[newlib-cygwin] Cygwin: New tool: profiler

[newlib-cygwin] Cygwin: New tool: profiler

[Jon TURNEY]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9bd6c0b2b1081ae72d8273038309887fb27f6126

commit 9bd6c0b2b1081ae72d8273038309887fb27f6126
Author: Mark Geisert <mark@maxrnd.com>
Date:   Thu Jul 15 21:49:55 2021 -0700

    Cygwin: New tool: profiler
    
    The new tool formerly known as cygmon is renamed to 'profiler'.  For the
    name I considered 'ipsampler' and could not think of any others.  I'm open
    to a different name if any is suggested.
    
    I decided that a discussion of the pros and cons of this profiler vs the
    existing ssp should probably be in the "Profiling Cygwin Programs" section
    of the Cygwin User's Guide rather than in the help for either.  That
    material will be supplied at some point.
    
    CONTEXT buffers are made child-specific and thus thread-specific since
    there is one profiler thread for each child program being profiled.
    
    The SetThreadPriority() warning comment has been expanded.
    
    chmod() works on Cygwin so the "//XXX ineffective" comment is gone.
    
    I decided to make the "sample all executable sections" and "sample
    dynamically generated code" suggestions simply expanded comments for now.
    
    The profiler program is now a Cygwin exe rather than a native exe.

Diff:
---
 winsup/utils/profiler.cc | 1109 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1109 insertions(+)

diff --git a/winsup/utils/profiler.cc b/winsup/utils/profiler.cc
new file mode 100644
index 000000000..d1a01c3a2
--- /dev/null
+++ b/winsup/utils/profiler.cc
@@ -0,0 +1,1109 @@
+/*
+    profiler.cc
+    Periodically samples IP of a process and its DLLs; writes gprof data files.
+
+    Written by Mark Geisert <mark@maxrnd.com>, who admits to
+    copying pretty liberally from strace.cc.  h/t to cgf for strace!
+
+    This file is part of Cygwin.
+
+    This software is a copyrighted work licensed under the terms of the
+    Cygwin license.  Please consult the file "CYGWIN_LICENSE" for details.
+*/
+
+#define WIN32_LEAN_AND_MEAN
+#include <winternl.h>
+
+#define cygwin_internal cygwin_internal_dontuse
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <io.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/cygwin.h>
+#include "cygwin/version.h"
+#include "cygtls_padsize.h"
+#include "gcc_seh.h"
+typedef unsigned short ushort;
+typedef uint16_t u_int16_t; // Non-standard sized type needed by ancient gmon.h
+#define NO_GLOBALS_H
+#include "gmon.h"
+#include "path.h"
+#undef cygwin_internal
+
+/* Undo this #define from winsup.h. */
+#ifdef ExitThread
+#undef ExitThread
+#endif
+
+#define SCALE_SHIFT 2 // == 4 bytes of address space per bucket
+#define MS_VC_EXCEPTION 0x406D1388 // thread name notification from child
+
+DWORD       child_pid;
+int         debugging = 0;
+void       *drive_map;
+int         events = 0;
+int         forkprofile = 0;
+int         new_window;
+int         numprocesses;
+FILE       *ofile = stdout;
+const char *pgm;
+char       *prefix = (char *) "gmon.out";
+int         samplerate = 100; // in Hz; up to 1000 might work
+int         verbose = 0;
+
+void __attribute__ ((__noreturn__))
+usage (FILE *where = stderr)
+{
+  fprintf (where, "\
+Usage: %s [OPTIONS] <command-line>\n\
+   or: %s [OPTIONS] -p <pid>\n\
+\n\
+Profiles a command or process by sampling its IP (instruction pointer).\n\
+OPTIONS are:\n\
+\n\
+  -d, --debug            Display debugging messages (toggle: default false)\n\
+  -e, --events           Display Windows DEBUG_EVENTS (toggle: default false)\n\
+  -f, --fork-profile     Profile child processes (toggle: default false)\n\
+  -h, --help             Display usage information and exit\n\
+  -o, --output=FILENAME  Write output to file FILENAME rather than stdout\n\
+  -p, --pid=N            Attach to running program with Cygwin pid N\n\
+                         ...                    or with Windows pid -N\n\
+  -s, --sample-rate=N    Set IP sampling rate to N Hz (default 100)\n\
+  -v, --verbose          Display more status messages (toggle: default false)\n\
+  -V, --version          Display version information and exit\n\
+  -w, --new-window       Launch given command in a new window\n\
+\n", pgm, pgm);
+
+  exit (where == stderr ? 1 : 0 );
+}
+
+/* A span is a memory address range covering an EXE's or DLL's .text segment. */
+struct span_list
+{
+  WCHAR  *name;
+  LPVOID  base;
+  size_t  textlo;
+  size_t  texthi;
+  int     hitcount;
+  int     hitbuckets;
+  int     numbuckets;
+  int    *buckets;
+  struct span_list *next;
+};
+
+/* A thread. */
+struct thread_list
+{
+  DWORD   tid;
+  HANDLE  hthread;
+  WCHAR  *name;
+  struct thread_list *next;
+};
+
+/* A child is any process being sampled in this profiler run. */
+struct child_list
+{
+  DWORD  pid;
+  volatile int profiling;
+  HANDLE hproc;
+  HANDLE hquitevt;
+  HANDLE hprofthr;
+  CONTEXT            *context;
+  struct thread_list *threads;
+  struct span_list   *spans;
+  struct child_list  *next;
+};
+
+child_list children;
+typedef struct child_list child;
+
+void
+note (const char *fmt, ...)
