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Add support for unwinding during prologue/epilogue
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@Keno
Keno committed Aug 26, 2013
1 parent 76776d6 commit ca57a5b
Showing 1 changed file with 176 additions and 1 deletion.
177 changes: 176 additions & 1 deletion src/CompactUnwinder.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -559,6 +559,55 @@ int CompactUnwinder_x86_64<A>::stepWithCompactEncodingRBPFrame(compact_unwind_en
uint32_t savedRegistersOffset = EXTRACT_BITS(compactEncoding, UNWIND_X86_64_RBP_FRAME_OFFSET);
uint32_t savedRegistersLocations = EXTRACT_BITS(compactEncoding, UNWIND_X86_64_RBP_FRAME_REGISTERS);

// If we have not stored EBP yet
if (functionStart == registers.getIP())
{
uint64_t rsp = registers.getSP();
// old esp is ebp less return address
registers.setSP(rsp+8);
// pop return address into eip
registers.setIP(addressSpace.get64(rsp));

return UNW_STEP_SUCCESS;
} else if (functionStart+1 == registers.getIP())
{
uint64_t rsp = registers.getSP();
// old esp is ebp less return address
registers.setSP(rsp+16);
// pop return address into eip
registers.setIP(addressSpace.get64(rsp+8));

return UNW_STEP_SUCCESS;
}

// If we're about to return, we've already popped the base pointer
uint8_t b = addressSpace.get8(registers.getIP());

// This is a hack to detect VZEROUPPER but in between popq rbp and ret
// It's not pretty but it works
if (b == 0xC5) {
if ((b = addressSpace.get8(registers.getIP() + 1)) == 0xF8 &&
(b = addressSpace.get8(registers.getIP() + 2)) == 0x77)
{
b = addressSpace.get8(registers.getIP() + 3);
} else {
goto skip_ret;
}
}

if (b == 0xC3 || b == 0xCB || b == 0xC2 || b == 0xCA)
{
uint64_t rbp = registers.getSP();
// old esp is ebp less return address
registers.setSP(rbp+16);
// pop return address into eip
registers.setIP(addressSpace.get64(rbp+8));

return UNW_STEP_SUCCESS;
}

skip_ret:

uint64_t savedRegisters = registers.getRBP() - 8*savedRegistersOffset;
for (int i=0; i < 5; ++i) {
switch (savedRegistersLocations & 0x7) {
Expand Down Expand Up @@ -590,7 +639,6 @@ int CompactUnwinder_x86_64<A>::stepWithCompactEncodingRBPFrame(compact_unwind_en
frameUnwind(addressSpace, registers);
return UNW_STEP_SUCCESS;
}


template <typename A>
int CompactUnwinder_x86_64<A>::stepWithCompactEncodingFrameless(compact_unwind_encoding_t encoding, uint64_t functionStart,
Expand All @@ -606,10 +654,12 @@ int CompactUnwinder_x86_64<A>::stepWithCompactEncodingFrameless(compact_unwind_e
uint32_t subl = addressSpace.get32(functionStart+stackSizeEncoded);
stackSize = subl + 8*stackAdjust;
}

// decompress permutation
int permunreg[6];
switch ( regCount ) {
case 6:

permunreg[0] = permutation/120;
permutation -= (permunreg[0]*120);
permunreg[1] = permutation/24;
Expand Down Expand Up @@ -673,6 +723,131 @@ int CompactUnwinder_x86_64<A>::stepWithCompactEncodingFrameless(compact_unwind_e
}
}
}



// Note that the order of these registers is so that
// registersSaved[0] is the one that will be pushed onto the stack last.
// Thus, if we want to walk this from the top, we need to go in reverse.
assert(regCount <= 6);

// check whether we are still in the prologue
uint64_t curAddr = functionStart;
if (regCount > 0)
{
for (int8_t i=regCount-1; i >= 0; --i) {
if (registers.getIP() == curAddr)
{
// None of the registers have been modified yet, so we don't need to reload them
framelessUnwind(addressSpace, registers.getSP() + 8*(regCount-(i+1)), registers);
return UNW_STEP_SUCCESS;
} else
{
assert(curAddr < registers.getIP());
}


// pushq %rbp and pushq %rbx is 1 byte. Everything else 2
if ((UNWIND_X86_64_REG_RBP == registersSaved[i]) ||
(UNWIND_X86_64_REG_RBX == registersSaved[i]))
curAddr += 1;
else
curAddr += 2;
}
}
if (registers.getIP() == curAddr)
{
// None of the registers have been modified yet, so we don't need to reload them
framelessUnwind(addressSpace, registers.getSP() + 8*regCount, registers);
return UNW_STEP_SUCCESS;
} else
{
assert(curAddr < registers.getIP());
}


// And now for the epilogue
uint8_t i = 0;
uint64_t p = registers.getIP();
uint8_t b = 0;

while (true)
{
b = addressSpace.get8(p++);
// This is a hack to detect VZEROUPPER but in between the popq's and ret
// It's not pretty but it works
if (b == 0xC5) {
if ((b = addressSpace.get8(p++)) == 0xF8 &&
(b = addressSpace.get8(p++)) == 0x77)
{
b = addressSpace.get8(p++);
} else {
break;
}
}
// popq %rbx popq %rbp
if (b == 0x5B || b == 0x5D)
{
i++;
} else if (b == 0x41)
{
b = addressSpace.get8(p++);
if (b == 0x5C || b == 0x5D || b == 0x5E || b == 0x5F)
{
i++;
} else {
break;
}
} else if (b == 0xC3 || b == 0xCB || b == 0xC2 || b == 0xCA)
{
// i pop's haven't happened yet
uint64_t savedRegisters = registers.getSP() + 8*i;
if (regCount>0) {
for (int8_t j = regCount-1; j>=(int8_t)(regCount-i); --j)
{
uint64_t addr = savedRegisters - 8*(regCount-j);
switch ( registersSaved[j] ) {
case UNWIND_X86_64_REG_RBX:
registers.setRBX(addressSpace.get64(addr));
break;
case UNWIND_X86_64_REG_R12:
registers.setR12(addressSpace.get64(addr));
break;
case UNWIND_X86_64_REG_R13:
registers.setR13(addressSpace.get64(addr));
break;
case UNWIND_X86_64_REG_R14:
registers.setR14(addressSpace.get64(addr));
break;
case UNWIND_X86_64_REG_R15:
registers.setR15(addressSpace.get64(addr));
break;
case UNWIND_X86_64_REG_RBP:
registers.setRBP(addressSpace.get64(addr));
break;
default:
DEBUG_MESSAGE("bad register for frameless, encoding=%08X for function starting at 0x%llX\n", encoding, functionStart);
ABORT("invalid compact unwind encoding");
}
}
}
framelessUnwind(addressSpace, savedRegisters, registers);
return UNW_STEP_SUCCESS;
} else {
break;
}
}

/*
0x10fe2733a: 5b popq %rbx
0x10fe2733b: 41 5c popq %r12
0x10fe2733d: 41 5d popq %r13
0x10fe2733f: 41 5e popq %r14
0x10fe27341: 41 5f popq %r15
0x10fe27343: 5d popq %rbp
*/


uint64_t savedRegisters = registers.getSP() + stackSize - 8 - 8*regCount;
for (uint32_t i=0; i < regCount; ++i) {
switch ( registersSaved[i] ) {
Expand Down

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