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authorJeff Hostetler <jeffhost@microsoft.com>2019-02-22 22:25:02 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-02-22 23:27:59 (GMT)
commit353d3d77f4fdd1582e3b60824deebca27c7b2790 (patch)
treef5d5aa0bd3da34c5266fdc4e9b4a67573903eca5
parentee4512ed481a126dadd33334186e0e759d7f2f47 (diff)
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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>
-rw-r--r--common-main.c1
-rw-r--r--compat/win32/trace2_win32_process_info.c147
-rw-r--r--config.mak.uname2
-rw-r--r--trace2.h14
4 files changed, 164 insertions, 0 deletions
diff --git a/common-main.c b/common-main.c
index 6dbdc4a..d484aec 100644
--- a/common-main.c
+++ b/common-main.c
@@ -37,6 +37,7 @@ int main(int argc, const char **argv)
trace2_initialize();
trace2_cmd_start(argv);
+ trace2_collect_process_info();
git_resolve_executable_dir(argv[0]);
diff --git a/compat/win32/trace2_win32_process_info.c b/compat/win32/trace2_win32_process_info.c
new file mode 100644
index 0000000..52bd620
--- /dev/null
+++ b/compat/win32/trace2_win32_process_info.c
@@ -0,0 +1,147 @@
+#include "../../cache.h"
+#include "../../json-writer.h"
+#include <Psapi.h>
+#include <tlHelp32.h>
+
+/*
+ * An arbitrarily chosen value to limit the size of the ancestor
+ * array built in git_processes().
+ */
+#define NR_PIDS_LIMIT 10
+
+/*
+ * Find the process data for the given PID in the given snapshot
+ * and update the PROCESSENTRY32 data.
+ */
+static int find_pid(DWORD pid, HANDLE hSnapshot, PROCESSENTRY32 *pe32)
+{
+ pe32->dwSize = sizeof(PROCESSENTRY32);
+
+ if (Process32First(hSnapshot, pe32)) {
+ do {
+ if (pe32->th32ProcessID == pid)
+ return 1;
+ } while (Process32Next(hSnapshot, pe32));
+ }
+ return 0;
+}
+
+/*
+ * Accumulate JSON array of our parent processes:
+ * [
+ * exe-name-parent,
+ * exe-name-grand-parent,
+ * ...
+ * ]
+ *
+ * Note: we only report the filename of the process executable; the
+ * only way to get its full pathname is to use OpenProcess()
+ * and GetModuleFileNameEx() or QueryfullProcessImageName()
+ * and that seems rather expensive (on top of the cost of
+ * getting the snapshot).
+ *
+ * Note: we compute the set of parent processes by walking the PPID
+ * link in each visited PROCESSENTRY32 record. This search
+ * stops when an ancestor process is not found in the snapshot
+ * (because it exited before the current or intermediate parent
+ * process exited).
+ *
+ * This search may compute an incorrect result if the PPID link
+ * refers to the PID of an exited parent and that PID has been
+ * recycled and given to a new unrelated process.
+ *
+ * Worse, it is possible for a child or descendant of the
+ * current process to be given the recycled PID and cause a
+ * PPID-cycle. This would cause an infinite loop building our
+ * parent process array.
+ *
+ * Note: for completeness, the "System Idle" process has PID=0 and
+ * PPID=0 and could cause another PPID-cycle. We don't expect
+ * Git to be a descendant of the idle process, but because of
+ * PID recycling, it might be possible to get a PPID link value
+ * of 0. This too would cause an infinite loop.
+ *
+ * Therefore, we keep an array of the visited PPIDs to guard against
+ * cycles.
+ *
+ * We use a fixed-size array rather than ALLOC_GROW to keep things
+ * simple and avoid the alloc/realloc overhead. It is OK if we
+ * truncate the search and return a partial answer.
