types.h

// Provides type definitions shared by the eBPF and Go components

#ifndef OPTI_TYPES_H
#define OPTI_TYPES_H

#include "kernel.h"
#include "errors.h"

// ID values used as index to maps/metrics array.
// If you add enums below please update the following places too:
//  - The host agent ebpf metricID to DB IDMetric translation table in:
//    tracer/tracer.go/(StartMapMonitors).
//  - The ebpf userland test code metricID stringification table in:
//    support/ebpf/tests/tostring.c
enum {
  // number of calls to interpreter unwinding in get_next_interpreter()
  metricID_UnwindCallInterpreter = 0,

  // number of failures due to PC == 0 in unwind_next_frame()
  metricID_UnwindErrZeroPC,

  // number of times MAX_STACK_LEN has been exceeded
  metricID_UnwindErrStackLengthExceeded,

  // number of failures to read the TSD address
  metricID_UnwindErrBadTSDAddr,

  // number of failures to read the TSD base in get_tls_base()
  metricID_UnwindErrBadTPBaseAddr,

  // number of attempted unwinds
  metricID_UnwindNativeAttempts,

  // number of unwound frames
  metricID_UnwindNativeFrames,

  // number of native unwinds successfully ending with a stop delta
  metricID_UnwindNativeStackDeltaStop,

  // number of failures to look up ranges for text section in get_stack_delta()
  metricID_UnwindNativeErrLookupTextSection,

  // number of failed range searches within 20 steps in get_stack_delta()
  metricID_UnwindNativeErrLookupIterations,

  // number of failures to get StackUnwindInfo from stack delta map in get_stack_delta()
  metricID_UnwindNativeErrLookupRange,

  // number of kernel addresses passed to get_text_section()
  metricID_UnwindNativeErrKernelAddress,

  // number of failures to find the text section in get_text_section()
  metricID_UnwindNativeErrWrongTextSection,

  // number of invalid stack deltas in the native unwinder
  metricID_UnwindNativeErrStackDeltaInvalid,

  // number of failures to read PC from stack
  metricID_UnwindNativeErrPCRead,

  // number of attempted perl unwinds
  metricID_UnwindPerlAttempts,

  // number of perl frames unwound
  metricID_UnwindPerlFrames,

  // number of failures to read perl TSD info
  metricID_UnwindPerlTSD,

  // number of failures to read perl stack info
  metricID_UnwindPerlReadStackInfo,

  // number of failures to read perl context stack entry
  metricID_UnwindPerlReadContextStackEntry,

  // number of failures to resolve perl EGV
  metricID_UnwindPerlResolveEGV,

  // number of attempted python unwinds
  metricID_UnwindPythonAttempts,

  // number of unwound python frames
  metricID_UnwindPythonFrames,

  // number of failures to read from pyinfo->pyThreadStateCurrentAddr
  metricID_UnwindPythonErrBadPyThreadStateCurrentAddr,

  // number of PyThreadState being 0x0
  metricID_UnwindPythonErrZeroThreadState,

  // number of failures to read PyThreadState.frame in unwind_python()
  metricID_UnwindPythonErrBadThreadStateFrameAddr,

  // number of failures to read PyFrameObject->f_back in walk_python_stack()
  metricID_UnwindPythonErrBadFrameObjectBackAddr,

  // number of failures to read PyFrameObject->f_code in process_python_frame()
  metricID_UnwindPythonErrBadFrameCodeObjectAddr,

  // number of NULL code objects found in process_python_frame()
  metricID_UnwindPythonZeroFrameCodeObject,

  // number of failures to get the last instruction address in process_python_frame()
  metricID_UnwindPythonErrBadFrameLastInstructionAddr,

  // number of failures to get code object's argcount in process_python_frame()
  metricID_UnwindPythonErrBadCodeObjectArgCountAddr,

  // number of failures to get code object's kwonlyargcount in process_python_frame()
  metricID_UnwindPythonErrBadCodeObjectKWOnlyArgCountAddr,

  // number of failures to get code object's flags in process_python_frame()
  metricID_UnwindPythonErrBadCodeObjectFlagsAddr,

