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Date:	Tue, 28 May 2024 10:58:00 +0900
To:	cygwin AT cygwin DOT com
Cc:	Jeremy Drake <cygwin AT jdrake DOT com>
Subject:	Re: frequent hangs running ldd
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From:	Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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On Fri, 24 May 2024 19:29:43 -0700 (PDT)
Jeremy Drake wrote:
> On Fri, 24 May 2024, Jeremy Drake wrote:
> 
> > On Fri, 24 May 2024, Jeremy Drake wrote:
> >
> > > Looking at !address, it seems Windows put the PEB, TEBs, and stacks in the
> > > area where the cygheap should be.  Way to go, ASLR :P
> >
> > I think the fix for this would be to add -Wl,--disable-high-entropy-va to
> > ldh_LDFLAGS, as was done for strace and cygcheck at least.  I used peflags
> > -d0 /usr/bin/ldh.exe and I'm not seeing a hang after that.
> 
> Sorry, that was peflags -e0 not -d0 (dynamicbase is still on):
> $ peflags -v /usr/bin/ldh.exe
> /usr/bin/ldh.exe:
> coff(0x0226[+executable_image,+line_nums_stripped,+bigaddr,+sepdbg])
> pe(0x0140[+dynamicbase,+nxcompat])

You are right!

It seems that VirtualAlloc() in cygheap_init() in mm/cygheap.cc
fails when the address range which cygwin uses is occupied due to
high-entropy-va in ldh.exe.

Thanks for the analysis.

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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