michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /*
michael@0:  * This is an implementation of stack unwinding according to a subset
michael@0:  * of the ARM Exception Handling ABI, as described in:
michael@0:  *   http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
michael@0:  *
michael@0:  * This handles only the ARM-defined "personality routines" (chapter
michael@0:  * 9), and don't track the value of FP registers, because profiling
michael@0:  * needs only chain of PC/SP values.
michael@0:  *
michael@0:  * Because the exception handling info may not be accurate for all
michael@0:  * possible places where an async signal could occur (e.g., in a
michael@0:  * prologue or epilogue), this bounds-checks all stack accesses.
michael@0:  *
michael@0:  * This file uses "struct" for structures in the exception tables and
michael@0:  * "class" otherwise.  We should avoid violating the C++11
michael@0:  * standard-layout rules in the former.
michael@0:  */
michael@0: 
michael@0: #include "EHABIStackWalk.h"
michael@0: 
michael@0: #include "shared-libraries.h"
michael@0: #include "platform.h"
michael@0: 
michael@0: #include "mozilla/Atomics.h"
michael@0: #include "mozilla/Attributes.h"
michael@0: #include "mozilla/DebugOnly.h"
michael@0: #include "mozilla/Endian.h"
michael@0: 
michael@0: #include <algorithm>
michael@0: #include <elf.h>
michael@0: #include <stdint.h>
michael@0: #include <vector>
michael@0: #include <string>
michael@0: 
michael@0: #ifndef PT_ARM_EXIDX
michael@0: #define PT_ARM_EXIDX 0x70000001
michael@0: #endif
michael@0: 
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: struct EHEntry;
michael@0: 
michael@0: class EHState {
michael@0:   // Note that any core register can be used as a "frame pointer" to
michael@0:   // influence the unwinding process, so this must track all of them.
michael@0:   uint32_t mRegs[16];
michael@0: public:
michael@0:   bool unwind(const EHEntry *aEntry, const void *stackBase);
michael@0:   uint32_t &operator[](int i) { return mRegs[i]; }
michael@0:   const uint32_t &operator[](int i) const { return mRegs[i]; }
michael@0:   EHState(const mcontext_t &);
michael@0: };
michael@0: 
michael@0: enum {
michael@0:   R_SP = 13,
michael@0:   R_LR = 14,
michael@0:   R_PC = 15
michael@0: };
michael@0: 
michael@0: class EHEntryHandle {
michael@0:   const EHEntry *mValue;
michael@0: public:
michael@0:   EHEntryHandle(const EHEntry *aEntry) : mValue(aEntry) { }
michael@0:   const EHEntry *value() const { return mValue; }
michael@0: };
michael@0: 
michael@0: class EHTable {
michael@0:   uint32_t mStartPC;
michael@0:   uint32_t mEndPC;
michael@0:   uint32_t mLoadOffset;
michael@0:   // In principle we should be able to binary-search the index section in
michael@0:   // place, but the ICS toolchain's linker is noncompliant and produces
michael@0:   // indices that aren't entirely sorted (e.g., libc).  So we have this:
michael@0:   std::vector<EHEntryHandle> mEntries;
michael@0:   std::string mName;
michael@0: public:
michael@0:   EHTable(const void *aELF, size_t aSize, const std::string &aName);
michael@0:   const EHEntry *lookup(uint32_t aPC) const;
michael@0:   bool isValid() const { return mEntries.size() > 0; }
michael@0:   const std::string &name() const { return mName; }
michael@0:   uint32_t startPC() const { return mStartPC; }
michael@0:   uint32_t endPC() const { return mEndPC; }
michael@0:   uint32_t loadOffset() const { return mLoadOffset; }
michael@0: };
michael@0: 
michael@0: class EHAddrSpace {
michael@0:   std::vector<uint32_t> mStarts;
michael@0:   std::vector<EHTable> mTables;
michael@0:   static mozilla::Atomic<const EHAddrSpace*> sCurrent;
michael@0: public:
michael@0:   explicit EHAddrSpace(const std::vector<EHTable>& aTables);
michael@0:   const EHTable *lookup(uint32_t aPC) const;
michael@0:   static void Update();
michael@0:   static const EHAddrSpace *Get();
michael@0: };
michael@0: 
michael@0: 
michael@0: void EHABIStackWalkInit()
michael@0: {
michael@0:   EHAddrSpace::Update();
michael@0: }
michael@0: 
michael@0: size_t EHABIStackWalk(const mcontext_t &aContext, void *stackBase,
michael@0:                       void **aSPs, void **aPCs, const size_t aNumFrames)
michael@0: {
michael@0:   const EHAddrSpace *space = EHAddrSpace::Get();
michael@0:   EHState state(aContext);
michael@0:   size_t count = 0;
michael@0: 
michael@0:   while (count < aNumFrames) {
michael@0:     uint32_t pc = state[R_PC], sp = state[R_SP];
michael@0:     aPCs[count] = reinterpret_cast<void *>(pc);
michael@0:     aSPs[count] = reinterpret_cast<void *>(sp);
michael@0:     count++;
michael@0: 
michael@0:     if (!space)
michael@0:       break;
michael@0:     // TODO: cache these lookups.  Binary-searching libxul is
michael@0:     // expensive (possibly more expensive than doing the actual
michael@0:     // unwind), and even a small cache should help.