+{
+  va_list args;
+  char    buf[4096];
+
+  va_start (args, fmt);
+  vsprintf (buf, fmt, args);
+  va_end (args);
+
+  fputs (buf, ofile);
+  fflush (ofile);
+}
+
+void
+warn (int geterrno, const char *fmt, ...)
+{
+  va_list args;
+  char    buf[4096];
+
+  va_start (args, fmt);
+  sprintf (buf, "%s: ", pgm);
+  vsprintf (strchr (buf, '\0'), fmt, args);
+  va_end (args);
+  if (geterrno)
+    perror (buf);
+  else
+    {
+      fputs (buf, ofile);
+      fputs ("\n", ofile);
+      fflush (ofile);
+    }
+}
+
+void __attribute__ ((noreturn))
+error (int geterrno, const char *fmt, ...)
+{
+  va_list args;
+
+  va_start (args, fmt);
+  warn (geterrno, fmt, args);
+  va_end (args);
+
+  exit (1);
+}
+
+size_t
+sample (CONTEXT *context, HANDLE h)
+{
+  size_t status;
+
+  if (-1U == SuspendThread (h))
+    return 0ULL;
+  status = GetThreadContext (h, context);
+  if (-1U == ResumeThread (h))
+    if (verbose)
+      note ("*** unable to resume thread %d; continuing anyway\n", h);
+
+  if (0 == status)
+    {
+      if (verbose)
+        note ("*** unable to get context for thread %d\n", h);
+      return 0ULL;
+    }
+  else
+//TODO this approach does not support 32-bit executables on 64-bit
+#ifdef __x86_64__
+    return context->Rip;
+#else
+    return context->Eip;
+#endif
+}
+
+void
+bump_bucket (child *c, size_t pc)
+{
+  span_list *s = c->spans;
+
+//note ("%lu %p\n", c->pid, pc);
+  if (pc == 0ULL)
+    return;
+  while (s)
+    {
+      if (pc >= s->textlo && pc < s->texthi)
+        {
+          if (0 == s->buckets[(pc - s->textlo) >> SCALE_SHIFT]++)
+            ++s->hitbuckets;
+          ++s->hitcount;
+          return;
+        }
+      s = s->next;
+    }
+
+  /*TODO If the child has dynamically created an executable memory region, we
+   *     won't notice it until the profiler thread happens to sample an
+   *     instruction in that region.  We could then add a new span to record
+   *     hits on this new region. (QueryVirtualMemory to obtain limits?)
+   *
+   *     Note that if the app dynamically adds and deletes such regions, the
+   *     profiling info on them will be confusing if their addresses overlap.
+   */
+  if (verbose)
+    note ("*** pc %p out of range for pid %lu\n", pc, c->pid);
+}
+
+/* profiler runs on its own thread; each child has a separate profiler. */
+DWORD WINAPI
+profiler (void *vp)
+{
+  child *c = (child *) vp;
+
+  while (c->profiling)
+    {
+      thread_list *t = c->threads;
+
+      while (t)
+        {
+          if (t->hthread)
+            bump_bucket (c, sample (c->context, t->hthread));
+          t = t->next;
+        }
+
+      if (WaitForSingleObject (c->hquitevt, 1000 / samplerate) == WAIT_OBJECT_0)
+        break;
+    }
+
+  return 0;
+}
+
+void
+start_profiler (child *c)
+{
+  DWORD  tid;
+
+  if (verbose)
+    note ("*** start profiler thread on pid %lu\n", c->pid);
+  c->context = (CONTEXT *) calloc (1, sizeof (CONTEXT));
+  if (!c->context)
+    error (0, "unable to allocate CONTEXT buffer\n");
+  c->context->ContextFlags = CONTEXT_CONTROL;
+  c->hquitevt = CreateEvent (NULL, TRUE, FALSE, NULL);
+  if (!c->hquitevt)
+    error (0, "unable to create quit event\n");
+  c->profiling = 1;
+  c->hprofthr = CreateThread (NULL, 0, profiler, (void *) c, 0, &tid);
+  if (!c->hprofthr)
+    error (0, "unable to create profiling thread\n");
+
+  /* There is a temptation to raise the execution priority of the profiling
+   * threads.  Don't do this, or at least don't do it this way.  Testing
+   * showed that it was possible to starve system processes which makes the
+   * system unresponsive.  Raising prio doesn't seem to be needed at all.
