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    <p>Pretty hard to verify that you got the address correct, it is unusually low. I just wrote another program to test this. It enumerates the regions in kernel32.dll and calls VirtualProtect() on them:</p> <pre><code>#include &lt;Windows.h&gt; #include &lt;assert.h&gt; #include &lt;iostream&gt; int main() { HMODULE hmod = GetModuleHandle(L"kernel32.dll"); MEMORY_BASIC_INFORMATION info; // Start at PE32 header SIZE_T len = VirtualQuery(hmod, &amp;info, sizeof(info)); assert(len &gt; 0); BYTE* dllBase = (BYTE*)info.AllocationBase; BYTE* address = dllBase; for (;;) { len = VirtualQuery(address, &amp;info, sizeof(info)); assert(len &gt; 0); if (info.AllocationBase != dllBase) break; std::cout &lt;&lt; "Address: " &lt;&lt; std::hex &lt;&lt; info.BaseAddress; std::cout &lt;&lt; " (" &lt;&lt; std::hex &lt;&lt; info.RegionSize &lt;&lt; ") "; std::cout &lt;&lt; " protect = " &lt;&lt; std::hex &lt;&lt; info.Protect; DWORD oldprotect; if (info.Protect == 0) std::cout &lt;&lt; ", VirtualProtect skipped" &lt;&lt; std::endl; else { BOOL ok = VirtualProtect(info.BaseAddress, info.RegionSize, PAGE_EXECUTE_READWRITE, &amp;oldprotect); std::cout &lt;&lt; ", VirtualProtect = " &lt;&lt; (ok ? "okay" : "Failed!") &lt;&lt; std::endl; } address = (BYTE*)info.BaseAddress + info.RegionSize; } return 0; } </code></pre> <p>Output of this program on my machine, running Windows 8.1 x64:</p> <pre><code>Address: 77470000 (1000) protect = 2, VirtualProtect = okay Address: 77471000 (f000) protect = 0, VirtualProtect skipped Address: 77480000 (62000) protect = 20, VirtualProtect = okay Address: 774E2000 (e000) protect = 0, VirtualProtect skipped Address: 774F0000 (7e000) protect = 2, VirtualProtect = okay Address: 7756E000 (2000) protect = 0, VirtualProtect skipped Address: 77570000 (1000) protect = 4, VirtualProtect = okay Address: 77571000 (f000) protect = 0, VirtualProtect skipped Address: 77580000 (1000) protect = 2, VirtualProtect = okay Address: 77581000 (f000) protect = 0, VirtualProtect skipped Address: 77590000 (1a000) protect = 2, VirtualProtect = okay Address: 775AA000 (6000) protect = 0, VirtualProtect skipped </code></pre> <p>Running it in 64-bit mode:</p> <pre><code>Address: 00007FFC4F870000 (1000) protect = 2, VirtualProtect = okay Address: 00007FFC4F871000 (112000) protect = 20, VirtualProtect = okay Address: 00007FFC4F983000 (1000) protect = 4, VirtualProtect = okay Address: 00007FFC4F984000 (1000) protect = 8, VirtualProtect = okay Address: 00007FFC4F985000 (24000) protect = 2, VirtualProtect = okay </code></pre> <p>Clearly you have a different Windows version so be sure to run this program on your machine to get comparable results.</p> <p>The conclusion I draw is there is no fundamental reason for this kind of code to fail. And if it does on your machine then that's likely to be environmental. With a very obvious candidate to be your anti-malware software, which of course has a great stake in preventing code from messing with kernel32.dll. I'm running minimal protection on my machine.</p>
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