michael@0:     const EHTable *table = space->lookup(pc);
michael@0:     if (!table)
michael@0:       break;
michael@0:     const EHEntry *entry = table->lookup(pc);
michael@0:     if (!entry)
michael@0:       break;
michael@0:     if (!state.unwind(entry, stackBase))
michael@0:       break;
michael@0:   }
michael@0:   
michael@0:   return count;
michael@0: }
michael@0: 
michael@0: 
michael@0: struct PRel31 {
michael@0:   uint32_t mBits;
michael@0:   bool topBit() const { return mBits & 0x80000000; }
michael@0:   uint32_t value() const { return mBits & 0x7fffffff; }
michael@0:   int32_t offset() const { return (static_cast<int32_t>(mBits) << 1) >> 1; }
michael@0:   const void *compute() const {
michael@0:     return reinterpret_cast<const char *>(this) + offset();
michael@0:   }
michael@0: private:
michael@0:   PRel31(const PRel31 &copied) MOZ_DELETE;
michael@0:   PRel31() MOZ_DELETE;
michael@0: };
michael@0: 
michael@0: struct EHEntry {
michael@0:   PRel31 startPC;
michael@0:   PRel31 exidx;
michael@0: private:
michael@0:   EHEntry(const EHEntry &copied) MOZ_DELETE;
michael@0:   EHEntry() MOZ_DELETE;
michael@0: };
michael@0: 
michael@0: 
michael@0: class EHInterp {
michael@0: public:
michael@0:   // Note that stackLimit is exclusive and stackBase is inclusive
michael@0:   // (i.e, stackLimit < SP <= stackBase), following the convention
michael@0:   // set by the AAPCS spec.
michael@0:   EHInterp(EHState &aState, const EHEntry *aEntry,
michael@0:            uint32_t aStackLimit, uint32_t aStackBase)
michael@0:     : mState(aState),
michael@0:       mStackLimit(aStackLimit),
michael@0:       mStackBase(aStackBase),
michael@0:       mNextWord(0),
michael@0:       mWordsLeft(0),
michael@0:       mFailed(false)
michael@0:   {
michael@0:     const PRel31 &exidx = aEntry->exidx;
michael@0:     uint32_t firstWord;
michael@0: 
michael@0:     if (exidx.mBits == 1) {  // EXIDX_CANTUNWIND
michael@0:       mFailed = true;
michael@0:       return;
michael@0:     }
michael@0:     if (exidx.topBit()) {
michael@0:       firstWord = exidx.mBits;
michael@0:     } else {
michael@0:       mNextWord = reinterpret_cast<const uint32_t *>(exidx.compute());
michael@0:       firstWord = *mNextWord++;
michael@0:     }
michael@0: 
michael@0:     switch (firstWord >> 24) {
michael@0:     case 0x80: // short
michael@0:       mWord = firstWord << 8;
michael@0:       mBytesLeft = 3;
michael@0:       break;
michael@0:     case 0x81: case 0x82: // long; catch descriptor size ignored
michael@0:       mWord = firstWord << 16;
michael@0:       mBytesLeft = 2;
michael@0:       mWordsLeft = (firstWord >> 16) & 0xff;
michael@0:       break;
michael@0:     default:
michael@0:       // unknown personality
michael@0:       mFailed = true;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   bool unwind();
michael@0: 
michael@0: private:
michael@0:   // TODO: GCC has been observed not CSEing repeated reads of
michael@0:   // mState[R_SP] with writes to mFailed between them, suggesting that
michael@0:   // it hasn't determined that they can't alias and is thus missing
michael@0:   // optimization opportunities.  So, we may want to flatten EHState
michael@0:   // into this class; this may also make the code simpler.