+   *
+  SetThreadPriority (c->hprofthr, THREAD_PRIORITY_TIME_CRITICAL);
+   */
+}
+
+void
+stop_profiler (child *c)
+{
+  if (verbose)
+    note ("*** stop profiler thread on pid %lu\n", c->pid);
+  c->profiling = 0;
+  SignalObjectAndWait (c->hquitevt, c->hprofthr, INFINITE, FALSE);
+  CloseHandle (c->hquitevt);
+  CloseHandle (c->hprofthr);
+  c->hquitevt = c->hprofthr = 0;
+}
+
+/* Create a gmon.out file for each EXE or DLL that has at least one sample. */
+void
+dump_profile_data (child *c)
+{
+  int        fd;
+  char       filename[MAX_PATH + 1];
+  struct gmonhdr hdr;
+  span_list *s = c->spans;
+
+  while (s)
+    {
+      if (s->hitbuckets == 0)
+        {
+          s = s->next;
+          continue;
+        }
+
+      if (s->name)
+        {
+          WCHAR *name = 1 + wcsrchr (s->name, L'\\');
+          sprintf (filename, "%s.%u.%ls", prefix, c->pid, name);
+        }
+      else
+        sprintf (filename, "%s.%u", prefix, c->pid);
+
+      fd = open (filename, O_CREAT | O_TRUNC | O_WRONLY | O_BINARY);
+      if (fd < 0)
+        error (0, "dump_profile_data: unable to create %s\n", filename);
+
+      memset (&hdr, 0, sizeof (hdr));
+      hdr.lpc = s->textlo;
+      hdr.hpc = s->texthi;
+      hdr.ncnt = s->numbuckets * sizeof (short) + sizeof (hdr);
+      hdr.version = GMONVERSION;
+      hdr.profrate = samplerate;
+
+      /* Our buckets hold more than gmon standard buckets, so truncate here. */
+      ushort *gmonbuckets = (ushort *) calloc (s->numbuckets, sizeof (ushort));
+      for (int i = 0; i < s->numbuckets; i++)
+        {
+          if (s->buckets[i])
+            {
+              if (s->buckets[i] > 65535)
+                {
+                  note ("  WARNING: bucket %d: value %d truncated to %d\n",
+                        i, s->buckets[i], 65535);
+                  gmonbuckets[i] = 65535;
+                }
+              else
+                gmonbuckets[i] = s->buckets[i];
+            }
+        }
+
+      write (fd, &hdr, sizeof (hdr));
+      write (fd, gmonbuckets, hdr.ncnt - sizeof (hdr));
+      note ("%d %s across %d %s written to %s\n", s->hitcount,
+            s->hitcount == 1 ? "sample" : "samples", s->hitbuckets,
+            s->hitbuckets == 1 ? "bucket" : "buckets", filename);
+      close (fd);
+      chmod (filename, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+      free (gmonbuckets);
+
+      s = s->next;
+    }
+}
+
+HANDLE lasth;
+DWORD  lastpid = 0;
+
+child *
+get_child (DWORD pid)
+{
+  child *c;
+
+  for (c = &children; (c = c->next) != NULL;)
+    if (c->pid == pid)
+      return (child *) c;
+
+  return NULL;
+}
+
+void add_span (DWORD, WCHAR *, LPVOID, HANDLE);
+
+void
+add_child (DWORD pid, WCHAR *name, LPVOID base, HANDLE hproc)
+{
+  if (!get_child (pid))
+    {
+      child *c = children.next;
+      children.next = (child *) calloc (1, sizeof (child));
+      children.next->next = c;
+      lastpid = children.next->pid = pid;
+      lasth = children.next->hproc = hproc;
+      add_span (pid, name, base, hproc);
+      start_profiler (children.next);
+      numprocesses++;
+      if (verbose)
+        note ("*** Windows process %lu attached\n", pid);
+    }
+}
+
+void
+remove_child (DWORD pid)
+{
+  child *c;
+
+  if (pid == lastpid)
+    lastpid = 0;
+  for (c = &children; c->next != NULL; c = c->next)
+    if (c->next->pid == pid)
+      {
+        child *c1 = c->next;
+        c->next = c1->next;
+        stop_profiler (c1);
+        dump_profile_data (c1);
+        CloseHandle (c1->hproc);
+        c1->hproc = 0;
+        free (c1);
+        if (verbose)
+          note ("*** Windows process %lu detached\n", pid);
+        numprocesses--;
+        return;
+      }
+
+  error (0, "no process id %d found", pid);
+}
+
+void
+add_thread (DWORD pid, DWORD tid, HANDLE h, WCHAR *name)
+{
+  child *c = get_child (pid);
+
+  if (!c)
+    error (0, "add_thread: pid %lu not found\n", pid);
+
