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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LulMainInt_h
+#define LulMainInt_h
+
+#include "LulPlatformMacros.h"
+#include "LulMain.h" // for TaggedUWord
+
+#include <vector>
+
+#include "mozilla/Assertions.h"
+
+// This file is provides internal interface inside LUL. If you are an
+// end-user of LUL, do not include it in your code. The end-user
+// interface is in LulMain.h.
+
+
+namespace lul {
+
+using std::vector;
+
+////////////////////////////////////////////////////////////////
+// DW_REG_ constants //
+////////////////////////////////////////////////////////////////
+
+// These are the Dwarf CFI register numbers, as (presumably) defined
+// in the ELF ABI supplements for each architecture.
+
+enum DW_REG_NUMBER {
+ // No real register has this number. It's convenient to be able to
+ // treat the CFA (Canonical Frame Address) as "just another
+ // register", though.
+ DW_REG_CFA = -1,
+#if defined(LUL_ARCH_arm)
+ // ARM registers
+ DW_REG_ARM_R7 = 7,
+ DW_REG_ARM_R11 = 11,
+ DW_REG_ARM_R12 = 12,
+ DW_REG_ARM_R13 = 13,
+ DW_REG_ARM_R14 = 14,
+ DW_REG_ARM_R15 = 15,
+#elif defined(LUL_ARCH_x64)
+ // Because the X86 (32 bit) and AMD64 (64 bit) summarisers are
+ // combined, a merged set of register constants is needed.
+ DW_REG_INTEL_XBP = 6,
+ DW_REG_INTEL_XSP = 7,
+ DW_REG_INTEL_XIP = 16,
+#elif defined(LUL_ARCH_x86)
+ DW_REG_INTEL_XBP = 5,
+ DW_REG_INTEL_XSP = 4,
+ DW_REG_INTEL_XIP = 8,
+#else
+# error "Unknown arch"
+#endif
+};
+
+
+////////////////////////////////////////////////////////////////
+// PfxExpr //
+////////////////////////////////////////////////////////////////
+
+enum PfxExprOp {
+ // meaning of mOperand effect on stack
+ PX_Start, // bool start-with-CFA? start, with CFA on stack, or not
+ PX_End, // none stop; result is at top of stack
+ PX_SImm32, // int32 push signed int32
+ PX_DwReg, // DW_REG_NUMBER push value of the specified reg
+ PX_Deref, // none pop X ; push *X
+ PX_Add, // none pop X ; pop Y ; push Y + X
+ PX_Sub, // none pop X ; pop Y ; push Y - X
+ PX_And, // none pop X ; pop Y ; push Y & X
+ PX_Or, // none pop X ; pop Y ; push Y | X
+ PX_CmpGES, // none pop X ; pop Y ; push (Y >=s X) ? 1 : 0
+ PX_Shl // none pop X ; pop Y ; push Y << X
+};
+
+struct PfxInstr {
+ PfxInstr(PfxExprOp opcode, int32_t operand)
+ : mOpcode(opcode)
+ , mOperand(operand)
+ {}
+ explicit PfxInstr(PfxExprOp opcode)
+ : mOpcode(opcode)
+ , mOperand(0)
+ {}
+ bool operator==(const PfxInstr& other) {
+ return mOpcode == other.mOpcode && mOperand == other.mOperand;
+ }
+ PfxExprOp mOpcode;
+ int32_t mOperand;
+};
+
+static_assert(sizeof(PfxInstr) <= 8, "PfxInstr size changed unexpectedly");
+
+// Evaluate the prefix expression whose PfxInstrs start at aPfxInstrs[start].
+// In the case of any mishap (stack over/underflow, running off the end of
+// the instruction vector, obviously malformed sequences),
+// return an invalid TaggedUWord.
