How to fix “invalid access to memory location” error? - windbg - windbg

Question

I am new to using windbg, and I am trying to set a breakpoint inside of the main function of a .net assembly that I am trying to debug, but am getting:
Unable to insert breakpoint 0 at 000001d1`4465384e, Win32 error 0n998 "Invalid access to memory location."
I have tried using bp and bu $exentry to set a break point for the entry to the program, but even that is giving me the same error. I've tried searching other old stackoverflow topics on this issue and through google, but still haven't found a solution.
Any help would be greatly appreciated.

Answer 1

Given a trivial .NET Console application compiled for .NET framework 4.7
using System;
namespace DebugNetMainMethod
{
class Program
{
static void Main()
{
Console.WriteLine("If you can read this, it's too late. You wanted to set a breakpoint earlier.");
Console.ReadLine();
}
}
}
you can use WinDbg Preview to debug it.
Run WinDbg Preview
Choose "Launch Executable" and select the EXE
WinDbg will stop at the initial breakpoint
ntdll!LdrpDoDebuggerBreak+0x2b:
7743ecc2 cc int 3
At this point, you get the problem you described:
0:000> bp $exentry
0:000> bl
0 e Disable Clear 007a27c6 0001 (0001) 0:**** DebugNetMainMethod!COM+_Entry_Point <PERF> (DebugNetMainMethod+0x27c6)
0:000> g
Unable to insert breakpoint 0 at 007a27c6, Win32 error 0n998
"Invalid access to memory location."
0:000> bc 0
0:000> bl
Note: In the future you want to provide exactly the information above, so everyone can reproduce your issue.
WinDbg is not made for .NET but for debugging "native code", i.e. code that was compiled for a specific processor like x86 or AMD64. WinDbg does not work well for Java, Python or .NET. However, for .NET, Microsoft provides an extension called SOS. You would typically load it like this:
0:000> .loadby sos clr
Unable to find module 'clr'
But at this early stage of debugging, not many DLLs have been loaded and the clr is still missing. So let's postpone this:
0:000> sxe ld clrjit
0:000> g
[...]
ModLoad: 72950000 729da000 C:\Windows\Microsoft.NET\Framework\v4.0.30319\clrjit.dll
[...]
0:000> .loadby sos clr
No output means it worked.
0:000> !bpmd DebugNetMainMethod Program.Main
Found 1 methods in module 00914044...
MethodDesc = 00914d5c
Adding pending breakpoints...
0:000> g
[...]
(2658.2e08): CLR notification exception - code e0444143 (first chance)
JITTED DebugNetMainMethod!DebugNetMainMethod.Program.Main()
Setting breakpoint: bp 00BA085F [DebugNetMainMethod.Program.Main()]
Breakpoint 2 hit
0:000> !clrstack
OS Thread Id: 0x2e08 (0)
Child SP IP Call Site
0075eff4 00ba085f DebugNetMainMethod.Program.Main() [C:\...\Program.cs # 8]
0075f170 63dff036 [GCFrame: 0075f170]
0:000> !u eip
Normal JIT generated code
DebugNetMainMethod.Program.Main()
Begin 00ba0848, size 32
[...]