michael@0:   EHState &mState;
michael@0:   uint32_t mStackLimit;
michael@0:   uint32_t mStackBase;
michael@0:   const uint32_t *mNextWord;
michael@0:   uint32_t mWord;
michael@0:   uint8_t mWordsLeft;
michael@0:   uint8_t mBytesLeft;
michael@0:   bool mFailed;
michael@0: 
michael@0:   enum {
michael@0:     I_ADDSP    = 0x00, // 0sxxxxxx (subtract if s)
michael@0:     M_ADDSP    = 0x80,
michael@0:     I_POPMASK  = 0x80, // 1000iiii iiiiiiii (if any i set)
michael@0:     M_POPMASK  = 0xf0,
michael@0:     I_MOVSP    = 0x90, // 1001nnnn
michael@0:     M_MOVSP    = 0xf0,
michael@0:     I_POPN     = 0xa0, // 1010lnnn
michael@0:     M_POPN     = 0xf0,
michael@0:     I_FINISH   = 0xb0, // 10110000
michael@0:     I_POPLO    = 0xb1, // 10110001 0000iiii (if any i set)
michael@0:     I_ADDSPBIG = 0xb2, // 10110010 uleb128
michael@0:     I_POPFDX   = 0xb3, // 10110011 sssscccc
michael@0:     I_POPFDX8  = 0xb8, // 10111nnn
michael@0:     M_POPFDX8  = 0xf8,
michael@0:     // "Intel Wireless MMX" extensions omitted.
michael@0:     I_POPFDD   = 0xc8, // 1100100h sssscccc
michael@0:     M_POPFDD   = 0xfe,
michael@0:     I_POPFDD8  = 0xd0, // 11010nnn
michael@0:     M_POPFDD8  = 0xf8
michael@0:   };
michael@0: 
michael@0:   uint8_t next() {
michael@0:     if (mBytesLeft == 0) {
michael@0:       if (mWordsLeft == 0) {
michael@0:         return I_FINISH;
michael@0:       }
michael@0:       mWordsLeft--;
michael@0:       mWord = *mNextWord++;
michael@0:       mBytesLeft = 4;
michael@0:     }
michael@0:     mBytesLeft--;
michael@0:     mWord = (mWord << 8) | (mWord >> 24); // rotate
michael@0:     return mWord;
michael@0:   }
michael@0: 
michael@0:   uint32_t &vSP() { return mState[R_SP]; }
michael@0:   uint32_t *ptrSP() { return reinterpret_cast<uint32_t *>(vSP()); }
michael@0: 
michael@0:   void checkStackBase() { if (vSP() > mStackBase) mFailed = true; }
michael@0:   void checkStackLimit() { if (vSP() <= mStackLimit) mFailed = true; }
michael@0:   void checkStackAlign() { if ((vSP() & 3) != 0) mFailed = true; }
michael@0:   void checkStack() {
michael@0:     checkStackBase();
michael@0:     checkStackLimit();
michael@0:     checkStackAlign();
michael@0:   }
michael@0: 
michael@0:   void popRange(uint8_t first, uint8_t last, uint16_t mask) {
michael@0:     bool hasSP = false;
michael@0:     uint32_t tmpSP;
michael@0:     if (mask == 0)
michael@0:       mFailed = true;
michael@0:     for (uint8_t r = first; r <= last; ++r) {
michael@0:       if (mask & 1) {
michael@0:         if (r == R_SP) {
michael@0:           hasSP = true;
michael@0:           tmpSP = *ptrSP();
michael@0:         } else
michael@0:           mState[r] = *ptrSP();
michael@0:         vSP() += 4;
michael@0:         checkStackBase();
michael@0:         if (mFailed)
michael@0:           return;
michael@0:       }
michael@0:       mask >>= 1;
michael@0:     }
michael@0:     if (hasSP) {
michael@0:       vSP() = tmpSP;
michael@0:       checkStack();
michael@0:     }
michael@0:   }
michael@0: };
michael@0: 
michael@0: 
michael@0: bool EHState::unwind(const EHEntry *aEntry, const void *stackBasePtr) {
michael@0:   // The unwinding program cannot set SP to less than the initial value.
