirt probes, BUG().

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>

3 files changed, 6 insertions, 6 deletions

diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 97f1e961d684..223969377de4 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -41,8 +41,6 @@ obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
 obj-$(CONFIG_K8_NB)             += k8.o
 
 obj-$(CONFIG_VMI)               += vmi.o vmitime.o
-
-# Make sure this is linked after any other paravirt_ops structs: see head.S
 obj-$(CONFIG_PARAVIRT)          += paravirt.o
 
 EXTRA_AFLAGS   := -traditional
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 734be5572eb9..b322f72ffaad 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -513,10 +513,11 @@ startup_paravirt:
         pushl   %ecx
         pushl   %eax
 
-        /* paravirt.o is last in link, and that probe fn never returns */
         pushl   $__start_paravirtprobe
 1:
         movl    0(%esp), %eax
+        cmpl    $__stop_paravirtprobe, %eax
+        je      unhandled_paravirt
         pushl   (%eax)
         movl    8(%esp), %eax
         call    *(%esp)
@@ -528,6 +529,10 @@ startup_paravirt:
 
         addl    $4, (%esp)
         jmp     1b
+
+unhandled_paravirt:
+        /* Nothing wanted us: we're screwed. */
+        ud2
 #endif
 
 /*
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index ebe82552ad30..c156ecfa3872 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -482,9 +482,6 @@ static int __init print_banner(void)
 }
 core_initcall(print_banner);
 
-/* We simply declare start_kernel to be the paravirt probe of last resort. */
-paravirt_probe(start_kernel);
-
 struct paravirt_ops paravirt_ops = {
         .name = "bare hardware",
         .paravirt_enabled = 0,