LulDwarfSummariser.cpp
/* -*- 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
