Identifies a signal handler frame on the stack.
- -There are a few different algorithms for doing this, and - they vary from platform to platform. For example, based on a - conversation with Dave Dice, Solaris/x86 will be substantially - simpler to handle than Solaris/SPARC because the signal handler - frame can be identified because of a program counter == -1.
- -The dbx group provided code and advice on these topics; the - code below evolved from theirs, but is not correct/robust. - Without going into too many details, it seems that looking for - the incoming argument to the sigacthandler frame (which is what - this code identifies) is not guaranteed to be stable across - versions of Solaris, since that function is supplied by - libthread and is not guaranteed not to clobber I2 before it - calls __sighndlr later. From discussions, it sounds like a - robust algorithm which wouldn't require traversal of the - ucontext chain (used by dbx, but which Dave Dice thinks isn't - robust in the face of libthread -- need to follow up) would be - to be able to properly identify the __sighndlr frame, then get - I2 and treat that as a ucontext. To identify __sighndlr we would - need to look up that symbol in the remote process and look for a - program counter within a certain (small) distance.
- -If the underlying Debugger supports CDebugger interface, we - take the approach of __sighnldr symbol. This approach is more robust - compared to the original hueristic approach. Of course, if there - is no CDebugger support, we fallback to the hueristic approach.
- -The current implementation seems to work with Solaris 2.8. - A nice property of this system is that if we find a core file - this algorithm doesn't work on, we can change the code and try - again, so I'm putting this in as the current mechanism for - finding signal handler frames on Solaris/SPARC.
*/ - public boolean isSignalHandlerFrameDbg() { - CDebugger cdbg = VM.getVM().getDebugger().getCDebugger(); - if (cdbg != null) { - LoadObject dso = cdbg.loadObjectContainingPC(getPC()); - if (dso != null) { - ClosestSymbol cs = dso.closestSymbolToPC(getPC()); - if (cs != null && cs.getName().equals("__sighndlr")) { - return true; - } else { - return false; - } - } else { - return false; - } - } else { - if (getYoungerSP() == null) { - // System.err.println(" SPARCFrame.isSignalHandlerFrameDbg: youngerSP = " + getYoungerSP()); - return false; - } - Address i2 = getSP().getAddressAt(SPARCRegisters.I2.spOffsetInSavedWindow()); - if (i2 == null) { - return false; - } - Address fp = getFP(); - // My (mistaken) understanding of the dbx group's code was that - // the signal handler frame could be identified by testing the - // incoming argument to see whether it was a certain distance - // below the frame pointer; in fact, their code did substantially - // more than this (traversal of the ucontext chain, which this - // code can't do because the topmost ucontext is not currently - // available via the proc_service APIs in dbx). The current code - // appears to work, but is probably not robust. - int MAJOR_HACK_OFFSET = 8; // Difference between expected location of the ucontext and reality - // System.err.println(" SPARCFrame.isSignalHandlerFrameDbg: I2 = " + i2 + - // ", fp = " + fp + ", raw_youngerSP = " + getYoungerSP()); - boolean res = i2.equals(fp.addOffsetTo(VM.getVM().getAddressSize() * (REGISTER_SAVE_WORDS + MAJOR_HACK_OFFSET))); - if (res) { - // Qualify this with another test (FIXME: this is a gross heuristic found while testing) - Address sigInfoAddr = getSP().getAddressAt(SPARCRegisters.I5.spOffsetInSavedWindow()); - if (sigInfoAddr == null) { - System.err.println("Frame with fp = " + fp + " looked like a signal handler frame but wasn't"); - res = false; - } - } - return res; - } - } - - public int getSignalNumberDbg() { - // From looking at the stack trace in dbx, it looks like the - // siginfo* comes into sigacthandler in I5. It would be much more - // robust to look at the __sighndlr frame instead, but we can't - // currently identify that frame. - - Address sigInfoAddr = getSP().getAddressAt(SPARCRegisters.I5.spOffsetInSavedWindow()); - // Read si_signo out of siginfo* - return (int) sigInfoAddr.getCIntegerAt(0, 4, false); - } - - public String getSignalNameDbg() { - return POSIXSignals.getSignalName(getSignalNumberDbg()); - } - - public boolean isInterpretedFrameValid() { - if (Assert.ASSERTS_ENABLED) { - Assert.that(isInterpretedFrame(), "Not an interpreted frame"); - } - // These are reasonable sanity checks - if (getFP() == null || (getFP().andWithMask(2 * VM.getVM().getAddressSize() - 1)) != null) { - return false; - } - if (getSP() == null || (getSP().andWithMask(2 * VM.getVM().getAddressSize() - 1)) != null) { - return false; - } - if (getFP().addOffsetTo(INTERPRETER_FRAME_VM_LOCAL_WORDS * VM.getVM().getAddressSize()).lessThan(getSP())) { - return false; - } - - Address methodHandle = addressOfInterpreterFrameMethod().getAddressAt(0); - - if (VM.getVM().getObjectHeap().isValidMethod(methodHandle) == false) { - return false; - } - - // These are hacks to keep us out of trouble. - // The problem with these is that they mask other problems - if (getFP().lessThanOrEqual(getSP())) { // this attempts to deal with unsigned comparison above - return false; - } - if (getFP().minus(getSP()) > 4096 * VM.getVM().getAddressSize()) { // stack frames shouldn't be large. - return false; - } - // FIXME: this is not atomic with respect to GC and is unsuitable - // for use in a non-debugging, or reflective, system. Need to - // figure out how to express this. - Address bcx = addressOfInterpreterFrameBCX().getAddressAt(0); - - Method method; - try { - method = (Method)Metadata.instantiateWrapperFor(methodHandle); - } catch (UnknownOopException ex) { - return false; - } - int bci = bcpToBci(bcx, method); - //validate bci - if (bci < 0) return false; - - return true; - } - - //-------------------------------------------------------------------------------- - // Accessors: - // - - /** Accessors */ - - public long frameSize() { - return (getSenderSP().minus(getSP()) / VM.getVM().getAddressSize()); - } - - public Address getLink() { - return unBiasSP(getFP().getAddressAt(SPARCRegisters.FP.spOffsetInSavedWindow())); - } - - // FIXME: not implementable yet - // public void setLink(Address addr) { - // if (Assert.ASSERTS_ENABLED) { - // Assert.that(getLink().equals(addr), "frame nesting is controlled by hardware"); - // } - // } - - public Frame sender(RegisterMap regMap, CodeBlob cb) { - SPARCRegisterMap map = (SPARCRegisterMap) regMap; - - if (Assert.ASSERTS_ENABLED) { - Assert.that(map != null, "map must be set"); - } - - // Default is we don't have to follow them. The sender_for_xxx - // will update it accordingly - map.setIncludeArgumentOops(false); - - if (isEntryFrame()) { - return senderForEntryFrame(map); - } - - Address youngerSP = getSP(); - Address sp = getSenderSP(); - boolean isInterpreted = false; - - // FIXME: this is a hack to get stackwalking to work in the face - // of a signal like a SEGV. For debugging purposes it's important - // that (a) we are able to traverse the stack if we take a signal - // and (b) that we get the correct program counter in this - // situation. If we are not using alternate signal stacks then (a) - // seems to work all the time (on SPARC), but (b) is violated for - // the frame just below the signal handler. - - // The mechanism for finding the ucontext is not robust. In - // addition, we may find that we need to be able to fetch more - // registers from the ucontext than just the program counter, - // since the register windows on the stack are "stale". This will - // require substantial restructuring of this frame code, so has - // been avoided for now. - - // It is difficult to find a clean solution for mixing debugging - // situations with VM frame traversal. One could consider - // implementing generic frame traversal in