+  thread_list *t = (thread_list *) calloc (1, sizeof (thread_list));
+  t->tid = tid;
+  t->hthread = h;
+  t->name = name;
+
+  t->next = c->threads;
+  c->threads = t;
+}
+
+void
+remove_thread (DWORD pid, DWORD tid)
+{
+  child *c = get_child (pid);
+
+  if (!c)
+    error (0, "remove_thread: pid %lu not found\n", pid);
+
+  thread_list *t = c->threads;
+  while (t)
+    {
+      if (t->tid == tid)
+        {
+          /*TODO We don't free(t), we just zero it out.  Maybe revisit this. */
+          t->tid = 0;
+          CloseHandle (t->hthread);
+          t->hthread = 0;
+          if (t->name)
+            free (t->name);
+          t->name = NULL;
+          return;
+        }
+      t = t->next;
+    }
+
+  error (0, "remove_thread: pid %lu tid %lu not found\n", pid, tid);
+}
+
+void
+read_child (void *buf, SIZE_T size, void *addr, HANDLE h)
+{
+  SIZE_T len;
+
+  if (debugging)
+    note ("read %d bytes at %p from handle %d\n", size, addr, h);
+  if (0 == ReadProcessMemory (h, addr, buf, size, &len))
+    error (0, "read_child: failed\n");
+  if (len != size)
+    error (0, "read_child: asked for %d bytes but got %d\n", size, len);
+}
+
+IMAGE_SECTION_HEADER *
+find_text_section (LPVOID base, HANDLE h)
+{
+  static IMAGE_SECTION_HEADER asect;
+  DWORD  lfanew;
+  WORD   machine;
+  WORD   nsects;
+  DWORD  ntsig;
+  char  *ptr = (char *) base;
+
+  IMAGE_DOS_HEADER *idh = (IMAGE_DOS_HEADER *) ptr;
+  read_child ((void *) &lfanew, sizeof (lfanew), &idh->e_lfanew, h);
+  ptr += lfanew;
+
+  /* Code handles 32- or 64-bit headers depending on compilation environment. */
+  /*TODO It doesn't yet handle 32-bit headers on 64-bit Cygwin or v/v.        */
+  IMAGE_NT_HEADERS *inth = (IMAGE_NT_HEADERS *) ptr;
+  read_child ((void *) &ntsig, sizeof (ntsig), &inth->Signature, h);
+  if (ntsig != IMAGE_NT_SIGNATURE)
+    error (0, "find_text_section: NT signature not found\n");
+
+  read_child ((void *) &machine, sizeof (machine),
+              &inth->FileHeader.Machine, h);
+#ifdef __x86_64__
+  if (machine != IMAGE_FILE_MACHINE_AMD64)
+#else
+  if (machine != IMAGE_FILE_MACHINE_I386)
+#endif
+    error (0, "target program was built for different machine architecture\n");
+
+  read_child ((void *) &nsects, sizeof (nsects),
+              &inth->FileHeader.NumberOfSections, h);
+  ptr += sizeof (*inth);
+
+  IMAGE_SECTION_HEADER *ish = (IMAGE_SECTION_HEADER *) ptr;
+  for (int i = 0; i < nsects; i++)
+    {
+      read_child ((void *) &asect, sizeof (asect), ish, h);
+      if (0 == memcmp (".text\0\0\0", &asect.Name, 8))
+        return &asect;
+      ish++;
+    }
+
+  error (0, ".text section not found\n");
+}
+
+//TODO Extend add_span to add all executable sections of this exe/dll
+void
+add_span (DWORD pid, WCHAR *name, LPVOID base, HANDLE h)
+{
+  child *c = get_child (pid);
+
+  if (!c)
+    error (0, "add_span: pid %lu not found\n", pid);
+
+  IMAGE_SECTION_HEADER *sect = find_text_section (base, c->hproc);
+  span_list *s = (span_list *) calloc (1, sizeof (span_list));
+  s->name = name;
+  s->base = base;
+  s->textlo = sect->VirtualAddress + (size_t) base;
+  s->texthi = s->textlo + sect->Misc.VirtualSize;
+  s->numbuckets = (s->texthi - s->textlo) >> SCALE_SHIFT;
+  s->buckets = (int *) calloc (s->numbuckets, sizeof (int));
+  if (debugging)
+    note ("    span %p - %p, size %X, numbuckets %d\n",
+          s->textlo, s->texthi, s->texthi - s->textlo, s->numbuckets);
+
+  s->next = c->spans;
+  c->spans = s;
+}
+
+#define LINE_BUF_CHUNK 128
+
+class linebuf
+{
+  size_t  alloc;
+public:
+  size_t  ix;
+  char   *buf;
+  linebuf ()
+  {
+    ix = 0;
+    alloc = 0;
+    buf = NULL;
+  }
+ ~linebuf ()
+  {
+    if (buf)
+      free (buf);
+  }
+  void add (const char *what, int len);
+  void add (const char *what)
+  {
+    add (what, strlen (what));
+  }
+  void prepend (const char *what, int len);
+};
+
+void
+linebuf::add (const char *what, int len)
+{
+  size_t newix;
+
+  if ((newix = ix + len) >= alloc)