+ */
+static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
+{
+ PROCESSENTRY32 pe32;
+ DWORD pid;
+ DWORD pid_list[NR_PIDS_LIMIT];
+ int k, nr_pids = 0;
+
+ pid = GetCurrentProcessId();
+ while (find_pid(pid, hSnapshot, &pe32)) {
+ /* Only report parents. Omit self from the JSON output. */
+ if (nr_pids)
+ jw_array_string(jw, pe32.szExeFile);
+
+ /* Check for cycle in snapshot. (Yes, it happened.) */
+ for (k = 0; k < nr_pids; k++)
+ if (pid == pid_list[k]) {
+ jw_array_string(jw, "(cycle)");
+ return;
+ }
+
+ if (nr_pids == NR_PIDS_LIMIT) {
+ jw_array_string(jw, "(truncated)");
+ return;
+ }
+
+ pid_list[nr_pids++] = pid;
+
+ pid = pe32.th32ParentProcessID;
+ }
+}
+
+/*
+ * Emit JSON data for the current and parent processes. Individual
+ * trace2 targets can decide how to actually print it.
+ */
+static void get_ancestry(void)
+{
+ HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
+
+ if (hSnapshot != INVALID_HANDLE_VALUE) {
+ struct json_writer jw = JSON_WRITER_INIT;
+
+ jw_array_begin(&jw, 0);
+ get_processes(&jw, hSnapshot);
+ jw_end(&jw);
+
+ trace2_data_json("process", the_repository, "windows/ancestry",
+ &jw);
+
+ jw_release(&jw);
+ CloseHandle(hSnapshot);
+ }
+}
+
+/*
+ * Is a debugger attached to the current process?
+ *
+ * This will catch debug runs (where the debugger started the process).
+ * This is the normal case. Since this code is called during our startup,
+ * it will not report instances where a debugger is attached dynamically
+ * to a running git process, but that is relatively rare.
+ */
+static void get_is_being_debugged(void)
+{
+ if (IsDebuggerPresent())
+ trace2_data_intmax("process", the_repository,
+ "windows/debugger_present", 1);
+}
+
+void trace2_collect_process_info(void)
+{
+ if (!trace2_is_enabled())
+ return;
+
+ get_is_being_debugged();
+ get_ancestry();
+}
diff --git a/config.mak.uname b/config.mak.uname
index b37fa84..c8b0e34 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -393,6 +393,7 @@ ifeq ($(uname_S),Windows)
BASIC_CFLAGS = -nologo -I. -I../zlib -Icompat/vcbuild -Icompat/vcbuild/include -DWIN32 -D_CONSOLE -DHAVE_STRING_H -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE
COMPAT_OBJS = compat/msvc.o compat/winansi.o \
compat/win32/pthread.o compat/win32/syslog.o \
+ compat/win32/trace2_win32_process_info.o \
compat/win32/dirent.o
COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -SUBSYSTEM:CONSOLE
@@ -546,6 +547,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
COMPAT_CFLAGS += -DNOGDI -Icompat -Icompat/win32
COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"
COMPAT_OBJS += compat/mingw.o compat/winansi.o \
+ compat/win32/trace2_win32_process_info.o \
compat/win32/path-utils.o \
compat/win32/pthread.o compat/win32/syslog.o \
compat/win32/dirent.o
diff --git a/trace2.h b/trace2.h
index fce9891..ae5020d 100644
--- a/trace2.h
+++ b/trace2.h
@@ -368,4 +368,18 @@ void trace2_printf(const char *fmt, ...);
/* clang-format on */
#endif
+/*
+ * Optional platform-specific code to dump information about the
+ * current and any parent process(es). This is intended to allow
+ * post-processors to know who spawned this git instance and anything
+ * else the platform may be able to tell us about the current process.
+ */
+#if defined(GIT_WINDOWS_NATIVE)
+void trace2_collect_process_info(void);
+#else
+#define trace2_collect_process_info() \
+ do { \
+ } while (0)
+#endif
+
#endif /* TRACE2_H */