Mercurial > hg > truffle
diff agent/src/share/classes/sun/jvm/hotspot/runtime/amd64/AMD64CurrentFrameGuess.java @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
parents | |
children | c18cbe5936b8 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/agent/src/share/classes/sun/jvm/hotspot/runtime/amd64/AMD64CurrentFrameGuess.java Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,215 @@ +/* + * Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +package sun.jvm.hotspot.runtime.amd64; + +import sun.jvm.hotspot.debugger.*; +import sun.jvm.hotspot.debugger.amd64.*; +import sun.jvm.hotspot.code.*; +import sun.jvm.hotspot.interpreter.*; +import sun.jvm.hotspot.runtime.*; + +/** <P> Should be able to be used on all amd64 platforms we support + (Linux/amd64) to implement JavaThread's + "currentFrameGuess()" functionality. Input is an AMD64ThreadContext; + output is SP, FP, and PC for an AMD64Frame. Instantiation of the + AMD64Frame is left to the caller, since we may need to subclass + AMD64Frame to support signal handler frames on Unix platforms. </P> + + <P> Algorithm is to walk up the stack within a given range (say, + 512K at most) looking for a plausible PC and SP for a Java frame, + also considering those coming in from the context. If we find a PC + that belongs to the VM (i.e., in generated code like the + interpreter or CodeCache) then we try to find an associated EBP. + We repeat this until we either find a complete frame or run out of + stack to look at. </P> */ + +public class AMD64CurrentFrameGuess { + private AMD64ThreadContext context; + private JavaThread thread; + private Address spFound; + private Address fpFound; + private Address pcFound; + + private static final boolean DEBUG = System.getProperty("sun.jvm.hotspot.runtime.amd64.AMD64Frame.DEBUG") + != null; + + public AMD64CurrentFrameGuess(AMD64ThreadContext context, + JavaThread thread) { + this.context = context; + this.thread = thread; + } + + /** Returns false if not able to find a frame within a reasonable range. */ + public boolean run(long regionInBytesToSearch) { + Address sp = context.getRegisterAsAddress(AMD64ThreadContext.RSP); + Address pc = context.getRegisterAsAddress(AMD64ThreadContext.RIP); + Address fp = context.getRegisterAsAddress(AMD64ThreadContext.RBP); + if (sp == null) { + // Bail out if no last java frame either + if (thread.getLastJavaSP() != null) { + setValues(thread.getLastJavaSP(), thread.getLastJavaFP(), null); + return true; + } + return false; + } + Address end = sp.addOffsetTo(regionInBytesToSearch); + VM vm = VM.getVM(); + + setValues(null, null, null); // Assume we're not going to find anything + + if (vm.isJavaPCDbg(pc)) { + if (vm.isClientCompiler()) { + // If the topmost frame is a Java frame, we are (pretty much) + // guaranteed to have a viable EBP. We should be more robust + // than this (we have the potential for losing entire threads' + // stack traces) but need to see how much work we really have + // to do here. Searching the stack for an (SP, FP) pair is + // hard since it's easy to misinterpret inter-frame stack + // pointers as base-of-frame pointers; we also don't know the + // sizes of C1 frames (not registered in the nmethod) so can't + // derive them from ESP. + + setValues(sp, fp, pc); + return true; + } else { + if (vm.getInterpreter().contains(pc)) { + if (DEBUG) { + System.out.println("CurrentFrameGuess: choosing interpreter frame: sp = " + + sp + ", fp = " + fp + ", pc = " + pc); + } + setValues(sp, fp, pc); + return true; + } + + // For the server compiler, EBP is not guaranteed to be valid + // for compiled code. In addition, an earlier attempt at a + // non-searching algorithm (see below) failed because the + // stack pointer from the thread context was pointing + // (considerably) beyond the ostensible end of the stack, into + // garbage; walking from the topmost frame back caused a crash. + // + // This algorithm takes the current PC as a given and tries to + // find the correct corresponding SP by walking up the stack + // and repeatedly performing stackwalks (very inefficient). + // + // FIXME: there is something wrong with stackwalking across + // adapter frames...this is likely to be the root cause of the + // failure with the simpler algorithm below. + + for (long offset = 0; + offset < regionInBytesToSearch; + offset += vm.getAddressSize()) { + try { + Address curSP = sp.addOffsetTo(offset); + Frame frame = new AMD64Frame(curSP, null, pc); + RegisterMap map = thread.newRegisterMap(false); + while (frame != null) { + if (frame.isEntryFrame() && frame.entryFrameIsFirst()) { + // We were able to traverse all the way to the + // bottommost Java frame. + // This sp looks good. Keep it. + if (DEBUG) { + System.out.println("CurrentFrameGuess: Choosing sp = " + curSP + ", pc = " + pc); + } + setValues(curSP, null, pc); + return true; + } + frame = frame.sender(map); + } + } catch (Exception e) { + if (DEBUG) { + System.out.println("CurrentFrameGuess: Exception " + e + " at offset " + offset); + } + // Bad SP. Try another. + } + } + + // Were not able to find a plausible SP to go with this PC. + // Bail out. + return false; + + /* + // Original algorithm which does not work because SP was + // pointing beyond where it should have: + + // For the server compiler, EBP is not guaranteed to be valid + // for compiled code. We see whether the PC is in the + // interpreter and take care of that, otherwise we run code + // (unfortunately) duplicated from AMD64Frame.senderForCompiledFrame. + + CodeCache cc = vm.getCodeCache(); + if (cc.contains(pc)) { + CodeBlob cb = cc.findBlob(pc); + + // See if we can derive a frame pointer from SP and PC + // NOTE: This is the code duplicated from AMD64Frame + Address saved_fp = null; + int llink_offset = cb.getLinkOffset(); + if (llink_offset >= 0) { + // Restore base-pointer, since next frame might be an interpreter frame. + Address fp_addr = sp.addOffsetTo(VM.getVM().getAddressSize() * llink_offset); + saved_fp = fp_addr.getAddressAt(0); + } + + setValues(sp, saved_fp, pc); + return true; + } + */ + } + } else { + // If the current program counter was not known to us as a Java + // PC, we currently assume that we are in the run-time system + // and attempt to look to thread-local storage for saved ESP and + // EBP. Note that if these are null (because we were, in fact, + // in Java code, i.e., vtable stubs or similar, and the SA + // didn't have enough insight into the target VM to understand + // that) then we are going to lose the entire stack trace for + // the thread, which is sub-optimal. FIXME. + + if (DEBUG) { + System.out.println("CurrentFrameGuess: choosing last Java frame: sp = " + + thread.getLastJavaSP() + ", fp = " + thread.getLastJavaFP()); + } + if (thread.getLastJavaSP() == null) { + return false; // No known Java frames on stack + } + setValues(thread.getLastJavaSP(), thread.getLastJavaFP(), null); + return true; + } + } + + public Address getSP() { return spFound; } + public Address getFP() { return fpFound; } + /** May be null if getting values from thread-local storage; take + care to call the correct AMD64Frame constructor to recover this if + necessary */ + public Address getPC() { return pcFound; } + + private void setValues(Address sp, Address fp, Address pc) { + spFound = sp; + fpFound = fp; + pcFound = pc; + } +}