tracy/client/TracyCallstack.cpp

#include <new>
#include <stdio.h>
#include <string.h>
#include "TracyCallstack.hpp"
#include "TracyFastVector.hpp"
#include "../common/TracyAlloc.hpp"

#ifdef TRACY_HAS_CALLSTACK

#if TRACY_HAS_CALLSTACK == 1
#  ifndef NOMINMAX
#    define NOMINMAX
#  endif
#  include <windows.h>
#  include <psapi.h>
#  ifdef _MSC_VER
#    pragma warning( push )
#    pragma warning( disable : 4091 )
#  endif
#  include <dbghelp.h>
#  ifdef _MSC_VER
#    pragma warning( pop )
#  endif
#elif TRACY_HAS_CALLSTACK == 2 || TRACY_HAS_CALLSTACK == 3 || TRACY_HAS_CALLSTACK == 4 || TRACY_HAS_CALLSTACK == 6
#  include "../libbacktrace/backtrace.hpp"
#  include <dlfcn.h>
#  include <cxxabi.h>
#elif TRACY_HAS_CALLSTACK == 5
#  include <dlfcn.h>
#  include <cxxabi.h>
#endif

#ifdef TRACY_DBGHELP_LOCK
#  include "TracyProfiler.hpp"

#  define DBGHELP_INIT TracyConcat( TRACY_DBGHELP_LOCK, Init() )
#  define DBGHELP_LOCK TracyConcat( TRACY_DBGHELP_LOCK, Lock() );
#  define DBGHELP_UNLOCK TracyConcat( TRACY_DBGHELP_LOCK, Unlock() );

extern "C"
{
    void DBGHELP_INIT;
    void DBGHELP_LOCK;
    void DBGHELP_UNLOCK;
};
#endif

#ifdef __ANDROID__
#  include <sys/mman.h>
#  include <stdio.h>
#  include <stdint.h>
#  include <algorithm>
#  include <vector>
#endif

namespace tracy
{

static inline char* CopyString( const char* src, size_t sz )
{
    assert( strlen( src ) == sz );
    auto dst = (char*)tracy_malloc( sz + 1 );
    memcpy( dst, src, sz );
    dst[sz] = '\0';
    return dst;
}

static inline char* CopyString( const char* src )
{
    const auto sz = strlen( src );
    auto dst = (char*)tracy_malloc( sz + 1 );
    memcpy( dst, src, sz );
    dst[sz] = '\0';
    return dst;
}


#if TRACY_HAS_CALLSTACK == 1

enum { MaxCbTrace = 16 };
enum { MaxNameSize = 8*1024 };

int cb_num;
CallstackEntry cb_data[MaxCbTrace];

extern "C"
{
    typedef unsigned long (__stdcall *t_RtlWalkFrameChain)( void**, unsigned long, unsigned long );
    t_RtlWalkFrameChain RtlWalkFrameChain = 0;
}

#if defined __MINGW32__ && API_VERSION_NUMBER < 12
extern "C" {
// Actual required API_VERSION_NUMBER is unknown because it is undocumented. These functions are not present in at least v11.
DWORD IMAGEAPI SymAddrIncludeInlineTrace(HANDLE hProcess, DWORD64 Address);
BOOL IMAGEAPI SymQueryInlineTrace(HANDLE hProcess, DWORD64 StartAddress, DWORD StartContext, DWORD64 StartRetAddress,
    DWORD64 CurAddress, LPDWORD CurContext, LPDWORD CurFrameIndex);
BOOL IMAGEAPI SymFromInlineContext(HANDLE hProcess, DWORD64 Address, ULONG InlineContext, PDWORD64 Displacement,
    PSYMBOL_INFO Symbol);
BOOL IMAGEAPI SymGetLineFromInlineContext(HANDLE hProcess, DWORD64 qwAddr, ULONG InlineContext,
    DWORD64 qwModuleBaseAddress, PDWORD pdwDisplacement, PIMAGEHLP_LINE64 Line64);
};
#endif

#ifndef __CYGWIN__
struct ModuleCache
{
    uint64_t start;
    uint64_t end;
    char* name;
};

static FastVector<ModuleCache>* s_modCache;
#endif

void InitCallstack()
{
    RtlWalkFrameChain = (t_RtlWalkFrameChain)GetProcAddress( GetModuleHandleA( "ntdll.dll" ), "RtlWalkFrameChain" );