+// RUNS IN NO-MALLOC CONTEXT
+TaggedUWord EvaluatePfxExpr(int32_t start,
+ const UnwindRegs* aOldRegs,
+ TaggedUWord aCFA, const StackImage* aStackImg,
+ const vector<PfxInstr>& aPfxInstrs);
+
+
+////////////////////////////////////////////////////////////////
+// LExpr //
+////////////////////////////////////////////////////////////////
+
+// An expression -- very primitive. Denotes either "register +
+// offset", a dereferenced version of the same, or a reference to a
+// prefix expression stored elsewhere. So as to allow convenient
+// handling of Dwarf-derived unwind info, the register may also denote
+// the CFA. A large number of these need to be stored, so we ensure
+// it fits into 8 bytes. See comment below on RuleSet to see how
+// expressions fit into the bigger picture.
+
+enum LExprHow {
+ UNKNOWN=0, // This LExpr denotes no value.
+ NODEREF, // Value is (mReg + mOffset).
+ DEREF, // Value is *(mReg + mOffset).
+ PFXEXPR // Value is EvaluatePfxExpr(secMap->mPfxInstrs[mOffset])
+};
+
+inline static const char* NameOf_LExprHow(LExprHow how) {
+ switch (how) {
+ case UNKNOWN: return "UNKNOWN";
+ case NODEREF: return "NODEREF";
+ case DEREF: return "DEREF";
+ case PFXEXPR: return "PFXEXPR";
+ default: return "LExpr-??";
+ }
+}
+
+
+struct LExpr {
+ // Denotes an expression with no value.
+ LExpr()
+ : mHow(UNKNOWN)
+ , mReg(0)
+ , mOffset(0)
+ {}
+
+ // Denotes any expressible expression.
+ LExpr(LExprHow how, int16_t reg, int32_t offset)
+ : mHow(how)
+ , mReg(reg)
+ , mOffset(offset)
+ {
+ switch (how) {
+ case UNKNOWN: MOZ_ASSERT(reg == 0 && offset == 0); break;
+ case NODEREF: break;
+ case DEREF: break;
+ case PFXEXPR: MOZ_ASSERT(reg == 0 && offset >= 0); break;
+ default: MOZ_ASSERT(0, "LExpr::LExpr: invalid how");
+ }
+ }
+
+ // Change the offset for an expression that references memory.
+ LExpr add_delta(long delta)
+ {
+ MOZ_ASSERT(mHow == NODEREF);
+ // If this is a non-debug build and the above assertion would have
+ // failed, at least return LExpr() so that the machinery that uses
+ // the resulting expression fails in a repeatable way.
+ return (mHow == NODEREF) ? LExpr(mHow, mReg, mOffset+delta)
+ : LExpr(); // Gone bad
+ }
+
+ // Dereference an expression that denotes a memory address.
+ LExpr deref()
+ {
+ MOZ_ASSERT(mHow == NODEREF);
+ // Same rationale as for add_delta().
+ return (mHow == NODEREF) ? LExpr(DEREF, mReg, mOffset)
+ : LExpr(); // Gone bad
+ }
+
+ // Print a rule for recovery of |aNewReg| whose recovered value
+ // is this LExpr.
+ string ShowRule(const char* aNewReg) const;
+
+ // Evaluate this expression, producing a TaggedUWord. |aOldRegs|
+ // holds register values that may be referred to by the expression.
+ // |aCFA| holds the CFA value, if any, that applies. |aStackImg|
+ // contains a chuck of stack that will be consulted if the expression
+ // references memory. |aPfxInstrs| holds the vector of PfxInstrs
+ // that will be consulted if this is a PFXEXPR.
+ // RUNS IN NO-MALLOC CONTEXT
+ TaggedUWord EvaluateExpr(const UnwindRegs* aOldRegs,
+ TaggedUWord aCFA, const StackImage* aStackImg,
+ const vector<PfxInstr>* aPfxInstrs) const;
+
+ // Representation of expressions. If |mReg| is DW_REG_CFA (-1) then
+ // it denotes the CFA. All other allowed values for |mReg| are
+ // nonnegative and are DW_REG_ values.
