tunables: Fix comparison of tunable values

The simplification of tunable_set interfaces took care of
signed/unsigned conversions while setting values, but comparison with
bounds ended up being incorrect; comparing TUNABLE_SIZE_T values for
example will fail because SIZE_MAX is seen as -1.

Add comparison helpers that take tunable types into account and use
them to do comparison instead.

elf/dl-tunable-types.h

@@ -81,4 +81,21 @@ struct _tunable
 
 typedef struct _tunable tunable_t;
 
+static __always_inline bool
+unsigned_tunable_type (tunable_type_code_t t)
+{
+  switch (t)
+    {
+    case TUNABLE_TYPE_INT_32:
+      return false;
+    case TUNABLE_TYPE_UINT_64:
+    case TUNABLE_TYPE_SIZE_T:
+      return true;
+    case TUNABLE_TYPE_STRING:
+    default:
+      break;
+    }
+  __builtin_unreachable ();
+}
+
 #endif

elf/dl-tunables.c

@@ -107,32 +107,35 @@ do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
       return;
     }
 
+  bool unsigned_cmp = unsigned_tunable_type (cur->type.type_code);
+
   val = valp->numval;
   min = minp != NULL ? *minp : cur->type.min;
   max = maxp != NULL ? *maxp : cur->type.max;
 
   /* We allow only increasingly restrictive bounds.  */
-  if (min < cur->type.min)
+  if (tunable_val_lt (min, cur->type.min, unsigned_cmp))
     min = cur->type.min;
 
-  if (max > cur->type.max)
+  if (tunable_val_gt (max, cur->type.max, unsigned_cmp))
     max = cur->type.max;
 
   /* Skip both bounds if they're inconsistent.  */
-  if (min > max)
+  if (tunable_val_gt (min, max, unsigned_cmp))
     {
       min = cur->type.min;
       max = cur->type.max;
     }
 
-  /* Write everything out if the value and the bounds are valid.  */
-  if (min <= val && val <= max)
-    {
-      cur->val.numval = val;
-      cur->type.min = min;
-      cur->type.max = max;
-      cur->initialized = true;
-    }
+  /* Bail out if the bounds are not valid.  */
+  if (tunable_val_lt (val, min, unsigned_cmp)
+      || tunable_val_lt (max, val, unsigned_cmp))
+    return;
+
+  cur->val.numval = val;
+  cur->type.min = min;
+  cur->type.max = max;
+  cur->initialized = true;
 }
 
 /* Validate range of the input value and initialize the tunable CUR if it looks

elf/dl-tunables.h

@@ -115,6 +115,24 @@ rtld_hidden_proto (__tunable_set_val)
 /* The default value for TUNABLES_FRONTEND.  */
 # define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
 
+static __always_inline bool
+tunable_val_lt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp)
+{
+  if (unsigned_cmp)
+    return (uintmax_t) lhs < (uintmax_t) rhs;
+  else
+    return lhs < rhs;
+}
+
+static __always_inline bool
+tunable_val_gt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp)
+{
+  if (unsigned_cmp)
+    return (uintmax_t) lhs > (uintmax_t) rhs;
+  else
+    return lhs > rhs;
+}
+
 /* Compare two name strings, bounded by the name hardcoded in glibc.  */
 static __always_inline bool
 tunable_is_name (const char *orig, const char *envname)