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