  // number of failures to get code object's first line number in process_python_frame()
  metricID_UnwindPythonErrBadCodeObjectFirstLineNumberAddr,

  // number of attempted PHP unwinds
  metricID_UnwindPHPAttempts,

  // number of unwound PHP frames
  metricID_UnwindPHPFrames,

  // number of failures to read PHP current execute data pointer
  metricID_UnwindPHPErrBadCurrentExecuteData,

  // number of failures to read PHP execute data contents
  metricID_UnwindPHPErrBadZendExecuteData,

  // number of failures to read PHP zend function contents
  metricID_UnwindPHPErrBadZendFunction,

  // number of failures to read PHP zend opline contents
  metricID_UnwindPHPErrBadZendOpline,

  // number of times unwind_stop is called without a trace
  metricID_ErrEmptyStack,

  // number of attempted Hotspot unwinds
  metricID_UnwindHotspotAttempts,

  // number of unwound Hotspot frames
  metricID_UnwindHotspotFrames,

  // number of failures to get codeblob address (no heap or bad segmap)
  metricID_UnwindHotspotErrNoCodeblob,

  // number of failures to get codeblob data or match it to current unwind state
  metricID_UnwindHotspotErrInvalidCodeblob,

  // number of failures to unwind interpreter due to invalid FP
  metricID_UnwindHotspotErrInterpreterFP,

  // number of failures to unwind because return address was not found with heuristic
  metricID_UnwindHotspotErrInvalidRA,

  // number of times the unwind instructions requested LR unwinding mid-trace
  metricID_UnwindHotspotErrLrUnwindingMidTrace,

  // number of times we encountered frame sizes larger than the supported maximum
  metricID_UnwindHotspotUnsupportedFrameSize,

  // number of times that PC hold a value smaller than 0x1000
  metricID_UnwindNativeSmallPC,

  // number of times that a lookup of a inner map for stack deltas failed
  metricID_UnwindNativeErrLookupStackDeltaInnerMap,

  // number of times that a lookup of the outer map for stack deltas failed
  metricID_UnwindNativeErrLookupStackDeltaOuterMap,

  // number of times the bpf helper failed to get the current comm of the task
  metricID_ErrBPFCurrentComm,

  // number of attempted Ruby unwinds
  metricID_UnwindRubyAttempts,

  // number of unwound Ruby frames
  metricID_UnwindRubyFrames,

  // number of attempted V8 unwinds
  metricID_UnwindV8Attempts,

  // number of unwound V8 frames
  metricID_UnwindV8Frames,

  // number of failures to read V8 frame pointer data
  metricID_UnwindV8ErrBadFP,

  // number of failures to read V8 JSFunction object
  metricID_UnwindV8ErrBadJSFunc,

  // number of failures to read V8 Code object
  metricID_UnwindV8ErrBadCode,

  // number of times frame unwinding failed because of LR == 0
  metricID_UnwindNativeLr0,

  // number of times we failed to update maps/reported_pids
  metricID_ReportedPIDsErr,

  // number of times we failed to update maps/pid_events
  metricID_PIDEventsErr,

  // number of "process new" PIDs written to maps/pid_events
  metricID_NumProcNew,

  // number of "process exit" PIDs written to maps/pid_events
  metricID_NumProcExit,

  // number of "unknown PC" PIDs written to maps/pid_events
  metricID_NumUnknownPC,

  // number of GENERIC_PID event sent to user space (perf_event)
  metricID_NumGenericPID,

  // number of failures to read _PyCFrame.current_frame in unwind_python()
  metricID_UnwindPythonErrBadCFrameFrameAddr,

  // number of times stack unwinding was stopped to not exceed the limit of tail calls
  metricID_MaxTailCalls,

  // number of times we didn't find an entry for this process in the Python process info array
  metricID_UnwindPythonErrNoProcInfo,

  // number of failures to read autoTLSkey
  metricID_UnwindPythonErrBadAutoTlsKeyAddr,

  // number of failures to read the thread state pointer from TLD
  metricID_UnwindPythonErrReadThreadStateAddr,

  // number of failures to determine the base address for thread-specific data
  metricID_UnwindPythonErrReadTsdBase,

