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[GR-49305] Allow sampling in method prologue and epilogue.
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PullRequest: graal/15830
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@jovanstevanovic
jovanstevanovic committed Nov 8, 2023
2 parents 921cfea + dc864ae commit 0bcc583
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Showing 2 changed files with 112 additions and 18 deletions.
128 changes: 111 additions & 17 deletions .../com.oracle.svm.core/src/com/oracle/svm/core/jfr/sampler/AbstractJfrExecutionSampler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,8 @@
*/
package com.oracle.svm.core.jfr.sampler;

import jdk.graal.compiler.api.replacements.Fold;
import static com.oracle.svm.core.Uninterruptible.CALLED_FROM_UNINTERRUPTIBLE_CODE;

import org.graalvm.nativeimage.CurrentIsolate;
import org.graalvm.nativeimage.ImageSingletons;
import org.graalvm.nativeimage.IsolateThread;
Expand All @@ -33,13 +34,18 @@
import org.graalvm.nativeimage.StackValue;
import org.graalvm.nativeimage.c.function.CodePointer;
import org.graalvm.word.Pointer;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordFactory;

import com.oracle.svm.core.FrameAccess;
import com.oracle.svm.core.SubstrateOptions;
import com.oracle.svm.core.Uninterruptible;
import com.oracle.svm.core.code.CodeInfo;
import com.oracle.svm.core.code.CodeInfoAccess;
import com.oracle.svm.core.code.CodeInfoQueryResult;
import com.oracle.svm.core.code.CodeInfoTable;
import com.oracle.svm.core.code.SimpleCodeInfoQueryResult;
import com.oracle.svm.core.config.ConfigurationValues;
import com.oracle.svm.core.heap.VMOperationInfos;
import com.oracle.svm.core.jdk.UninterruptibleUtils;
import com.oracle.svm.core.jfr.JfrEvent;
Expand All @@ -58,6 +64,9 @@
import com.oracle.svm.core.thread.VMThreads;
import com.oracle.svm.core.threadlocal.FastThreadLocalFactory;
import com.oracle.svm.core.threadlocal.FastThreadLocalInt;
import com.oracle.svm.core.util.PointerUtils;

import jdk.graal.compiler.api.replacements.Fold;

/*
* Base class for different sampler implementations that emit JFR ExecutionSample events.
Expand Down Expand Up @@ -233,21 +242,12 @@ private static void doUninterruptibleStackWalk(CodePointer initialIp, Pointer in
}
}

if (!isSPInsideStackBoundaries(ip, sp)) {
JfrThreadLocal.increaseUnparseableStacks();
return;
}

/* Try to do a stack walk. */
SamplerSampleWriterData data = StackValue.get(SamplerSampleWriterData.class);
if (SamplerSampleWriterDataAccess.initialize(data, 0, false)) {
JfrThreadLocal.setSamplerWriterData(data);
try {
SamplerSampleWriter.begin(data);
SamplerStackWalkVisitor visitor = ImageSingletons.lookup(SamplerStackWalkVisitor.class);
if (JavaStackWalker.walkCurrentThread(sp, ip, visitor) || data.getTruncated()) {
SamplerSampleWriter.end(data, SamplerSampleWriter.EXECUTION_SAMPLE_END);
}
doUninterruptibleStackWalk(data, sp, ip);
} finally {
JfrThreadLocal.setSamplerWriterData(WordFactory.nullPointer());
}
Expand All @@ -266,13 +266,107 @@ private static boolean isInAOTCompiledCode(CodePointer ip) {
* might be positioned outside the stack's boundaries if a signal interrupted the execution at
* the beginning of a method, before the SP was adjusted to its correct value.
*/
@Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
private static boolean isSPInsideStackBoundaries(CodePointer ip, Pointer sp) {
@Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
private static boolean isSPOutsideStackBoundaries(Pointer sp) {
UnsignedWord stackBase = VMThreads.StackBase.get();
assert stackBase.notEqual(0);
Pointer returnAddressLocation = FrameAccess.singleton().getReturnAddressLocation(sp).add(FrameAccess.returnAddressSize());
return returnAddressLocation.aboveThan(stackBase) || returnAddressLocation.belowOrEqual(VMThreads.StackEnd.get());
}

@Uninterruptible(reason = "This method must be uninterruptible since it uses untethered code info.", callerMustBe = true)
private static Pointer getCallerSP(CodeInfo codeInfo, Pointer sp, CodePointer ip) {
long relativeIP = CodeInfoAccess.relativeIP(codeInfo, ip);
long totalFrameSize = CodeInfoAccess.lookupTotalFrameSize(codeInfo, relativeIP);
return sp.add(WordFactory.unsigned(totalFrameSize));
}

@Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
private static boolean isSPAligned(Pointer sp) {
return PointerUtils.isAMultiple(sp, WordFactory.unsigned(ConfigurationValues.getTarget().stackAlignment));
}

@Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
private static boolean isEntryPoint(CodeInfo codeInfo, CodePointer ip) {
long relativeIP = CodeInfoAccess.relativeIP(codeInfo, ip);
SimpleCodeInfoQueryResult queryResult = StackValue.get(SimpleCodeInfoQueryResult.class);
CodeInfoAccess.lookupCodeInfo(codeInfo, relativeIP, queryResult);
return CodeInfoQueryResult.isEntryPoint(queryResult.getEncodedFrameSize());
}

@Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
private static JavaFrameAnchor findLastJavaFrameAnchor(Pointer callerSP) {
JavaFrameAnchor anchor = JavaFrameAnchors.getFrameAnchor();
while (anchor.isNonNull() && anchor.getLastJavaSP().belowOrEqual(callerSP)) {
/* Skip anchors that are in parts of the stack we are not traversing. */
anchor = anchor.getPreviousAnchor();
}
assert anchor.isNull() || anchor.getLastJavaSP().aboveThan(callerSP);
return anchor;
}

@Uninterruptible(reason = "This method must be uninterruptible since it uses untethered code info.", callerMustBe = true)
private static void doUninterruptibleStackWalk(SamplerSampleWriterData data, Pointer sp, CodePointer ip) {
SamplerSampleWriter.begin(data);
/*
* Visit the top frame.
*
* No matter where in the AOT-compiled code the signal has interrupted the execution, we
* know how to decode it.
*/
assert isInAOTCompiledCode(ip);
CodeInfo codeInfo = CodeInfoTable.getImageCodeInfo();
long totalFrameSize = CodeInfoAccess.lookupTotalFrameSize(codeInfo, CodeInfoAccess.relativeIP(codeInfo, ip));
Pointer returnAddressAddress = FrameAccess.singleton().getReturnAddressLocation(sp.add(WordFactory.unsigned(totalFrameSize)))
.add(FrameAccess.returnAddressSize());
return returnAddressAddress.aboveThan(VMThreads.StackEnd.get()) && returnAddressAddress.belowOrEqual(VMThreads.StackBase.get());
SamplerStackWalkVisitor visitor = ImageSingletons.lookup(SamplerStackWalkVisitor.class);
if (!visitor.visitFrame(sp, ip, codeInfo, null, null)) {
/* The top frame is also the last one. */
SamplerSampleWriter.end(data, SamplerSampleWriter.EXECUTION_SAMPLE_END);
return;
}

Pointer callerSP;
if (isSPAligned(sp)) {
/* Stack is probably in a normal, walkable state. */
callerSP = getCallerSP(codeInfo, sp, ip);
if (SubstrateOptions.PreserveFramePointer.getValue() && (isSPOutsideStackBoundaries(callerSP) || !isInAOTCompiledCode(FrameAccess.singleton().readReturnAddress(callerSP)))) {
/*
* We are in the prologue or epilogue. Frame pointer and return address are on top
* of the stack.
*/
callerSP = sp.add(FrameAccess.wordSize()).add(FrameAccess.singleton().savedBasePointerSize());
}
} else {
/* We are in the prologue or epilogue. Return address is at the top of the stack. */
callerSP = sp.add(FrameAccess.wordSize());
}

if (isSPOutsideStackBoundaries(callerSP)) {
/* We made an incorrect assumption earlier, the stack is not walkable. */
JfrThreadLocal.increaseUnparseableStacks();
return;
}

CodePointer returnAddressIP = FrameAccess.singleton().readReturnAddress(callerSP);
if (!isInAOTCompiledCode(returnAddressIP)) {
if (isEntryPoint(codeInfo, ip)) {
JavaFrameAnchor anchor = findLastJavaFrameAnchor(callerSP);
if (anchor.isNonNull()) {
callerSP = anchor.getLastJavaSP();
returnAddressIP = anchor.getLastJavaIP();
} else {
SamplerSampleWriter.end(data, SamplerSampleWriter.EXECUTION_SAMPLE_END);
return;
}
} else {
/* We made an incorrect assumption earlier, the stack is not walkable. */
JfrThreadLocal.increaseUnparseableStacks();
return;
}
}

/* Start a stack walk but from the frame after the top one. */
if (JavaStackWalker.walkCurrentThread(callerSP, returnAddressIP, visitor) || data.getTruncated()) {
SamplerSampleWriter.end(data, SamplerSampleWriter.EXECUTION_SAMPLE_END);
}
}

/**
Expand Down
2 changes: 1 addition & 1 deletion ...tevm/src/com.oracle.svm.core/src/com/oracle/svm/core/sampler/SamplerStackWalkVisitor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ public SamplerStackWalkVisitor() {

@Override
@Uninterruptible(reason = "The method executes during signal handling.", callerMustBe = true)
protected boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame, Object data) {
public boolean visitFrame(Pointer sp, CodePointer ip, CodeInfo codeInfo, DeoptimizedFrame deoptimizedFrame, Object data) {
return recordIp(ip);
}

Expand Down

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