+    {
+      alloc += LINE_BUF_CHUNK + len;
+      buf = (char *) realloc (buf, alloc + 1);
+    }
+  memcpy (buf + ix, what, len);
+  ix = newix;
+  buf[ix] = '\0';
+}
+
+void
+linebuf::prepend (const char *what, int len)
+{
+  int    buflen;
+  size_t newix;
+
+  if ((newix = ix + len) >= alloc)
+    {
+      alloc += LINE_BUF_CHUNK + len;
+      buf = (char *) realloc (buf, alloc + 1);
+      buf[ix] = '\0';
+    }
+  if ((buflen = strlen (buf)))
+    memmove (buf + len, buf, buflen + 1);
+  else
+    buf[newix] = '\0';
+  memcpy (buf, what, len);
+  ix = newix;
+}
+
+void
+make_command_line (linebuf & one_line, char **argv)
+{
+  for (; *argv; argv++)
+    {
+      char *p = NULL;
+      const char *a = *argv;
+
+      int len = strlen (a);
+      if (len != 0 && !(p = strpbrk (a, " \t\n\r\"")))
+        one_line.add (a, len);
+      else
+        {
+          one_line.add ("\"", 1);
+          for (; p; a = p, p = strchr (p, '"'))
+            {
+              one_line.add (a, ++p - a);
+              if (p[-1] == '"')
+                one_line.add ("\"", 1);
+            }
+          if (*a)
+            one_line.add (a);
+          one_line.add ("\"", 1);
+        }
+      one_line.add (" ", 1);
+    }
+
+  if (one_line.ix)
+    one_line.buf[one_line.ix - 1] = '\0';
+  else
+    one_line.add ("", 1);
+}
+
+BOOL WINAPI
+ctrl_c (DWORD)
+{
+  static int tic = 1;
+
+  if ((tic ^= 1) && !GenerateConsoleCtrlEvent (CTRL_C_EVENT, 0))
+    error (0, "couldn't send CTRL-C to child, win32 error %d\n",
+           GetLastError ());
+  return TRUE;
+}
+
+/* Set up interfaces to Cygwin internal funcs and path.cc helper funcs. */
+extern "C" {
+uintptr_t cygwin_internal (int, ...);
+WCHAR cygwin_dll_path[32768];
+}
+
+#define DEBUG_PROCESS_DETACH_ON_EXIT    0x00000001
+#define DEBUG_PROCESS_ONLY_THIS_PROCESS 0x00000002
+
+void
+attach_process (pid_t pid)
+{
+  child_pid = pid < 0 ? (DWORD) -pid :
+        (DWORD) cygwin_internal (CW_CYGWIN_PID_TO_WINPID, pid);
+
+  if (!DebugActiveProcess (child_pid))
+    error (0, "couldn't attach to pid %d for debugging", child_pid);
+
+  if (forkprofile)
+    {
+      HANDLE h = OpenProcess (PROCESS_ALL_ACCESS, FALSE, child_pid);
+
+      if (h)
+        {
+          /* Try to turn off DEBUG_ONLY_THIS_PROCESS so we can follow forks. */
+          ULONG DebugFlags = DEBUG_PROCESS_DETACH_ON_EXIT;
+          NTSTATUS status = NtSetInformationProcess (h, ProcessDebugFlags,
+                                        &DebugFlags, sizeof (DebugFlags));
+          if (!NT_SUCCESS (status))
+            warn (0, "Could not clear DEBUG_ONLY_THIS_PROCESS (%x), "
+                  "will not trace child processes", status);
+
+          CloseHandle (h);
+        }
+    }
+
+  return;
+}
+
+void
+create_child (char **argv)
+{
+  DWORD               flags;
+  linebuf             one_line;
+  PROCESS_INFORMATION pi;
+  BOOL                ret;
+  STARTUPINFO         si;
+
+  if (strchr (*argv, '/'))
+      *argv = cygpath (*argv, NULL);
+  memset (&si, 0, sizeof (si));
+  si.cb = sizeof (si);
+
+  flags = CREATE_DEFAULT_ERROR_MODE
+          | (forkprofile ? DEBUG_PROCESS : DEBUG_ONLY_THIS_PROCESS);
+  if (new_window)
+    flags |= CREATE_NEW_CONSOLE | CREATE_NEW_PROCESS_GROUP;
+
+  make_command_line (one_line, argv);
+
+  SetConsoleCtrlHandler (NULL, 0);
+
+  const char *cygwin_env = getenv ("CYGWIN");
+  const char *space;
+
+  if (cygwin_env && strlen (cygwin_env) <= 256) /* sanity check */
+    space = " ";
+  else
+    space = cygwin_env = "";
+
+  char *newenv = (char *) malloc (sizeof ("CYGWIN=noglob") +
+                                  strlen (space) + strlen (cygwin_env));
+  sprintf (newenv, "CYGWIN=noglob%s%s", space, cygwin_env);
+  putenv (newenv);
+  ret = CreateProcess (0, one_line.buf, /* command line */
+                       NULL,    /* Security */
+                       NULL,    /* thread */
+                       TRUE,    /* inherit handles */