michael@0:   uint32_t stackLimit = mRegs[R_SP] - 4;
michael@0:   uint32_t stackBase = reinterpret_cast<uint32_t>(stackBasePtr);
michael@0:   EHInterp interp(*this, aEntry, stackLimit, stackBase);
michael@0:   return interp.unwind();
michael@0: }
michael@0: 
michael@0: bool EHInterp::unwind() {
michael@0:   mState[R_PC] = 0;
michael@0:   checkStack();
michael@0:   while (!mFailed) {
michael@0:     uint8_t insn = next();
michael@0: #if DEBUG_EHABI_UNWIND
michael@0:     LOGF("unwind insn = %02x", (unsigned)insn);
michael@0: #endif
michael@0:     // Try to put the common cases first.
michael@0: 
michael@0:     // 00xxxxxx: vsp = vsp + (xxxxxx << 2) + 4
michael@0:     // 01xxxxxx: vsp = vsp - (xxxxxx << 2) - 4
michael@0:     if ((insn & M_ADDSP) == I_ADDSP) {
michael@0:       uint32_t offset = ((insn & 0x3f) << 2) + 4;
michael@0:       if (insn & 0x40) {
michael@0:         vSP() -= offset;
michael@0:         checkStackLimit();
michael@0:       } else {
michael@0:         vSP() += offset;
michael@0:         checkStackBase();
michael@0:       }
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 10100nnn: Pop r4-r[4+nnn]
michael@0:     // 10101nnn: Pop r4-r[4+nnn], r14
michael@0:     if ((insn & M_POPN) == I_POPN) {
michael@0:       uint8_t n = (insn & 0x07) + 1;
michael@0:       bool lr = insn & 0x08;
michael@0:       uint32_t *ptr = ptrSP();
michael@0:       vSP() += (n + (lr ? 1 : 0)) * 4;
michael@0:       checkStackBase();
michael@0:       for (uint8_t r = 4; r < 4 + n; ++r)
michael@0:         mState[r] = *ptr++;
michael@0:       if (lr)
michael@0:         mState[R_LR] = *ptr++;
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 1011000: Finish
michael@0:     if (insn == I_FINISH) {
michael@0:       if (mState[R_PC] == 0) {
michael@0:         mState[R_PC] = mState[R_LR];
michael@0:         // Non-standard change (bug 916106): Prevent the caller from
michael@0:         // re-using LR.  Since the caller is by definition not a leaf
michael@0:         // routine, it will have to restore LR from somewhere to
michael@0:         // return to its own caller, so we can safely zero it here.
michael@0:         // This makes a difference only if an error in unwinding
michael@0:         // (e.g., caused by starting from within a prologue/epilogue)
michael@0:         // causes us to load a pointer to a leaf routine as LR; if we
michael@0:         // don't do something, we'll go into an infinite loop of
michael@0:         // "returning" to that same function.
michael@0:         mState[R_LR] = 0;
michael@0:       }
michael@0:       return true;
michael@0:     }
michael@0: 
michael@0:     // 1001nnnn: Set vsp = r[nnnn]
michael@0:     if ((insn & M_MOVSP) == I_MOVSP) {
michael@0:       vSP() = mState[insn & 0x0f];
michael@0:       checkStack();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 11001000 sssscccc: Pop VFP regs D[16+ssss]-D[16+ssss+cccc] (as FLDMFDD)
michael@0:     // 11001001 sssscccc: Pop VFP regs D[ssss]-D[ssss+cccc] (as FLDMFDD)
michael@0:     if ((insn & M_POPFDD) == I_POPFDD) {
michael@0:       uint8_t n = (next() & 0x0f) + 1;
michael@0:       // Note: if the 16+ssss+cccc > 31, the encoding is reserved.
michael@0:       // As the space is currently unused, we don't try to check.
michael@0:       vSP() += 8 * n;
michael@0:       checkStackBase();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 11010nnn: Pop VFP regs D[8]-D[8+nnn] (as FLDMFDD)
michael@0:     if ((insn & M_POPFDD8) == I_POPFDD8) {
michael@0:       uint8_t n = (insn & 0x07) + 1;
michael@0:       vSP() += 8 * n;
michael@0:       checkStackBase();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 10110010 uleb128: vsp = vsp + 0x204 + (uleb128 << 2)
michael@0:     if (insn == I_ADDSPBIG) {
michael@0:       uint32_t acc = 0;
michael@0:       uint8_t shift = 0;
michael@0:       uint8_t byte;
michael@0:       do {
michael@0:         if (shift >= 32)
michael@0:           return false;
michael@0:         byte = next();
michael@0:         acc |= (byte & 0x7f) << shift;
michael@0:         shift += 7;
michael@0:       } while (byte & 0x80);
michael@0:       uint32_t offset = 0x204 + (acc << 2);
michael@0:       // The calculations above could have overflowed.
michael@0:       // But the one we care about is this:
michael@0:       if (vSP() + offset < vSP())
michael@0:         mFailed = true;
michael@0:       vSP() += offset;
michael@0:       // ...so that this is the only other check needed:
michael@0:       checkStackBase();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 1000iiii iiiiiiii (i not all 0): Pop under masks {r15-r12}, {r11-r4}
michael@0:     if ((insn & M_POPMASK) == I_POPMASK) {
michael@0:       popRange(4, 15, ((insn & 0x0f) << 8) | next());
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 1011001 0000iiii (i not all 0): Pop under mask {r3-r0}
michael@0:     if (insn == I_POPLO) {
michael@0:       popRange(0, 3, next() & 0x0f);
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 10110011 sssscccc: Pop VFP regs D[ssss]-D[ssss+cccc] (as FLDMFDX)
michael@0:     if (insn == I_POPFDX) {
michael@0:       uint8_t n = (next() & 0x0f) + 1;
michael@0:       vSP() += 8 * n + 4;
michael@0:       checkStackBase();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // 10111nnn: Pop VFP regs D[8]-D[8+nnn] (as FLDMFDX)
michael@0:     if ((insn & M_POPFDX8) == I_POPFDX8) {
michael@0:       uint8_t n = (insn & 0x07) + 1;
michael@0:       vSP() += 8 * n + 4;
michael@0:       checkStackBase();
michael@0:       continue;
michael@0:     }
michael@0: 
michael@0:     // unhandled instruction
michael@0: #ifdef DEBUG_EHABI_UNWIND
michael@0:     LOGF("Unhandled EHABI instruction 0x%02x", insn);
michael@0: #endif
michael@0:     mFailed = true;
michael@0:   }
michael@0:   return false;
michael@0: }
michael@0: 
michael@0: 
michael@0: bool operator<(const EHTable &lhs, const EHTable &rhs) {
michael@0:   return lhs.startPC() < rhs.endPC();
michael@0: }
michael@0: 
michael@0: // Async signal unsafe.
michael@0: EHAddrSpace::EHAddrSpace(const std::vector<EHTable>& aTables)
michael@0:   : mTables(aTables)
michael@0: {
michael@0:   std::sort(mTables.begin(), mTables.end());
michael@0:   DebugOnly<uint32_t> lastEnd = 0;
michael@0:   for (std::vector<EHTable>::iterator i = mTables.begin();
michael@0:        i != mTables.end(); ++i) {
michael@0:     MOZ_ASSERT(i->startPC() >= lastEnd);
michael@0:     mStarts.push_back(i->startPC());
michael@0:     lastEnd = i->endPC();
michael@0:   }
michael@0: }
michael@0: 
michael@0: const EHTable *EHAddrSpace::lookup(uint32_t aPC) const {
michael@0:   ptrdiff_t i = (std::upper_bound(mStarts.begin(), mStarts.end(), aPC)
michael@0:                  - mStarts.begin()) - 1;
michael@0: 
michael@0:   if (i < 0 || aPC >= mTables[i].endPC())
michael@0:     return 0;
michael@0:   return &mTables[i];
michael@0: }
michael@0: 
michael@0: 
michael@0: bool operator<(const EHEntryHandle &lhs, const EHEntryHandle &rhs) {
michael@0:   return lhs.value()->startPC.compute() < rhs.value()->startPC.compute();
michael@0: }
michael@0: 
michael@0: const EHEntry *EHTable::lookup(uint32_t aPC) const {
michael@0:   MOZ_ASSERT(aPC >= mStartPC);
michael@0:   if (aPC >= mEndPC)
michael@0:     return nullptr;
michael@0: 
michael@0:   std::vector<EHEntryHandle>::const_iterator begin = mEntries.begin();
michael@0:   std::vector<EHEntryHandle>::const_iterator end = mEntries.end();
michael@0:   MOZ_ASSERT(begin < end);
michael@0:   if (aPC < reinterpret_cast<uint32_t>(begin->value()->startPC.compute()))
michael@0:     return nullptr;
michael@0: 
michael@0:   while (end - begin > 1) {
michael@0:     std::vector<EHEntryHandle>::const_iterator mid = begin + (end - begin) / 2;
michael@0:     if (aPC < reinterpret_cast<uint32_t>(mid->value()->startPC.compute()))
michael@0:       end = mid;
michael@0:     else
michael@0:       begin = mid;
michael@0:   }
michael@0:   return begin->value();
michael@0: }
michael@0: 
michael@0: 
michael@0: #if MOZ_LITTLE_ENDIAN
michael@0: static const unsigned char hostEndian = ELFDATA2LSB;
michael@0: #elif MOZ_BIG_ENDIAN
michael@0: static const unsigned char hostEndian = ELFDATA2MSB;
michael@0: #else
michael@0: #error "No endian?"
michael@0: #endif
michael@0: 
michael@0: // Async signal unsafe.  (Note use of std::vector::reserve.)
michael@0: EHTable::EHTable(const void *aELF, size_t aSize, const std::string &aName)
michael@0:   : mStartPC(~0), // largest uint32_t
michael@0:     mEndPC(0),
michael@0:     mName(aName)
michael@0: {
michael@0:   const uint32_t base = reinterpret_cast<uint32_t>(aELF);
michael@0: 
michael@0:   if (aSize < sizeof(Elf32_Ehdr))
michael@0:     return;
michael@0: 
michael@0:   const Elf32_Ehdr &file = *(reinterpret_cast<Elf32_Ehdr *>(base));
michael@0:   if (memcmp(&file.e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||
michael@0:       file.e_ident[EI_CLASS] != ELFCLASS32 ||
michael@0:       file.e_ident[EI_DATA] != hostEndian ||
michael@0:       file.e_ident[EI_VERSION] != EV_CURRENT ||
michael@0:       file.e_ident[EI_OSABI] != ELFOSABI_SYSV ||
michael@0: #ifdef EI_ABIVERSION
michael@0:       file.e_ident[EI_ABIVERSION] != 0 ||
michael@0: #endif
michael@0:       file.e_machine != EM_ARM ||
michael@0:       file.e_version != EV_CURRENT)
michael@0:     // e_flags?
michael@0:     return;
michael@0: 
michael@0:   MOZ_ASSERT(file.e_phoff + file.e_phnum * file.e_phentsize <= aSize);
michael@0:   const Elf32_Phdr *exidxHdr = 0, *zeroHdr = 0;
michael@0:   for (unsigned i = 0; i < file.e_phnum; ++i) {
michael@0:     const Elf32_Phdr &phdr =
michael@0:       *(reinterpret_cast<Elf32_Phdr *>(base + file.e_phoff
michael@0:                                        + i * file.e_phentsize));
michael@0:     if (phdr.p_type == PT_ARM_EXIDX) {
michael@0:       exidxHdr = &phdr;
michael@0:     } else if (phdr.p_type == PT_LOAD) {
michael@0:       if (phdr.p_offset == 0) {
michael@0:         zeroHdr = &phdr;
michael@0:       }
michael@0:       if (phdr.p_flags & PF_X) {
michael@0:         mStartPC = std::min(mStartPC, phdr.p_vaddr);
michael@0:         mEndPC = std::max(mEndPC, phdr.p_vaddr + phdr.p_memsz);
michael@0:       }
michael@0:     }
michael@0:   }
michael@0:   if (!exidxHdr)
michael@0:     return;
michael@0:   if (!zeroHdr)
michael@0:     return;
michael@0:   mLoadOffset = base - zeroHdr->p_vaddr;
michael@0:   mStartPC += mLoadOffset;
michael@0:   mEndPC += mLoadOffset;
michael@0: 
michael@0:   // Create a sorted index of the index to work around linker bugs.