the dbx style and only - // using the VM's stack walking mechanism on a per-frame basis, - // for example to traverse Java-level activations in a compiled - // frame. However, this will probably not interact well with the - // mechanism for finding oops on the stack. - - if (VM.getVM().isDebugging()) { - // If we are a signal handler frame, use a trick: make the - // youngerSP of the caller frame point to the top of the - // ucontext's contained register set. This should allow fetching - // of the registers for the frame just below the signal handler - // frame in the usual fashion. - if (isSignalHandlerFrameDbg()) { - - if (DEBUG) { - System.out.println("SPARCFrame.sender: found signal handler frame"); - } - - // Try to give a valid SP and PC for a "deficient frame" since - // we don't have a real register save area; making this class - // work by reading its information from a ucontext as well as - // a register save area is a major undertaking and has been - // deferred for now. It is very important that the PC is - // correct, which is why we don't just fall through to the - // other code (which would read the PC from the stale register - // window and thereby fail to get the actual location of the - // fault). - - long offset = getMContextAreaOffsetInUContext(); - Address fp = sp; - // System.out.println(" FP: " + fp); - fp = fp.addOffsetTo(getUContextOffset() + getMContextAreaOffsetInUContext()); - // System.out.println(" start of mcontext: " + fp); - // FIXME: put these elsewhere. These are the register numbers - // in /usr/include/sys/regset.h. They might belong in - // SPARCReigsters.java, but we currently don't have that list - // of numbers in the SA code (because all of the registers are - // listed as instances of SPARCRegister) and it appears that - // our numbering of the registers and this one don't match up. - int PC_OFFSET_IN_GREGSET = 1; - int SP_OFFSET_IN_GREGSET = 17; - raw_sp = fp.getAddressAt(VM.getVM().getAddressSize() * SP_OFFSET_IN_GREGSET); - Address pc = fp.getAddressAt(VM.getVM().getAddressSize() * PC_OFFSET_IN_GREGSET); - return new SPARCFrame(raw_sp, pc); - } - } - - // Note: The version of this operation on any platform with callee-save - // registers must update the register map (if not null). - // In order to do this correctly, the various subtypes of - // of frame (interpreted, compiled, glue, native), - // must be distinguished. There is no need on SPARC for - // such distinctions, because all callee-save registers are - // preserved for all frames via SPARC-specific mechanisms. - // - // *** HOWEVER, *** if and when we make any floating-point - // registers callee-saved, then we will have to copy over - // the RegisterMap update logic from the Intel code. - - // The constructor of the sender must know whether this frame is interpreted so it can set the - // sender's _interpreter_sp_adjustment field. - if (VM.getVM().getInterpreter().contains(pc)) { - isInterpreted = true; - map.makeIntegerRegsUnsaved(); - map.shiftWindow(sp, youngerSP); - } else { - // Find a CodeBlob containing this frame's pc or elide the lookup and use the - // supplied blob which is already known to be associated with this frame. - cb = VM.getVM().getCodeCache().findBlob(pc); - if (cb != null) { - // Update the location of all implicitly saved registers - // as the address of these registers in the register save - // area (for %o registers we use the address of the %i - // register in the next younger frame) - map.shiftWindow(sp, youngerSP); - if (map.getUpdateMap()) { - if (cb.callerMustGCArguments()) { - map.setIncludeArgumentOops(true); - } - if (cb.getOopMaps() != null) { - ImmutableOopMapSet.updateRegisterMap(this, cb, map, VM.getVM().isDebugging()); - } - } - } - } - - return new SPARCFrame(biasSP(sp), biasSP(youngerSP), isInterpreted); - } - - protected boolean hasSenderPD() { - try { - // FIXME: should not happen!!! - if (getSP() == null) { - return false; - } - if ( unBiasSP(getSP().getAddressAt(SPARCRegisters.FP.spOffsetInSavedWindow())) == null ) { - return false; - } - return true; - } catch (RuntimeException e) { - if (DEBUG) { - System.out.println("Bad frame " + this); - } - throw e; - } - } - - //-------------------------------------------------------------------------------- - // Return address: - // - - public Address getSenderPC() { - return addressOfI7().getAddressAt(0).addOffsetTo(PC_RETURN_OFFSET); - } - - // FIXME: currently unimplementable - // inline void frame::set_sender_pc(address addr) { *I7_addr() = addr - pc_return_offset; } - - public Address getUnextendedSP() { - return getSP().addOffsetTo(interpreterSPAdjustmentOffset); - } - - public Address getSenderSP() { - return getFP(); - } - - /** Given the next-younger sp for a given frame's sp, compute the - frame. We need the next-younger sp, because its register save - area holds the flushed copy of its I7, which is the PC of the - frame we are interested in. */ - public SPARCFrame afterSave() { - return new SPARCFrame(biasSP(getYoungerSP()), null); - } - - /** Accessors for the instance variables */ - public Address getFP() { - Address sp = getSP(); - if (sp == null) { - System.out.println("SPARCFrame.getFP(): sp == null"); - } - Address fpAddr = sp.addOffsetTo(SPARCRegisters.FP.spOffsetInSavedWindow()); - try { - Address fp = unBiasSP(fpAddr.getAddressAt(0)); - if (fp == null) { - System.out.println("SPARCFrame.getFP(): fp == null (&fp == " + fpAddr + ")"); - } - return fp; - } catch (RuntimeException e) { - System.out.println("SPARCFrame.getFP(): is bad (&fp == " + fpAddr + " sp = " + sp + ")"); - return null; - } - } - - private Address addressOfFPSlot(int index) { - return getFP().addOffsetTo(index * VM.getVM().getAddressSize()); - } - - // FIXME: temporarily elided - // // All frames - // - // intptr_t* fp_addr_at(int index) const { return &fp()[index]; } - // intptr_t* sp_addr_at(int index) const { return &sp()[index]; } - // intptr_t fp_at( int index) const { return *fp_addr_at(index); } - // intptr_t sp_at( int index) const { return *sp_addr_at(index); } - // - // private: - // inline address* I7_addr() const; - // inline address* O7_addr() const; - // - // inline address* I0_addr() const; - // inline address* O0_addr() const; - // - // public: - // // access to SPARC arguments and argument registers - // - // intptr_t* register_addr(Register reg) const { - // return sp_addr_at(reg.sp_offset_in_saved_window()); - // } - // intptr_t* memory_param_addr(int param_ix, bool is_in) const { - // int offset = callee_register_argument_save_area_sp_offset + param_ix; - // if (is_in) - // return fp_addr_at(offset); - // else - // return sp_addr_at(offset); - // } - // intptr_t* param_addr(int param_ix, bool is_in) const { - // if (param_ix >= callee_register_argument_save_area_words) - // return memory_param_addr(param_ix, is_in); - // else if (is_in) - // return register_addr(Argument(param_ix, true).as_register()); - // else { - // // the registers are stored in the next younger frame - // // %%% is this really necessary? - // frame next_younger = after_save(); - // return next_younger.register_addr(Argument(param_ix, true).as_register()); - // } - // } - - //-------------------------------------------------------------------------------- - // Interpreter frames: - // - - /** 2 words, also used to save float regs across calls to C */ - public static final int INTERPRETER_FRAME_D_SCRATCH_FP_OFFSET = -2; - public static final int INTERPRETER_FRAME_L_SCRATCH_FP_OFFSET = -4; - public static final int INTERPRETER_FRAME_MIRROR_OFFSET = -5; - public static final int INTERPRETER_FRAME_VM_LOCALS_FP_OFFSET = -6; - public static final int INTERPRETER_FRAME_VM_LOCAL_WORDS = -INTERPRETER_FRAME_VM_LOCALS_FP_OFFSET; - - /** Interpreter frame set-up needs to save 2 extra words in outgoing - param area for class and jnienv arguments for native stubs (see - nativeStubGen_sparc.cpp) */ - public static final int