Go a step further than bed9ae54df44 ("x86/time: switch platform timer
hooks to altcall") did and eliminate the "real" read_tsc() altogether:
It's not used except in pointer comparisons, and hence it looks overall
more safe to simply poison plt_tsc's read_counter hook.
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
I wasn't really sure whether it would be better to use simply void * for
the type of the expression, resulting in an undesirable data -> function
pointer conversion, but making it impossible to mistakenly try and call
the (fake) function directly.
---
v2: Comment wording.
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -607,10 +607,12 @@ static s64 __init cf_check init_tsc(stru
return ret;
}
-static uint64_t __init cf_check read_tsc(void)
-{
- return rdtsc_ordered();
-}
+/*
+ * plt_tsc's read_counter hook is not (and should not be) invoked via the
+ * struct field. To avoid carrying an unused, indirectly reachable function,
+ * poison the field with an easily identifiable non-canonical pointer.
+ */
+#define read_tsc ((uint64_t(*)(void))0x75C75C75C75C75C0ul)
static struct platform_timesource __initdata_cf_clobber plt_tsc =
{