+ LExprHow mHow:8;
+ int16_t mReg; // A DW_REG_ value
+ int32_t mOffset; // 32-bit signed offset should be more than enough.
+};
+
+static_assert(sizeof(LExpr) <= 8, "LExpr size changed unexpectedly");
+
+
+////////////////////////////////////////////////////////////////
+// RuleSet //
+////////////////////////////////////////////////////////////////
+
+// This is platform-dependent. For some address range, describes how
+// to recover the CFA and then how to recover the registers for the
+// previous frame.
+//
+// The set of LExprs contained in a given RuleSet describe a DAG which
+// says how to compute the caller's registers ("new registers") from
+// the callee's registers ("old registers"). The DAG can contain a
+// single internal node, which is the value of the CFA for the callee.
+// It would be possible to construct a DAG that omits the CFA, but
+// including it makes the summarisers simpler, and the Dwarf CFI spec
+// has the CFA as a central concept.
+//
+// For this to make sense, |mCfaExpr| can't have
+// |mReg| == DW_REG_CFA since we have no previous value for the CFA.
+// All of the other |Expr| fields can -- and usually do -- specify
+// |mReg| == DW_REG_CFA.
+//
+// With that in place, the unwind algorithm proceeds as follows.
+//
+// (0) Initially: we have values for the old registers, and a memory
+// image.
+//
+// (1) Compute the CFA by evaluating |mCfaExpr|. Add the computed
+// value to the set of "old registers".
+//
+// (2) Compute values for the registers by evaluating all of the other
+// |Expr| fields in the RuleSet. These can depend on both the old
+// register values and the just-computed CFA.
+//
+// If we are unwinding without computing a CFA, perhaps because the
+// RuleSets are derived from EXIDX instead of Dwarf, then
+// |mCfaExpr.mHow| will be LExpr::UNKNOWN, so the computed value will
+// be invalid -- that is, TaggedUWord() -- and so any attempt to use
+// that will result in the same value. But that's OK because the
+// RuleSet would make no sense if depended on the CFA but specified no
+// way to compute it.
+//
+// A RuleSet is not allowed to cover zero address range. Having zero
+// length would break binary searching in SecMaps and PriMaps.
+
+class RuleSet {
+public:
+ RuleSet();
+ void Print(void(*aLog)(const char*)) const;
+
+ // Find the LExpr* for a given DW_REG_ value in this class.
+ LExpr* ExprForRegno(DW_REG_NUMBER aRegno);
+
+ uintptr_t mAddr;
+ uintptr_t mLen;
+ // How to compute the CFA.
+ LExpr mCfaExpr;
+ // How to compute caller register values. These may reference the
+ // value defined by |mCfaExpr|.
+#if defined(LUL_ARCH_x64) || defined(LUL_ARCH_x86)
+ LExpr mXipExpr; // return address
+ LExpr mXspExpr;
+ LExpr mXbpExpr;
+#elif defined(LUL_ARCH_arm)
+ LExpr mR15expr; // return address
+ LExpr mR14expr;
+ LExpr mR13expr;
+ LExpr mR12expr;
+ LExpr mR11expr;
+ LExpr mR7expr;
+#else
+# error "Unknown arch"
+#endif
+};
+
+// Returns |true| for Dwarf register numbers which are members
+// of the set of registers that LUL unwinds on this target.
+static inline bool registerIsTracked(DW_REG_NUMBER reg) {
+ switch (reg) {
+# if defined(LUL_ARCH_x64) || defined(LUL_ARCH_x86)
+ case DW_REG_INTEL_XBP: case DW_REG_INTEL_XSP: case DW_REG_INTEL_XIP:
+ return true;
+# elif defined(LUL_ARCH_arm)
+ case DW_REG_ARM_R7: case DW_REG_ARM_R11: case DW_REG_ARM_R12:
+ case DW_REG_ARM_R13: case DW_REG_ARM_R14: case DW_REG_ARM_R15:
+ return true;
+# else
+# error "Unknown arch"
+# endif
+ default:
+ return false;
+ }
+}
+
+
+////////////////////////////////////////////////////////////////
+// SecMap //
+////////////////////////////////////////////////////////////////
+
+// A SecMap may have zero address range, temporarily, whilst RuleSets
+// are being added to it. But adding a zero-range SecMap to a PriMap
+// will make it impossible to maintain the total order of the PriMap
+// entries, and so that can't be allowed to happen.
