mozglue/baseprofiler/lul/LulDwarfSummariser.cpp
author Masayuki Nakano <masayuki@d-toybox.com>
Sun, 16 Jan 2022 06:21:17 +0000
changeset 604634 9ef0614a59629916c1e182eb8eda055b0b0e8b32
parent 528274 aea741f601bdd780aa5ce08d584dbae822a35f46
permissions -rw-r--r--
Bug 1749299 - Make `HTMLEditor::HandleInsertLinefeed()` stop handling it if insertion point cannot have text nodes r=m_kato Ideally, it should not be called when the editor cannot insert new text node. However, the callers are complicated. Therefore, let's check in it for avoiding making the callers more complicated. Fortunately, this is not realistic path for normal web apps. Therefore, the compatibility of the behavior is not matter. That's the reason why this patch does not have a test comparing the result. Differential Revision: https://phabricator.services.mozilla.com/D135826

/* -*- 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"
#include "mozilla/Sprintf.h"

#include "LulDwarfExt.h"

// Set this to 1 for verbose logging
#define DEBUG_SUMMARISER 0

namespace lul {

// Do |s64|'s lowest 32 bits sign extend back to |s64| itself?
static inline bool fitsIn32Bits(int64 s64) {
  return s64 == ((s64 & 0xffffffff) ^ 0x80000000) - 0x80000000;
}

// Check a LExpr prefix expression, starting at pfxInstrs[start] up to
// the next PX_End instruction, to ensure that:
// * It only mentions registers that are tracked on this target
// * The start point is sane
// If the expression is ok, return NULL.  Else return a pointer
// a const char* holding a bit of text describing the problem.
static const char* checkPfxExpr(const vector<PfxInstr>* pfxInstrs,
                                int64_t start) {
  size_t nInstrs = pfxInstrs->size();
  if (start < 0 || start >= (ssize_t)nInstrs) {
    return "bogus start point";
  }
  size_t i;
  for (i = start; i < nInstrs; i++) {
    PfxInstr pxi = (*pfxInstrs)[i];
    if (pxi.mOpcode == PX_End) break;
    if (pxi.mOpcode == PX_DwReg &&
        !registerIsTracked((DW_REG_NUMBER)pxi.mOperand)) {
      return "uses untracked reg";
    }
  }
  return nullptr;  // success
}

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];
    SprintfLiteral(buf, "LUL Entry(%llx, %llu)\n",
                   (unsigned long long int)aAddress,
                   (unsigned long long int)aLength);
    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, LExprHow how,
                      int16_t oldReg, int64_t offset) {
  aAddress += mTextBias;
  if (DEBUG_SUMMARISER) {
    char buf[100];
    if (how == NODEREF || how == DEREF) {
      bool deref = how == DEREF;
      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = %sr%d + %lld%s\n",
                     (unsigned long long int)aAddress, aNewReg,
                     deref ? "*(" : "", (int)oldReg, (long long int)offset,
                     deref ? ")" : "");
    } else if (how == PFXEXPR) {
      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = pfx-expr-at %lld\n",
                     (unsigned long long int)aAddress, aNewReg,
                     (long long int)offset);
    } else {
      SprintfLiteral(buf, "LUL  0x%llx  old-r%d = (invalid LExpr!)\n",
                     (unsigned long long int)aAddress, aNewReg);
    }
    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;
  }

  // If for some reason summarisation fails, either or both of these
  // become non-null and point at constant text describing the
  // problem.  Using two rather than just one avoids complications of
  // having to concatenate two strings to produce a complete error message.
  const char* reason1 = nullptr;
  const char* reason2 = nullptr;

  // |offset| needs to be a 32 bit value that sign extends to 64 bits
  // on a 64 bit target.  We will need to incorporate |offset| into
  // any LExpr made here.  So we may as well check it right now.
  if (!fitsIn32Bits(offset)) {
    reason1 = "offset not in signed 32-bit range";
    goto cant_summarise;
  }

