https://sourceware.org/bugzilla/show_bug.cgi?id=20979
Bug ID: 20979
Summary: DLL relocation totally broken
Product: binutils
Version: 2.25
Status: UNCONFIRMED
Severity: critical
Priority: P2
Component: binutils
Assignee: unassigned at sourceware dot org
Reporter: lindasc at qq dot com
Target Milestone: ---
Created attachment 9707
--> https://sourceware.org/bugzilla/attachment.cgi?id=9707&action=edit
minimal case for the DLL relocation bug
OS: Win7 SP1
Toolchain: Mingw-w64 i686-6.2.0-release-win32-dwarf-rt_v5-rev1
Binutils: 2.25.1
I don't know whether it's a GCC bug or a binutils bug, but I think it's not a
mingw bug. I can't submit bug to GCC bugzilla because it is rejecting new
account creation.
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.
Not only x86-dw2 builds produces the broken DLL, but x86-sjlj, x64-sjlj,
x64-seh, all gcc 6.2 builds with binutils 2.25.1 have the same problem. OH MY
GOD. I believe previous builds also have the same problem.
Minical 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.
I don't know what's going wrong, GCC or binutils? Nothing is wrong when using
Microsoft Visual C++. It's really annoying to see GCC compiled programs showing
0xC0000005 frequently and randomly.
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