Etaash Mathamsetty (@etaash.mathamsetty) commented about dlls/ntdll/unix/signal_x86_64.c:
/* push rbp-based kernel stack cfi */ __ASM_CFI(".cfi_remember_state\n\t") __ASM_CFI_CFA_IS_AT2(rcx, 0xa8, 0x01) /* frame->syscall_cfa */ - "leaq 0x70(%rcx),%rsp\n\t" /* %rsp > frame means no longer inside syscall */ + + /* switch to user stack */ + /* %rsp outside kernel stack means no longer inside syscall */ + "movq 0x88(%rcx),%rsp\n\t" + + "movl 0xb4(%rcx),%edx\n\t" /* frame->restore_flags */ + "testl $0x1,%edx\n\t" /* CONTEXT_CONTROL | CONTEXT_INTEGER */
`CONTEXT_CONTROL | CONTEXT_INTEGER` is 0x3 not 0x1 -- https://gitlab.winehq.org/wine/wine/-/merge_requests/10232#note_131349