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

#if defined(GP_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 (how != NODEREF) {
        reason1 = "rule for DW_REG_CFA: invalid |how|";
        goto cant_summarise;
      }
      switch (oldReg) {
        case DW_REG_ARM_R7:
        case DW_REG_ARM_R11:
        case DW_REG_ARM_R12:
        case DW_REG_ARM_R13:
          break;
        default:
          reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
          goto cant_summarise;
      }
      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
      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: {
      // This is a new rule for R7, R11, R12, R13 (SP), R14 (LR) or
      // R15 (the return address).
      switch (how) {
        case NODEREF:
        case DEREF:
          // Check the old register is one we're tracking.
          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
              oldReg != DW_REG_CFA) {
            reason1 = "rule for R7/11/12/13/14/15: uses untracked reg";
            goto cant_summarise;
          }
          break;
        case PFXEXPR: {
          // Check that the prefix expression only mentions tracked registers.
          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
          reason2 = checkPfxExpr(pfxInstrs, offset);
          if (reason2) {
            reason1 = "rule for R7/11/12/13/14/15: ";
            goto cant_summarise;
          }
          break;
        }
        default:
          goto cant_summarise;
      }
      LExpr expr = LExpr(how, oldReg, offset);
      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:
      // Leave |reason1| and |reason2| unset here.  This program point
      // is reached so often that it causes a flood of "Can't
      // summarise" messages.  In any case, we don't really care about
      // the fact that this summary would produce a new value for a
      // register that we're not tracking.  We do on the other hand
      // care if the summary's expression *uses* a register that we're
      // not tracking.  But in that case one of the above failures
      // should tell us which.
      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 == UNKNOWN) {
    mCurrRules.mR7expr = LExpr(NODEREF, DW_REG_ARM_R7, 0);
  }
  if (mCurrRules.mR11expr.mHow == UNKNOWN) {
    mCurrRules.mR11expr = LExpr(NODEREF, DW_REG_ARM_R11, 0);
  }
  if (mCurrRules.mR12expr.mHow == UNKNOWN) {
    mCurrRules.mR12expr = 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(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 == UNKNOWN) {
    mCurrRules.mR15expr = LExpr(NODEREF, DW_REG_ARM_R14, 0);
  }

#elif defined(GP_ARCH_arm64)

  // ----------------- arm64 ----------------- //

  switch (aNewReg) {
    case DW_REG_CFA:
      if (how != NODEREF) {
        reason1 = "rule for DW_REG_CFA: invalid |how|";
        goto cant_summarise;
      }
      switch (oldReg) {
        case DW_REG_AARCH64_X29:
        case DW_REG_AARCH64_SP:
          break;
        default:
          reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
          goto cant_summarise;
      }
      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
      break;

    case DW_REG_AARCH64_X29:
    case DW_REG_AARCH64_X30:
    case DW_REG_AARCH64_SP: {
      switch (how) {
        case NODEREF:
        case DEREF:
          // Check the old register is one we're tracking.
          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
              oldReg != DW_REG_CFA) {
            reason1 = "rule for X29/X30/SP: uses untracked reg";
            goto cant_summarise;
          }
          break;
        case PFXEXPR: {
          // Check that the prefix expression only mentions tracked registers.
          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
          reason2 = checkPfxExpr(pfxInstrs, offset);
          if (reason2) {
            reason1 = "rule for X29/X30/SP: ";
            goto cant_summarise;
          }
          break;
        }
        default:
          goto cant_summarise;
      }
      LExpr expr = LExpr(how, oldReg, offset);
      switch (aNewReg) {
        case DW_REG_AARCH64_X29:
          mCurrRules.mX29expr = expr;
          break;
        case DW_REG_AARCH64_X30:
          mCurrRules.mX30expr = expr;
          break;
        case DW_REG_AARCH64_SP:
          mCurrRules.mSPexpr = expr;
          break;
        default:
          MOZ_ASSERT(0);
      }
      break;
    }
    default:
      // Leave |reason1| and |reason2| unset here, for the reasons explained
      // in the analogous point
      goto cant_summarise;
  }

  if (mCurrRules.mX29expr.mHow == UNKNOWN) {
    mCurrRules.mX29expr = LExpr(NODEREF, DW_REG_AARCH64_X29, 0);
  }
  if (mCurrRules.mX30expr.mHow == UNKNOWN) {
    mCurrRules.mX30expr = LExpr(NODEREF, DW_REG_AARCH64_X30, 0);
  }
  // On aarch64, 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.mSPexpr.mHow == UNKNOWN) {
    mCurrRules.mSPexpr = LExpr(NODEREF, DW_REG_CFA, 0);
  }
#elif defined(GP_ARCH_amd64) || defined(GP_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.
  switch (aNewReg) {
    case DW_REG_CFA: {
      // This is a rule that defines the CFA.  The only forms we choose to
      // represent are: = SP+offset, = FP+offset, or =prefix-expr.
      switch (how) {
        case NODEREF:
          if (oldReg != DW_REG_INTEL_XSP && oldReg != DW_REG_INTEL_XBP) {
            reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
            goto cant_summarise;
          }
          break;
        case DEREF:
          reason1 = "rule for DW_REG_CFA: invalid |how|";
          goto cant_summarise;
        case PFXEXPR: {
          // Check that the prefix expression only mentions tracked registers.
          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
          reason2 = checkPfxExpr(pfxInstrs, offset);
          if (reason2) {
            reason1 = "rule for CFA: ";
            goto cant_summarise;
          }
          break;
        }
        default:
          goto cant_summarise;
      }
      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
      break;
    }

