No, sorry, I don't have the setup to build mingw. Not likely that I will
have time to do it any time soon either.
I meant this as a bug report. I hope the problem has been investigated
sufficiently for mingw devs to act on it.
Vadim
On Mon, Aug 18, 2014 at 9:34 PM, dw <limegreenso...@yahoo.com> wrote:
> Did you ever get this sorted out?
>
> dw
>
>
> On 8/15/2014 10:53 PM, dw wrote:
>
> So, it looks like what has happened is that newer OSs (ie >= Vista) set
> the page protect to PAGE_EXECUTE_WRITECOPY when doing a LoadLibrary. This
> is a (relatively) new flag and apparently Mingw still assumes the old
> values are always in use.
>
> There are 3 places in pseudo-reloc.c that do comparisons of b.Protect to
> PAGE_EXECUTE_READWRITE. I believe all three should also check for
> PAGE_EXECUTE_WRITECOPY.
>
> It also looks like a minor perf improvement in __write_memory is possible
> by adding an #else for that VirtualQuery / VirtualProtect stuff:
>
> static void
> __write_memory (void *addr, const void *src, size_t len)
> {
> if (!len)
> return;
>
> #ifdef __MINGW64_VERSION_MAJOR
>
> /* Mark the section writable once, and unset it in
> * restore_modified_sections. */
> mark_section_writable ((LPVOID) addr);
>
> #else /* __MINGW64_VERSION_MAJOR */
>
> MEMORY_BASIC_INFORMATION b;
> DWORD oldprot = 0;
> int call_unprotect = 0;
>
> if (!VirtualQuery (addr, &b, sizeof(b)))
> {
> __report_error (" VirtualQuery failed for %d bytes at address %p",
> (int) sizeof(b), addr);
> }
>
> /* Temporarily allow write access to read-only protected memory. */
> if (b.Protect != PAGE_EXECUTE_READWRITE && b.Protect != PAGE_READWRITE
> && b.Protect != PAGE_EXECUTE_WRITECOPY)
> {
> call_unprotect = 1;
> VirtualProtect (b.BaseAddress, b.RegionSize, PAGE_EXECUTE_READWRITE,
> &oldprot);
> }
>
> #endif /* __MINGW64_VERSION_MAJOR */
>
> /* write the data. */
> memcpy (addr, src, len);
>
> #ifndef __MINGW64_VERSION_MAJOR
>
> /* Restore original protection. */
> if (call_unprotect && b.Protect != PAGE_EXECUTE_READWRITE && b.Protect
> != PAGE_READWRITE && b.Protect != PAGE_EXECUTE_WRITECOPY)
> VirtualProtect (b.BaseAddress, b.RegionSize, oldprot, &oldprot);
>
> #endif /* __MINGW64_VERSION_MAJOR */
> }
>
> If setting the protection in mark_section_writable was unsuccessful
> (unlikely as that is), trying to set it again here is not likely to help.
>
> NB: I haven't tried this, but you have the setup to test it anyway. Also,
> this code snippet only fixes 2 of the 3 places that use
> PAGE_EXECUTE_WRITECOPY. Remember to change the comparison in
> mark_section_writable() as well.
>
> FWIW,
> dw
>
> On 8/15/2014 8:17 PM, Vadim Chugunov wrote:
>
> Okay, I was wrong about __MINGW64_VERSION_MAJOR: it *was* defined.
>
> What apparently happens is that the VirtualQuery() call that follows
> mark_section_writable(), returns page protection status of 0x80
> (PAGE_EXECUTE_WRITECOPY), which is unexpected by the relocator code, so it
> falls back to calling VirtualProtect() per relocation entry.
>
> I am not entirely sure how this situation comes about, but here you go...
>
> On Fri, Aug 15, 2014 at 1:01 AM, Vadim Chugunov <vadi...@gmail.com> wrote:
>
>> Hi,
>> I am trying to figure out the cause of a slow application startup, and
>> the evidence I have so far, points to mingw's _pei386_runtime_relocator()
>> routine as the culprit. When I start my app under debugger, I see this
>> function calling VirtualProtect() about a zillion times in a row.
>>
>> Looking at the source, I see that __pei386_runtime_relocator() is
>> supposed to change memory protection just once per executable section, but
>> only if __MINGW64_VERSION_MAJOR is defined at compilation time.
>> Otherwise, it reverts to changing protection once per relocation entry,
>> for compatibility (?).
>> Unfortunately, I don't see any headers included by pseudo-reloc.c that
>> would define this symbol. And, indeed, the behavior I am seeing at runtime
>> indicates that if was not defined...
>>
>> Am I reading this right?
>>
>> Thanks!
>> Vadim
>>
>
>
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