IDE Solver Strategy #669

fabianbs96 · 2023-09-21T17:13:20Z

Currently, the IDESolver propagates data-flow information to the successor instruction of the current instruction.
While this makes the implementation easier, for users this is sometimes unintuitive, mostly because the Dragonbook defines data-flow propagations differently: The effects of an instruction to the data flows should be visible at that same instruction already.
In addition, some information at branching statements may have already been merged with the current approach; therefore, it may not always be possible to determine the origin basicblock of a particular data-flow fact (see LLVM's invoke instruction).

This PR addresses above issues by adding the following contributions:

Implements a variant of the IDESolver that propagates onto the current statement instead of propagating to the successors.
Adds a SolverStrategy that allows to switch between both IDE solver versions via tag-dispatch.
Out-factors common parts of both IDE solver variants into a common base class IDESolverImpl

…- phase II)

…de duplication

yuffon · 2023-11-03T04:04:40Z

Hi @fabianbs96, I have an issue with the PropagateOnto strategy.
If I use the default PropagateOver strategy, my typestate code works well.
But when using PropagateOnto strategy, some dataflow facts vanish.

The analyzed code is

#include <stdio.h>
#include <malloc.h>

int use_after_free()
{
    int *p = (int *)malloc(16);
    *p = 1;
    free(p);
    *p = 2;
    return 0;
}

int main(void)
{

    int (* p)() = & use_after_free; 
    int i = p();

    return 0;
}

The IR file is

; ModuleID = 'func-pointer-use-after-free.c'
source_filename = "func-pointer-use-after-free.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i32 @use_after_free() #0 {
entry:
  %p = alloca i32*, align 8
  %call = call noalias i8* @malloc(i64 noundef 16) #2
  %0 = bitcast i8* %call to i32*
  store i32* %0, i32** %p, align 8
  %1 = load i32*, i32** %p, align 8
  store i32 1, i32* %1, align 4
  %2 = load i32*, i32** %p, align 8
  %3 = bitcast i32* %2 to i8*
  call void @free(i8* noundef %3) #2
  %4 = load i32*, i32** %p, align 8
  store i32 2, i32* %4, align 4
  ret i32 0
}

; Function Attrs: nounwind
declare dso_local noalias i8* @malloc(i64 noundef) #1

; Function Attrs: nounwind
declare dso_local void @free(i8* noundef) #1

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i32 @main() #0 {
entry:
  %retval = alloca i32, align 4
  %p = alloca i32 (...)*, align 8
  %i = alloca i32, align 4
  store i32 0, i32* %retval, align 4
  store i32 (...)* bitcast (i32 ()* @use_after_free to i32 (...)*), i32 (...)** %p, align 8
  %0 = load i32 (...)*, i32 (...)** %p, align 8
  %call = call i32 (...) %0()
  store i32 %call, i32* %i, align 4
  ret i32 0
}

attributes #0 = { noinline nounwind optnone uwtable "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #1 = { nounwind "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #2 = { nounwind }

!llvm.module.flags = !{!0, !1, !2}
!llvm.ident = !{!3}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 7, !"uwtable", i32 1}
!2 = !{i32 7, !"frame-pointer", i32 2}
!3 = !{!"clang version 14.0.6 (https://github.com/llvm/llvm-project.git f28c006a5895fc0e329fe15fead81e37457cb1d1)"}

The dumped results of using PropagateOver strategy is

N: %p = alloca i32*, align 8, !psr.id !4 | ID: 0
------------------------------------------------
	D: Fact :{ Obj:11,state:0 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: %call = call noalias i8* @malloc(i64 noundef 16) #2, !psr.id !5 | ID: 1
--------------------------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:0 } | V: BOTTOM


N: %0 = bitcast i8* %call to i32*, !psr.id !6 | ID: 2
-----------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: store i32* %0, i32** %p, align 8, !psr.id !7 | ID: 3
-------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %1 = load i32*, i32** %p, align 8, !psr.id !8 | ID: 4
--------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: store i32 1, i32* %1, align 4, !psr.id !9 | ID: 5
----------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %2 = load i32*, i32** %p, align 8, !psr.id !10 | ID: 6
---------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %3 = bitcast i32* %2 to i8*, !psr.id !11 | ID: 7
---------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: call void @free(i8* noundef %3) #2, !psr.id !12 | ID: 8
----------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %4 = load i32*, i32** %p, align 8, !psr.id !13 | ID: 9
---------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:2 } | V: BOTTOM


