Re: [Xen-devel] [PATCH 4/4] xen/ubsan: Introduce and use CONFIG_UBSAN

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/10/17 19:07, Andrew Cooper wrote:
> TODO at some future point: Fix the following known issues:
>
>   Clang 3.9 - linker error in shadow/multi.c with fetch_type_names[].  With
>   UBSAN enabled, it appears that dead code elimination doesn't remove the
>   single reference to fetch_type_names[] which lives behind DEBUG_TRACE_DUMP.

FYI, the linking error is:

prelink.o: In function `_sh_propagate':
/local/xen.git/xen/arch/x86/mm/shadow/multi.c:731: undefined reference
to `fetch_type_names'

And this patch works around the error:

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 28030ac..7a7ad3d 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -75,15 +75,11 @@ typedef enum {
     ft_demand_write = FETCH_TYPE_DEMAND | FETCH_TYPE_WRITE,
 } fetch_type_t;
 
-extern const char *const fetch_type_names[];
-
-#if defined(DEBUG_TRACE_DUMP) && CONFIG_PAGING_LEVELS ==
GUEST_PAGING_LEVELS
-const char *const fetch_type_names[] = {
+static const char *const fetch_type_names[] = {
     [ft_prefetch]     = "prefetch",
     [ft_demand_read]  = "demand read",
     [ft_demand_write] = "demand write",
 };
-#endif
 
 /**************************************************************************/
 /* Hash table mapping from guest pagetables to shadows


However, this goes against the intended purpose of c/s 89173c1051a0

~Andrew

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