f4609b896f
This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because there is some breakage in the git build related to the netrc credentials helper which someone has taken care of in nixpkgs. The stable channel is not used for anything other than git, so this should be fine. Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb
112 lines
2.9 KiB
C
112 lines
2.9 KiB
C
#include "cache.h"
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#include "trace2/tr2_tbuf.h"
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#include "trace2/tr2_sid.h"
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#define TR2_ENVVAR_PARENT_SID "GIT_TRACE2_PARENT_SID"
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static struct strbuf tr2sid_buf = STRBUF_INIT;
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static int tr2sid_nr_git_parents;
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/*
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* Compute the final component of the SID representing the current process.
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* This should uniquely identify the process and be a valid filename (to
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* allow writing trace2 data to per-process files). It should also be fixed
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* length for possible use as a database key.
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*
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* "<yyyymmdd>T<hhmmss>.<fraction>Z-<host>-<process>"
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*
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* where <host> is a 9 character string:
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* "H<first_8_chars_of_sha1_of_hostname>"
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* "Localhost" when no hostname.
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*
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* where <process> is a 9 character string containing the least significant
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* 32 bits in the process-id.
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* "P<pid>"
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* (This is an abribrary choice. On most systems pid_t is a 32 bit value,
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* so limit doesn't matter. On larger systems, a truncated value is fine
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* for our purposes here.)
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*/
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static void tr2_sid_append_my_sid_component(void)
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{
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const struct git_hash_algo *algo = &hash_algos[GIT_HASH_SHA1];
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struct tr2_tbuf tb_now;
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git_hash_ctx ctx;
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pid_t pid = getpid();
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unsigned char hash[GIT_MAX_RAWSZ + 1];
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char hex[GIT_MAX_HEXSZ + 1];
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char hostname[HOST_NAME_MAX + 1];
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tr2_tbuf_utc_datetime(&tb_now);
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strbuf_addstr(&tr2sid_buf, tb_now.buf);
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strbuf_addch(&tr2sid_buf, '-');
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if (xgethostname(hostname, sizeof(hostname)))
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strbuf_add(&tr2sid_buf, "Localhost", 9);
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else {
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algo->init_fn(&ctx);
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algo->update_fn(&ctx, hostname, strlen(hostname));
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algo->final_fn(hash, &ctx);
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hash_to_hex_algop_r(hex, hash, algo);
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strbuf_addch(&tr2sid_buf, 'H');
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strbuf_add(&tr2sid_buf, hex, 8);
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}
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strbuf_addf(&tr2sid_buf, "-P%08"PRIx32, (uint32_t)pid);
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}
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/*
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* Compute a "unique" session id (SID) for the current process. This allows
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* all events from this process to have a single label (much like a PID).
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*
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* Export this into our environment so that all child processes inherit it.
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*
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* If we were started by another git instance, use our parent's SID as a
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* prefix. (This lets us track parent/child relationships even if there
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* is an intermediate shell process.)
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*
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* Additionally, count the number of nested git processes.
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*/
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static void tr2_sid_compute(void)
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{
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const char *parent_sid;
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if (tr2sid_buf.len)
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return;
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parent_sid = getenv(TR2_ENVVAR_PARENT_SID);
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if (parent_sid && *parent_sid) {
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const char *p;
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for (p = parent_sid; *p; p++)
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if (*p == '/')
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tr2sid_nr_git_parents++;
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strbuf_addstr(&tr2sid_buf, parent_sid);
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strbuf_addch(&tr2sid_buf, '/');
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tr2sid_nr_git_parents++;
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}
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tr2_sid_append_my_sid_component();
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setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);
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}
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const char *tr2_sid_get(void)
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{
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if (!tr2sid_buf.len)
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tr2_sid_compute();
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return tr2sid_buf.buf;
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}
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int tr2_sid_depth(void)
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{
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if (!tr2sid_buf.len)
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tr2_sid_compute();
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return tr2sid_nr_git_parents;
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}
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void tr2_sid_release(void)
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{
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strbuf_release(&tr2sid_buf);
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}
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