+                       flags,   /* start flags */
+                       NULL,    /* default environment */
+                       NULL,    /* current directory */
+                       &si, &pi);
+  if (!ret)
+    error (0, "error creating process %s, (error %d)", *argv,
+           GetLastError ());
+
+  CloseHandle (pi.hThread);
+  CloseHandle (pi.hProcess);
+  child_pid = pi.dwProcessId;
+  SetConsoleCtrlHandler (ctrl_c, 1);
+}
+
+void
+handle_output_debug_string (DWORD pid, OUTPUT_DEBUG_STRING_INFO *ev)
+{
+  char  *buf = (char *) alloca (ev->nDebugStringLength);
+  child *c = get_child (pid);
+
+  if (!c)
+    error (0, "handle_output_debug_string: pid %lu not found\n", pid);
+
+  read_child (buf, ev->nDebugStringLength, ev->lpDebugStringData, c->hproc);
+  if (strncmp (buf, "cYg", 3))
+    { // string is not from Cygwin, it's from the target app; just display it
+      if (ev->fUnicode)
+        note ("%ls", buf);
+      else
+        note ("%s", buf);
+    }
+  //else TODO Possibly decode and display Cygwin-internal debug string
+}
+
+BOOL
+GetFileNameFromHandle (HANDLE hFile, WCHAR pszFilename[MAX_PATH+1])
+{
+  BOOL     result = FALSE;
+  ULONG    len = 0;
+  OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) alloca (65536);
+  NTSTATUS status = NtQueryObject (hFile, ObjectNameInformation,
+                                   ntfn, 65536, &len);
+  if (NT_SUCCESS (status))
+    {
+      PWCHAR win32path = ntfn->Name.Buffer;
+      win32path[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
+
+      /* NtQueryObject returns a native NT path.  (Try to) convert to Win32. */
+      if (drive_map)
+        win32path = (PWCHAR) cygwin_internal (CW_MAP_DRIVE_MAP, drive_map,
+                                              win32path);
+      pszFilename[0] = L'\0';
+      wcsncat (pszFilename, win32path, MAX_PATH);
+      result = TRUE;
+    }
+
+  return result;
+}
+
+char *
+cygwin_pid (DWORD winpid)
+{
+  static char  buf[48];
+  DWORD        cygpid;
+  static DWORD max_cygpid = 0;
+
+  if (!max_cygpid)
+    max_cygpid = (DWORD) cygwin_internal (CW_MAX_CYGWIN_PID);
+
+  cygpid = (DWORD) cygwin_internal (CW_WINPID_TO_CYGWIN_PID, winpid);
+
+  if (cygpid >= max_cygpid)
+    snprintf (buf, sizeof buf, "%u", winpid);
+  else
+    snprintf (buf, sizeof buf, "%u (pid: %u)", winpid, cygpid);
+  return buf;
+}
+
+DWORD
+profile1 (FILE *ofile, pid_t pid)
+{
+  DEBUG_EVENT ev;
+  DWORD       res = 0;
+
+  SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_HIGHEST);
+  while (1)
+    {
+      BOOL debug_event = WaitForDebugEvent (&ev, INFINITE);
+      DWORD status = DBG_CONTINUE;
+
+      if (!debug_event)
+        continue;
+
+      /* Usually continue event here so child resumes while we process event. */
+      if (ev.dwDebugEventCode != EXCEPTION_DEBUG_EVENT &&
+          ev.dwDebugEventCode != OUTPUT_DEBUG_STRING_EVENT)
+        debug_event = ContinueDebugEvent (ev.dwProcessId, ev.dwThreadId, status);
+
+      switch (ev.dwDebugEventCode)
+        {
+        case CREATE_PROCESS_DEBUG_EVENT:
+          WCHAR exename[MAX_PATH+1];
+
+          if (!GetFileNameFromHandle (ev.u.CreateProcessInfo.hFile, exename))
+            wcscpy (exename, L"(unknown)");
+          if (events)
+            {
+              note ("--- Process %s created from %ls\n",
+                    cygwin_pid (ev.dwProcessId), exename);
+              note ("--- Process %s thread %lu created at %p\n",
+                    cygwin_pid (ev.dwProcessId), ev.dwThreadId,
+                    ev.u.CreateProcessInfo.lpStartAddress);
+            }
+          if (ev.u.CreateProcessInfo.hFile)
+            CloseHandle (ev.u.CreateProcessInfo.hFile);
+          add_child (ev.dwProcessId, wcsdup (exename),
+                     ev.u.CreateProcessInfo.lpBaseOfImage,
+                     ev.u.CreateProcessInfo.hProcess);
+          add_thread (ev.dwProcessId, ev.dwThreadId,
