[ARM/FDPIC v4 08/20] [ARM] FDPIC: Enforce local/global binding for function descriptors

[Christophe Lyon]

Use local binding rules to decide whether we can use GOTOFFFUNCDESC to
compute the function address.

2018-XX-XX  Christophe Lyon  <christophe.l...@st.com>
        Mickaël Guêné <mickael.gu...@st.com>

        gcc/
        * config/arm/arm.c (arm_local_funcdesc_p): New function.
        (legitimize_pic_address): Enforce binding rules on function
        pointers in FDPIC mode.
        (arm_assemble_integer): Likewise.

Change-Id: I3fa0b63bc0f672903f405aa72cc46052de1c0feb

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 7e7f747..ca53eae 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3777,6 +3777,42 @@ arm_options_perform_arch_sanity_checks (void)
     }
 }
 
+/* Test whether a local function descriptor is canonical, i.e.,
+   whether we can use GOTOFFFUNCDESC to compute the address of the
+   function.  */
+static bool
+arm_fdpic_local_funcdesc_p (rtx fnx)
+{
+  tree fn;
+  enum symbol_visibility vis;
+  bool ret;
+
+  if (!TARGET_FDPIC)
+    return TRUE;
+
+  if (! SYMBOL_REF_LOCAL_P (fnx))
+    return FALSE;
+
+  fn = SYMBOL_REF_DECL (fnx);
+
+  if (! fn)
+    return FALSE;
+
+  vis = DECL_VISIBILITY (fn);
+
+  if (vis == VISIBILITY_PROTECTED)
+    /* Private function descriptors for protected functions are not
+       canonical.  Temporarily change the visibility to global so that
+       we can ensure uniqueness of funcdesc pointers.  */
+    DECL_VISIBILITY (fn) = VISIBILITY_DEFAULT;
+
+  ret = default_binds_local_p_1 (fn, flag_pic);
+
+  DECL_VISIBILITY (fn) = vis;
+
+  return ret;
+}
+
 static void
 arm_add_gc_roots (void)
 {
@@ -7494,7 +7530,9 @@ legitimize_pic_address (rtx orig, machine_mode mode, rtx 
reg)
           || (GET_CODE (orig) == SYMBOL_REF
               && SYMBOL_REF_LOCAL_P (orig)
               && (SYMBOL_REF_DECL (orig)
-                  ? !DECL_WEAK (SYMBOL_REF_DECL (orig)) : 1)))
+                  ? !DECL_WEAK (SYMBOL_REF_DECL (orig)) : 1)
+              && (!SYMBOL_REF_FUNCTION_P (orig)
+                  || arm_fdpic_local_funcdesc_p (orig))))
          && NEED_GOT_RELOC
          && arm_pic_data_is_text_relative)
        insn = arm_pic_static_addr (orig, reg);
@@ -23060,7 +23098,9 @@ arm_assemble_integer (rtx x, unsigned int size, int 
aligned_p)
              || (GET_CODE (x) == SYMBOL_REF
                  && (!SYMBOL_REF_LOCAL_P (x)
                      || (SYMBOL_REF_DECL (x)
-                         ? DECL_WEAK (SYMBOL_REF_DECL (x)) : 0))))
+                         ? DECL_WEAK (SYMBOL_REF_DECL (x)) : 0)
+                     || (SYMBOL_REF_FUNCTION_P (x)
+                         && !arm_fdpic_local_funcdesc_p (x)))))
            {
              if (TARGET_FDPIC && SYMBOL_REF_FUNCTION_P (x))
                fputs ("(GOTFUNCDESC)", asm_out_file);
-- 
2.6.3