N: store i32 2, i32* %4, align 4, !psr.id !14 | ID: 10
------------------------------------------------------
	D: Fact :{ Obj:11,state:2 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: ret i32 0, !psr.id !15 | ID: 11
----------------------------------
	D: Fact :{ Obj:11,state:3 } | V: BOTTOM
	D: Λ | V: BOTTOM


============ Results for function 'main' ============


N: %p = alloca i32 (...)*, align 8, !psr.id !17 | ID: 13
--------------------------------------------------------
	D: Fact :{ Obj:11,state:0 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: %i = alloca i32, align 4, !psr.id !18 | ID: 14
-------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: store i32 0, i32* %retval, align 4, !psr.id !19 | ID: 15
-----------------------------------------------------------
	D: Fact :{ Obj:11,state:0 } | V: TOP
	D: Λ | V: TOP


N: store i32 (...)* bitcast (i32 ()* @use_after_free to i32 (...)*), i32 (...)** %p, align 8, !psr.id !20 | ID: 16
------------------------------------------------------------------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: %0 = load i32 (...)*, i32 (...)** %p, align 8, !psr.id !21 | ID: 17
----------------------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: %call = call i32 (...) %0(), !psr.id !22 | ID: 18
----------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:0 } | V: BOTTOM


N: store i32 %call, i32* %i, align 4, !psr.id !23 | ID: 19
----------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:3 } | V: TOP


N: ret i32 0, !psr.id !24 | ID: 20
----------------------------------
	D: Fact :{ Obj:11,state:3 } | V: TOP
	D: Λ | V: TOP

Everything is OK up to now.
But with the propagateOnto strategy, the dumped results are


N: %p = alloca i32*, align 8, !psr.id !4 | ID: 0
------------------------------------------------
	D: Fact :{ Obj:11,state:0 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: %call = call noalias i8* @malloc(i64 noundef 16) #2, !psr.id !5 | ID: 1
--------------------------------------------------------------------------
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: %0 = bitcast i8* %call to i32*, !psr.id !6 | ID: 2
-----------------------------------------------------
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: store i32* %0, i32** %p, align 8, !psr.id !7 | ID: 3
-------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %1 = load i32*, i32** %p, align 8, !psr.id !8 | ID: 4
--------------------------------------------------------
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: store i32 1, i32* %1, align 4, !psr.id !9 | ID: 5
----------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM


N: %2 = load i32*, i32** %p, align 8, !psr.id !10 | ID: 6
---------------------------------------------------------
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: %3 = bitcast i32* %2 to i8*, !psr.id !11 | ID: 7
---------------------------------------------------
	D: Fact :{ Obj:11,state:1 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: call void @free(i8* noundef %3) #2, !psr.id !12 | ID: 8
----------------------------------------------------------
	D: Λ | V: BOTTOM
	D: Fact :{ Obj:11,state:2 } | V: BOTTOM


N: %4 = load i32*, i32** %p, align 8, !psr.id !13 | ID: 9
---------------------------------------------------------
	D: Fact :{ Obj:11,state:2 } | V: BOTTOM
	D: Λ | V: BOTTOM


N: store i32 2, i32* %4, align 4, !psr.id !14 | ID: 10
------------------------------------------------------
	D: Fact :{ Obj:11,state:3 } | V: BOTTOM
	D: Λ | V: BOTTOM


============ Results for function 'main' ============


N: %p = alloca i32 (...)*, align 8, !psr.id !17 | ID: 13
--------------------------------------------------------
	D: Fact :{ Obj:11,state:0 } | V: TOP
	D: Λ | V: TOP