INTERPRETER_FRAME_EXTRA_OUTGOING_ARGUMENT_WORDS = 2; - - // FIXME: elided for now - // - // // the compiler frame has many of the same fields as the interpreter frame - // // %%%%% factor out declarations of the shared fields - // enum compiler_frame_fixed_locals { - // compiler_frame_d_scratch_fp_offset = -2, - // compiler_frame_vm_locals_fp_offset = -2, // should be same as above - // - // compiler_frame_vm_local_words = -compiler_frame_vm_locals_fp_offset - // }; - // - // private: - // - // // where LcpoolCache is saved: - // ConstantPoolCache** interpreter_frame_cpoolcache_addr() const { - // return (ConstantPoolCache**)sp_addr_at( LcpoolCache.sp_offset_in_saved_window()); - // } - // - // // where Lmonitors is saved: - // BasicObjectLock** interpreter_frame_monitors_addr() const { - // return (BasicObjectLock**) sp_addr_at( Lmonitors.sp_offset_in_saved_window()); - // } - // intptr_t** interpreter_frame_esp_addr() const { - // return (intptr_t**)sp_addr_at( Lesp.sp_offset_in_saved_window()); - // } - // - // inline void interpreter_frame_set_tos_address(intptr_t* x); - // - // // next two fns read and write Lmonitors value, - // private: - // BasicObjectLock* interpreter_frame_monitors() const { return *interpreter_frame_monitors_addr(); } - // void interpreter_frame_set_monitors(BasicObjectLock* monitors) { *interpreter_frame_monitors_addr() = monitors; } - // - //#ifndef CORE - //inline oop *frame::pd_compiled_argument_to_location(VMReg::Name reg, RegisterMap reg_map, int arg_size) const { - // COMPILER1_ONLY(return (oop *) (arg_size - 1 - reg + sp() + memory_parameter_word_sp_offset); ) - // COMPILER2_ONLY(return oopmapreg_to_location(reg, ®_map); ) - //} - //#endif - - // FIXME: NOT FINISHED - public Address addressOfInterpreterFrameLocals() { - return getSP().addOffsetTo(SPARCRegisters.Llocals.spOffsetInSavedWindow()); - } - - // FIXME: this is not atomic with respect to GC and is unsuitable - // for use in a non-debugging, or reflective, system. - private Address addressOfInterpreterFrameBCX() { - // %%%%% reinterpreting Lbcp as a bcx - return getSP().addOffsetTo(SPARCRegisters.Lbcp.spOffsetInSavedWindow()); - } - - public int getInterpreterFrameBCI() { - // FIXME: this is not atomic with respect to GC and is unsuitable - // for use in a non-debugging, or reflective, system. Need to - // figure out how to express this. - Address bcp = addressOfInterpreterFrameBCX().getAddressAt(0); - Address methodHandle = addressOfInterpreterFrameMethod().getAddressAt(0); - Method method = (Method)Metadata.instantiateWrapperFor(methodHandle); - return bcpToBci(bcp, method); - } - - public Address addressOfInterpreterFrameExpressionStack() { - return addressOfInterpreterFrameMonitors().addOffsetTo(-1 * VM.getVM().getAddressSize()); - } - - public int getInterpreterFrameExpressionStackDirection() { - return -1; - } - - /** Top of expression stack */ - public Address addressOfInterpreterFrameTOS() { - return getSP().getAddressAt(SPARCRegisters.Lesp.spOffsetInSavedWindow()).addOffsetTo(VM.getVM().getAddressSize()); - } - - /** Expression stack from top down */ - public Address addressOfInterpreterFrameTOSAt(int slot) { - return addressOfInterpreterFrameTOS().addOffsetTo(slot * VM.getVM().getAddressSize()); - } - - public Address getInterpreterFrameSenderSP() { - if (Assert.ASSERTS_ENABLED) { - Assert.that(isInterpretedFrame(), "interpreted frame expected"); - } - return getFP(); - } - - // FIXME: elided for now - //inline void frame::interpreter_frame_set_tos_address( intptr_t* x ) { - // *interpreter_frame_esp_addr() = x - 1; - //} - - //-------------------------------------------------------------------------------- - // Monitors: - // - - private Address addressOfInterpreterFrameMonitors() { - return getSP().addOffsetTo(SPARCRegisters.Lmonitors.spOffsetInSavedWindow()).getAddressAt(0); - } - - // Monitors - public BasicObjectLock interpreterFrameMonitorBegin() { - int roundedVMLocalWords = Bits.roundTo(INTERPRETER_FRAME_VM_LOCAL_WORDS, WORDS_PER_LONG); - return