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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/. */

 #include "LulDwarfSummariser.h"

 #include "mozilla/Assertions.h"

 // Set this to 1 for verbose logging

 #define DEBUG_SUMMARISER 0

 namespace lul {

 Summariser::Summariser(SecMap* aSecMap, uintptr_t aTextBias,

                        void(*aLog)(const char*))

   : mSecMap(aSecMap)

   , mTextBias(aTextBias)

   , mLog(aLog)

 {

   mCurrAddr = 0;

   mMax1Addr = 0; // Gives an empty range.

   // Initialise the running RuleSet to "haven't got a clue" status.

   new (&mCurrRules) RuleSet();

 }

 void

 Summariser::Entry(uintptr_t aAddress, uintptr_t aLength)

 {

   aAddress += mTextBias;

   if (DEBUG_SUMMARISER) {

     char buf[100];

     snprintf(buf, sizeof(buf), "LUL Entry(%llx, %llu)\n",

              (unsigned long long int)aAddress,

              (unsigned long long int)aLength);

     buf[sizeof(buf)-1] = 0;

     mLog(buf);

   }

   // This throws away any previous summary, that is, assumes

   // that the previous summary, if any, has been properly finished

   // by a call to End().

   mCurrAddr = aAddress;

   mMax1Addr = aAddress + aLength;

   new (&mCurrRules) RuleSet();

 }

 void

 Summariser::Rule(uintptr_t aAddress,

                  int aNewReg, int aOldReg, intptr_t aOffset, bool aDeref)

 {

   aAddress += mTextBias;

   if (DEBUG_SUMMARISER) {

     char buf[100];

     snprintf(buf, sizeof(buf),

              "LUL  0x%llx  old-r%d = %sr%d + %ld%s\n",

              (unsigned long long int)aAddress, aNewReg,

              aDeref ? "*(" : "", aOldReg, (long)aOffset, aDeref ? ")" : "");

     buf[sizeof(buf)-1] = 0;

     mLog(buf);

   }

   if (mCurrAddr < aAddress) {

     // Flush the existing summary first.

     mCurrRules.mAddr = mCurrAddr;

     mCurrRules.mLen  = aAddress - mCurrAddr;

     mSecMap->AddRuleSet(&mCurrRules);

     if (DEBUG_SUMMARISER) {

       mLog("LUL  "); mCurrRules.Print(mLog);

       mLog("\n");

     }

     mCurrAddr = aAddress;

   }

   // FIXME: factor out common parts of the arch-dependent summarisers.

 #if defined(LUL_ARCH_arm)

   // ----------------- arm ----------------- //

   // Now, can we add the rule to our summary?  This depends on whether

   // the registers and the overall expression are representable.  This

   // is the heart of the summarisation process.

   switch (aNewReg) {

     case DW_REG_CFA:

       // This is a rule that defines the CFA.  The only forms we

       // choose to represent are: r7/11/12/13 + offset.  The offset

       // must fit into 32 bits since 'uintptr_t' is 32 bit on ARM,

       // hence there is no need to check it for overflow.

       if (aDeref) {

         goto cant_summarise;

       }

       switch (aOldReg) {

         case DW_REG_ARM_R7:  case DW_REG_ARM_R11:

         case DW_REG_ARM_R12: case DW_REG_ARM_R13:

           break;

         default:

           goto cant_summarise;

       }

       mCurrRules.mCfaExpr = LExpr(LExpr::NODEREF, aOldReg, aOffset);

       break;

     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: {

       // Check the aOldReg is valid.

       switch (aOldReg) {

         case DW_REG_CFA:

         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:

           break;

         default:

           goto cant_summarise;

       }

       // This is a new rule for one of r{7,11,12,13,14,15} and has a

       // representable offset.  In particular the new value of r15 is

       // going to be the return address.

       LExpr expr = LExpr(aDeref ? LExpr::DEREF : LExpr::NODEREF,

                          aOldReg, aOffset);

       switch (aNewReg) {

         case DW_REG_ARM_R7:  mCurrRules.mR7expr  = expr; break;

         case DW_REG_ARM_R11: mCurrRules.mR11expr = expr; break;

         case DW_REG_ARM_R12: mCurrRules.mR12expr = expr; break;

         case DW_REG_ARM_R13: mCurrRules.mR13expr = expr; break;

         case DW_REG_ARM_R14: mCurrRules.mR14expr = expr; break;

         case DW_REG_ARM_R15: mCurrRules.mR15expr = expr; break;

         default: MOZ_ASSERT(0);

       }

       break;