#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_INIT;
    DBGHELP_LOCK;
#endif

    SymInitialize( GetCurrentProcess(), nullptr, true );
    SymSetOptions( SYMOPT_LOAD_LINES );

#ifndef __CYGWIN__
    HMODULE mod[1024];
    DWORD needed;
    HANDLE proc = GetCurrentProcess();

    s_modCache = (FastVector<ModuleCache>*)tracy_malloc( sizeof( FastVector<ModuleCache> ) );
    new(s_modCache) FastVector<ModuleCache>( 512 );

    if( EnumProcessModules( proc, mod, sizeof( mod ), &needed ) != 0 )
    {
        const auto sz = needed / sizeof( HMODULE );
        for( size_t i=0; i<sz; i++ )
        {
            MODULEINFO info;
            if( GetModuleInformation( proc, mod[i], &info, sizeof( info ) ) != 0 )
            {
                const auto base = uint64_t( info.lpBaseOfDll );
                char name[1024];
                const auto res = GetModuleFileNameA( mod[i], name, 1021 );
                if( res > 0 )
                {
                    auto ptr = name + res;
                    while( ptr > name && *ptr != '\\' && *ptr != '/' ) ptr--;
                    if( ptr > name ) ptr++;
                    const auto namelen = name + res - ptr;
                    auto cache = s_modCache->push_next();
                    cache->start = base;
                    cache->end = base + info.SizeOfImage;
                    cache->name = (char*)tracy_malloc( namelen+3 );
                    cache->name[0] = '[';
                    memcpy( cache->name+1, ptr, namelen );
                    cache->name[namelen+1] = ']';
                    cache->name[namelen+2] = '\0';
                }
            }
        }
    }
#endif

#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_UNLOCK;
#endif
}

TRACY_API uintptr_t* CallTrace( int depth )
{
    auto trace = (uintptr_t*)tracy_malloc( ( 1 + depth ) * sizeof( uintptr_t ) );
    const auto num = RtlWalkFrameChain( (void**)( trace + 1 ), depth, 0 );
    *trace = num;
    return trace;
}

const char* DecodeCallstackPtrFast( uint64_t ptr )
{
    static char ret[MaxNameSize];
    const auto proc = GetCurrentProcess();

    char buf[sizeof( SYMBOL_INFO ) + MaxNameSize];
    auto si = (SYMBOL_INFO*)buf;
    si->SizeOfStruct = sizeof( SYMBOL_INFO );
    si->MaxNameLen = MaxNameSize;

#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_LOCK;
#endif
    if( SymFromAddr( proc, ptr, nullptr, si ) == 0 )
    {
        *ret = '\0';
    }
    else
    {
        memcpy( ret, si->Name, si->NameLen );
        ret[si->NameLen] = '\0';
    }
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_UNLOCK;
#endif
    return ret;
}

static const char* GetModuleName( uint64_t addr )
{
    if( ( addr & 0x8000000000000000 ) != 0 ) return "[kernel]";

#ifndef __CYGWIN__
    for( auto& v : *s_modCache )
    {
        if( addr >= v.start && addr < v.end )
        {
            return v.name;
        }
    }

    HMODULE mod[1024];
    DWORD needed;
    HANDLE proc = GetCurrentProcess();

    if( EnumProcessModules( proc, mod, sizeof( mod ), &needed ) != 0 )
    {
        const auto sz = needed / sizeof( HMODULE );
        for( size_t i=0; i<sz; i++ )
        {
            MODULEINFO info;
            if( GetModuleInformation( proc, mod[i], &info, sizeof( info ) ) != 0 )
            {
                const auto base = uint64_t( info.lpBaseOfDll );
                if( addr >= base && addr < base + info.SizeOfImage )
                {
                    char name[1024];
                    const auto res = GetModuleFileNameA( mod[i], name, 1021 );
                    if( res > 0 )
                    {
                        auto ptr = name + res;
                        while( ptr > name && *ptr != '\\' && *ptr != '/' ) ptr--;
                        if( ptr > name ) ptr++;
                        const auto namelen = name + res - ptr;
                        auto cache = s_modCache->push_next();
                        cache->start = base;
                        cache->end = base + info.SizeOfImage;
                        cache->name = (char*)tracy_malloc( namelen+3 );
                        cache->name[0] = '[';
                        memcpy( cache->name+1, ptr, namelen );
                        cache->name[namelen+1] = ']';
                        cache->name[namelen+2] = '\0';
                        return cache->name;
                    }
                }
            }
        }
    }
#endif