michael@0:   const EHEntry *startTable =
michael@0:     reinterpret_cast<const EHEntry *>(mLoadOffset + exidxHdr->p_vaddr);
michael@0:   const EHEntry *endTable =
michael@0:     reinterpret_cast<const EHEntry *>(mLoadOffset + exidxHdr->p_vaddr
michael@0:                                     + exidxHdr->p_memsz);
michael@0:   mEntries.reserve(endTable - startTable);
michael@0:   for (const EHEntry *i = startTable; i < endTable; ++i)
michael@0:     mEntries.push_back(i);
michael@0:   std::sort(mEntries.begin(), mEntries.end());
michael@0: }
michael@0: 
michael@0: 
michael@0: mozilla::Atomic<const EHAddrSpace*> EHAddrSpace::sCurrent(nullptr);
michael@0: 
michael@0: // Async signal safe; can fail if Update() hasn't returned yet.
michael@0: const EHAddrSpace *EHAddrSpace::Get() {
michael@0:   return sCurrent;
michael@0: }
michael@0: 
michael@0: // Collect unwinding information from loaded objects.  Calls after the
michael@0: // first have no effect.  Async signal unsafe.
michael@0: void EHAddrSpace::Update() {
michael@0:   const EHAddrSpace *space = sCurrent;
michael@0:   if (space)
michael@0:     return;
michael@0: 
michael@0:   SharedLibraryInfo info = SharedLibraryInfo::GetInfoForSelf();
michael@0:   std::vector<EHTable> tables;
michael@0: 
michael@0:   for (size_t i = 0; i < info.GetSize(); ++i) {
michael@0:     const SharedLibrary &lib = info.GetEntry(i);
michael@0:     if (lib.GetOffset() != 0)
michael@0:       // TODO: if it has a name, and we haven't seen a mapping of
michael@0:       // offset 0 for that file, try opening it and reading the
michael@0:       // headers instead.  The only thing I've seen so far that's
michael@0:       // linked so as to need that treatment is the dynamic linker
michael@0:       // itself.
michael@0:       continue;
michael@0:     EHTable tab(reinterpret_cast<const void *>(lib.GetStart()),
michael@0:               lib.GetEnd() - lib.GetStart(), lib.GetName());
michael@0:     if (tab.isValid())
michael@0:       tables.push_back(tab);
michael@0:   }
michael@0:   space = new EHAddrSpace(tables);
michael@0: 
michael@0:   if (!sCurrent.compareExchange(nullptr, space)) {
michael@0:     delete space;
michael@0:     space = sCurrent;
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: EHState::EHState(const mcontext_t &context) {
michael@0: #ifdef linux
michael@0:   mRegs[0] = context.arm_r0;
michael@0:   mRegs[1] = context.arm_r1;
michael@0:   mRegs[2] = context.arm_r2;
michael@0:   mRegs[3] = context.arm_r3;
michael@0:   mRegs[4] = context.arm_r4;
michael@0:   mRegs[5] = context.arm_r5;
michael@0:   mRegs[6] = context.arm_r6;
michael@0:   mRegs[7] = context.arm_r7;
michael@0:   mRegs[8] = context.arm_r8;
michael@0:   mRegs[9] = context.arm_r9;
michael@0:   mRegs[10] = context.arm_r10;
michael@0:   mRegs[11] = context.arm_fp;
michael@0:   mRegs[12] = context.arm_ip;
michael@0:   mRegs[13] = context.arm_sp;
michael@0:   mRegs[14] = context.arm_lr;
michael@0:   mRegs[15] = context.arm_pc;
michael@0: #else
michael@0: # error "Unhandled OS for ARM EHABI unwinding"
michael@0: #endif
michael@0: }
michael@0: 
michael@0: } // namespace mozilla
michael@0: