feature/native-comp 543e6e6 1/4: * Sanitize frame slot access in final

[Andrea Corallo]

branch: feature/native-comp
commit 543e6e664cf1f25fd7df04e75ffb582f5c7feab4
Author: Andrea Corallo <akrl@sdf.org>
Commit: Andrea Corallo <akrl@sdf.org>

    * Sanitize frame slot access in final
    
        * src/comp.c (comp_t): Add 'frame_size' field.
        (emit_mvar_lval): Add sanity check on frame element access.
        (compile_function): Initialize 'comp.frame_size' and
        'comp.frame_size'.
---
 src/comp.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/comp.c b/src/comp.c
index df770c6..0ab7ab6 100644
--- a/src/comp.c
+++ b/src/comp.c
@@ -560,6 +560,7 @@ typedef struct {
   EMACS_INT func_speed; /* From comp-func speed slot.  */
   gcc_jit_block *block;  /* Current basic block being compiled.  */
   gcc_jit_lvalue *scratch; /* Used as scratch slot for some code sequence 
(switch).  */
+  ptrdiff_t frame_size; /* Size of the following array in elements. */
   gcc_jit_lvalue **frame; /* Frame slot n -> gcc_jit_lvalue *.  */
   gcc_jit_rvalue *zero;
   gcc_jit_rvalue *one;
@@ -785,7 +786,9 @@ emit_mvar_lval (Lisp_Object mvar)
       return comp.scratch;
     }
 
-  return comp.frame[XFIXNUM (mvar_slot)];
+  EMACS_INT slot_n = XFIXNUM (mvar_slot);
+  eassert (slot_n < comp.frame_size);
+  return comp.frame[slot_n];
 }
 
 static void
@@ -3857,7 +3860,7 @@ static void
 compile_function (Lisp_Object func)
 {
   USE_SAFE_ALLOCA;
-  EMACS_INT frame_size = XFIXNUM (CALL1I (comp-func-frame-size, func));
+  comp.frame_size = XFIXNUM (CALL1I (comp-func-frame-size, func));
 
   comp.func = xmint_pointer (Fgethash (CALL1I (comp-func-c-name, func),
                                       comp.exported_funcs_h, Qnil));
@@ -3871,7 +3874,7 @@ compile_function (Lisp_Object func)
                                comp.func_relocs_ptr_type,
                                "freloc");
 
-  comp.frame = SAFE_ALLOCA (frame_size * sizeof (*comp.frame));
+  comp.frame = SAFE_ALLOCA (comp.frame_size * sizeof (*comp.frame));
   if (comp.func_has_non_local || !comp.func_speed)
     {
       /* FIXME: See bug#42360.  */
@@ -3882,10 +3885,10 @@ compile_function (Lisp_Object func)
           gcc_jit_context_new_array_type (comp.ctxt,
                                           NULL,
                                           comp.lisp_obj_type,
-                                          frame_size),
+                                          comp.frame_size),
           "frame");
 
-      for (ptrdiff_t i = 0; i < frame_size; ++i)
+      for (ptrdiff_t i = 0; i < comp.frame_size; ++i)
        comp.frame[i] =
           gcc_jit_context_new_array_access (
             comp.ctxt,
@@ -3896,7 +3899,7 @@ compile_function (Lisp_Object func)
                                                  i));
     }
   else
-    for (ptrdiff_t i = 0; i < frame_size; ++i)
+    for (ptrdiff_t i = 0; i < comp.frame_size; ++i)
       comp.frame[i] =
        gcc_jit_function_new_local (comp.func,
                                    NULL,