  // number of times no entry for a process existed in the Ruby process info array
  metricID_UnwindRubyErrNoProcInfo,

  // number of failures to read the stack pointer from the Ruby context
  metricID_UnwindRubyErrReadStackPtr,

  // number of failures to read the size of the VM stack from the Ruby context
  metricID_UnwindRubyErrReadStackSize,

  // number of failures to read the control frame pointer from the Ruby context
  metricID_UnwindRubyErrReadCfp,

  // number of failures to read the expression path from the Ruby frame
  metricID_UnwindRubyErrReadEp,

  // number of failures to read the instruction sequence body
  metricID_UnwindRubyErrReadIseqBody,

  // number of failures to read the instruction sequence encoded size
  metricID_UnwindRubyErrReadIseqEncoded,

  // number of failures to read the instruction sequence size
  metricID_UnwindRubyErrReadIseqSize,

  // number of times the unwind instructions requested LR unwinding mid-trace
  metricID_UnwindNativeErrLrUnwindingMidTrace,

  // number of failures to read the kernel-mode registers
  metricID_UnwindNativeErrReadKernelModeRegs,

  // number of failures to read the IRQ stack link
  metricID_UnwindNativeErrChaseIrqStackLink,

  // number of times no entry for a process exists in the V8 process info array
  metricID_UnwindV8ErrNoProcInfo,

  // number of times an unwind_info_array index was invalid
  metricID_UnwindNativeErrBadUnwindInfoIndex,

  // number of failures to get TSD base for APM correlation
  metricID_UnwindApmIntErrReadTsdBase,

  // number of failures read the APM correlation pointer
  metricID_UnwindApmIntErrReadCorrBufPtr,

  // number of failures read the APM correlation buffer
  metricID_UnwindApmIntErrReadCorrBuf,

  // number of successful reads of APM correlation info
  metricID_UnwindApmIntReadSuccesses,

  // number of attempted Dotnet unwinds
  metricID_UnwindDotnetAttempts,

  // number of unwound Dotnet frames
  metricID_UnwindDotnetFrames,

  // number of times no entry for a process exists in the Dotnet process info array
  metricID_UnwindDotnetErrNoProcInfo,

  // number of failures to read Dotnet frame pointer data
  metricID_UnwindDotnetErrBadFP,

  // number of failures to read Dotnet CodeHeader object
  metricID_UnwindDotnetErrCodeHeader,

  // number of failures to unwind code object due to its large size
  metricID_UnwindDotnetErrCodeTooLarge,

  //
  // Metric IDs above are for counters (cumulative values)
  //

  metricID_BeginCumulative,

  //
  // Metric IDs below are for gauges (instantaneous values)
  //

  // used as size for maps/metrics (BPF_MAP_TYPE_PERCPU_ARRAY)
  metricID_Max
};

// TracePrograms provide the offset for each eBPF trace program in the
// map that holds them.
// The values of this enum must fit in a single byte.
typedef enum TracePrograms {
  PROG_UNWIND_STOP,
  PROG_UNWIND_NATIVE,
  PROG_UNWIND_HOTSPOT,
  PROG_UNWIND_PERL,
  PROG_UNWIND_PYTHON,
  PROG_UNWIND_PHP,
  PROG_UNWIND_RUBY,
  PROG_UNWIND_V8,
  PROG_UNWIND_DOTNET,
  NUM_TRACER_PROGS,
} TracePrograms;

// MAX_FRAME_UNWINDS defines the maximum number of frames per
// Trace we can unwind and respect the limit of eBPF instructions,
// limit of tail calls and limit of stack size per eBPF program.
#define MAX_FRAME_UNWINDS 128

// MAX_NON_ERROR_FRAME_UNWINDS defines the maximum number of frames
// to be pushed by unwinders while still leaving space for an error frame.
// This is used to make sure that there is always space for an error
// frame reporting that we ran out of stack space.
#define MAX_NON_ERROR_FRAME_UNWINDS (MAX_FRAME_UNWINDS - 1)

// Type to represent a globally-unique file id to be used as key for a BPF hash map
typedef u64 FileID;

// Individual frame in a stack-trace.
typedef struct Frame {
  // IDs that uniquely identify a file combination
  FileID file_id;
  // For PHP this is the line numbers, corresponding to the files in `stack`.
  // For Python, each value provides information to allow for the recovery of
  // the line number associated with its corresponding offset in `stack`.
  // The lower 32 bits provide the co_firstlineno value and the upper 32 bits
  // provide the f_lasti value. Other interpreter handlers use the field in
  // a similarly domain-specific fashion.
  u64 addr_or_line;
  // Indicates the type of the frame (Python, PHP, native etc.).
  u8 kind;
  // Indicates that the address is a return address.
  u8 return_address;
  // Explicit padding bytes that the compiler would have inserted anyway.
  // Here to make it clear to readers that there are spare bytes that could
  // be put to work without extra cost in case an interpreter needs it.
  u8 pad[6];
} Frame;

_Static_assert(sizeof(Frame) == 3 * 8, "frame padding not working as expected");

// TSDInfo contains data needed to extract Thread Specific Data (TSD) values
typedef struct TSDInfo {
  s16 offset;
  u8 multiplier;
  u8 indirect;
} TSDInfo;

// DotnetProcInfo is a container for the data needed to build stack trace for a dotnet process.
typedef struct DotnetProcInfo {
  u32 version;
} DotnetProcInfo;

// PerlProcInfo is a container for the data needed to build a stack trace for a Perl process.
typedef struct PerlProcInfo {
  u64 stateAddr;
  u32 version;
  TSDInfo tsdInfo;
  // Introspection data
  u16 interpreter_curcop, interpreter_curstackinfo;
  u8 stateInTSD, si_cxstack, si_next, si_cxix, si_type;
  u8 context_type, context_blk_oldcop, context_blk_sub_retop, context_blk_sub_cv, context_sizeof;
  u8 sv_flags, sv_any, svu_gp, xcv_flags, xcv_gv, gp_egv;
} PerlProcInfo;

// PyProcInfo is a container for the data needed to build a stack trace for a Python process.
typedef struct PyProcInfo {
  // The address of the autoTLSkey variable
  u64 autoTLSKeyAddr;
  u16 version;
  TSDInfo tsdInfo;
  // The Python object member offsets
  u8 PyThreadState_frame;
  u8 PyCFrame_current_frame;
  u8 PyFrameObject_f_back, PyFrameObject_f_code, PyFrameObject_f_lasti;
  u8 PyFrameObject_entry_member, PyFrameObject_entry_val;
  u8 PyCodeObject_co_argcount, PyCodeObject_co_kwonlyargcount;
  u8 PyCodeObject_co_flags, PyCodeObject_co_firstlineno;
  u8 PyCodeObject_sizeof;
} PyProcInfo;

// PHPProcInfo is a container for the data needed to build a stack trace for a PHP process.
typedef struct PHPProcInfo {
  u64 current_execute_data;
  // Return address for JIT code (in Hybrid mode)
  u64 jit_return_address;
  // Offsets for structures we need to access in ebpf
  u8 zend_execute_data_function, zend_execute_data_opline, zend_execute_data_prev_execute_data;
  u8 zend_execute_data_this_type_info, zend_function_type, zend_op_lineno;
} PHPProcInfo;

// HotspotProcInfo is a container for the data needed to build a stack trace
// for a Java Hotspot VM process.
typedef struct HotspotProcInfo {
  // The global JIT heap mapping. All JIT code is between these two address.
  u64 codecache_start, codecache_end;

  // Offsets of large structures, sizeof it is near or over 256 bytes.
  u16 compiledmethod_deopt_handler, nmethod_compileid, nmethod_orig_pc_offset;

  // Offsets and other data fitting in a uchar
  u8 codeblob_name;
  u8 codeblob_codestart, codeblob_codeend;
  u8 codeblob_framecomplete, codeblob_framesize;
  u8 heapblock_size, method_constmethod, cmethod_size;
  u8 jvm_version, segment_shift;
} HotspotProcInfo;

// RubyProcInfo is a container for the data needed to build a stack trace for a Ruby process.
typedef struct RubyProcInfo {
  // version of the Ruby interpreter.
  u32 version;

  // current_ctx_ptr holds the address of the symbol ruby_current_execution_context_ptr.
  u64 current_ctx_ptr;

