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(*
*
* Copyright (c) 2001-2002,
* George C. Necula <necula@cs.berkeley.edu>
* Scott McPeak <smcpeak@cs.berkeley.edu>
* Wes Weimer <weimer@cs.berkeley.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. The names of the contributors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*)
module H = Hashtbl
open Cil
open Pretty
module E = Errormsg
let debug = false
(* For each function we have a node *)
type node = { name: string;
mutable scanned: bool;
mutable mustcheck: bool;
mutable succs: node list }
(* We map names to nodes *)
let functionNodes: (string, node) H.t = H.create 113
let getFunctionNode (n: string) : node =
Util.memoize
functionNodes
n
(fun _ -> { name = n; mustcheck = false; scanned = false; succs = [] })
(** Dump the function call graph. Assume that there is a main *)
let dumpGraph = true
let dumpFunctionCallGraph () =
H.iter (fun _ x -> x.scanned <- false) functionNodes;
let rec dumpOneNode (ind: int) (n: node) : unit =
output_string !E.logChannel "\n";
for i = 0 to ind do
output_string !E.logChannel " "
done;
output_string !E.logChannel (n.name ^ " ");
if n.scanned then (* Already dumped *)
output_string !E.logChannel " <rec> "
else begin
n.scanned <- true;
List.iter (dumpOneNode (ind + 1)) n.succs
end
in
try
let main = H.find functionNodes "main" in
dumpOneNode 0 main
with Not_found -> begin
ignore (E.log
"I would like to dump the function graph but there is no main");
end
(* We add a dummy function whose name is "@@functionPointer@@" that is called
* at all invocations of function pointers and itself calls all functions
* whose address is taken. *)
let functionPointerName = "@@functionPointer@@"
let checkSomeFunctions = ref false
let init () =
H.clear functionNodes;
checkSomeFunctions := false
let addCall (caller: string) (callee: string) =
let callerNode = getFunctionNode caller in
let calleeNode = getFunctionNode callee in
if not (List.exists (fun n -> n.name = callee) callerNode.succs) then begin
if debug then
ignore (E.log "found call from %s to %s\n" caller callee);
callerNode.succs <- calleeNode :: callerNode.succs;
end;
()
class findCallsVisitor (host: string) : cilVisitor = object
inherit nopCilVisitor
method vinst i =
match i with
| Call(_,Lval(Var(vi),NoOffset),_,l) ->
addCall host vi.vname;
SkipChildren
| Call(_,e,_,l) -> (* Calling a function pointer *)
addCall host functionPointerName;
SkipChildren
| _ -> SkipChildren (* No calls in other instructions *)
(* There are no calls in expressions and types *)
method vexpr e = SkipChildren
method vtype t = SkipChildren
end
(* Now detect the cycles in the call graph. Do a depth first search of the
* graph (stack is the list of nodes already visited in the current path).
* Return true if we have found a cycle. *)
let rec breakCycles (stack: node list) (n: node) : bool =
if n.scanned then (* We have already scanned this node. There are no cycles
* going through this node *)
false
else if n.mustcheck then
(* We are reaching a node that we already know we much check. Return with
* no new cycles. *)
false
else if List.memq n stack then begin
(* We have found a cycle. Mark the node n to be checked and return *)
if debug then
ignore (E.log "Will place an overflow check in %s\n" n.name);
checkSomeFunctions := true;
n.mustcheck <- true;
n.scanned <- true;
true
end else begin
let res = List.exists (fun nd -> breakCycles (n :: stack) nd) n.succs in
n.scanned <- true;
if res && n.mustcheck then
false
else
res
end
let findCheckPlacement () =
H.iter (fun _ nd ->
if nd.name <> functionPointerName
&& not nd.scanned && not nd.mustcheck then begin
ignore (breakCycles [] nd)
end)
functionNodes
let makeFunctionCallGraph (f: Cil.file) : unit =
init ();
(* Scan the file and construct the control-flow graph *)
List.iter
(function
GFun(fdec, _) ->
if fdec.svar.vaddrof then
addCall functionPointerName fdec.svar.vname;
let vis = new findCallsVisitor fdec.svar.vname in
ignore (visitCilBlock vis fdec.sbody)
| _ -> ())
f.globals
let makeAndDumpFunctionCallGraph (f: file) =
makeFunctionCallGraph f;
dumpFunctionCallGraph ()
let addCheck (f: Cil.file) : unit =
makeFunctionCallGraph f;
findCheckPlacement ();
if !checkSomeFunctions then begin
(* Add a declaration for the stack threshhold variable. The program is
* stopped when the stack top is less than this value. *)
let stackThreshholdVar = makeGlobalVar "___stack_threshhold" !upointType in
stackThreshholdVar.vstorage <- Extern;
(* And the initialization function *)
let computeStackThreshhold =
makeGlobalVar "___compute_stack_threshhold"
(TFun(!upointType, Some [], false, [])) in
computeStackThreshhold.vstorage <- Extern;
(* And the failure function *)
let stackOverflow =
makeGlobalVar "___stack_overflow"
(TFun(voidType, Some [], false, [])) in
stackOverflow.vstorage <- Extern;
f.globals <-
GVar(stackThreshholdVar, {init=None}, locUnknown) ::
GVarDecl(computeStackThreshhold, locUnknown) ::
GVarDecl(stackOverflow, locUnknown) :: f.globals;
(* Now scan and instrument each function definition *)
List.iter
(function
GFun(fdec, l) ->
(* If this is main we must introduce the initialization of the
* bottomOfStack *)
let nd = getFunctionNode fdec.svar.vname in
if fdec.svar.vname = "main" then begin
if nd.mustcheck then
E.s (E.error "The \"main\" function is recursive!!");
let loc = makeLocalVar fdec "__a_local" intType in
loc.vaddrof <- true;
fdec.sbody <-
mkBlock
[ mkStmtOneInstr
(Call (Some(var stackThreshholdVar),
Lval(var computeStackThreshhold), [], l));
mkStmt (Block fdec.sbody) ]
end else if nd.mustcheck then begin
let loc = makeLocalVar fdec "__a_local" intType in
loc.vaddrof <- true;
fdec.sbody <-
mkBlock
[ mkStmt
(If(BinOp(Le,
CastE(!upointType, AddrOf (var loc)),
Lval(var stackThreshholdVar), intType),
mkBlock [mkStmtOneInstr
(Call(None, Lval(var stackOverflow),
[], l))],
mkBlock [],
l));
mkStmt (Block fdec.sbody) ]
end else
()
| _ -> ())
f.globals;
()
end
|
