From 46f7bcc1e575826f6d3e4a5770ae61423d9be5a9 Mon Sep 17 00:00:00 2001 From: Jeremy Drake Date: Wed, 27 Nov 2024 11:22:49 -0800 Subject: [PATCH] Cygwin: cache IsWow64Process2 host arch in wincap. This was already used in the FAST_CWD check, and could be used in a couple other places. I found the "emulated"/process value returned from the function largely useless, so I did not cache it. It is useless because, as the docs say, it is set to IMAGE_FILE_MACHINE_UNKNOWN (0) if the process is not running under WOW64, but Microsoft also doesn't consider x64-on-ARM64 to be WOW64, so it is set to 0 regardless if the process is ARM64 or x64. You can tell the difference via GetProcessInformation(ProcessMachineTypeInfo), but for the current process even that's overkill: what we really want to know is the IMAGE_FILE_MACHINE_* constant for the Cygwin dll itself, which is conveniently located in memory already, so cache that in wincap also for easy comparisons. Signed-off-by: Jeremy Drake --- winsup/cygwin/local_includes/wincap.h | 4 ++++ winsup/cygwin/path.cc | 6 ++---- winsup/cygwin/wincap.cc | 19 +++++++++++++++++++ 3 files changed, 25 insertions(+), 4 deletions(-) diff --git a/winsup/cygwin/local_includes/wincap.h b/winsup/cygwin/local_includes/wincap.h index c14872787..250866f06 100644 --- a/winsup/cygwin/local_includes/wincap.h +++ b/winsup/cygwin/local_includes/wincap.h @@ -42,6 +42,8 @@ class wincapc RTL_OSVERSIONINFOEXW version; char osnam[40]; const void *caps; + USHORT host_mach; + USHORT cygwin_mach; bool _is_server; public: @@ -61,6 +63,8 @@ public: { return (size_t) system_info.dwAllocationGranularity; } const char *osname () const { return osnam; } const DWORD build_number () const { return version.dwBuildNumber; } + const USHORT host_machine () const { return host_mach; } + const USHORT cygwin_machine () const { return cygwin_mach; } #define IMPLEMENT(cap) cap() const { return ((wincaps *) this->caps)->cap; } diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc index 5cfcbc0f2..869383c83 100644 --- a/winsup/cygwin/path.cc +++ b/winsup/cygwin/path.cc @@ -4617,14 +4617,12 @@ find_fast_cwd_pointer () static fcwd_access_t ** find_fast_cwd () { - USHORT emulated, hosted; fcwd_access_t **f_cwd_ptr; - /* First check if we're running in WOW64 on ARM64 emulating AMD64. Skip + /* First check if we're running on an ARM64 system. Skip fetching FAST_CWD pointer as long as there's no solution for finding it on that system. */ - if (IsWow64Process2 (GetCurrentProcess (), &emulated, &hosted) - && hosted == IMAGE_FILE_MACHINE_ARM64) + if (wincap.host_machine () == IMAGE_FILE_MACHINE_ARM64) return NULL; /* Fetch the pointer but don't set the global fast_cwd_ptr yet. First diff --git a/winsup/cygwin/wincap.cc b/winsup/cygwin/wincap.cc index 30d9c14e8..deecf8ba5 100644 --- a/winsup/cygwin/wincap.cc +++ b/winsup/cygwin/wincap.cc @@ -235,9 +235,15 @@ static const wincaps wincap_11 = { wincapc wincap __attribute__((section (".cygwin_dll_common"), shared)); +extern IMAGE_DOS_HEADER +__image_base__; + void wincapc::init () { + PIMAGE_NT_HEADERS ntheader; + USHORT emul_mach; + if (caps) return; // already initialized @@ -282,4 +288,17 @@ wincapc::init () __small_sprintf (osnam, "NT-%d.%d", version.dwMajorVersion, version.dwMinorVersion); + + if (!IsWow64Process2 (GetCurrentProcess (), &emul_mach, &host_mach)) + { + /* If IsWow64Process2 succeeded, it filled in host_mach. Assume the only + way it fails for the current process is that we're running on an OS + version where it's not implemented yet. As such, the only realistic + option for host_mach is AMD64 */ + host_mach = IMAGE_FILE_MACHINE_AMD64; + } + + ntheader = (PIMAGE_NT_HEADERS)((LPBYTE) &__image_base__ + + __image_base__.e_lfanew); + cygwin_mach = ntheader->FileHeader.Machine; }