MSDN – Windows API Documentation

The CONTEXT structure contains processor-specific register data. It is used by GetThreadContext and SetThreadContext to retrieve or set a thread's execution context.

#if defined(_M_IX86) || defined(_M_X64)
typedef struct _CONTEXT {
    DWORD64 P1Home;
    DWORD64 P2Home;
    DWORD64 P3Home;
    DWORD64 P4Home;
    DWORD64 P5Home;
    DWORD64 P6Home;
    DWORD   ContextFlags;
    DWORD   MxCsr;
    WORD    SegCs;
    WORD    SegDs;
    WORD    SegEs;
    WORD    SegFs;
    WORD    SegGs;
    WORD    SegSs;
    DWORD   EFlags;
    DWORD64 Dr0;
    DWORD64 Dr1;
    DWORD64 Dr2;
    DWORD64 Dr3;
    DWORD64 Dr6;
    DWORD64 Dr7;
    DWORD64 Rax;
    DWORD64 Rcx;
    DWORD64 Rdx;
    DWORD64 Rbx;
    DWORD64 Rsp;
    DWORD64 Rbp;
    DWORD64 Rsi;
    DWORD64 Rdi;
    DWORD64 R8;
    DWORD64 R9;
    DWORD64 R10;
    DWORD64 R11;
    DWORD64 R12;
    DWORD64 R13;
    DWORD64 R14;
    DWORD64 R15;
    DWORD64 Rip;
    XMM_SAVE_AREA32 FloatSave;
    DWORD64 VectorRegister[26];
    DWORD64 VectorControl;
    DWORD64 DebugControl;
    DWORD64 LastBranchToRip;
    DWORD64 LastBranchFromRip;
    DWORD64 LastExceptionToRip;
    DWORD64 LastExceptionFromRip;
} CONTEXT, *PCONTEXT;
#endif

// Retrieve the current thread's context
CONTEXT ctx = {0};
ctx.ContextFlags = CONTEXT_FULL;
if (GetThreadContext(GetCurrentThread(), &ctx)) {
    // ctx now contains register values
}

// Modify the instruction pointer
ctx.Rip = (DWORD64)MyFunction;
SetThreadContext(GetCurrentThread(), &ctx);

• Always initialize ContextFlags before calling GetThreadContext or SetThreadContext.
• On x86, use CONTEXT32 instead of CONTEXT.
• The structure layout differs between 32‑bit and 64‑bit builds.
• Use Wow64GetThreadContext to query the context of a 32‑bit thread from a 64‑bit process.

• XMM_SAVE_AREA32
• EXCEPTION_RECORD
• GetThreadContext
• SetThreadContext