From: Steve Schnepp steve.schnepp@pwkf.org
Windows has a 2G/2G split by default, but some addresses are fixed in the win32 ABI, so we have to ensure that those addresses are still available in the virtual memory space and not taken by Linux.
Kudos to stefand for taking the time to explain on IRC. --- dlls/ntdll/unix/loader.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/dlls/ntdll/unix/loader.c b/dlls/ntdll/unix/loader.c index 65934acfc36..5a12ee64038 100644 --- a/dlls/ntdll/unix/loader.c +++ b/dlls/ntdll/unix/loader.c @@ -2309,6 +2309,22 @@ static int pre_exec(void)
#elif defined(__linux__) && (defined(__i386__) || defined(__arm__))
+/* In the Win32 ABI, KUSER_SHARED_DATA is at a fixed address (0x7ffe0000), so + * it needs to be mapped precisely there in every virtual process space by the + * wine process loader. + * + * It is used to map kernel address space pages to user space, so that it is + * user-space readable without any syscall overhead. + * + * For that, we need to ensure that Linux doesn't map anything internal in that + * area, which it does if configured with a 2G/2G split. Unfortunately, Linux + * does initially map the stack there, along with its own vDSO. + * + * More information: + * + * https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntdd... + * https://msrc-blog.microsoft.com/2022/04/05/randomizing-the-kuser_shared_data... + */ static void check_vmsplit( void *stack ) { if (stack < (void *)0x80000000)