    return "[unknown]";
}

CallstackSymbolData DecodeSymbolAddress( uint64_t ptr )
{
    CallstackSymbolData sym;
    IMAGEHLP_LINE64 line;
    DWORD displacement = 0;
    line.SizeOfStruct = sizeof(IMAGEHLP_LINE64);
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_LOCK;
#endif
    const auto res = SymGetLineFromAddr64( GetCurrentProcess(), ptr, &displacement, &line );
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_UNLOCK;
#endif
    if( res == 0 )
    {
        sym.file = "[unknown]";
        sym.line = 0;
    }
    else
    {
        sym.file = line.FileName;
        sym.line = line.LineNumber;
    }
    sym.needFree = false;
    return sym;
}

CallstackSymbolData DecodeCodeAddress( uint64_t ptr )
{
    CallstackSymbolData sym;
    const auto proc = GetCurrentProcess();
    bool done = false;

    IMAGEHLP_LINE64 line;
    DWORD displacement = 0;
    line.SizeOfStruct = sizeof(IMAGEHLP_LINE64);

#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_LOCK;
#endif
#ifndef __CYGWIN__
    DWORD inlineNum = SymAddrIncludeInlineTrace( proc, ptr );
    DWORD ctx = 0;
    DWORD idx;
    BOOL doInline = FALSE;
    if( inlineNum != 0 ) doInline = SymQueryInlineTrace( proc, ptr, 0, ptr, ptr, &ctx, &idx );
    if( doInline )
    {
        if( SymGetLineFromInlineContext( proc, ptr, ctx, 0, &displacement, &line ) != 0 )
        {
            sym.file = line.FileName;
            sym.line = line.LineNumber;
            done = true;
        }
    }
#endif
    if( !done )
    {
        if( SymGetLineFromAddr64( proc, ptr, &displacement, &line ) == 0 )
        {
            sym.file = "[unknown]";
            sym.line = 0;
        }
        else
        {
            sym.file = line.FileName;
            sym.line = line.LineNumber;
        }
    }
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_UNLOCK;
#endif
    sym.needFree = false;
    return sym;
}

CallstackEntryData DecodeCallstackPtr( uint64_t ptr )
{
    int write;
    const auto proc = GetCurrentProcess();
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_LOCK;
#endif
#ifndef __CYGWIN__
    DWORD inlineNum = SymAddrIncludeInlineTrace( proc, ptr );
    if( inlineNum > MaxCbTrace - 1 ) inlineNum = MaxCbTrace - 1;
    DWORD ctx = 0;
    DWORD idx;
    BOOL doInline = FALSE;
    if( inlineNum != 0 ) doInline = SymQueryInlineTrace( proc, ptr, 0, ptr, ptr, &ctx, &idx );
    if( doInline )
    {
        write = inlineNum;
        cb_num = 1 + inlineNum;
    }
    else
#endif
    {
        write = 0;
        cb_num = 1;
    }

    char buf[sizeof( SYMBOL_INFO ) + MaxNameSize];
    auto si = (SYMBOL_INFO*)buf;
    si->SizeOfStruct = sizeof( SYMBOL_INFO );
    si->MaxNameLen = MaxNameSize;

    const auto moduleName = GetModuleName( ptr );
    const auto symValid = SymFromAddr( proc, ptr, nullptr, si ) != 0;

    IMAGEHLP_LINE64 line;
    DWORD displacement = 0;
    line.SizeOfStruct = sizeof(IMAGEHLP_LINE64);

