[Xen-devel] [PATCH 6/8] xen/x86: Avoid overriding initialisers in arrays

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Clang objects to having multiple initialisers when creating an array.

As this warning is useful for spotting obscure bugs, disabling it is
unhelpful.  Instead, fix our two deliberate usecases.

In the p2m-ept case, pull the array out into a helper function, so the helper
can guarentee to cover the NULL pointer case.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
CC: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/arch/x86/cpu/mtrr/generic.c |  3 +--
 xen/arch/x86/mm/p2m-ept.c       | 27 ++++++++++++++++-----------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
index ea0efe2..8839f8d 100644
--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -91,7 +91,6 @@ static const char *__init mtrr_attrib_to_str(mtrr_type x)
 {
        static const char __initconst strings[MTRR_NUM_TYPES][16] =
        {
-               [0 ... MTRR_NUM_TYPES - 1] = "?",
                [MTRR_TYPE_UNCACHABLE]     = "uncachable",
                [MTRR_TYPE_WRCOMB]         = "write-combining",
                [MTRR_TYPE_WRTHROUGH]      = "write-through",
@@ -99,7 +98,7 @@ static const char *__init mtrr_attrib_to_str(mtrr_type x)
                [MTRR_TYPE_WRBACK]         = "write-back",
        };
 
-       return x < MTRR_NUM_TYPES ? strings[x] : "?";
+       return x < MTRR_NUM_TYPES ? (strings[x] ?: "?") : "?";
 }
 
 static unsigned int __initdata last_fixed_start;
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index c094320..c5fe906 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -1201,6 +1201,20 @@ void ept_p2m_uninit(struct p2m_domain *p2m)
     free_cpumask_var(ept->invalidate);
 }
 
+static const char *memory_type_to_str(unsigned int x)
+{
+    static const char memory_types[8][2] = {
+        [MTRR_TYPE_UNCACHABLE]     = "UC",
+        [MTRR_TYPE_WRCOMB]         = "WC",
+        [MTRR_TYPE_WRTHROUGH]      = "WT",
+        [MTRR_TYPE_WRPROT]         = "WP",
+        [MTRR_TYPE_WRBACK]         = "WB",
+        [MTRR_NUM_TYPES]           = "??"
+    };
+
+    return x < ARRAY_SIZE(memory_types) ? (memory_types[x] ?: "?") : "?";
+}
+
 static void ept_dump_p2m_table(unsigned char key)
 {
     struct domain *d;
@@ -1212,15 +1226,6 @@ static void ept_dump_p2m_table(unsigned char key)
     unsigned long record_counter = 0;
     struct p2m_domain *p2m;
     struct ept_data *ept;
-    static const char memory_types[8][2] = {
-        [0 ... 7] = "?",
-        [MTRR_TYPE_UNCACHABLE]     = "UC",
-        [MTRR_TYPE_WRCOMB]         = "WC",
-        [MTRR_TYPE_WRTHROUGH]      = "WT",
-        [MTRR_TYPE_WRPROT]         = "WP",
-        [MTRR_TYPE_WRBACK]         = "WB",
-        [MTRR_NUM_TYPES]           = "??"
-    };
 
     for_each_domain(d)
     {
@@ -1260,8 +1265,8 @@ static void ept_dump_p2m_table(unsigned char key)
                            ept_entry->r ? 'r' : ' ',
                            ept_entry->w ? 'w' : ' ',
                            ept_entry->x ? 'x' : ' ',
-                           memory_types[ept_entry->emt][0],
-                           memory_types[ept_entry->emt][1]
+                           memory_type_to_str(ept_entry->emt)[0],
+                           memory_type_to_str(ept_entry->emt)[1]
                            ?: ept_entry->emt + '0',
                            c ?: ept_entry->ipat ? '!' : ' ');
 
-- 
2.1.4


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