  // Offsets and sizes of Ruby internal structs

  // rb_execution_context_struct offsets:
  u8 vm_stack, vm_stack_size, cfp;

  // rb_control_frame_struct offsets:
  u8 pc, iseq, ep, size_of_control_frame_struct;

  // rb_iseq_struct offsets:
  u8 body;

  // rb_iseq_constant_body:
  u8 iseq_type, iseq_encoded, iseq_size;

  // size_of_value holds the size of the macro VALUE as defined in
  // https://github.com/ruby/ruby/blob/5445e0435260b449decf2ac16f9d09bae3cafe72/vm_core.h#L1136
  u8 size_of_value;

  // rb_ractor_struct offset:
  u16 running_ec;

} RubyProcInfo;

// V8ProcInfo is a container for the data needed to build a stack trace for a V8 process.
typedef struct V8ProcInfo {
  u32 version;
  // Introspection data
  u16 type_JSFunction_first, type_JSFunction_last, type_Code, type_SharedFunctionInfo;
  u8 off_HeapObject_map, off_Map_instancetype, off_JSFunction_code, off_JSFunction_shared;
  u8 off_Code_instruction_start, off_Code_instruction_size, off_Code_flags;
  u8 fp_marker, fp_function, fp_bytecode_offset;
  u8 codekind_shift, codekind_mask, codekind_baseline;
} V8ProcInfo;

// COMM_LEN defines the maximum length we will receive for the comm of a task.
#define COMM_LEN 16

// 128-bit APM trace ID.
typedef union ApmTraceID {
  u8 raw[16];
  struct {
    u64 lo;
    u64 hi;
  } as_int;
} ApmTraceID;

_Static_assert(sizeof(ApmTraceID) == 16, "unexpected trace ID size");

// 64-bit APM transaction / span ID.
typedef union ApmSpanID {
  u8 raw[8];
  u64 as_int;
} ApmSpanID;

_Static_assert(sizeof(ApmSpanID) == 8, "unexpected trace ID size");

// Defines the format of the APM correlation TLS buffer.
//
// Specification: https://github.com/elastic/apm/blob/bd5fa9c1/specs/agents/universal-profiling-integration.md#thread-local-storage-layout
typedef struct __attribute__((packed)) ApmCorrelationBuf {
  u16 layout_minor_ver;
  u8 valid;
  u8 trace_present;
  u8 trace_flags;
  ApmTraceID trace_id;
  ApmSpanID span_id;
  ApmSpanID transaction_id;
} ApmCorrelationBuf;

// Container for a stack trace
typedef struct Trace {
  // The process ID
  u32 pid;
  // The thread ID
  u32 tid;
  // Monotonic kernel time in nanosecond precision.
  u64 ktime;
  // The current COMM of the thread of this Trace.
  char comm[COMM_LEN];
  // APM transaction ID or all-zero if not present.
  ApmSpanID apm_transaction_id;
  // APM trace ID or all-zero if not present.
  ApmTraceID apm_trace_id;
  // The kernel stack ID.
  s32 kernel_stack_id;
  // The number of frames in the stack.
  u32 stack_len;
  // The frames of the stack trace.
  Frame frames[MAX_FRAME_UNWINDS];

  // NOTE: both send_trace in BPF and loadBpfTrace in UM code require `frames`
  // to be the last item in the struct. Do not add new members here without also
  // adjusting the UM code.
} Trace;

// Container for unwinding state
typedef struct UnwindState {
  // Current register value for Program Counter
  u64 pc;
  // Current register value for Stack Pointer
  u64 sp;
  // Current register value for Frame Pointer
  u64 fp;

#if defined(__x86_64__)
  // Current register values for named registers
  u64 rax, r9, r11, r13, r15;
#elif defined(__aarch64__)
  // Current register values for named registers
  u64 lr, r22;
#endif

  // The executable ID/hash associated with PC
  u64 text_section_id;
  // PC converted into the offset relative to the executables text section
  u64 text_section_offset;
  // The current mapping load bias
  u64 text_section_bias;

  // Unwind error condition to process and report in unwind_stop()
  s32 error_metric;
  // If unwinding was aborted due to an error, this contains the reason why.
  ErrorCode unwind_error;

