ARM: kprobes: Add decoding table self-consistency tests

These check that the bitmask and match value used in the decoding tables
are self consistent.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

1 files changed, 99 insertions, 4 deletions

diff --git a/arch/arm/kernel/kprobes-test.c b/arch/arm/kernel/kprobes-test.c
index b12be0fe183c..6c0946c023f8 100644
--- a/arch/arm/kernel/kprobes-test.c
+++ b/arch/arm/kernel/kprobes-test.c
@@ -443,6 +443,92 @@ static int run_api_tests(long (*func)(long, long))
 
 
 /*
+ * Decoding table self-consistency tests
+ */
+
+static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
+        [DECODE_TYPE_TABLE]     = sizeof(struct decode_table),
+        [DECODE_TYPE_CUSTOM]    = sizeof(struct decode_custom),
+        [DECODE_TYPE_SIMULATE]  = sizeof(struct decode_simulate),
+        [DECODE_TYPE_EMULATE]   = sizeof(struct decode_emulate),
+        [DECODE_TYPE_OR]        = sizeof(struct decode_or),
+        [DECODE_TYPE_REJECT]    = sizeof(struct decode_reject)
+};
+
+static int table_iter(const union decode_item *table,
+                        int (*fn)(const struct decode_header *, void *),
+                        void *args)
+{
+        const struct decode_header *h = (struct decode_header *)table;
+        int result;
+
+        for (;;) {
+                enum decode_type type = h->type_regs.bits & DECODE_TYPE_MASK;
+
+                if (type == DECODE_TYPE_END)
+                        return 0;
+
+                result = fn(h, args);
+                if (result)
+                        return result;
+
+                h = (struct decode_header *)
+                        ((uintptr_t)h + decode_struct_sizes[type]);
+
+        }
+}
+
+static int table_test_fail(const struct decode_header *h, const char* message)
+{
+
+        pr_err("FAIL: kprobes test failure \"%s\" (mask %08x, value %08x)\n",
+                                        message, h->mask.bits, h->value.bits);
+        return -EINVAL;
+}
+
+struct table_test_args {
+        const union decode_item *root_table;
+        u32                     parent_mask;
+        u32                     parent_value;
+};
+
+static int table_test_fn(const struct decode_header *h, void *args)
+{
+        struct table_test_args *a = (struct table_test_args *)args;
+        enum decode_type type = h->type_regs.bits & DECODE_TYPE_MASK;
+
+        if (h->value.bits & ~h->mask.bits)
+                return table_test_fail(h, "Match value has bits not in mask");
+
+        if ((h->mask.bits & a->parent_mask) != a->parent_mask)
+                return table_test_fail(h, "Mask has bits not in parent mask");
+
+        if ((h->value.bits ^ a->parent_value) & a->parent_mask)
+                return table_test_fail(h, "Value is inconsistent with parent");
+
+        if (type == DECODE_TYPE_TABLE) {
+                struct decode_table *d = (struct decode_table *)h;
+                struct table_test_args args2 = *a;
+                args2.parent_mask = h->mask.bits;
+                args2.parent_value = h->value.bits;
+                return table_iter(d->table.table, table_test_fn, &args2);
+        }
+
+        return 0;
+}
+
+static int table_test(const union decode_item *table)
+{
+        struct table_test_args args = {
+                .root_table     = table,
+                .parent_mask    = 0,
+                .parent_value   = 0
+        };
+        return table_iter(args.root_table, table_test_fn, &args);
+}
+
+
+/*
  * Framework for instruction set test cases
  */
 
@@ -1117,8 +1203,15 @@ end:
  * Top level test functions
  */
 
-static int run_test_cases(void (*tests)(void))
+static int run_test_cases(void (*tests)(void), const union decode_item *table)
 {
+        int ret;
+
+        pr_info("    Check decoding tables\n");
+        ret = table_test(table);
+        if (ret)
+                return ret;
+
         pr_info("    Run test cases\n");
         tests();
 
@@ -1140,7 +1233,7 @@ static int __init run_all_tests(void)
                 goto out;
 
         pr_info("ARM instruction simulation\n");
-        ret = run_test_cases(kprobe_arm_test_cases);
+        ret = run_test_cases(kprobe_arm_test_cases, kprobe_decode_arm_table);
         if (ret)
                 goto out;
 
@@ -1162,12 +1255,14 @@ static int __init run_all_tests(void)
                 goto out;
 
         pr_info("16-bit Thumb instruction simulation\n");
-        ret = run_test_cases(kprobe_thumb16_test_cases);
+        ret = run_test_cases(kprobe_thumb16_test_cases,
+                                kprobe_decode_thumb16_table);
         if (ret)
                 goto out;
 
         pr_info("32-bit Thumb instruction simulation\n");
-        ret = run_test_cases(kprobe_thumb32_test_cases);
+        ret = run_test_cases(kprobe_thumb32_test_cases,
+                                kprobe_decode_thumb32_table);
         if (ret)
                 goto out;
 #endif