compat/win32/trace2_win32_process_info.c

   1 #include "../../git-compat-util.h"
   2 #include "../../json-writer.h"
   3 #include "../../repository.h"
   4 #include "../../trace2.h"
   5 #include "lazyload.h"
   6 #include <psapi.h>
   7 #include <tlhelp32.h>
   8
   9 /*
  10  * An arbitrarily chosen value to limit the size of the ancestor
  11  * array built in git_processes().
  12  */
  13 #define NR_PIDS_LIMIT 10
  14
  15 /*
  16  * Find the process data for the given PID in the given snapshot
  17  * and update the PROCESSENTRY32 data.
  18  */
  19 static int find_pid(DWORD pid, HANDLE hSnapshot, PROCESSENTRY32 *pe32)
  20 {
  21         pe32->dwSize = sizeof(PROCESSENTRY32);
  22
  23         if (Process32First(hSnapshot, pe32)) {
  24                 do {
  25                         if (pe32->th32ProcessID == pid)
  26                                 return 1;
  27                 } while (Process32Next(hSnapshot, pe32));
  28         }
  29         return 0;
  30 }
  31
  32 /*
  33  * Accumulate JSON array of our parent processes:
  34  *     [
  35  *         exe-name-parent,
  36  *         exe-name-grand-parent,
  37  *         ...
  38  *     ]
  39  *
  40  * Note: we only report the filename of the process executable; the
  41  *       only way to get its full pathname is to use OpenProcess()
  42  *       and GetModuleFileNameEx() or QueryfullProcessImageName()
  43  *       and that seems rather expensive (on top of the cost of
  44  *       getting the snapshot).
  45  *
  46  * Note: we compute the set of parent processes by walking the PPID
  47  *       link in each visited PROCESSENTRY32 record.  This search
  48  *       stops when an ancestor process is not found in the snapshot
  49  *       (because it exited before the current or intermediate parent
  50  *       process exited).
  51  *
  52  *       This search may compute an incorrect result if the PPID link
  53  *       refers to the PID of an exited parent and that PID has been
  54  *       recycled and given to a new unrelated process.
  55  *
  56  *       Worse, it is possible for a child or descendant of the
  57  *       current process to be given the recycled PID and cause a
  58  *       PPID-cycle.  This would cause an infinite loop building our
  59  *       parent process array.
  60  *
  61  * Note: for completeness, the "System Idle" process has PID=0 and
  62  *       PPID=0 and could cause another PPID-cycle.  We don't expect
  63  *       Git to be a descendant of the idle process, but because of
  64  *       PID recycling, it might be possible to get a PPID link value
  65  *       of 0.  This too would cause an infinite loop.
  66  *
  67  * Therefore, we keep an array of the visited PPIDs to guard against
  68  * cycles.
  69  *
  70  * We use a fixed-size array rather than ALLOC_GROW to keep things
  71  * simple and avoid the alloc/realloc overhead.  It is OK if we
  72  * truncate the search and return a partial answer.
  73  */
  74 static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
  75 {
  76         PROCESSENTRY32 pe32;
  77         DWORD pid;
  78         DWORD pid_list[NR_PIDS_LIMIT];
  79         int k, nr_pids = 0;
  80
  81         pid = GetCurrentProcessId();
  82         while (find_pid(pid, hSnapshot, &pe32)) {
  83                 /* Only report parents. Omit self from the JSON output. */
  84                 if (nr_pids)
  85                         jw_array_string(jw, pe32.szExeFile);
  86
  87                 /* Check for cycle in snapshot. (Yes, it happened.) */
  88                 for (k = 0; k < nr_pids; k++)
  89                         if (pid == pid_list[k]) {
  90                                 jw_array_string(jw, "(cycle)");
  91                                 return;
  92                         }
  93
  94                 if (nr_pids == NR_PIDS_LIMIT) {
  95                         jw_array_string(jw, "(truncated)");
  96                         return;
  97                 }
  98
  99                 pid_list[nr_pids++] = pid;
 100
 101                 pid = pe32.th32ParentProcessID;
 102         }
 103 }
 104
 105 /*
 106  * Emit JSON data for the current and parent processes.  Individual
 107  * trace2 targets can decide how to actually print it.
 108  */
 109 static void get_ancestry(void)
 110 {
 111         HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
 112
 113         if (hSnapshot != INVALID_HANDLE_VALUE) {
 114                 struct json_writer jw = JSON_WRITER_INIT;
 115
 116                 jw_array_begin(&jw, 0);
 117                 get_processes(&jw, hSnapshot);
 118                 jw_end(&jw);
 119
 120                 trace2_data_json("process", the_repository, "windows/ancestry",
 121                                  &jw);
 122
 123                 jw_release(&jw);
 124                 CloseHandle(hSnapshot);
 125         }
 126 }
 127
 128 /*
 129  * Is a debugger attached to the current process?
 130  *
 131  * This will catch debug runs (where the debugger started the process).
 132  * This is the normal case.  Since this code is called during our startup,
 133  * it will not report instances where a debugger is attached dynamically
 134  * to a running git process, but that is relatively rare.
 135  */
 136 static void get_is_being_debugged(void)
 137 {
 138         if (IsDebuggerPresent())
 139                 trace2_data_intmax("process", the_repository,
 140                                    "windows/debugger_present", 1);
 141 }
 142
 143 /*
 144  * Emit JSON data with the peak memory usage of the current process.
 145  */
 146 static void get_peak_memory_info(void)
 147 {
 148         DECLARE_PROC_ADDR(psapi.dll, BOOL, WINAPI, GetProcessMemoryInfo,
 149                           HANDLE, PPROCESS_MEMORY_COUNTERS, DWORD);
 150
 151         if (INIT_PROC_ADDR(GetProcessMemoryInfo)) {
 152                 PROCESS_MEMORY_COUNTERS pmc;
 153
 154                 if (GetProcessMemoryInfo(GetCurrentProcess(), &pmc,
 155                                          sizeof(pmc))) {
 156                         struct json_writer jw = JSON_WRITER_INIT;
 157
 158                         jw_object_begin(&jw, 0);
 159
 160 #define KV(kv) #kv, (intmax_t)pmc.kv
 161
 162                         jw_object_intmax(&jw, KV(PageFaultCount));
 163                         jw_object_intmax(&jw, KV(PeakWorkingSetSize));
 164                         jw_object_intmax(&jw, KV(PeakPagefileUsage));
 165
 166                         jw_end(&jw);
 167
 168                         trace2_data_json("process", the_repository,
 169                                          "windows/memory", &jw);
 170                         jw_release(&jw);
 171                 }
 172         }
 173 }
 174
 175 void trace2_collect_process_info(enum trace2_process_info_reason reason)
 176 {
 177         if (!trace2_is_enabled())
 178                 return;
 179
 180         switch (reason) {
 181         case TRACE2_PROCESS_INFO_STARTUP:
 182                 get_is_being_debugged();
 183                 get_ancestry();
 184                 return;
 185
 186         case TRACE2_PROCESS_INFO_EXIT:
 187                 get_peak_memory_info();
 188                 return;
 189
 190         default:
 191                 BUG("trace2_collect_process_info: unknown reason '%d'", reason);
 192         }
 193 }