  // Set if the PC is a return address. That is, it points to the next instruction
  // after a CALL instruction, and requires to be adjusted during symbolization.
  // On aarch64, this additionally means that LR register can not be used.
  bool return_address;
} UnwindState;

// Container for unwinding state needed by the Perl unwinder. Keeping track of
// current stackinfo, first seen COP, and the info about current context stack.
typedef struct PerlUnwindState {
  // Pointer to the next stackinfo to unwind
  const void *stackinfo;
  // First Control OP seen for the frame filename/linenumber info for next function frame
  const void *cop;
  // Current context state, pointer to the base and current entries
  const void *cxbase, *cxcur;
} PerlUnwindState;

// Container for unwinding state needed by the Python unwinder. At the moment
// the only thing we need to pass between invocations of the unwinding programs
// is the pointer to the next PyFrameObject to unwind.
typedef struct PythonUnwindState {
  // Pointer to the next PyFrameObject to unwind
  void *py_frame;
} PythonUnwindState;

// Container for unwinding state needed by the PHP unwinder. At the moment
// the only thing we need to pass between invocations of the unwinding programs
// is the pointer to the next zend_execute_data to unwind.
typedef struct PHPUnwindState {
  // Pointer to the next zend_execute_data to unwind
  const void *zend_execute_data;
} PHPUnwindState;

// Container for unwinding state needed by the Ruby unwinder.
typedef struct RubyUnwindState {
  // Pointer to the next control frame struct in the Ruby VM stack we want to unwind.
  void *stack_ptr;
  // Pointer to the last control frame struct in the Ruby VM stack we want to handle.
  void *last_stack_frame;
} RubyUnwindState;

// Container for additional scratch space needed by the HotSpot unwinder.
typedef struct DotnetUnwindScratchSpace {
  // Buffer to read nibble map to locate code start. One map entry allows seeking backwards
  // 32*8 = 256 bytes of code. This defines the maximum size for a JITted function we
  // can reconize: 256 bytes/element * 128 elements = 32kB function size.
  u32 map[128];
  // Extra space to read to map fixed amount of bytes, but to dynamic offset.
  u32 extra[128];
} DotnetUnwindScratchSpace;

// Container for additional scratch space needed by the HotSpot unwinder.
typedef struct HotspotUnwindScratchSpace {
  // Read buffer for storing the codeblob. It's not needed across calls, but the buffer is too
  // large to be allocated on stack. With my debug build of JDK17, the largest possible variant of
  // codeblob that we care about (nmethod) is 376 bytes in size. 512 bytes should thus be plenty.
  u8 codeblob[512];
} HotspotUnwindScratchSpace;

// The number of bytes read from frame pointer for V8 context
#define V8_FP_CONTEXT_SIZE      64

// Container for additional scratch space needed by the V8 unwinder.
typedef struct V8UnwindScratchSpace {
  // Read buffer for storing the V8 FP stored context. Needs to be in non-stack
  // area to allow variable indexing.
  u8 fp_ctx[V8_FP_CONTEXT_SIZE];
  // Read buffer for V8 Code object. Currently we need about 60 bytes to get
  // code instruction_size and flags.
  u8 code[96];
} V8UnwindScratchSpace;

// Container for additional scratch space needed by the Python unwinder.
typedef struct PythonUnwindScratchSpace {
  // Read buffer for storing the PyInterpreterFrame (PyFrameObject).
  // Python 3.11 is about 80 bytes, but Python 3.7 has larger requirement.
  u8 frame[128];
  // Read buffer for storing the PyCodeObject. Currently we need 148 bytes of the header. But
  // the structure is 192 bytes in Python 3.11.
  u8 code[192];
} PythonUnwindScratchSpace;

