AlkantarClanX12
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/*
* this is the internal transfer function.
*
* HISTORY
* 24-Nov-02 Christian Tismer <tismer@tismer.com>
* needed to add another magic constant to insure
* that f in slp_eval_frame(PyFrameObject *f)
* STACK_REFPLUS will probably be 1 in most cases.
* gets included into the saved stack area.
* 26-Sep-02 Christian Tismer <tismer@tismer.com>
* again as a result of virtualized stack access,
* the compiler used less registers. Needed to
* explicit mention registers in order to get them saved.
* Thanks to Jeff Senn for pointing this out and help.
* 17-Sep-02 Christian Tismer <tismer@tismer.com>
* after virtualizing stack save/restore, the
* stack size shrunk a bit. Needed to introduce
* an adjustment STACK_MAGIC per platform.
* 15-Sep-02 Gerd Woetzel <gerd.woetzel@GMD.DE>
* slightly changed framework for sparc
* 01-Mar-02 Christian Tismer <tismer@tismer.com>
* Initial final version after lots of iterations for i386.
*/
#define alloca _alloca
#define STACK_REFPLUS 1
#ifdef SLP_EVAL
#define STACK_MAGIC 0
/* Some magic to quell warnings and keep slp_switch() from crashing when built
with VC90. Disable global optimizations, and the warning: frame pointer
register 'ebp' modified by inline assembly code.
We used to just disable global optimizations ("g") but upstream stackless
Python, as well as stackman, turn off all optimizations.
References:
https://github.com/stackless-dev/stackman/blob/dbc72fe5207a2055e658c819fdeab9731dee78b9/stackman/platforms/switch_x86_msvc.h
https://github.com/stackless-dev/stackless/blob/main-slp/Stackless/platf/switch_x86_msvc.h
*/
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#pragma optimize("", off) /* so that autos are stored on the stack */
#pragma warning(disable:4731)
#pragma warning(disable:4733) /* disable warning about modifying FS[0] */
/**
* Most modern compilers and environments handle C++ exceptions without any
* special help from us. MSVC on 32-bit windows is an exception. There, C++
* exceptions are dealt with using Windows' Structured Exception Handling
* (SEH).
*
* SEH is implemented as a singly linked list of <function*, prev*> nodes. The
* head of this list is stored in the Thread Information Block, which itself
* is pointed to from the FS register. It's the first field in the structure,
* or offset 0, so we can access it using assembly FS:[0], or the compiler
* intrinsics and field offset information from the headers (as we do below).
* Somewhat unusually, the tail of the list doesn't have prev == NULL, it has
* prev == 0xFFFFFFFF.
*
* SEH was designed for C, and traditionally uses the MSVC compiler
* intrinsincs __try{}/__except{}. It is also utilized for C++ exceptions by
* MSVC; there, every throw of a C++ exception raises a SEH error with the
* ExceptionCode 0xE06D7363; the SEH handler list is then traversed to
* deal with the exception.
*
* If the SEH list is corrupt, then when a C++ exception is thrown the program
* will abruptly exit with exit code 1. This does not use std::terminate(), so
* std::set_terminate() is useless to debug this.
*
* The SEH list is closely tied to the call stack; entering a function that
* uses __try{} or most C++ functions will push a new handler onto the front
* of the list. Returning from the function will remove the handler. Saving
* and restoring the head node of the SEH list (FS:[0]) per-greenlet is NOT
* ENOUGH to make SEH or exceptions work.
*
* Stack switching breaks SEH because the call stack no longer necessarily
* matches the SEH list. For example, given greenlet A that switches to
* greenlet B, at the moment of entering greenlet B, we will have any SEH
* handlers from greenlet A on the SEH list; greenlet B can then add its own
* handlers to the SEH list. When greenlet B switches back to greenlet A,
* greenlet B's handlers would still be on the SEH stack, but when switch()
* returns control to greenlet A, we have replaced the contents of the stack
* in memory, so all the address that greenlet B added to the SEH list are now
* invalid: part of the call stack has been unwound, but the SEH list was out
* of sync with the call stack. The net effect is that exception handling
* stops working.
*
* Thus, when switching greenlets, we need to be sure that the SEH list
* matches the effective call stack, "cutting out" any handlers that were
* pushed by the greenlet that switched out and which are no longer valid.
*
* The easiest way to do this is to capture the SEH list at the time the main
* greenlet for a thread is created, and, when initially starting a greenlet,
* start a new SEH list for it, which contains nothing but the handler
* established for the new greenlet itself, with the tail being the handlers
* for the main greenlet. If we then save and restore the SEH per-greenlet,
* they won't interfere with each others SEH lists. (No greenlet can unwind
* the call stack past the handlers established by the main greenlet).
*
* By observation, a new thread starts with three SEH handlers on the list. By
* the time we get around to creating the main greenlet, though, there can be
* many more, established by transient calls that lead to the creation of the
* main greenlet. Therefore, 3 is a magic constant telling us when to perform
* the initial slice.
*
* All of this can be debugged using a vectored exception handler, which
* operates independently of the SEH handler list, and is called first.
* Walking the SEH list at key points can also be helpful.
*
* References:
* https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
* https://devblogs.microsoft.com/oldnewthing/20100730-00/?p=13273
* https://docs.microsoft.com/en-us/cpp/cpp/try-except-statement?view=msvc-160
* https://docs.microsoft.com/en-us/cpp/cpp/structured-exception-handling-c-cpp?view=msvc-160
* https://docs.microsoft.com/en-us/windows/win32/debug/structured-exception-handling
* https://docs.microsoft.com/en-us/windows/win32/debug/using-a-vectored-exception-handler
* https://bytepointer.com/resources/pietrek_crash_course_depths_of_win32_seh.htm
*/
#define GREENLET_NEEDS_EXCEPTION_STATE_SAVED
typedef struct _GExceptionRegistration {
struct _GExceptionRegistration* prev;
void* handler_f;
} GExceptionRegistration;
static void
slp_set_exception_state(const void *const seh_state)
{
// Because the stack from from which we do this is ALSO a handler, and
// that one we want to keep, we need to relink the current SEH handler
// frame to point to this one, cutting out the middle men, as it were.
//
// Entering a try block doesn't change the SEH frame, but entering a
// function containing a try block does.
GExceptionRegistration* current_seh_state = (GExceptionRegistration*)__readfsdword(FIELD_OFFSET(NT_TIB, ExceptionList));
current_seh_state->prev = (GExceptionRegistration*)seh_state;
}
static GExceptionRegistration*
x86_slp_get_third_oldest_handler()
{
GExceptionRegistration* a = NULL; /* Closest to the top */
GExceptionRegistration* b = NULL; /* second */
GExceptionRegistration* c = NULL;
GExceptionRegistration* seh_state = (GExceptionRegistration*)__readfsdword(FIELD_OFFSET(NT_TIB, ExceptionList));
a = b = c = seh_state;
while (seh_state && seh_state != (GExceptionRegistration*)0xFFFFFFFF) {
if ((void*)seh_state->prev < (void*)100) {
fprintf(stderr, "\tERROR: Broken SEH chain.\n");
return NULL;
}
a = b;
b = c;
c = seh_state;
seh_state = seh_state->prev;
}
return a ? a : (b ? b : c);
}
static void*
slp_get_exception_state()
{
// XXX: There appear to be three SEH handlers on the stack already at the
// start of the thread. Is that a guarantee? Almost certainly not. Yet in
// all observed cases it has been three. This is consistent with
// faulthandler off or on, and optimizations off or on. It may not be
// consistent with other operating system versions, though: we only have
// CI on one or two versions (don't ask what there are).
// In theory we could capture the number of handlers on the chain when
// PyInit__greenlet is called: there are probably only the default
// handlers at that point (unless we're embedded and people have used
// __try/__except or a C++ handler)?
return x86_slp_get_third_oldest_handler();
}
static int
slp_switch(void)
{
/* MASM syntax is typically reversed from other assemblers.