+                      ev.u.CreateProcessInfo.hThread, wcsdup (exename));
+          break;
+
+        case CREATE_THREAD_DEBUG_EVENT:
+          if (events)
+            note ("--- Process %s thread %lu created at %p\n",
+                  cygwin_pid (ev.dwProcessId), ev.dwThreadId,
+                  ev.u.CreateThread.lpStartAddress);
+          add_thread (ev.dwProcessId, ev.dwThreadId,
+                      ev.u.CreateThread.hThread, NULL);
+          break;
+
+        case LOAD_DLL_DEBUG_EVENT:
+          WCHAR dllname[MAX_PATH+1];
+
+          /* lpImageName is not always populated, so find the filename for
+             hFile instead. */
+          if (!GetFileNameFromHandle (ev.u.LoadDll.hFile, dllname))
+            wcscpy (dllname, L"(unknown)");
+
+          if (events)
+              note ("--- Process %s loaded %ls at %p\n",
+                    cygwin_pid (ev.dwProcessId), dllname,
+                    ev.u.LoadDll.lpBaseOfDll);
+          add_span (ev.dwProcessId, wcsdup (dllname),
+                    ev.u.LoadDll.lpBaseOfDll, ev.u.LoadDll.hFile);
+
+          if (ev.u.LoadDll.hFile)
+            CloseHandle (ev.u.LoadDll.hFile);
+          break;
+
+        case UNLOAD_DLL_DEBUG_EVENT:
+          if (events)
+            note ("--- Process %s unloaded DLL at %p\n",
+                  cygwin_pid (ev.dwProcessId), ev.u.UnloadDll.lpBaseOfDll);
+          break;
+
+        case OUTPUT_DEBUG_STRING_EVENT:
+          handle_output_debug_string (ev.dwProcessId, &ev.u.DebugString);
+          status = DBG_EXCEPTION_HANDLED;
+          debug_event = ContinueDebugEvent (ev.dwProcessId,
+                                            ev.dwThreadId, status);
+          break;
+
+        case EXIT_PROCESS_DEBUG_EVENT:
+          if (events)
+            note ("--- Process %s exited with status 0x%lx\n",
+                  cygwin_pid (ev.dwProcessId), ev.u.ExitProcess.dwExitCode);
+          res = ev.u.ExitProcess.dwExitCode;
+          remove_child (ev.dwProcessId);
+          break;
+
+        case EXIT_THREAD_DEBUG_EVENT:
+          if (events)
+            note ("--- Process %s thread %lu exited with status 0x%lx\n",
+                  cygwin_pid (ev.dwProcessId), ev.dwThreadId,
+                  ev.u.ExitThread.dwExitCode);
+          remove_thread (ev.dwProcessId, ev.dwThreadId);
+          break;
+
+        case EXCEPTION_DEBUG_EVENT:
+          status = DBG_EXCEPTION_HANDLED;
+          switch (ev.u.Exception.ExceptionRecord.ExceptionCode)
+            {
+            case MS_VC_EXCEPTION:
+              //TODO Decode exception info to get thread name; set it internally
+              // fall thru
+
+            case STATUS_BREAKPOINT:
+              break;
+
+#ifdef __x86_64__
+            case STATUS_GCC_THROW:
+            case STATUS_GCC_UNWIND:
+            case STATUS_GCC_FORCED:
+              status = DBG_EXCEPTION_NOT_HANDLED;
+              break;
+#endif
+
+            default:
+              status = DBG_EXCEPTION_NOT_HANDLED;
+              if (ev.u.Exception.dwFirstChance)
+                note ("--- Process %s thread %lu exception %08x at %p\n",
+                      cygwin_pid (ev.dwProcessId), ev.dwThreadId,
+                      ev.u.Exception.ExceptionRecord.ExceptionCode,
+                      ev.u.Exception.ExceptionRecord.ExceptionAddress);
+              break;
+            }
+          debug_event = ContinueDebugEvent (ev.dwProcessId,
+                                            ev.dwThreadId, status);
+          break;
+        }
+
+      if (!debug_event)
+        error (0, "couldn't continue debug event, windows error %d",
+               GetLastError ());
+      if (!numprocesses)
+        break;
+    }
+
+  return res;
+}
+
+DWORD
+doprofile (FILE *ofile, pid_t pid, char **argv)
+{
+  if (pid)
+    attach_process (pid);
+  else
+    create_child (argv);
+
+  return profile1 (ofile, pid);
+}
+
+struct option longopts[] = {
+  {"debug",       no_argument,       NULL, 'd'},