    case DW_REG_INTEL_XSP:
    case DW_REG_INTEL_XBP:
    case DW_REG_INTEL_XIP: {
      // This is a new rule for XSP, XBP or XIP (the return address).
      switch (how) {
        case NODEREF:
        case DEREF:
          // Check the old register is one we're tracking.
          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
              oldReg != DW_REG_CFA) {
            reason1 = "rule for XSP/XBP/XIP: uses untracked reg";
            goto cant_summarise;
          }
          break;
        case PFXEXPR: {
          // Check that the prefix expression only mentions tracked registers.
          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
          reason2 = checkPfxExpr(pfxInstrs, offset);
          if (reason2) {
            reason1 = "rule for XSP/XBP/XIP: ";
            goto cant_summarise;
          }
          break;
        }
        default:
          goto cant_summarise;
      }
      LExpr expr = LExpr(how, oldReg, offset);
      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");
      }
      break;
    }

    default:
      // Leave |reason1| and |reason2| unset here, for the reasons
      // explained in the analogous point in the ARM case just above.
      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 == UNKNOWN) {
    mCurrRules.mXspExpr = LExpr(NODEREF, DW_REG_CFA, 0);
  }

  // Also, gcc says "Undef" for BP when it is unchanged.
  if (mCurrRules.mXbpExpr.mHow == UNKNOWN) {
    mCurrRules.mXbpExpr = LExpr(NODEREF, DW_REG_INTEL_XBP, 0);
  }

#elif defined(GP_ARCH_mips64)
  // ---------------- mips ---------------- //
  //
  // 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 can
      // represent are: = SP+offset or = FP+offset.
      if (how != NODEREF) {
        reason1 = "rule for DW_REG_CFA: invalid |how|";
        goto cant_summarise;
      }
      if (oldReg != DW_REG_MIPS_SP && oldReg != DW_REG_MIPS_FP) {
        reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
        goto cant_summarise;
      }
      mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
      break;

    case DW_REG_MIPS_SP:
    case DW_REG_MIPS_FP:
    case DW_REG_MIPS_PC: {
      // This is a new rule for SP, FP or PC (the return address).
      switch (how) {
        case NODEREF:
        case DEREF:
          // Check the old register is one we're tracking.
          if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
              oldReg != DW_REG_CFA) {
            reason1 = "rule for SP/FP/PC: uses untracked reg";
            goto cant_summarise;
          }
          break;
        case PFXEXPR: {
          // Check that the prefix expression only mentions tracked registers.
          const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
          reason2 = checkPfxExpr(pfxInstrs, offset);
          if (reason2) {
            reason1 = "rule for SP/FP/PC: ";
            goto cant_summarise;
          }
          break;
        }
        default:
          goto cant_summarise;
      }
      LExpr expr = LExpr(how, oldReg, offset);
      switch (aNewReg) {
        case DW_REG_MIPS_FP:
          mCurrRules.mFPexpr = expr;
          break;
        case DW_REG_MIPS_SP:
          mCurrRules.mSPexpr = expr;
          break;
        case DW_REG_MIPS_PC:
          mCurrRules.mPCexpr = expr;
          break;
        default:
          MOZ_CRASH("impossible value for aNewReg");
      }
      break;
    }
    default:
      // Leave |reason1| and |reason2| unset here, for the reasons
      // explained in the analogous point in the ARM case just above.
      goto cant_summarise;
  }

  // On MIPS, 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.mSPexpr.mHow == UNKNOWN) {
    mCurrRules.mSPexpr = LExpr(NODEREF, DW_REG_CFA, 0);
  }

  // Also, gcc says "Undef" for FP when it is unchanged.
  if (mCurrRules.mFPexpr.mHow == UNKNOWN) {
    mCurrRules.mFPexpr = LExpr(NODEREF, DW_REG_MIPS_FP, 0);
  }

#else

#  error "Unsupported arch"
#endif

  return;

cant_summarise:
  if (reason1 || reason2) {
    char buf[200];
    SprintfLiteral(buf,
                   "LUL  can't summarise: "
                   "SVMA=0x%llx: %s%s, expr=LExpr(%s,%u,%lld)\n",
                   (unsigned long long int)(aAddress - mTextBias),
                   reason1 ? reason1 : "", reason2 ? reason2 : "",
                   NameOf_LExprHow(how), (unsigned int)oldReg,
                   (long long int)offset);
    mLog(buf);
  }
}

uint32_t Summariser::AddPfxInstr(PfxInstr pfxi) {
  return mSecMap->AddPfxInstr(pfxi);
}

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