зеркало из https://github.com/mozilla/gecko-dev.git
359 строки
12 KiB
C++
359 строки
12 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "LulDwarfSummariser.h"
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#include "mozilla/Assertions.h"
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// Set this to 1 for verbose logging
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#define DEBUG_SUMMARISER 0
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namespace lul {
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// Do |s64|'s lowest 32 bits sign extend back to |s64| itself?
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static inline bool fitsIn32Bits(int64 s64) {
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return s64 == ((s64 & 0xffffffff) ^ 0x80000000) - 0x80000000;
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}
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// Check a LExpr prefix expression, starting at pfxInstrs[start] up to
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// the next PX_End instruction, to ensure that:
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// * It only mentions registers that are tracked on this target
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// * The start point is sane
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// If the expression is ok, return NULL. Else return a pointer
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// a const char* holding a bit of text describing the problem.
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static const char*
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checkPfxExpr(const vector<PfxInstr>* pfxInstrs, int64_t start)
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{
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size_t nInstrs = pfxInstrs->size();
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if (start < 0 || start >= (ssize_t)nInstrs) {
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return "bogus start point";
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}
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size_t i;
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for (i = start; i < nInstrs; i++) {
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PfxInstr pxi = (*pfxInstrs)[i];
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if (pxi.mOpcode == PX_End)
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break;
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if (pxi.mOpcode == PX_DwReg &&
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!registerIsTracked((DW_REG_NUMBER)pxi.mOperand)) {
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return "uses untracked reg";
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}
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}
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return nullptr; // success
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}
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Summariser::Summariser(SecMap* aSecMap, uintptr_t aTextBias,
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void(*aLog)(const char*))
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: mSecMap(aSecMap)
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, mTextBias(aTextBias)
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, mLog(aLog)
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{
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mCurrAddr = 0;
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mMax1Addr = 0; // Gives an empty range.
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// Initialise the running RuleSet to "haven't got a clue" status.
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new (&mCurrRules) RuleSet();
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}
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void
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Summariser::Entry(uintptr_t aAddress, uintptr_t aLength)
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{
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aAddress += mTextBias;
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if (DEBUG_SUMMARISER) {
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char buf[100];
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snprintf_literal(buf, "LUL Entry(%llx, %llu)\n",
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(unsigned long long int)aAddress,
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(unsigned long long int)aLength);
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mLog(buf);
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}
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// This throws away any previous summary, that is, assumes
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// that the previous summary, if any, has been properly finished
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// by a call to End().
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mCurrAddr = aAddress;
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mMax1Addr = aAddress + aLength;
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new (&mCurrRules) RuleSet();
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}
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void
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Summariser::Rule(uintptr_t aAddress, int aNewReg,
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LExprHow how, int16_t oldReg, int64_t offset)
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{
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aAddress += mTextBias;
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if (DEBUG_SUMMARISER) {
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char buf[100];
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if (how == NODEREF || how == DEREF) {
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bool deref = how == DEREF;
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snprintf_literal(buf,
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"LUL 0x%llx old-r%d = %sr%d + %lld%s\n",
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(unsigned long long int)aAddress, aNewReg,
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deref ? "*(" : "", (int)oldReg, (long long int)offset,
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deref ? ")" : "");
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} else if (how == PFXEXPR) {
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snprintf_literal(buf,
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"LUL 0x%llx old-r%d = pfx-expr-at %lld\n",
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(unsigned long long int)aAddress, aNewReg,
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(long long int)offset);
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} else {
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snprintf_literal(buf,
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"LUL 0x%llx old-r%d = (invalid LExpr!)\n",
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(unsigned long long int)aAddress, aNewReg);
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}
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mLog(buf);
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}
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if (mCurrAddr < aAddress) {
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// Flush the existing summary first.
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mCurrRules.mAddr = mCurrAddr;
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mCurrRules.mLen = aAddress - mCurrAddr;
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mSecMap->AddRuleSet(&mCurrRules);
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if (DEBUG_SUMMARISER) {
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mLog("LUL "); mCurrRules.Print(mLog);
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mLog("\n");
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}
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mCurrAddr = aAddress;
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}
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// If for some reason summarisation fails, either or both of these
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// become non-null and point at constant text describing the
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// problem. Using two rather than just one avoids complications of
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// having to concatenate two strings to produce a complete error message.