+  {"events",      no_argument,       NULL, 'e'},
+  {"help",        no_argument,       NULL, 'h'},
+  {"new-window",  no_argument,       NULL, 'w'},
+  {"output",      required_argument, NULL, 'o'},
+  {"pid",         required_argument, NULL, 'p'},
+  {"fork-profile",no_argument,       NULL, 'f'},
+  {"sample-rate", required_argument, NULL, 's'},
+  {"verbose",     no_argument,       NULL, 'v'},
+  {"version",     no_argument,       NULL, 'V'},
+  {NULL,          0,                 NULL, 0  }
+};
+
+const char *const opts = "+dehfo:p:s:vVw";
+
+void __attribute__ ((__noreturn__))
+print_version ()
+{
+  char *year_of_build = strrchr (__DATE__, ' ') + 1;
+  printf ("profiler (cygwin) %d.%d.%d\n"
+          "IP-Sampling Profiler\n"
+          "Copyright (C) %s%s Cygwin Authors\n"
+          "This is free software; see the source for copying conditions.  "
+          "There is NO\nwarranty; not even for MERCHANTABILITY or FITNESS "
+          "FOR A PARTICULAR PURPOSE.\n",
+          CYGWIN_VERSION_DLL_MAJOR / 1000,
+          CYGWIN_VERSION_DLL_MAJOR % 1000,
+          CYGWIN_VERSION_DLL_MINOR,
+          strncmp (year_of_build, "2021", 4) ? "2021 - " : "",
+          year_of_build);
+  exit (0);
+}
+
+int
+main2 (int argc, char **argv)
+{
+  int    opt;
+  pid_t  pid = 0;
+  char  *ptr;
+  DWORD  ret = 0;
+
+  _setmode (1, O_BINARY);
+  _setmode (2, O_BINARY);
+
+  if (!(pgm = strrchr (*argv, '\\')) && !(pgm = strrchr (*argv, '/')))
+    pgm = *argv;
+  else
+    pgm++;
+
+  while ((opt = getopt_long (argc, argv, opts, longopts, NULL)) != EOF)
+    switch (opt)
+      {
+      case 'd':
+        debugging ^= 1;
+        if (debugging)
+          verbose = events = 1; // debugging turns these on too
+        break;
+
+      case 'e':
+        events ^= 1;
+        events |= debugging; // debugging turns on events too
+        break;
+
+      case 'f':
+        forkprofile ^= 1;
+        break;
+
+      case 'h':
+        /* Print help and exit. */
+        usage (ofile);
+
+      case 'o':
+        if ((ofile = fopen (cygpath (optarg, NULL), "wb")) == NULL)
+          error (1, "can't open %s", optarg);
+#ifdef F_SETFD
+        (void) fcntl (fileno (ofile), F_SETFD, 0);
+#endif
+        break;
+
+      case 'p':
+        pid = strtoul (optarg, NULL, 10);
+        break;
+
+      case 's':
+        samplerate = strtoul (optarg, NULL, 10);
+        if (samplerate < 1 || samplerate > 1000)
+          error (0, "sample rate must be between 1 and 1000 inclusive");
+        break;
+
+      case 'v':
+        verbose ^= 1;
+        verbose |= debugging; // debugging turns on verbose too
+        break;
+
+      case 'V':
+        /* Print version info and exit. */
+        print_version ();
+
+      case 'w':
+        new_window ^= 1;
+        break;
+
+      default:
+        note ("Try `%s --help' for more information.\n", pgm);
+        exit (1);
+      }
+
+  if (pid && argv[optind])
+    error (0, "cannot provide both a command line and a process id");
+
+  if (!pid && !argv[optind])
+    error (0, "must provide either a command line or a process id");
+
+  /* Honor user-supplied gmon file name prefix, if available. */
+  ptr = getenv ("GMON_OUT_PREFIX");
+  if (ptr && strlen (ptr) > 0)
+    prefix = ptr;
+
+  drive_map = (void *) cygwin_internal (CW_ALLOC_DRIVE_MAP);
+  ret = doprofile (ofile, pid, argv + optind);
+  if (drive_map)
+    cygwin_internal (CW_FREE_DRIVE_MAP, drive_map);
+
+  if (ofile && ofile != stdout)
+    fclose (ofile);
+  return (ret);
+}
+
+int
+main (int argc, char **argv)
+{
+  /* Make sure to have room for the _cygtls area *and* to initialize it.
+   * This is required to make sure cygwin_internal calls into Cygwin work
+   * reliably.  This problem has been noticed under AllocationPreference
+   * registry setting to 0x100000 (TOP_DOWN).
+   */
+  char buf[CYGTLS_PADSIZE];
+
+  RtlSecureZeroMemory (buf, sizeof (buf));
+  exit (main2 (argc, argv));
+}