     }

     default:

       goto cant_summarise;

   }

   // Mark callee-saved registers (r4 .. r11) as unchanged, if there is

   // no other information about them.  FIXME: do this just once, at

   // the point where the ruleset is committed.

   if (mCurrRules.mR7expr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mR7expr = LExpr(LExpr::NODEREF, DW_REG_ARM_R7, 0);

   }

   if (mCurrRules.mR11expr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mR11expr = LExpr(LExpr::NODEREF, DW_REG_ARM_R11, 0);

   }

   if (mCurrRules.mR12expr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mR12expr = LExpr(LExpr::NODEREF, DW_REG_ARM_R12, 0);

   }

   // The old r13 (SP) value before the call is always the same as the

   // CFA.

   mCurrRules.mR13expr = LExpr(LExpr::NODEREF, DW_REG_CFA, 0);

   // If there's no information about R15 (the return address), say

   // it's a copy of R14 (the link register).

   if (mCurrRules.mR15expr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mR15expr = LExpr(LExpr::NODEREF, DW_REG_ARM_R14, 0);

   }

 #elif defined(LUL_ARCH_x64) || defined(LUL_ARCH_x86)

   // ---------------- x64/x86 ---------------- //

   // Now, can we add the rule to our summary?  This depends on whether

   // the registers and the overall expression are representable.  This

   // is the heart of the summarisation process.  In the 64 bit case

   // we need to check that aOffset will fit into an int32_t.  In the

   // 32 bit case it is expected that the compiler will fold out the

   // test since it always succeeds.

   if (aNewReg == DW_REG_CFA) {

     // This is a rule that defines the CFA.  The only forms we can

     // represent are: = SP+offset or = FP+offset.

     if (!aDeref && aOffset == (intptr_t)(int32_t)aOffset &&

         (aOldReg == DW_REG_INTEL_XSP || aOldReg == DW_REG_INTEL_XBP)) {

       mCurrRules.mCfaExpr = LExpr(LExpr::NODEREF, aOldReg, aOffset);

     } else {

       goto cant_summarise;

     }

   }

   else

   if ((aNewReg == DW_REG_INTEL_XSP ||

        aNewReg == DW_REG_INTEL_XBP || aNewReg == DW_REG_INTEL_XIP) &&

       (aOldReg == DW_REG_CFA ||

        aOldReg == DW_REG_INTEL_XSP ||

        aOldReg == DW_REG_INTEL_XBP || aOldReg == DW_REG_INTEL_XIP) &&

       aOffset == (intptr_t)(int32_t)aOffset) {

     // This is a new rule for SP, BP or the return address

     // respectively, and has a representable offset.

     LExpr expr = LExpr(aDeref ? LExpr::DEREF : LExpr::NODEREF,

                        aOldReg, aOffset);

     switch (aNewReg) {

       case DW_REG_INTEL_XBP: mCurrRules.mXbpExpr = expr; break;

       case DW_REG_INTEL_XSP: mCurrRules.mXspExpr = expr; break;

       case DW_REG_INTEL_XIP: mCurrRules.mXipExpr = expr; break;

       default: MOZ_CRASH("impossible value for aNewReg");

     }

   }

   else {

     goto cant_summarise;

   }

   // On Intel, it seems the old SP value before the call is always the

   // same as the CFA.  Therefore, in the absence of any other way to

   // recover the SP, specify that the CFA should be copied.

   if (mCurrRules.mXspExpr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mXspExpr = LExpr(LExpr::NODEREF, DW_REG_CFA, 0);

   }

   // Also, gcc says "Undef" for BP when it is unchanged.

   if (mCurrRules.mXbpExpr.mHow == LExpr::UNKNOWN) {

     mCurrRules.mXbpExpr = LExpr(LExpr::NODEREF, DW_REG_INTEL_XBP, 0);

   }

 #else

 # error "Unsupported arch"

 #endif

   return;

  cant_summarise:

   if (0) {

     mLog("LUL  can't summarise\n");

   }

 }

 void

 Summariser::End()

 {

   if (DEBUG_SUMMARISER) {

     mLog("LUL End\n");

   }

   if (mCurrAddr < mMax1Addr) {

     mCurrRules.mAddr = mCurrAddr;

     mCurrRules.mLen  = mMax1Addr - mCurrAddr;

     mSecMap->AddRuleSet(&mCurrRules);

     if (DEBUG_SUMMARISER) {

       mLog("LUL  "); mCurrRules.Print(mLog);

       mLog("\n");

     }

   }

 }

 } // namespace lul