mirror of
https://github.com/git/git
synced 2024-08-27 19:49:21 +00:00
Merge branch 'ab/tr2-leaks-and-fixes'
The tracing of process ancestry information has been enhanced. * ab/tr2-leaks-and-fixes: tr2: log N parent process names on Linux tr2: do compiler enum check in trace2_collect_process_info() tr2: leave the parent list empty upon failure & don't leak memory tr2: stop leaking "thread_name" memory tr2: clarify TRACE2_PROCESS_INFO_EXIT comment under Linux tr2: remove NEEDSWORK comment for "non-procfs" implementations
This commit is contained in:
commit
76f5fdc203
|
@ -4,51 +4,172 @@
|
|||
#include "strvec.h"
|
||||
#include "trace2.h"
|
||||
|
||||
static void get_ancestry_names(struct strvec *names)
|
||||
{
|
||||
/*
|
||||
* NEEDSWORK: We could gather the entire pstree into an array to match
|
||||
* functionality with compat/win32/trace2_win32_process_info.c.
|
||||
* To do so, we may want to examine /proc/<pid>/stat. For now, just
|
||||
* gather the immediate parent name which is readily accessible from
|
||||
* /proc/$(getppid())/comm.
|
||||
*/
|
||||
struct strbuf procfs_path = STRBUF_INIT;
|
||||
struct strbuf name = STRBUF_INIT;
|
||||
/*
|
||||
* We need more complex parsing in stat_parent_pid() and
|
||||
* parse_proc_stat() below than a dumb fscanf(). That's because while
|
||||
* the statcomm field is surrounded by parentheses, the process itself
|
||||
* is free to insert any arbitrary byte sequence its its name. That
|
||||
* can include newlines, spaces, closing parentheses etc.
|
||||
*
|
||||
* See do_task_stat() in fs/proc/array.c in linux.git, this is in
|
||||
* contrast with the escaped version of the name found in
|
||||
* /proc/%d/status.
|
||||
*
|
||||
* So instead of using fscanf() we'll read N bytes from it, look for
|
||||
* the first "(", and then the last ")", anything in-between is our
|
||||
* process name.
|
||||
*
|
||||
* How much N do we need? On Linux /proc/sys/kernel/pid_max is 2^15 by
|
||||
* default, but it can be raised set to values of up to 2^22. So
|
||||
* that's 7 digits for a PID. We have 2 PIDs in the first four fields
|
||||
* we're interested in, so 2 * 7 = 14.
|
||||
*
|
||||
* We then have 3 spaces between those four values, and we'd like to
|
||||
* get to the space between the 4th and the 5th (the "pgrp" field) to
|
||||
* make sure we read the entire "ppid" field. So that brings us up to
|
||||
* 14 + 3 + 1 = 18. Add the two parentheses around the "comm" value
|
||||
* and it's 20. The "state" value itself is then one character (now at
|
||||
* 21).
|
||||
*
|
||||
* Finally the maximum length of the "comm" name itself is 15
|
||||
* characters, e.g. a setting of "123456789abcdefg" will be truncated
|
||||
* to "123456789abcdef". See PR_SET_NAME in prctl(2). So all in all
|
||||
* we'd need to read 21 + 15 = 36 bytes.
|
||||
*
|
||||
* Let's just read 2^6 (64) instead for good measure. If PID_MAX ever
|
||||
* grows past 2^22 we'll be future-proof. We'll then anchor at the
|
||||
* last ")" we find to locate the parent PID.
|
||||
*/
|
||||
#define STAT_PARENT_PID_READ_N 64
|
||||
|
||||
/* try to use procfs if it's present. */
|
||||
strbuf_addf(&procfs_path, "/proc/%d/comm", getppid());
|
||||
if (strbuf_read_file(&name, procfs_path.buf, 0)) {
|
||||
strbuf_release(&procfs_path);
|
||||
strbuf_trim_trailing_newline(&name);
|
||||
strvec_push(names, strbuf_detach(&name, NULL));
|
||||
static int parse_proc_stat(struct strbuf *sb, struct strbuf *name,
|
||||
int *statppid)
|
||||
{
|
||||
const char *comm_lhs = strchr(sb->buf, '(');
|
||||
const char *comm_rhs = strrchr(sb->buf, ')');
|
||||
const char *ppid_lhs, *ppid_rhs;
|
||||
char *p;
|
||||
pid_t ppid;
|
||||
|
||||
if (!comm_lhs || !comm_rhs)
|
||||
goto bad_kernel;
|
||||
|
||||
/*
|
||||
* We're at the ")", that's followed by " X ", where X is a
|
||||
* single "state" character. So advance by 4 bytes.
|
||||
*/
|
||||
ppid_lhs = comm_rhs + 4;
|
||||
|
||||
/*
|
||||
* Read until the space between the "ppid" and "pgrp" fields
|
||||
* to make sure we're anchored after the untruncated "ppid"
|
||||
* field..