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const char* reason1 = nullptr;
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const char* reason2 = nullptr;
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// |offset| needs to be a 32 bit value that sign extends to 64 bits
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// on a 64 bit target. We will need to incorporate |offset| into
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// any LExpr made here. So we may as well check it right now.
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if (!fitsIn32Bits(offset)) {
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reason1 = "offset not in signed 32-bit range";
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goto cant_summarise;
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}
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// FIXME: factor out common parts of the arch-dependent summarisers.
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#if defined(LUL_ARCH_arm)
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// ----------------- arm ----------------- //
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// Now, can we add the rule to our summary? This depends on whether
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// the registers and the overall expression are representable. This
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// is the heart of the summarisation process.
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switch (aNewReg) {
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case DW_REG_CFA:
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// This is a rule that defines the CFA. The only forms we
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// choose to represent are: r7/11/12/13 + offset. The offset
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// must fit into 32 bits since 'uintptr_t' is 32 bit on ARM,
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// hence there is no need to check it for overflow.
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if (how != NODEREF) {
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reason1 = "rule for DW_REG_CFA: invalid |how|";
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goto cant_summarise;
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}
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switch (oldReg) {
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case DW_REG_ARM_R7: case DW_REG_ARM_R11:
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case DW_REG_ARM_R12: case DW_REG_ARM_R13:
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break;
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default:
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reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
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goto cant_summarise;
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}
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mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
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break;
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case DW_REG_ARM_R7: case DW_REG_ARM_R11: case DW_REG_ARM_R12:
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case DW_REG_ARM_R13: case DW_REG_ARM_R14: case DW_REG_ARM_R15: {
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// This is a new rule for R7, R11, R12, R13 (SP), R14 (LR) or
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// R15 (the return address).
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switch (how) {
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case NODEREF: case DEREF:
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// Check the old register is one we're tracking.
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if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
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oldReg != DW_REG_CFA) {
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reason1 = "rule for R7/11/12/13/14/15: uses untracked reg";
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goto cant_summarise;
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}
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break;
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case PFXEXPR: {
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// Check that the prefix expression only mentions tracked registers.
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const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
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reason2 = checkPfxExpr(pfxInstrs, offset);
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if (reason2) {
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reason1 = "rule for R7/11/12/13/14/15: ";
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goto cant_summarise;
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}
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break;
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}
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default:
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goto cant_summarise;
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}
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LExpr expr = LExpr(how, oldReg, offset);
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switch (aNewReg) {
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case DW_REG_ARM_R7: mCurrRules.mR7expr = expr; break;
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case DW_REG_ARM_R11: mCurrRules.mR11expr = expr; break;
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case DW_REG_ARM_R12: mCurrRules.mR12expr = expr; break;
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case DW_REG_ARM_R13: mCurrRules.mR13expr = expr; break;
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case DW_REG_ARM_R14: mCurrRules.mR14expr = expr; break;
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case DW_REG_ARM_R15: mCurrRules.mR15expr = expr; break;
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default: MOZ_ASSERT(0);
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}
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break;
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}
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default:
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// Leave |reason1| and |reason2| unset here. This program point
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// is reached so often that it causes a flood of "Can't
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// summarise" messages. In any case, we don't really care about
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// the fact that this summary would produce a new value for a
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// register that we're not tracking. We do on the other hand
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// care if the summary's expression *uses* a register that we're
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// not tracking. But in that case one of the above failures
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// should tell us which.
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goto cant_summarise;
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}
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// Mark callee-saved registers (r4 .. r11) as unchanged, if there is
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// no other information about them. FIXME: do this just once, at
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// the point where the ruleset is committed.
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if (mCurrRules.mR7expr.mHow == UNKNOWN) {
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mCurrRules.mR7expr = LExpr(NODEREF, DW_REG_ARM_R7, 0);
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}
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if (mCurrRules.mR11expr.mHow == UNKNOWN) {
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mCurrRules.mR11expr = LExpr(NODEREF, DW_REG_ARM_R11, 0);
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}
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if (mCurrRules.mR12expr.mHow == UNKNOWN) {
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mCurrRules.mR12expr = LExpr(NODEREF, DW_REG_ARM_R12, 0);
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}
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// The old r13 (SP) value before the call is always the same as the
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// CFA.
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mCurrRules.mR13expr = LExpr(NODEREF, DW_REG_CFA, 0);
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// If there's no information about R15 (the return address), say
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// it's a copy of R14 (the link register).