    {
        const char* filename;
        if( SymGetLineFromAddr64( proc, ptr, &displacement, &line ) == 0 )
        {
            filename = "[unknown]";
            cb_data[write].line = 0;
        }
        else
        {
            filename = line.FileName;
            cb_data[write].line = line.LineNumber;
        }

        cb_data[write].name = symValid ? CopyString( si->Name, si->NameLen ) : CopyString( moduleName );
        cb_data[write].file = CopyString( filename );
        if( symValid )
        {
            cb_data[write].symLen = si->Size;
            cb_data[write].symAddr = si->Address;
        }
        else
        {
            cb_data[write].symLen = 0;
            cb_data[write].symAddr = 0;
        }
    }

#ifndef __CYGWIN__
    if( doInline )
    {
        for( DWORD i=0; i<inlineNum; i++ )
        {
            auto& cb = cb_data[i];
            const auto symInlineValid = SymFromInlineContext( proc, ptr, ctx, nullptr, si ) != 0;
            const char* filename;
            if( SymGetLineFromInlineContext( proc, ptr, ctx, 0, &displacement, &line ) == 0 )
            {
                filename = "[unknown]";
                cb.line = 0;
            }
            else
            {
                filename = line.FileName;
                cb.line = line.LineNumber;
            }

            cb.name = symInlineValid ? CopyString( si->Name, si->NameLen ) : CopyString( moduleName );
            cb.file = CopyString( filename );
            if( symInlineValid )
            {
                cb.symLen = si->Size;
                cb.symAddr = si->Address;
            }
            else
            {
                cb.symLen = 0;
                cb.symAddr = 0;
            }

            ctx++;
        }
    }
#endif
#ifdef TRACY_DBGHELP_LOCK
    DBGHELP_UNLOCK;
#endif

    return { cb_data, uint8_t( cb_num ), moduleName };
}

#elif TRACY_HAS_CALLSTACK == 2 || TRACY_HAS_CALLSTACK == 3 || TRACY_HAS_CALLSTACK == 4 || TRACY_HAS_CALLSTACK == 6

enum { MaxCbTrace = 16 };

struct backtrace_state* cb_bts;
int cb_num;
CallstackEntry cb_data[MaxCbTrace];
int cb_fixup;

void InitCallstack()
{
    cb_bts = backtrace_create_state( nullptr, 0, nullptr, nullptr );
}

static int FastCallstackDataCb( void* data, uintptr_t pc, uintptr_t lowaddr, const char* fn, int lineno, const char* function )
{
    if( function )
    {
        strcpy( (char*)data, function );
    }
    else
    {
        const char* symname = nullptr;
        auto vptr = (void*)pc;
        Dl_info dlinfo;
        if( dladdr( vptr, &dlinfo ) )
        {
            symname = dlinfo.dli_sname;
        }
        if( symname )
        {
            strcpy( (char*)data, symname );
        }
        else
        {
            *(char*)data = '\0';
        }
    }
    return 1;
}

static void FastCallstackErrorCb( void* data, const char* /*msg*/, int /*errnum*/ )
{
    *(char*)data = '\0';
}

const char* DecodeCallstackPtrFast( uint64_t ptr )
{
    static char ret[1024];
    backtrace_pcinfo( cb_bts, ptr, FastCallstackDataCb, FastCallstackErrorCb, ret );
    return ret;
}

static int SymbolAddressDataCb( void* data, uintptr_t pc, uintptr_t lowaddr, const char* fn, int lineno, const char* function )
{
    auto& sym = *(CallstackSymbolData*)data;
    if( !fn )
    {
        sym.file = "[unknown]";
        sym.line = 0;
        sym.needFree = false;
    }
    else
    {
        sym.file = CopyString( fn );
        sym.line = lineno;
        sym.needFree = true;
    }

    return 1;
}

static void SymbolAddressErrorCb( void* data, const char* /*msg*/, int /*errnum*/ )
{
    auto& sym = *(CallstackSymbolData*)data;
    sym.file = "[unknown]";
    sym.line = 0;
    sym.needFree = false;
}

CallstackSymbolData DecodeSymbolAddress( uint64_t ptr )
{
    CallstackSymbolData sym;
#ifdef __ANDROID__
    if( !EnsureReadable(ptr) )
    {
        memset(&sym, 0, sizeof sym);
        return sym;
    }
#endif
    backtrace_pcinfo( cb_bts, ptr, SymbolAddressDataCb, SymbolAddressErrorCb, &sym );
    return sym;
}