N: %i = alloca i32, align 4, !psr.id !18 | ID: 14
-------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: store i32 0, i32* %retval, align 4, !psr.id !19 | ID: 15
-----------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: store i32 (...)* bitcast (i32 ()* @use_after_free to i32 (...)*), i32 (...)** %p, align 8, !psr.id !20 | ID: 16
------------------------------------------------------------------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: %0 = load i32 (...)*, i32 (...)** %p, align 8, !psr.id !21 | ID: 17
----------------------------------------------------------------------
	D: Λ | V: TOP
	D: Fact :{ Obj:11,state:0 } | V: TOP


N: %call = call i32 (...) %0(), !psr.id !22 | ID: 18
----------------------------------------------------
	D: Λ | V: TOP


N: store i32 %call, i32* %i, align 4, !psr.id !23 | ID: 19
----------------------------------------------------------
	D: Λ | V: TOP

As shown above, the last two instructions after calling the function have no dataflow facts.
It seems that dataflow facts do not come out from the invoked function.
In fact, I use identity flow function for all return edges.
Besides, the default strategy works well, so it may not be the fault of flow functions.

fabianbs96 · 2023-12-13T18:34:09Z

Hi @yuffon,

I have debugged your issue. There was indeed a bug in the PropagateOntoStrategy implementation. Can you check, whether the current version works?

In fact, I use identity flow function for all return edges.

Besides that, it is not a good idea to skip fact-mapping in the call-flow-function and in the ret-flow-function. This way you will not get context-sensitive results at the end

yuffon · 2023-12-14T06:28:54Z

It works on my problem now. Great. Thanks. At 2023-12-14 02:34:19, "Fabian Schiebel" ***@***.***> wrote: Hi @yuffon, I have debugged your issue. There was indeed a bug in the PropagateOntoStrategy implementation. Can you check, whether the current version works? In fact, I use identity flow function for all return edges. Besides that, it is not a good idea to skip fact-mapping in the call-flow-function and in the ret-flow-function. This way wou will not get context-sensitive results at the end — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you were mentioned.Message ID: ***@***.***>

fabianbs96 and others added 8 commits September 18, 2023 12:31

Small restructure of IDESolver

1ae6f5d

First draft with strategy

a3e8872

Add unittest (fact propagation works, need to fix value propagation -…

7957bd3

…- phase II)

Fix valud computation

361b849

Improve eager propagation

efbf9cf

Cleanup solvers + add SolverImpl (WIP)

408b00e

Generalize interface within IDESolverImpl

1f14b61

Make EagerIDESolver inherit the IDESolverImpl getting rid of a lot co…

c1d9632

…de duplication

fabianbs96 added the enhancement New feature or request label Sep 21, 2023

fabianbs96 self-assigned this Sep 21, 2023

fabianbs96 and others added 2 commits September 21, 2023 19:13

Merge branch 'development' into f-IDESolverStrategy

a5cd964

Huge cleanup

868faa3

fabianbs96 marked this pull request as ready for review September 24, 2023 11:32

fabianbs96 requested a review from MMory as a code owner September 24, 2023 11:32

fabianbs96 mentioned this pull request Sep 24, 2023

Is there a backward IFDS analysis example? #657

Closed

Merge branch 'development' into f-IDESolverStrategy

18ffb05

fabianbs96 and others added 4 commits November 14, 2023 21:43

Merge branch 'development' into f-IDESolverStrategy

b71d263

Merge branch 'development' into f-IDESolverStrategy

80c00c2

Fix invalid reverse lookup with PropagateOntoStrategy

a8e1998

Merge branch 'development' into f-IDESolverStrategy

4a2f4db

Better testing for EagerIDESolver

8f7f948

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IDE Solver Strategy #669

IDE Solver Strategy #669

fabianbs96 commented Sep 21, 2023

yuffon commented Nov 3, 2023 •

edited

fabianbs96 commented Dec 13, 2023 •

edited

yuffon commented Dec 14, 2023 via email

IDE Solver Strategy #669

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IDE Solver Strategy #669

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fabianbs96 commented Sep 21, 2023

yuffon commented Nov 3, 2023 • edited

fabianbs96 commented Dec 13, 2023 • edited

yuffon commented Dec 14, 2023 via email

yuffon commented Nov 3, 2023 •

edited

fabianbs96 commented Dec 13, 2023 •

edited