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Implement a new stack and error handling model for the SourcePawn VM.

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This has three major changes to SourcePawn. First, the API now supports the concept of "exceptions". The exception state is a global property of an instance of the SourcePawn VM. Exceptions can be caught or suppressed. Many places in SourceMod have been updated to check exceptions instead of errors.

The new API obsoletes major parts of the embedder API - all but one method of invoking functions is obsoleted, and the debug interface has been scrapped. Extensions using the native API will not be affected, however, ThrowNativeError has been deprecated in favor of ReportError.

Second, the SourcePawn concept of a "stack" has been unified at the API level. A stack frame iterator now iterates over all SourcePawn invocations, rather than the topmost plugin. This makes error handling more consistent and removes another dependency on context-per-plugin.

Finally, the implementation of stack frames has been changed dramatically. Rather than maintain a complicated and expensive return pointer stack, we now rely on the implicit one provided by the CPU. The stack frame iterator now walks the JIT stack directly. This removes many unnecessary bookkeeping instructions from the generated code, in particular making the CALL instruction 40% faster.

These changes required some fair surgery to the JIT. Its error paths are now slightly more complicated, as they have to throw an exception rather than return an error code. In addition, any path that can throw an exception is now responsible for creating an "exit frame", which exists to tell the stack frame iterator about transitions from the JIT to the VM.
This commit is contained in:
David Anderson
2015-03-04 23:45:30 -08:00
parent 04827466b0
commit a1afa23bc4
51 changed files with 2085 additions and 1766 deletions
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sourcepawn/jit/environment.cpp
+180 -32
View File
@@ -13,7 +13,6 @@
#include "environment.h"
#include "x86/jit_x86.h"
#include "watchdog_timer.h"
#include "debug-trace.h"
#include "api.h"
#include "code-stubs.h"
#include "watchdog_timer.h"
@@ -25,10 +24,12 @@ static Environment *sEnvironment = nullptr;
Environment::Environment()
: debugger_(nullptr),
exception_code_(SP_ERROR_NONE),
profiler_(nullptr),
jit_enabled_(true),
profiling_enabled_(false),
code_pool_(nullptr)
code_pool_(nullptr),
top_(nullptr)
{
}
@@ -150,7 +151,9 @@ static const char *sErrorMsgTable[] =
"Plugin format is too new",
"Out of memory",
"Integer overflow",
"Script execution timed out"
"Script execution timed out",
"Custom error",
"Fatal error"
};
const char *
@@ -161,17 +164,6 @@ Environment::GetErrorString(int error)
return sErrorMsgTable[error];
}
void
Environment::ReportError(PluginRuntime *runtime, int err, const char *errstr, cell_t rp_start)
{
if (!debugger_)
return;
CContextTrace trace(runtime, err, errstr, rp_start);
debugger_->OnContextExecuteError(runtime->GetDefaultContext(), &trace);
}
void *
Environment::AllocateCode(size_t size)
{
@@ -198,6 +190,15 @@ Environment::DeregisterRuntime(PluginRuntime *rt)
runtimes_.remove(rt);
}
static inline void
SwapLoopEdge(uint8_t *code, LoopEdge &e)
{
int32_t *loc = reinterpret_cast<int32_t *>(code + e.offset - 4);
int32_t new_disp32 = e.disp32;
e.disp32 = *loc;
*loc = new_disp32;
}
void
Environment::PatchAllJumpsForTimeout()
{
@@ -208,11 +209,8 @@ Environment::PatchAllJumpsForTimeout()
CompiledFunction *fun = rt->GetJitFunction(i);
uint8_t *base = reinterpret_cast<uint8_t *>(fun->GetEntryAddress());
for (size_t j = 0; j < fun->NumLoopEdges(); j++) {
const LoopEdge &e = fun->GetLoopEdge(j);
int32_t diff = intptr_t(code_stubs_->TimeoutStub()) - intptr_t(base + e.offset);
*reinterpret_cast<int32_t *>(base + e.offset - 4) = diff;
}
for (size_t j = 0; j < fun->NumLoopEdges(); j++)
SwapLoopEdge(base, fun->GetLoopEdge(j));
}
}
}
@@ -227,10 +225,8 @@ Environment::UnpatchAllJumpsFromTimeout()
CompiledFunction *fun = rt->GetJitFunction(i);
uint8_t *base = reinterpret_cast<uint8_t *>(fun->GetEntryAddress());