|
||||
*/
|
||||
ppid_rhs = strchr(ppid_lhs, ' ');
|
||||
if (!ppid_rhs)
|
||||
goto bad_kernel;
|
||||
|
||||
ppid = strtol(ppid_lhs, &p, 10);
|
||||
if (ppid_rhs == p) {
|
||||
const char *comm = comm_lhs + 1;
|
||||
size_t commlen = comm_rhs - comm;
|
||||
|
||||
strbuf_add(name, comm, commlen);
|
||||
*statppid = ppid;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
bad_kernel:
|
||||
/*
|
||||
* We were able to read our STAT_PARENT_PID_READ_N bytes from
|
||||
* /proc/%d/stat, but the content is bad. Broken kernel?
|
||||
* Should not happen, but handle it gracefully.
|
||||
*/
|
||||
return -1;
|
||||
}
|
||||
|
||||
static int stat_parent_pid(pid_t pid, struct strbuf *name, int *statppid)
|
||||
{
|
||||
struct strbuf procfs_path = STRBUF_INIT;
|
||||
struct strbuf sb = STRBUF_INIT;
|
||||
FILE *fp;
|
||||
int ret = -1;
|
||||
|
||||
/* try to use procfs if it's present. */
|
||||
strbuf_addf(&procfs_path, "/proc/%d/stat", pid);
|
||||
fp = fopen(procfs_path.buf, "r");
|
||||
if (!fp)
|
||||
goto cleanup;
|
||||
|
||||
/*
|
||||
* We could be more strict here and assert that we read at
|
||||
* least STAT_PARENT_PID_READ_N. My reading of procfs(5) is
|
||||
* that on any modern kernel (at least since 2.6.0 released in
|
||||
* 2003) even if all the mandatory numeric fields were zero'd
|
||||
* out we'd get at least 100 bytes, but let's just check that
|
||||
* we got anything at all and trust the parse_proc_stat()
|
||||
* function to handle its "Bad Kernel?" error checking.
|
||||
*/
|
||||
if (!strbuf_fread(&sb, STAT_PARENT_PID_READ_N, fp))
|
||||
goto cleanup;
|
||||
if (parse_proc_stat(&sb, name, statppid) < 0)
|
||||
goto cleanup;
|
||||
|
||||
ret = 0;
|
||||
cleanup:
|
||||
if (fp)
|
||||
fclose(fp);
|
||||
strbuf_release(&procfs_path);
|
||||
strbuf_release(&sb);
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
static void push_ancestry_name(struct strvec *names, pid_t pid)
|
||||
{
|
||||
struct strbuf name = STRBUF_INIT;
|
||||
int ppid;
|
||||
|
||||
if (stat_parent_pid(pid, &name, &ppid) < 0)
|
||||
goto cleanup;
|
||||
|
||||
strvec_push(names, name.buf);
|
||||
|
||||
/*
|
||||
* Both errors and reaching the end of the process chain are
|
||||
* reported as fields of 0 by proc(5)
|
||||
*/
|
||||
if (ppid)
|
||||
push_ancestry_name(names, ppid);
|
||||
cleanup:
|
||||
strbuf_release(&name);
|
||||
|
||||
return;
|
||||
/* NEEDSWORK: add non-procfs-linux implementations here */
|
||||
}
|
||||
|
||||
void trace2_collect_process_info(enum trace2_process_info_reason reason)
|
||||
{
|
||||
struct strvec names = STRVEC_INIT;
|
||||
|
||||
if (!trace2_is_enabled())
|
||||
return;
|
||||
|
||||
/* someday we may want to write something extra here, but not today */
|
||||
if (reason == TRACE2_PROCESS_INFO_EXIT)
|
||||
return;
|
||||
|
||||
if (reason == TRACE2_PROCESS_INFO_STARTUP) {
|
||||
switch (reason) {
|
||||
case TRACE2_PROCESS_INFO_EXIT:
|
||||
/*
|
||||
* NEEDSWORK: we could do the entire ptree in an array instead,
|
||||
* see compat/win32/trace2_win32_process_info.c.
|
||||
* The Windows version of this calls its
|
||||
* get_peak_memory_info() here. We may want to insert
|
||||
* similar process-end statistics here in the future.
|
||||
*/
|
||||
struct strvec names = STRVEC_INIT;
|
||||
|
||||
get_ancestry_names(&names);
|
||||
break;
|
||||
case TRACE2_PROCESS_INFO_STARTUP:
|
||||
push_ancestry_name(&names, getppid());
|
||||
|
||||
if (names.nr)
|
||||
trace2_cmd_ancestry(names.v);
|
||||
strvec_clear(&names);
|
||||
break;
|
||||
}
|
||||
|
||||
return;
|
||||
|
|
|
@ -95,6 +95,7 @@ void tr2tls_unset_self(void)
|
|||
|
||||
pthread_setspecific(tr2tls_key, NULL);
|
||||
|
||||
strbuf_release(&ctx->thread_name);
|
||||
free(ctx->array_us_start);
|
||||
free(ctx);
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue