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- implemented unwind data on Unix - does it work? no idea, there's no easy way to tell when the debugger doesn't support the interface..

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This commit is contained in:
Magnus Norddahl 2018-12-01 01:14:15 +01:00
parent 42b9a41421
commit c41603c171
1 changed files with 73 additions and 51 deletions
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124
src/scripting/vm/jit_runtime.cpp
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@ -287,11 +287,52 @@ extern "C"
{
void __register_frame(const void*);
void __deregister_frame(const void*);
}
static void WriteLength64(TArray<uint8_t> &stream, unsigned int pos, unsigned int v)
{
*(uint64_t*)(&stream[pos]) = v;
#if 0 // Someone needs to implement this if GDB/LLDB should produce correct call stacks
// GDB JIT interface (GG guys! Thank you SO MUCH for not hooking into the above functions. Really appreciate it!)
// To register code with GDB, the JIT should follow this protocol:
//
// * Generate an object file in memory with symbols and other desired debug information.
// The file must include the virtual addresses of the sections.
// * Create a code entry for the file, which gives the start and size of the symbol file.
// * Add it to the linked list in the JIT descriptor.
// * Point the relevant_entry field of the descriptor at the entry.
// * Set action_flag to JIT_REGISTER and call __jit_debug_register_code.
// Pure beauty! Now a JIT also has to create a full ELF object file. And is it a MACH-O on macOS? You guys ROCK!
typedef enum
{
JIT_NOACTION = 0,
JIT_REGISTER_FN,
JIT_UNREGISTER_FN
} jit_actions_t;
struct jit_code_entry
{
struct jit_code_entry *next_entry;
struct jit_code_entry *prev_entry;
const char *symfile_addr;
uint64_t symfile_size;
};
struct jit_descriptor
{
uint32_t version;
// This type should be jit_actions_t, but we use uint32_t to be explicit about the bitwidth.
uint32_t action_flag;
struct jit_code_entry *relevant_entry;
struct jit_code_entry *first_entry;
};
// GDB puts a breakpoint in this function.
void __attribute__((noinline)) __jit_debug_register_code() { };
// Make sure to specify the version statically, because the debugger may check the version before we can set it.
struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
#endif
}
static void WriteLength(TArray<uint8_t> &stream, unsigned int pos, unsigned int v)
@ -373,85 +414,56 @@ static void WritePadding(TArray<uint8_t> &stream)
}
}
static void WriteEmptyAugmentation(TArray<uint8_t> &stream)
{
int padding = (stream.Size() + 1) % 8;
if (padding == 0)
{
WriteULEB128(stream, 0);
}
else
{
padding = 8 - padding;
WriteULEB128(stream, padding);
for (int i = 0; i <= padding; i++) WriteUInt8(stream, 0);
}
}
static void WriteCIE(TArray<uint8_t> &stream, const TArray<uint8_t> &cieInstructions, uint8_t returnAddressReg)
{
#ifdef USE_DWARF64
WriteUInt32(stream, 0xffffffff); // this is a 64-bit entry
unsigned int lengthPos = stream.Size();
WriteUInt64(stream, 0); // Length
WriteUInt64(stream, 0); // CIE ID
#else
unsigned int lengthPos = stream.Size();
WriteUInt32(stream, 0); // Length
WriteUInt32(stream, 0); // CIE ID
#endif
WriteUInt8(stream, 1); // CIE Version
WriteUInt8(stream, 'z');
//WriteUInt8(stream, 'z');
//WriteUInt8(stream, 'L'); // LSDA (language specific data area)
//WriteUInt8(stream, 'R'); // fde encoding
WriteUInt8(stream, 0);
WriteULEB128(stream, 1);
WriteSLEB128(stream, -4);
WriteUInt8(stream, returnAddressReg);
WriteEmptyAugmentation(stream);
WriteSLEB128(stream, -1);
WriteULEB128(stream, returnAddressReg);
//unsigned int augmentStartPos = stream.Size();
//WriteULEB128(stream, 0); // LEB128 augmentation size
//WriteUInt8(stream, 0xff); // DW_EH_PE_omit (no LSDA)
//WriteUInt8(stream, 0); // DW_EH_PE_absptr (FDE uses absolute pointers)