It is usually <instruction> <destination> <source>
*/
int *stackref, stsizediff;
/* store the structured exception state for this stack */
DWORD seh_state = __readfsdword(FIELD_OFFSET(NT_TIB, ExceptionList));
__asm mov stackref, esp;
/* modify EBX, ESI and EDI in order to get them preserved */
__asm mov ebx, ebx;
__asm xchg esi, edi;
{
SLP_SAVE_STATE(stackref, stsizediff);
__asm {
mov eax, stsizediff
add esp, eax
add ebp, eax
}
SLP_RESTORE_STATE();
}
__writefsdword(FIELD_OFFSET(NT_TIB, ExceptionList), seh_state);
return 0;
}
/* re-enable ebp warning and global optimizations. */
#pragma optimize("", on)
#pragma warning(default:4731)
#pragma warning(default:4733) /* disable warning about modifying FS[0] */
#endif
/*
* further self-processing support
*/
/* we have IsBadReadPtr available, so we can peek at objects */
#define STACKLESS_SPY
#ifdef GREENLET_DEBUG
#define CANNOT_READ_MEM(p, bytes) IsBadReadPtr(p, bytes)
static int IS_ON_STACK(void*p)
{
int stackref;
int stackbase = ((int)&stackref) & 0xfffff000;
return (int)p >= stackbase && (int)p < stackbase + 0x00100000;
}
static void
x86_slp_show_seh_chain()
{
GExceptionRegistration* seh_state = (GExceptionRegistration*)__readfsdword(FIELD_OFFSET(NT_TIB, ExceptionList));
fprintf(stderr, "====== SEH Chain ======\n");
while (seh_state && seh_state != (GExceptionRegistration*)0xFFFFFFFF) {
fprintf(stderr, "\tSEH_chain addr: %p handler: %p prev: %p\n",
seh_state,
seh_state->handler_f, seh_state->prev);
if ((void*)seh_state->prev < (void*)100) {
fprintf(stderr, "\tERROR: Broken chain.\n");
break;
}
seh_state = seh_state->prev;
}
fprintf(stderr, "====== End SEH Chain ======\n");
fflush(NULL);
return;
}
//addVectoredExceptionHandler constants:
//CALL_FIRST means call this exception handler first;
//CALL_LAST means call this exception handler last
#define CALL_FIRST 1
#define CALL_LAST 0
LONG WINAPI
GreenletVectorHandler(PEXCEPTION_POINTERS ExceptionInfo)
{
// We get one of these for every C++ exception, with code
// E06D7363
// This is a special value that means "C++ exception from MSVC"
// https://devblogs.microsoft.com/oldnewthing/20100730-00/?p=13273
//
// Install in the module init function with:
// AddVectoredExceptionHandler(CALL_FIRST, GreenletVectorHandler);
PEXCEPTION_RECORD ExceptionRecord = ExceptionInfo->ExceptionRecord;
fprintf(stderr,
"GOT VECTORED EXCEPTION:\n"
"\tExceptionCode : %p\n"
"\tExceptionFlags : %p\n"
"\tExceptionAddr : %p\n"
"\tNumberparams : %ld\n",
ExceptionRecord->ExceptionCode,
ExceptionRecord->ExceptionFlags,
ExceptionRecord->ExceptionAddress,
ExceptionRecord->NumberParameters
);
if (ExceptionRecord->ExceptionFlags & 1) {
fprintf(stderr, "\t\tEH_NONCONTINUABLE\n" );
}
if (ExceptionRecord->ExceptionFlags & 2) {
fprintf(stderr, "\t\tEH_UNWINDING\n" );
}
if (ExceptionRecord->ExceptionFlags & 4) {
fprintf(stderr, "\t\tEH_EXIT_UNWIND\n" );
}
if (ExceptionRecord->ExceptionFlags & 8) {
fprintf(stderr, "\t\tEH_STACK_INVALID\n" );
}
if (ExceptionRecord->ExceptionFlags & 0x10) {
fprintf(stderr, "\t\tEH_NESTED_CALL\n" );
}
if (ExceptionRecord->ExceptionFlags & 0x20) {
fprintf(stderr, "\t\tEH_TARGET_UNWIND\n" );
}
if (ExceptionRecord->ExceptionFlags & 0x40) {
fprintf(stderr, "\t\tEH_COLLIDED_UNWIND\n" );
}
fprintf(stderr, "\n");
fflush(NULL);
for(DWORD i = 0; i < ExceptionRecord->NumberParameters; i++) {
fprintf(stderr, "\t\t\tParam %ld: %lX\n", i, ExceptionRecord->ExceptionInformation[i]);
}
if (ExceptionRecord->NumberParameters == 3) {
fprintf(stderr, "\tAbout to traverse SEH chain\n");
// C++ Exception records have 3 params.
x86_slp_show_seh_chain();
}
return EXCEPTION_CONTINUE_SEARCH;
}
#endif