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if (mCurrRules.mR15expr.mHow == UNKNOWN) {
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mCurrRules.mR15expr = LExpr(NODEREF, DW_REG_ARM_R14, 0);
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}
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#elif defined(LUL_ARCH_x64) || defined(LUL_ARCH_x86)
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// ---------------- x64/x86 ---------------- //
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// Now, can we add the rule to our summary? This depends on whether
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// the registers and the overall expression are representable. This
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// is the heart of the summarisation process.
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switch (aNewReg) {
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case DW_REG_CFA:
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// This is a rule that defines the CFA. The only forms we can
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// represent are: = SP+offset or = FP+offset.
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if (how != NODEREF) {
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reason1 = "rule for DW_REG_CFA: invalid |how|";
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goto cant_summarise;
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}
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if (oldReg != DW_REG_INTEL_XSP && oldReg != DW_REG_INTEL_XBP) {
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reason1 = "rule for DW_REG_CFA: invalid |oldReg|";
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goto cant_summarise;
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}
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mCurrRules.mCfaExpr = LExpr(how, oldReg, offset);
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break;
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case DW_REG_INTEL_XSP: case DW_REG_INTEL_XBP: case DW_REG_INTEL_XIP: {
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// This is a new rule for XSP, XBP or XIP (the return address).
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switch (how) {
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case NODEREF: case DEREF:
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// Check the old register is one we're tracking.
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if (!registerIsTracked((DW_REG_NUMBER)oldReg) &&
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oldReg != DW_REG_CFA) {
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reason1 = "rule for XSP/XBP/XIP: uses untracked reg";
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goto cant_summarise;
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}
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break;
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case PFXEXPR: {
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// Check that the prefix expression only mentions tracked registers.
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const vector<PfxInstr>* pfxInstrs = mSecMap->GetPfxInstrs();
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reason2 = checkPfxExpr(pfxInstrs, offset);
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if (reason2) {
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reason1 = "rule for XSP/XBP/XIP: ";
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goto cant_summarise;
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}
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break;
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}
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default:
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goto cant_summarise;
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}
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LExpr expr = LExpr(how, oldReg, offset);
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switch (aNewReg) {
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case DW_REG_INTEL_XBP: mCurrRules.mXbpExpr = expr; break;
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case DW_REG_INTEL_XSP: mCurrRules.mXspExpr = expr; break;
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case DW_REG_INTEL_XIP: mCurrRules.mXipExpr = expr; break;
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default: MOZ_CRASH("impossible value for aNewReg");
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}
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break;
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}
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default:
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// Leave |reason1| and |reason2| unset here, for the reasons
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// explained in the analogous point in the ARM case just above.
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goto cant_summarise;
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}
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// On Intel, it seems the old SP value before the call is always the
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// same as the CFA. Therefore, in the absence of any other way to
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// recover the SP, specify that the CFA should be copied.
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if (mCurrRules.mXspExpr.mHow == UNKNOWN) {
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mCurrRules.mXspExpr = LExpr(NODEREF, DW_REG_CFA, 0);
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}
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// Also, gcc says "Undef" for BP when it is unchanged.
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if (mCurrRules.mXbpExpr.mHow == UNKNOWN) {
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mCurrRules.mXbpExpr = LExpr(NODEREF, DW_REG_INTEL_XBP, 0);
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}
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#else
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# error "Unsupported arch"
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#endif
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return;
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cant_summarise:
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if (reason1 || reason2) {
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char buf[200];
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snprintf_literal(buf, "LUL can't summarise: "
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"SVMA=0x%llx: %s%s, expr=LExpr(%s,%u,%lld)\n",
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(unsigned long long int)(aAddress - mTextBias),
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reason1 ? reason1 : "", reason2 ? reason2 : "",
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NameOf_LExprHow(how),
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(unsigned int)oldReg, (long long int)offset);
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mLog(buf);
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}
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}
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uint32_t
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Summariser::AddPfxInstr(PfxInstr pfxi)
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{
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return mSecMap->AddPfxInstr(pfxi);
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}
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void
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Summariser::End()
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{
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if (DEBUG_SUMMARISER) {
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mLog("LUL End\n");
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}
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if (mCurrAddr < mMax1Addr) {
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mCurrRules.mAddr = mCurrAddr;
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mCurrRules.mLen = mMax1Addr - mCurrAddr;
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mSecMap->AddRuleSet(&mCurrRules);
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if (DEBUG_SUMMARISER) {
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mLog("LUL "); mCurrRules.Print(mLog);
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mLog("\n");
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}
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}
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}
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} // namespace lul
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