CallstackSymbolData DecodeCodeAddress( uint64_t ptr )
{
    return DecodeSymbolAddress( ptr );
}

static int CallstackDataCb( void* /*data*/, uintptr_t pc, uintptr_t lowaddr, const char* fn, int lineno, const char* function )
{
    enum { DemangleBufLen = 64*1024 };
    char demangled[DemangleBufLen];

    cb_data[cb_num].symLen = 0;
    cb_data[cb_num].symAddr = (uint64_t)lowaddr;

    if( !fn && !function )
    {
        const char* symname = nullptr;
        auto vptr = (void*)pc;
        ptrdiff_t symoff = 0;

        Dl_info dlinfo;
        if( dladdr( vptr, &dlinfo ) )
        {
            symname = dlinfo.dli_sname;
            symoff = (char*)pc - (char*)dlinfo.dli_saddr;

            if( symname && symname[0] == '_' )
            {
                size_t len = DemangleBufLen;
                int status;
                abi::__cxa_demangle( symname, demangled, &len, &status );
                if( status == 0 )
                {
                    symname = demangled;
                }
            }
        }

        if( !symname ) symname = "[unknown]";

        if( symoff == 0 )
        {
            cb_data[cb_num].name = CopyString( symname );
        }
        else
        {
            char buf[32];
            const auto offlen = sprintf( buf, " + %td", symoff );
            const auto namelen = strlen( symname );
            auto name = (char*)tracy_malloc( namelen + offlen + 1 );
            memcpy( name, symname, namelen );
            memcpy( name + namelen, buf, offlen );
            name[namelen + offlen] = '\0';
            cb_data[cb_num].name = name;
        }

        cb_data[cb_num].file = CopyString( "[unknown]" );
        cb_data[cb_num].line = 0;
    }
    else
    {
        if( !fn ) fn = "[unknown]";
        if( !function )
        {
            function = "[unknown]";
        }
        else
        {
            if( function[0] == '_' )
            {
                size_t len = DemangleBufLen;
                int status;
                abi::__cxa_demangle( function, demangled, &len, &status );
                if( status == 0 )
                {
                    function = demangled;
                }
            }
        }

        cb_data[cb_num].name = CopyString( function );
        cb_data[cb_num].file = CopyString( fn );
        cb_data[cb_num].line = lineno;
    }

    if( ++cb_num >= MaxCbTrace )
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

static void CallstackErrorCb( void* /*data*/, const char* /*msg*/, int /*errnum*/ )
{
    for( int i=0; i<cb_num; i++ )
    {
        tracy_free( (void*)cb_data[i].name );
        tracy_free( (void*)cb_data[i].file );
    }

    cb_data[0].name = CopyString( "[error]" );
    cb_data[0].file = CopyString( "[error]" );
    cb_data[0].line = 0;

    cb_num = 1;
}

void SymInfoCallback( void* /*data*/, uintptr_t pc, const char* symname, uintptr_t symval, uintptr_t symsize )
{
    cb_data[cb_num-1].symLen = (uint32_t)symsize;
    cb_data[cb_num-1].symAddr = (uint64_t)symval;
}

void SymInfoError( void* /*data*/, const char* /*msg*/, int /*errnum*/ )
{
    cb_data[cb_num-1].symLen = 0;
    cb_data[cb_num-1].symAddr = 0;
}

CallstackEntryData DecodeCallstackPtr( uint64_t ptr )
{
    cb_num = 0;
    backtrace_pcinfo( cb_bts, ptr, CallstackDataCb, CallstackErrorCb, nullptr );
    assert( cb_num > 0 );

    backtrace_syminfo( cb_bts, ptr, SymInfoCallback, SymInfoError, nullptr );

    const char* symloc = nullptr;
    Dl_info dlinfo;
    if( dladdr( (void*)ptr, &dlinfo ) ) symloc = dlinfo.dli_fname;

    return { cb_data, uint8_t( cb_num ), symloc ? symloc : "[unknown]" };
}

#elif TRACY_HAS_CALLSTACK == 5

void InitCallstack()
{
}

const char* DecodeCallstackPtrFast( uint64_t ptr )
{
    static char ret[1024];
    auto vptr = (void*)ptr;
    const char* symname = nullptr;
    Dl_info dlinfo;
    if( dladdr( vptr, &dlinfo ) && dlinfo.dli_sname )
    {
        symname = dlinfo.dli_sname;
    }
    if( symname )
    {
        strcpy( ret, symname );
    }
    else
    {
        *ret = '\0';
    }
    return ret;
}

CallstackSymbolData DecodeSymbolAddress( uint64_t ptr )
{
    const char* symloc = nullptr;
    Dl_info dlinfo;
    if( dladdr( (void*)ptr, &dlinfo ) ) symloc = dlinfo.dli_fname;
    if( !symloc ) symloc = "[unknown]";
    return CallstackSymbolData { symloc, 0, false };
}

CallstackSymbolData DecodeCodeAddress( uint64_t ptr )
{
    return DecodeSymbolAddress( ptr );
}

CallstackEntryData DecodeCallstackPtr( uint64_t ptr )
{
    static CallstackEntry cb;
    cb.line = 0;

    char* demangled = nullptr;
    const char* symname = nullptr;
    const char* symloc = nullptr;
    auto vptr = (void*)ptr;
    ptrdiff_t symoff = 0;
    void* symaddr = nullptr;

    Dl_info dlinfo;
    if( dladdr( vptr, &dlinfo ) )
    {
        symloc = dlinfo.dli_fname;
        symname = dlinfo.dli_sname;
        symoff = (char*)ptr - (char*)dlinfo.dli_saddr;
        symaddr = dlinfo.dli_saddr;

        if( symname && symname[0] == '_' )
        {
            size_t len = 0;
            int status;
            demangled = abi::__cxa_demangle( symname, nullptr, &len, &status );
            if( status == 0 )
            {
                symname = demangled;
            }
        }
    }

    if( !symname ) symname = "[unknown]";
    if( !symloc ) symloc = "[unknown]";

    if( symoff == 0 )
    {
        cb.name = CopyString( symname );
    }
    else
    {
        char buf[32];
        const auto offlen = sprintf( buf, " + %td", symoff );
        const auto namelen = strlen( symname );
        auto name = (char*)tracy_malloc( namelen + offlen + 1 );
        memcpy( name, symname, namelen );
        memcpy( name + namelen, buf, offlen );
        name[namelen + offlen] = '\0';
        cb.name = name;
    }

    cb.file = CopyString( "[unknown]" );
    cb.symLen = 0;
    cb.symAddr = (uint64_t)symaddr;

    if( demangled ) free( demangled );

    return { &cb, 1, symloc };
}

#endif

}

#endif

// The below is defined independently of TRACY_HAS_CALLSTACK because it's
// also used by TracyProfiler.cpp.
#ifdef __ANDROID__
namespace tracy {
namespace {

// Implementation helpers of EnsureReadable.
// This is so far only needed on Android, where it is common for libraries to be mapped
// with only executable, not readable, permissions. Typical example (line from /proc/self/maps):
/*
746b63b000-746b6dc000 --xp 00042000 07:48 35                             /apex/com.android.runtime/lib64/bionic/libc.so
*/
// See https://github.com/wolfpld/tracy/issues/125 .
// To work around this, we parse /proc/self/maps and we use mprotect to set read permissions
// on any mappings that contain symbols addresses hit by HandleSymbolCodeQuery.

// Holds some information about a single memory mapping.
struct MappingInfo {
    // Start of address range. Inclusive.
    uintptr_t start_address;
    // End of address range. Exclusive, so the mapping is the half-open interval
    // [start, end) and its length in bytes is `end - start`. As in /proc/self/maps.
    uintptr_t end_address;
    // Read/Write/Executable permissions.
    bool perm_r, perm_w, perm_x;
};