+
+class SecMap {
+public:
+ // These summarise the contained mRuleSets, in that they give
+ // exactly the lowest and highest addresses that any of the entries
+ // in this SecMap cover. Hence invariants:
+ //
+ // mRuleSets is nonempty
+ // <=> mSummaryMinAddr <= mSummaryMaxAddr
+ // && mSummaryMinAddr == mRuleSets[0].mAddr
+ // && mSummaryMaxAddr == mRuleSets[#rulesets-1].mAddr
+ // + mRuleSets[#rulesets-1].mLen - 1;
+ //
+ // This requires that no RuleSet has zero length.
+ //
+ // mRuleSets is empty
+ // <=> mSummaryMinAddr > mSummaryMaxAddr
+ //
+ // This doesn't constrain mSummaryMinAddr and mSummaryMaxAddr uniquely,
+ // so let's use mSummaryMinAddr == 1 and mSummaryMaxAddr == 0 to denote
+ // this case.
+
+ explicit SecMap(void(*aLog)(const char*));
+ ~SecMap();
+
+ // Binary search mRuleSets to find one that brackets |ia|, or nullptr
+ // if none is found. It's not allowable to do this until PrepareRuleSets
+ // has been called first.
+ RuleSet* FindRuleSet(uintptr_t ia);
+
+ // Add a RuleSet to the collection. The rule is copied in. Calling
+ // this makes the map non-searchable.
+ void AddRuleSet(const RuleSet* rs);
+
+ // Add a PfxInstr to the vector of such instrs, and return the index
+ // in the vector. Calling this makes the map non-searchable.
+ uint32_t AddPfxInstr(PfxInstr pfxi);
+
+ // Returns the entire vector of PfxInstrs.
+ const vector<PfxInstr>* GetPfxInstrs() { return &mPfxInstrs; }
+
+ // Prepare the map for searching. Also, remove any rules for code
+ // address ranges which don't fall inside [start, +len). |len| may
+ // not be zero.
+ void PrepareRuleSets(uintptr_t start, size_t len);
+
+ bool IsEmpty();
+
+ size_t Size() { return mRuleSets.size(); }
+
+ // The min and max addresses of the addresses in the contained
+ // RuleSets. See comment above for invariants.
+ uintptr_t mSummaryMinAddr;
+ uintptr_t mSummaryMaxAddr;
+
+private:
+ // False whilst adding entries; true once it is safe to call FindRuleSet.
+ // Transition (false->true) is caused by calling PrepareRuleSets().
+ bool mUsable;
+
+ // A vector of RuleSets, sorted, nonoverlapping (post Prepare()).
+ vector<RuleSet> mRuleSets;
+
+ // A vector of PfxInstrs, which are referred to by the RuleSets.
+ // These are provided as a representation of Dwarf expressions
+ // (DW_CFA_val_expression, DW_CFA_expression, DW_CFA_def_cfa_expression),
+ // are relatively expensive to evaluate, and and are therefore
+ // expected to be used only occasionally.
+ //
+ // The vector holds a bunch of separate PfxInstr programs, each one
+ // starting with a PX_Start and terminated by a PX_End, all
+ // concatenated together. When a RuleSet can't recover a value
+ // using a self-contained LExpr, it uses a PFXEXPR whose mOffset is
+ // the index in this vector of start of the necessary PfxInstr program.
+ vector<PfxInstr> mPfxInstrs;
+
+ // A logging sink, for debugging.
+ void (*mLog)(const char*);
+};
+
+} // namespace lul
+
+#endif // ndef LulMainInt_h