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jeffhostetlergitster
jeffhostetler
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trace2: collect Windows-specific process information
Add platform-specific interface to log information about the current process. On Windows, this interface is used to indicate whether the git process is running under a debugger and list names of the process ancestors. Information for other platforms is left for a future effort. Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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‎common-main.c‎

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@@ -37,6 +37,7 @@ int main(int argc, const char **argv)
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trace2_initialize();
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trace2_cmd_start(argv);
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trace2_collect_process_info();
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git_resolve_executable_dir(argv[0]);
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‎compat/win32/trace2_win32_process_info.c‎

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#include "../../cache.h"
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#include "../../json-writer.h"
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#include <Psapi.h>
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#include <tlHelp32.h>
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/*
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* An arbitrarily chosen value to limit the size of the ancestor
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* array built in git_processes().
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*/
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#define NR_PIDS_LIMIT 10
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/*
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* Find the process data for the given PID in the given snapshot
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* and update the PROCESSENTRY32 data.
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*/
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static int find_pid(DWORD pid, HANDLE hSnapshot, PROCESSENTRY32 *pe32)
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{
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pe32->dwSize = sizeof(PROCESSENTRY32);
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if (Process32First(hSnapshot, pe32)) {
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do {
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if (pe32->th32ProcessID == pid)
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return 1;
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} while (Process32Next(hSnapshot, pe32));
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}
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return 0;
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}
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/*
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* Accumulate JSON array of our parent processes:
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* [
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* exe-name-parent,
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* exe-name-grand-parent,
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* ...
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* ]
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*
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* Note: we only report the filename of the process executable; the
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* only way to get its full pathname is to use OpenProcess()
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* and GetModuleFileNameEx() or QueryfullProcessImageName()
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* and that seems rather expensive (on top of the cost of
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* getting the snapshot).
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*
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* Note: we compute the set of parent processes by walking the PPID
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* link in each visited PROCESSENTRY32 record. This search
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* stops when an ancestor process is not found in the snapshot
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* (because it exited before the current or intermediate parent
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* process exited).
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*
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* This search may compute an incorrect result if the PPID link
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* refers to the PID of an exited parent and that PID has been
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* recycled and given to a new unrelated process.
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*
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* Worse, it is possible for a child or descendant of the
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* current process to be given the recycled PID and cause a
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* PPID-cycle. This would cause an infinite loop building our
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* parent process array.
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*
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* Note: for completeness, the "System Idle" process has PID=0 and
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* PPID=0 and could cause another PPID-cycle. We don't expect
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* Git to be a descendant of the idle process, but because of
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* PID recycling, it might be possible to get a PPID link value
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* of 0. This too would cause an infinite loop.
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*
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* Therefore, we keep an array of the visited PPIDs to guard against
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* cycles.
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*
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* We use a fixed-size array rather than ALLOC_GROW to keep things
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* simple and avoid the alloc/realloc overhead. It is OK if we
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* truncate the search and return a partial answer.
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*/
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static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
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{
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PROCESSENTRY32 pe32;
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DWORD pid;
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DWORD pid_list[NR_PIDS_LIMIT];
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int k, nr_pids = 0;
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pid = GetCurrentProcessId();
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while (find_pid(pid, hSnapshot, &pe32)) {
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/* Only report parents. Omit self from the JSON output. */
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if (nr_pids)
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jw_array_string(jw, pe32.szExeFile);
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/* Check for cycle in snapshot. (Yes, it happened.) */
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for (k = 0; k < nr_pids; k++)
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if (pid == pid_list[k]) {
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jw_array_string(jw, "(cycle)");
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return;
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}
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if (nr_pids == NR_PIDS_LIMIT) {
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jw_array_string(jw, "(truncated)");
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return;
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}
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pid_list[nr_pids++] = pid;
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pid = pe32.th32ParentProcessID;
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}
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}
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/*
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* Emit JSON data for the current and parent processes. Individual
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* trace2 targets can decide how to actually print it.
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*/
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static void get_ancestry(void)
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{
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HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
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if (hSnapshot != INVALID_HANDLE_VALUE) {
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struct json_writer jw = JSON_WRITER_INIT;
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jw_array_begin(&jw, 0);
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get_processes(&jw, hSnapshot);
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jw_end(&jw);
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trace2_data_json("process", the_repository, "windows/ancestry",
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&jw);
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jw_release(&jw);
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CloseHandle(hSnapshot);
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}
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}
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/*
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* Is a debugger attached to the current process?
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*
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* This will catch debug runs (where the debugger started the process).
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* This is the normal case. Since this code is called during our startup,
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* it will not report instances where a debugger is attached dynamically
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* to a running git process, but that is relatively rare.
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*/
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static void get_is_being_debugged(void)
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{
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if (IsDebuggerPresent())
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trace2_data_intmax("process", the_repository,
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"windows/debugger_present", 1);
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}
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void trace2_collect_process_info(void)
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{
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if (!trace2_is_enabled())
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return;
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get_is_being_debugged();
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get_ancestry();
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}

‎config.mak.uname‎

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@@ -393,6 +393,7 @@ ifeq ($(uname_S),Windows)
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BASIC_CFLAGS = -nologo -I. -I../zlib -Icompat/vcbuild -Icompat/vcbuild/include -DWIN32 -D_CONSOLE -DHAVE_STRING_H -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE
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COMPAT_OBJS = compat/msvc.o compat/winansi.o \
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compat/win32/pthread.o compat/win32/syslog.o \
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compat/win32/trace2_win32_process_info.o \
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compat/win32/dirent.o
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COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
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BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -SUBSYSTEM:CONSOLE
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COMPAT_CFLAGS += -DNOGDI -Icompat -Icompat/win32
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COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"
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COMPAT_OBJS += compat/mingw.o compat/winansi.o \
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compat/win32/trace2_win32_process_info.o \
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compat/win32/path-utils.o \
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compat/win32/pthread.o compat/win32/syslog.o \
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compat/win32/dirent.o

‎trace2.h‎

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@@ -368,4 +368,18 @@ void trace2_printf(const char *fmt, ...);
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/* clang-format on */
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#endif
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/*
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* Optional platform-specific code to dump information about the
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* current and any parent process(es). This is intended to allow
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* post-processors to know who spawned this git instance and anything
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* else the platform may be able to tell us about the current process.
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*/
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#if defined(GIT_WINDOWS_NATIVE)
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void trace2_collect_process_info(void);
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#else
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#define trace2_collect_process_info() \
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do { \
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} while (0)
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#endif
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#endif /* TRACE2_H */

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