new BasicObjectLock(addressOfFPSlot(-1 * roundedVMLocalWords)); - } - - public BasicObjectLock interpreterFrameMonitorEnd() { - return new BasicObjectLock(addressOfInterpreterFrameMonitors()); - } - - public int interpreterFrameMonitorSize() { - return Bits.roundTo(BasicObjectLock.size(), WORDS_PER_LONG * (int) VM.getVM().getAddressSize()); - } - - // FIXME: elided for now - // // monitor elements - // - // // in keeping with Intel side: end is lower in memory than begin; - // // and beginning element is oldest element - // // Also begin is one past last monitor. - // - // inline BasicObjectLock* frame::interpreter_frame_monitor_begin() const { - // int rounded_vm_local_words = align_up(frame::interpreter_frame_vm_local_words, WordsPerLong); - // return (BasicObjectLock *)fp_addr_at(-rounded_vm_local_words); - // } - // - // inline BasicObjectLock* frame::interpreter_frame_monitor_end() const { - // return interpreter_frame_monitors(); - // } - // - // - // inline void frame::interpreter_frame_set_monitor_end(BasicObjectLock* value) { - // interpreter_frame_set_monitors(value); - // } - // - // - // inline int frame::interpreter_frame_monitor_size() { - // return align_up(BasicObjectLock::size(), WordsPerLong); - // } - - public Address addressOfInterpreterFrameMethod() { - return getSP().addOffsetTo(SPARCRegisters.Lmethod.spOffsetInSavedWindow()); - } - - public Address addressOfInterpreterFrameCPCache() { - return getSP().addOffsetTo(SPARCRegisters.LcpoolCache.spOffsetInSavedWindow()); - } - - //-------------------------------------------------------------------------------- - // Entry frames: - // - - public JavaCallWrapper getEntryFrameCallWrapper() { - // Note: adjust this code if the link argument in StubGenerator::call_stub() changes! - SPARCArgument link = new SPARCArgument(0, false); - return (JavaCallWrapper) VMObjectFactory.newObject(JavaCallWrapper.class, - getSP().getAddressAt(link.asIn().asRegister().spOffsetInSavedWindow())); - } - - // - // - // inline JavaCallWrapper* frame::entry_frame_call_wrapper() const { - // // note: adjust this code if the link argument in StubGenerator::call_stub() changes! - // const Argument link = Argument(0, false); - // return (JavaCallWrapper*)sp()[link.as_in().as_register().sp_offset_in_saved_window()]; - // } - - //-------------------------------------------------------------------------------- - // Safepoints: - // - - protected Address addressOfSavedOopResult() { - return addressOfO0(); - } - - protected Address addressOfSavedReceiver() { - return addressOfO0(); - } - - - //-------------------------------------------------------------------------------- - // Internals only below this point - // - - private Address addressOfI7() { - return getSP().addOffsetTo(SPARCRegisters.I7.spOffsetInSavedWindow()); - } - - private Address addressOfO7() { - return afterSave().addressOfI7(); - } - - private Address addressOfI0() { - return getSP().addOffsetTo(SPARCRegisters.I0.spOffsetInSavedWindow()); - } - - private Address addressOfO0() { - return afterSave().addressOfI0(); - } - - private static boolean addressesEqual(Address a1, Address a2) { - if ((a1 == null) && (a2 == null)) { - return true; - } - - if ((a1 == null) || (a2 == null)) { - return false; - } - - return (a1.equals(a2)); - } - - - private Frame senderForEntryFrame(RegisterMap regMap) { - SPARCRegisterMap map = (SPARCRegisterMap) regMap; - - if (Assert.ASSERTS_ENABLED) { - Assert.that(map != null, "map must be set"); - } - // Java frame called from C; skip all C frames and return top C - // frame of that chunk as the sender - JavaCallWrapper jcw = getEntryFrameCallWrapper(); - if (Assert.ASSERTS_ENABLED) { - Assert.that(!entryFrameIsFirst(), "next Java fp must be non zero"); - Assert.that(jcw.getLastJavaSP().greaterThan(getSP()), "must be above this frame on stack"); - } - Address lastJavaSP = jcw.getLastJavaSP(); - Address lastJavaPC = jcw.getLastJavaPC(); - map.clear(); - - map.makeIntegerRegsUnsaved(); - map.shiftWindow(lastJavaSP, null); - - if (Assert.ASSERTS_ENABLED) { - Assert.that(map.getIncludeArgumentOops(), "should be set by clear"); - } - - if (lastJavaPC != null) { - return new SPARCFrame(biasSP(lastJavaSP), lastJavaPC); - } else { - Address youngerSP = getNextYoungerSP(lastJavaSP, getSP()); - return new SPARCFrame(biasSP(lastJavaSP), biasSP(youngerSP), false); - } - } - - private static Address getNextYoungerSP(Address oldSP, Address youngSP) { - Address sp = getNextYoungerSPOrNull(oldSP, youngSP, null); - if (Assert.ASSERTS_ENABLED) { - Assert.that(sp != null, "missed the SP"); - } - return sp; - } - - private static Address getNextYoungerSPOrNull(Address oldSP, Address youngSP, Address sp) { - if (youngSP == null) { - // FIXME - throw new RuntimeException("can not handle null youngSP in debugging system (seems to require register window flush)"); - } - - if (sp == null) { - sp = youngSP; - } - - Address previousSP = null; - - /** Minimum frame size is 16 */ - int maxFrames = (int) (oldSP.minus(sp) / (16 * VM.getVM().getAddressSize())); - - while(!sp.equals(oldSP) && spIsValid(oldSP, youngSP, sp)) { - if (maxFrames-- <= 0) { - // too many frames have gone by; invalid parameters given to this function - break; - } - previousSP = sp; - sp = unBiasSP(sp.getAddressAt(SPARCRegisters.FP.spOffsetInSavedWindow())); - } - - return (sp.equals(oldSP) ? previousSP : null); - } - - private static boolean spIsValid(Address oldSP, Address youngSP, Address sp) { - long mask = VM.getVM().getAddressSize(); - mask = 2 * mask - 1; - return ((sp.andWithMask(mask) == null) && - (sp.lessThanOrEqual(oldSP)) && - (sp.greaterThanOrEqual(youngSP))); - } - - // FIXME: this is a hopefully temporary hack (not sure what is going on) - public long getUContextOffset() { - // FIXME: there is something I clearly don't understand about the - // way the signal handler frame is laid out, because I shouldn't need this extra offset - int MAJOR_HACK_OFFSET = 8; - // System.out.println(" SPARCFrame.isSignalHandlerFrameDbg: I2 = " + i2 + ", fp = " + fp + ", youngerSP = " + youngerSP); - return VM.getVM().getAddressSize() * (REGISTER_SAVE_WORDS + MAJOR_HACK_OFFSET); - } - - public long getMContextAreaOffsetInUContext() { - // From dbx-related sources: - // /* - // * struct sigframe is declaredf in the kernel sources in - // * .../uts/sun4c/os/machdep.c/sendsig() - // * unfortunately we only get a pointer to the 'uc' passed - // * to the sighandler so we need to do this stuff to get - // * to 'rwin'. - // * Have to do it like this to take account of alignment. - // */ - // static struct sigframe { - // struct rwindow rwin; - // ucontext_t uc; - // } sf_help; - - // From /usr/include/sys/ucontext.h: - // #if !defined(_XPG4_2) || defined(__EXTENSIONS__) - // struct ucontext { - // #else - // struct __ucontext { - // #endif - // uint_t uc_flags; - // ucontext_t *uc_link; - // sigset_t uc_sigmask; - // stack_t uc_stack; - // mcontext_t uc_mcontext; - // #ifdef __sparcv9 - // long uc_filler[4]; - // #else /* __sparcv9 */ - // long uc_filler[23]; - // #endif /* __sparcv9 */ - // }; - - // This walks to the start of the gregs in the mcontext_t - // (first entry in that data structure). Really should read - // this from header file. - - // Also not sure exactly how alignment works...maybe should read these offsets from the target VM - // (When you have a hammer, everything looks like a nail) - long offset = VM.getVM().alignUp(4, VM.getVM().getAddressSize()); // uc_flags - offset = VM.getVM().alignUp(offset + VM.getVM().getAddressSize(), 8); // uc_link plus - // doubleword alignment for structs? - offset += 16 + // uc_sigmask - 2 * VM.getVM().getAddressSize() + 4; // uc_stack - offset = VM.getVM().alignUp(offset + VM.getVM().getAddressSize(), 8); // doubleword alignment for structs? - - // System.out.println("SPARCFrame.getMContextAreaOffsetInUContext: offset = " + offset); - - return offset; - } -}