idk what the default should be or if anything is not working as expected
but i use -Wl,--dynamicbase to get a pass in the windows app cert kit
regarding ASLR
On Sat, Jan 7, 2017 at 4:19 AM Linda Zhang <lind...@qq.com> wrote:
> OS: Win7 SP1
> Toolchain: Mingw-w64 i686-6.2.0-release-win32-dwarf-rt_v5-rev1
> GCC: 4.8.x - 6.2.0
> Binutils: 2.21 - 2.25.1
> MinGW: official and w64, 4.x - 5.0.1
> Threading and except: all (dw2/sjlj/seh + win32/posix)
>
> Consider a dll whose base address is overlapped with an existing module,
> so that the operating system must relocate it, or for another word, rebase
> it, to work. Relocation is the fundamental part of the security feature
> ASLR and is enabled by default since Windows Vista. When ASLR is enabled,
> all executables are relocated.
>
> BUT, After relocation, the compiled DLL fails to load at all. That's to
> say, the compiled DLL is broken.
>
> Minimal case:
> =====================
> testexe.c
> =====================
> #include <stdio.h>
> __declspec(dllimport) int a();
> int main() {
> a();
> printf("hello world\n");
> return 0;
> }
>
> =====================
> testdll.c
> =====================
> __declspec(dllexport) int a() {return 0;}
>
> =====================
> test.def
> =====================
> EXPORTS
> a
>
> =====================
> makefile
> =====================
> all: test.dll test.exe
> clean:
> rm test.exe test.dll libtest.a
> test.exe: testexe.c
> gcc -o $@ $^ libtest.a -Wl,--image-base,0x400000
> test.dll: testdll.c
> dllwrap -o $@ $^ --def test.def --implib libtest.a
> -Wl,--image-base,0x400000
>
> =====================
> Case end. Also see the attachment. In this case, test.exe refuses to work
> with error 0xC0000005 because test.dll fails to load.
>
> Not only x86-dw2 builds produces the broken DLL, but x86-sjlj, x64-sjlj,
> x64-seh, all builds since 2010, that's to say, gcc 4.8.x to 6.2 with
> binutils 2.21 to 2.25.1, have the same problem. OH MY GOD.
>
> For I know, the only working MinGW bundle is the version comes with
> Dev-C++ 4.9.9.2 in 2005 (GCC 3.4.2 + binutils 2.15.91 + original MinGW32 +
> dw2 + win32).
>
> Nothing is wrong when using Microsoft Visual C++.
>
> I don't know what's wrong, GCC or binutils?. I can't submit bug to GCC
> bugzilla because it is rejecting new account creation. It's really annoying
> to see GCC produced broken DLLs and showing 0xC0000005 frequently and
> randomly. Could anyone help me?
>
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