// Internal implementation helper for LookUpMapping(address).
//
// Parses /proc/self/maps returning a vector<MappingInfo>.
// /proc/self/maps is assumed to be sorted by ascending address, so the resulting
// vector is sorted by ascending address too.
std::vector<MappingInfo> ParseMappings()
{
    std::vector<MappingInfo> result;
    FILE* file = fopen( "/proc/self/maps", "r" );
    if( !file ) return result;
    char line[1024];
    while( fgets( line, sizeof( line ), file ) )
    {
        uintptr_t start_addr;
        uintptr_t end_addr;
        if( sscanf( line, "%lx-%lx", &start_addr, &end_addr ) != 2 ) continue;
        char* first_space = strchr( line, ' ' );
        if( !first_space ) continue;
        char* perm = first_space + 1;
        char* second_space = strchr( perm, ' ' );
        if( !second_space || second_space - perm != 4 ) continue;
        result.emplace_back();
        auto& mapping = result.back();
        mapping.start_address = start_addr;
        mapping.end_address = end_addr;
        mapping.perm_r = perm[0] == 'r';
        mapping.perm_w = perm[1] == 'w';
        mapping.perm_x = perm[2] == 'x';
    }
    fclose( file );
    return result;
}

// Internal implementation helper for LookUpMapping(address).
//
// Takes as input an `address` and a
// known vector `mappings`, and returns a pointer to the MappingInfo
// describing the mapping that this address belongs to, or nullptr if
// the address isn't in `mappings`.
inline MappingInfo* LookUpMapping(std::vector<MappingInfo>& mappings, uintptr_t address)
{
    // We assume mappings to be sorted by address, as /proc/self/maps seems to be.
    // Construct a MappingInfo just for the purpose of using std::lower_bound.
    MappingInfo needle;
    needle.start_address = address;
    needle.end_address = address;
    // Comparison function for std::lower_bound. Returns true if all addresses in `m1`
    // are lower than all addresses in `m2`.
    auto Compare = []( const MappingInfo& m1, const MappingInfo& m2 ) {
        // '<=' because the address ranges are half-open intervals, [start, end).
        return m1.end_address <= m2.start_address;
    };
    auto iter = std::lower_bound( mappings.begin(), mappings.end(), needle, Compare );
    if( iter == mappings.end() || iter->end_address <= address) {
        return nullptr;
    }
    return &*iter;
}

// Internal implementation helper for EnsureReadable(address).
//
// Takes as input an `address` and returns a pointer to a MappingInfo
// describing the mapping that this address belongs to, or nullptr if
// the address isn't in any known mapping.
//
// This function is stateful and not reentrant (assumes to be called from)
// only one thread. It holds a vector of mappings parsed from /proc/self/maps.
//
// Attempts to react to mappings changes by re-parsing /proc/self/maps.
inline MappingInfo* LookUpMapping(uintptr_t address)
{
    // Static state managed by this function. Not constant, we mutate that state as
    // we turn some mappings readable. Initially parsed once here, updated as needed below.
    static std::vector<MappingInfo> s_mappings = ParseMappings();
    MappingInfo* mapping = LookUpMapping( s_mappings, address );
    if( mapping ) return mapping;

    // This address isn't in any known mapping. Try parsing again, maybe
    // mappings changed.
    s_mappings = ParseMappings();
    return LookUpMapping( s_mappings, address );
}

// Internal implementation helper for EnsureReadable(address).
//
// Attempts to make the specified `mapping` readable if it isn't already.
// Returns true if and only if the mapping is readable.
inline bool EnsureReadable( MappingInfo& mapping )
{
    if( mapping.perm_r )
    {
        // The mapping is already readable.
        return true;
    }
    int prot = PROT_READ;
    if( mapping.perm_w ) prot |= PROT_WRITE;
    if( mapping.perm_x ) prot |= PROT_EXEC;
    if( mprotect( reinterpret_cast<void*>( mapping.start_address ),
                  mapping.end_address - mapping.start_address, prot ) == -1 )
    {
        // Failed to make the mapping readable. Shouldn't happen, hasn't
        // been observed yet. If it happened in practice, we should consider
        // adding a bool to MappingInfo to track this to avoid retrying mprotect
        // everytime on such mappings.
        return false;
    }
    // The mapping is now readable. Update `mapping` so the next call will be fast.
    mapping.perm_r = true;
    return true;
}

}  // anonymous namespace - end of internal helpers for EnsureReadable(address)

// Attempts to set the read permission on the entire mapping containing the
// specified address.
bool EnsureReadable( uintptr_t address )
{
    MappingInfo* mapping = LookUpMapping(address);
    return mapping && EnsureReadable( *mapping );
}

}  // namespace tracy
#endif  // defined __ANDROID__