6365cf1bc0
This corresponds to https://github.com/msys2/msys2-runtime/pull/313 Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
68 lines
2.8 KiB
Diff
68 lines
2.8 KiB
Diff
From 0eeda3e131b580df38367f3c71df2cea2c18ee50 Mon Sep 17 00:00:00 2001
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From: Johannes Schindelin <johannes.schindelin@gmx.de>
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Date: Mon, 22 May 2023 13:36:27 +0200
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Subject: [PATCH 38/N] Cygwin: Adjust CWD magic to accommodate for the latest
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Windows previews
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Reportedly a very recent internal build of Windows 11 once again changed
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the current working directory logic a bit, and Cygwin's "magic" (or:
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"technologically sufficiently advanced") code needs to be adjusted
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accordingly.
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In particular, the following assembly code can be seen:
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ntdll!RtlpReferenceCurrentDirectory
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598 00000001`800c6925 488d0db4cd0f00 lea rcx,[ntdll!FastPebLock (00000001`801c36e0)]
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583 00000001`800c692c 4c897810 mov qword ptr [rax+10h],r15
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588 00000001`800c6930 0f1140c8 movups xmmword ptr [rax-38h],xmm0
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598 00000001`800c6934 e82774f4ff call ntdll!RtlEnterCriticalSection
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The change necessarily looks a bit different than 4840a56325 (Cygwin:
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Adjust CWD magic to accommodate for the latest Windows previews,
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2023-05-22): The needle `\x48\x8d\x0d` is already present, as the first
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version of the hack after Windows 8.1 was released. In that code,
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though, the `call` to `RtlEnterCriticalSection` followed the `lea`
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instruction immediately, but now there are two more instructions
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separating them.
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Note: In the long run, we may very well want to follow the insightful
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suggestion by a helpful Windows kernel engineer who pointed out that it
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may be less fragile to implement kind of a disassembler that has a
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better chance to adapt to the ever-changing code of
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`ntdll!RtlpReferenceCurrentDirectory` by skipping uninteresting
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instructions such as `mov %rsp,%rax`, `mov %rbx,0x20(%rax)`, `push %rsi`
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`sub $0x70,%rsp`, etc, and focuses on finding the `lea`, `call
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ntdll!RtlEnterCriticalSection` and `mov ..., rbx` instructions, much
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like it was prototyped out for ARM64 at
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https://gist.github.com/jeremyd2019/aa167df0a0ae422fa6ebaea5b60c80c9
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Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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---
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winsup/cygwin/path.cc | 12 ++++++++++++
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1 file changed, 12 insertions(+)
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diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
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index 688e7f7..c1298a4 100644
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--- a/winsup/cygwin/path.cc
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+++ b/winsup/cygwin/path.cc
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@@ -4899,6 +4899,18 @@ find_fast_cwd_pointer ()
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%rcx for the subsequent RtlEnterCriticalSection call. */
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lock = (const uint8_t *) memmem ((const char *) use_cwd, 80,
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"\x48\x8d\x0d", 3);
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+ if (lock)
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+ {
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+ /* A recent Windows 11 Preview calls `lea rel(rip),%rcx' then
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+ a `mov` and a `movups` instruction, and only then
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+ `callq RtlEnterCriticalSection'.
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+ */
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+ if (memmem (lock + 7, 8, "\x4c\x89\x78\x10\x0f\x11\x40\xc8", 8))
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+ {
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+ call_rtl_offset = 15;
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+ }
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+ }
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+
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if (!lock)
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{
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/* Windows 8.1 Preview calls `lea rel(rip),%r12' then some unrelated
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