//WritePadding(stream);
//stream[augmentStartPos] = stream.Size() - augmentStartPos - 1;
for (unsigned int i = 0; i < cieInstructions.Size(); i++)
stream.Push(cieInstructions[i]);
WritePadding(stream);
#ifdef USE_DWARF64
WriteLength64(stream, lengthPos, stream.Size() - lengthPos - 8);
#else
WriteLength(stream, lengthPos, stream.Size() - lengthPos - 4);
#endif
}
static void WriteFDE(TArray<uint8_t> &stream, const TArray<uint8_t> &fdeInstructions, uint32_t cieLocation, unsigned int &functionStart)
{
#ifdef USE_DWARF64
WriteUInt32(stream, 0xffffffff); // this is a 64-bit entry
unsigned int lengthPos = stream.Size();
WriteUInt64(stream, 0); // Length
uint32_t offsetToCIE = stream.Size() - cieLocation;
WriteUInt64(stream, offsetToCIE);
#else
unsigned int lengthPos = stream.Size();
WriteUInt32(stream, 0); // Length
uint32_t offsetToCIE = stream.Size() - cieLocation;
WriteUInt32(stream, offsetToCIE);
#endif
functionStart = stream.Size();
WriteUInt64(stream, 0); // func start
WriteUInt64(stream, 0); // func size
WriteEmptyAugmentation(stream);
//unsigned int augmentStartPos = stream.Size();
//WriteULEB128(stream, 0); // LEB128 augmentation size
//WritePadding(stream);
//stream[augmentStartPos] = stream.Size() - augmentStartPos - 1;
for (unsigned int i = 0; i < fdeInstructions.Size(); i++)
stream.Push(fdeInstructions[i]);
WritePadding(stream);
#ifdef USE_DWARF64
WriteLength64(stream, lengthPos, stream.Size() - lengthPos - 8);
#else
WriteLength(stream, lengthPos, stream.Size() - lengthPos - 4);
#endif
}
static void WriteAdvanceLoc(TArray<uint8_t> &fdeInstructions, uint64_t offset, uint64_t &lastOffset)
@ -485,6 +497,11 @@ static TArray<uint8_t> CreateUnwindInfoUnix(asmjit::CCFunc *func, unsigned int &
// The x64 specific details are described in "System V Application Binary Interface AMD64 Architecture Processor Supplement"
//
// See appendix D.6 "Call Frame Information Example" in the DWARF 5 spec.
//
// Unofficial description: https://www.airs.com/blog/archives/460
//
// The CFI_Parser<A>::decodeFDE parser on the other side..
// https://github.com/llvm-mirror/libunwind/blob/master/src/DwarfParser.hpp
// Asmjit -> DWARF register id
int dwarfRegId[16];
@ -512,18 +529,25 @@ static TArray<uint8_t> CreateUnwindInfoUnix(asmjit::CCFunc *func, unsigned int &
uint64_t lastOffset = 0;
uint8_t returnAddressReg = dwarfRegRAId;
int stackOffset = 8; // Offset from RSP to the Canonical Frame Address (CFA) - stack position where the CALL return address is stored
// Do we need to write register defaults into the CIE or does the defaults match the x64 calling convention?
// Great! the "System V Application Binary Interface AMD64 Architecture Processor Supplement" doesn't say what the defaults are..
// This is basically just the x64 calling convention..
WriteUInt8(cieInstructions, 0x0c); // DW_CFA_def_cfa
WriteULEB128(cieInstructions, dwarfRegId[X86Gp::kIdSp]);
WriteULEB128(cieInstructions, stackOffset);
WriteUInt8(cieInstructions, (2 << 6) | returnAddressReg); // DW_CFA_offset
WriteULEB128(cieInstructions, 0);
for (auto regId : { X86Gp::kIdAx, X86Gp::kIdDx, X86Gp::kIdCx, X86Gp::kIdSi, X86Gp::kIdDi, X86Gp::kIdSp, X86Gp::kIdR8, X86Gp::kIdR9, X86Gp::kIdR10, X86Gp::kIdR11 })
{
WriteUInt8(cieInstructions, 0x07); // DW_CFA_undefined
WriteULEB128(cieInstructions, dwarfRegId[regId]);
}
for (auto regId : { X86Gp::kIdBx, X86Gp::kIdBp, X86Gp::kIdR12, X86Gp::kIdR13, X86Gp::kIdR14, X86Gp::kIdR15 })
{
WriteUInt8(cieInstructions, 0x08); // DW_CFA_same_value
@ -550,8 +574,6 @@ static TArray<uint8_t> CreateUnwindInfoUnix(asmjit::CCFunc *func, unsigned int &
X86Gp saReg = emitter->zsp(); // Stack-arguments base register.
uint32_t gpSaved = layout.getSavedRegs(X86Reg::kKindGp);
int stackOffset = 0;
if (layout.hasPreservedFP())
{
// Emit: 'push zbp'