// Per-CPU info for the stack being built. This contains the stack as well as
// meta-data on the number of eBPF tail-calls used so far to construct it.
typedef struct PerCPURecord {
  // The output record, including the stack being built.
  Trace trace;
  // The current unwind state.
  UnwindState state;
  // The current Perl unwinder state
  PerlUnwindState perlUnwindState;
  // The current Python unwinder state.
  PythonUnwindState pythonUnwindState;
  // The current PHP unwinder state.
  PHPUnwindState phpUnwindState;
  // The current Ruby unwinder state.
  RubyUnwindState rubyUnwindState;
  union {
    // Scratch space for the Dotnet unwinder.
    DotnetUnwindScratchSpace dotnetUnwindScratch;
    // Scratch space for the HotSpot unwinder.
    HotspotUnwindScratchSpace hotspotUnwindScratch;
    // Scratch space for the V8 unwinder
    V8UnwindScratchSpace v8UnwindScratch;
    // Scratch space for the Python unwinder
    PythonUnwindScratchSpace pythonUnwindScratch;
  };
  // Mask to indicate which unwinders are complete
  u32 unwindersDone;

  // tailCalls tracks the number of calls to bpf_tail_call().
  u8 tailCalls;

  // ratelimitAction determines the PID event rate limiting mode
  u8 ratelimitAction;
} PerCPURecord;

// UnwindInfo contains the unwind information needed to unwind one frame
// from a specific address.
typedef struct UnwindInfo {
  u8 opcode;       // main opcode to unwind CFA
  u8 fpOpcode;     // opcode to unwind FP
  u8 mergeOpcode;  // opcode for generating next stack delta, see below
  s32 param;       // parameter for the CFA expression
  s32 fpParam;     // parameter for the FP expression
} UnwindInfo;

// The 8-bit mergeOpcode consists of two separate fields:
//  1 bit   the adjustment to 'param' is negative (-8), if not set positive (+8)
//  7 bits  the difference to next 'addrLow'
#define MERGEOPCODE_NEGATIVE 0x80

// An array entry that we will bsearch into that keeps address and stack unwind
// info, per executable.
typedef struct StackDelta {
  u16 addrLow;    // the low 16-bits of the ELF virtual address to which this stack delta applies
  u16 unwindInfo; // index of UnwindInfo, or UNWIND_COMMAND_* if STACK_DELTA_COMMAND_FLAG is set
} StackDelta;

// unwindInfo flag indicating that the value is UNWIND_COMMAND_* value and not an index to
// the unwind info array. When UnwindInfo.opcode is UNWIND_OPCODE_COMMAND the 'param' gives
// the UNWIND_COMMAND_* which describes the exact handling for this stack delta (all
// CFA/PC/FP recovery, or stop condition), and the eBPF code needs special code to handle it.
// This basically serves as a minor optimization to not take a slot from unwind info array,
// nor require a table lookup for these special cased stack deltas.
#define STACK_DELTA_COMMAND_FLAG 0x8000

// StackDeltaPageKey is the look up key for stack delta page map.
typedef struct StackDeltaPageKey {
  u64 fileID;
  u64 page;
} StackDeltaPageKey;

// StackDeltaPageInfo contains information of stack delta page so the correct map
// and range of StackDelta entries can be found.
typedef struct StackDeltaPageInfo {
  u32 firstDelta;
  u16 numDeltas;
  u16 mapID;
} StackDeltaPageInfo;


// Keep stack deltas in 64kB pages to limit search space and to fit the low address
// bits into the addrLow field of struct StackDelta.
#define STACK_DELTA_PAGE_BITS 16

// The binary mask for STACK_DELTA_PAGE_BITS, which can be used to and/nand an address
// for its page number and offset within that page.
#define STACK_DELTA_PAGE_MASK ((1 << STACK_DELTA_PAGE_BITS) - 1)

// In order to determine whether a given PC falls into the main interpreter loop
// of an interpreter, we need to store some data: The lower boundary of the loop,
// the upper boundary of the loop, and the relevant index to call in the prog
// array.
typedef struct OffsetRange {
  u64 lower_offset;
  u64 upper_offset;
  u16 program_index;  // The interpreter-specific program index to call.
} OffsetRange;

// SystemAnalysis is the structure in system_analysis map
typedef struct SystemAnalysis {
  u64 address;
  u32 pid;
  u8 code[128];
} SystemAnalysis;

// Event is the header for all events sent through the report_events
// perf event output channel (event_send_trigger).
typedef struct Event {
  u32 event_type; // EVENT_TYPE_xxx selector of event
} Event;

// Event types that notifications are sent for through event_send_trigger.
#define EVENT_TYPE_GENERIC_PID 1

// PIDPage represents the key of the eBPF map pid_page_to_mapping_info.
typedef struct PIDPage {
  u32 prefixLen;    // Number of bits for pid and page that defines the
                    // longest prefix.