for (size_t j = 0; j < fun->NumLoopEdges(); j++) {
const LoopEdge &e = fun->GetLoopEdge(j);
*reinterpret_cast<int32_t *>(base + e.offset - 4) = e.disp32;
}
for (size_t j = 0; j < fun->NumLoopEdges(); j++)
SwapLoopEdge(base, fun->GetLoopEdge(j));
}
}
}
@@ -238,16 +234,168 @@ Environment::UnpatchAllJumpsFromTimeout()
int
Environment::Invoke(PluginRuntime *runtime, CompiledFunction *fn, cell_t *result)
{
// Must be in an invoke frame.
assert(top_ && top_->cx() == runtime->GetBaseContext());
PluginContext *cx = runtime->GetBaseContext();
// Note that cip, hp, sp are saved and restored by Execute2().
*cx->addressOfCip() = fn->GetCodeOffset();
InvokeStubFn invoke = code_stubs_->InvokeStub();
EnterInvoke();
int err = invoke(cx, fn->GetEntryAddress(), result);
LeaveInvoke();
return err;
return invoke(cx, fn->GetEntryAddress(), result);
}
void
Environment::ReportError(int code)
{
const char *message = GetErrorString(code);
if (!message) {
char buffer[255];
UTIL_Format(buffer, sizeof(buffer), "Unknown error code %d", code);
ReportError(code, buffer);
} else {
ReportError(code, message);
}
}
class ErrorReport : public SourcePawn::IErrorReport
{
public:
ErrorReport(int code, const char *message, PluginContext *cx)
: code_(code),
message_(message),
context_(cx)
{}
const char *Message() const KE_OVERRIDE {
return message_;
}
bool IsFatal() const KE_OVERRIDE {
switch (code_) {
case SP_ERROR_HEAPLOW:
case SP_ERROR_INVALID_ADDRESS:
case SP_ERROR_STACKLOW:
case SP_ERROR_INVALID_INSTRUCTION:
case SP_ERROR_MEMACCESS:
case SP_ERROR_STACKMIN:
case SP_ERROR_HEAPMIN:
case SP_ERROR_INSTRUCTION_PARAM:
case SP_ERROR_STACKLEAK:
case SP_ERROR_HEAPLEAK:
case SP_ERROR_TRACKER_BOUNDS:
case SP_ERROR_PARAMS_MAX:
case SP_ERROR_ABORTED:
case SP_ERROR_OUT_OF_MEMORY:
case SP_ERROR_FATAL:
return true;
default:
return false;
}
}
IPluginContext *Context() const KE_OVERRIDE {
return context_;
}
private:
int code_;
const char *message_;
PluginContext *context_;
};
void
Environment::ReportErrorVA(const char *fmt, va_list ap)
{
ReportErrorVA(SP_ERROR_USER, fmt, ap);
}
void
Environment::ReportErrorVA(int code, const char *fmt, va_list ap)
{
// :TODO: right-size the string rather than rely on this buffer.
char buffer[1024];
UTIL_FormatVA(buffer, sizeof(buffer), fmt, ap);
ReportError(code, buffer);
}
void
Environment::ReportErrorFmt(int code, const char *message, ...)
{
va_list ap;
va_start(ap, message);
ReportErrorVA(code, message, ap);
va_end(ap);
}
void
Environment::ReportError(int code, const char *message)
{
FrameIterator iter;
ErrorReport report(code, message, top_ ? top_->cx() : nullptr);
// If this fires, someone forgot to propagate an error.
assert(!hasPendingException());
// Save the exception state.
if (eh_top_) {
exception_code_ = code;
UTIL_Format(exception_message_, sizeof(exception_message_), "%s", message);
}
// For now, we always report exceptions even if they might be handled.
if (debugger_)
debugger_->ReportError(report, iter);
}
void
Environment::EnterExceptionHandlingScope(ExceptionHandler *handler)
{
handler->next_ = eh_top_;
eh_top_ = handler;
}
void
Environment::LeaveExceptionHandlingScope(ExceptionHandler *handler)
{
assert(handler == eh_top_);
eh_top_ = eh_top_->next_;
// To preserve compatibility with older API, we clear the exception state
// when there is no EH handler.
if (!eh_top_ || handler->catch_)
exception_code_ = SP_ERROR_NONE;
}
bool
Environment::HasPendingException(const ExceptionHandler *handler)
{
// Note here and elsewhere - this is not a sanity assert. In the future, the
// API may need to query the handler.
assert(handler == eh_top_);
return hasPendingException();
}
const char *
Environment::GetPendingExceptionMessage(const ExceptionHandler *handler)
{
// Note here and elsewhere - this is not a sanity assert. In the future, the
// API may need to query the handler.
assert(handler == eh_top_);
assert(HasPendingException(handler));
return exception_message_;
}
bool
Environment::hasPendingException() const
{
return exception_code_ != SP_ERROR_NONE;
}
void
Environment::clearPendingException()
{
exception_code_ = SP_ERROR_NONE;
}
int
Environment::getPendingExceptionCode() const
{
return exception_code_;
}