  __be32 pid;       // Unique ID of the process.
  __be64 page;      // Address to a certain part of memory within PID.
} PIDPage;


// BIT_WIDTH_PID defines the number of bits used in the value pid of the PIDPage struct.
#define BIT_WIDTH_PID  32
// BIT_WIDTH_PAGE defines the number of bits used in the value page of the PIDPage struct.
#define BIT_WIDTH_PAGE 64

// Constants for accessing bitfields within HotSpot text_section_offset/file_id.
#define HS_TSID_IS_STUB_BIT       63
#define HS_TSID_HAS_FRAME_BIT     62
#define HS_TSID_STACK_DELTA_BIT   56
#define HS_TSID_STACK_DELTA_MASK  ((1UL << 6) - 1)
#define HS_TSID_STACK_DELTA_SCALE 8
#define HS_TSID_SEG_MAP_BIT       0
#define HS_TSID_SEG_MAP_MASK      ((1UL << 56) - 1)

// PIDPageMappingInfo represents the value of the eBPF map pid_page_to_mapping_info.
typedef struct PIDPageMappingInfo {
  u64 file_id;                  // Unique identifier for the executable file

    // Load bias (7 bytes) + unwinding program to use (1 byte, shifted 7 bytes to the left), encoded in a u64.
    // We can do so because the load bias is for userspace addresses, for which the most significant byte is always 0 on
    // relevant architectures.
    // This encoding may have to be changed if bias can be negative.
  u64 bias_and_unwind_program;
} PIDPageMappingInfo;

// UNKNOWN_FILE indicates for unknown files.
#define UNKNOWN_FILE 0x0
// FUNC_TYPE_UNKNOWN indicates an unknown interpreted function.
#define FUNC_TYPE_UNKNOWN 0xfffffffffffffffe

// Builds a bias_and_unwind_program value for PIDPageMappingInfo
static inline __attribute__((__always_inline__))
u64 encode_bias_and_unwind_program(u64 bias, int unwind_program) {
    return bias | (((u64)unwind_program) << 56);
}

// Reads a bias_and_unwind_program value from PIDPageMappingInfo
static inline __attribute__((__always_inline__))
void decode_bias_and_unwind_program(u64 bias_and_unwind_program, u64* bias, int* unwind_program) {
    *bias = bias_and_unwind_program & 0x00FFFFFFFFFFFFFF;
    *unwind_program = bias_and_unwind_program >> 56;
}

// Smallest stack delta bucket that holds up to 2^8 entries
#define STACK_DELTA_BUCKET_SMALLEST 8
// Largest stack delta bucket that holds up to 2^21 entries
#define STACK_DELTA_BUCKET_LARGEST 21

// Struct of the `system_config` map. Contains various configuration variables
// determined and set by the host agent.
typedef struct SystemConfig {
  // PAC mask that is determined by user-space and used in `normalize_pac_ptr`.
  // ARM64 specific, `MAX_U64` otherwise.
  u64 inverse_pac_mask;

  // The offset of the Thread Pointer Base variable in `task_struct`. It is
  // populated by the host agent based on kernel code analysis.
  u64 tpbase_offset;

  // The offset of stack base within `task_struct`.
  u32 task_stack_offset;

  // The offset of struct pt_regs within the kernel entry stack.
  u32 stack_ptregs_offset;

  // Enables the temporary hack that drops pure errors frames in unwind_stop.
  bool drop_error_only_traces;
} SystemConfig;

// Avoid including all of arch/arm64/include/uapi/asm/ptrace.h by copying the
// actually used values.
#define PSR_MODE32_BIT 0x00000010
#define PSR_MODE_MASK  0x0000000f
#define PSR_MODE_EL0t  0x00000000

typedef struct ApmIntProcInfo {
  u64 tls_offset;
} ApmIntProcInfo;

#endif