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util-lib: rework get_process_cmdline() (#3529)

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This reworks get_process_cmdline() quite substantially, fixing the following:

- Fixes:
  https://github.com/systemd/systemd/pull/3512/commits/a4e3bf4d7ac2de51191ce136ee9361ba319e106c#r66837630

- The passed max_length is also applied to the "comm" name, if comm_fallback is
  set.

- The right thing happens if max_length == 1 is specified

- when the cmdline "foobar" is abbreviated to 6 characters the result is not
  "foobar" instead of "foo...".

- trailing whitespace are removed before the ... suffix is appended. The 7
  character abbreviation of "foo barz" is hence "foo..." instead of "foo ...".

- leading whitespace are suppressed from the cmdline

- a comprehensive test case is added
This commit is contained in:
Lennart Poettering
2016-06-14 17:52:29 -04:00
committed by Zbigniew Jędrzejewski-Szmek
parent 8dd57192bc
commit 69281c49eb
2 changed files with 270 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/process-util.c
+79 -11
View File
@@ -110,6 +110,15 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
assert(line);
assert(pid >= 0);
/* Retrieves a process' command line. Replaces unprintable characters while doing so by whitespace (coalescing
* multiple sequential ones into one). If max_length is != 0 will return a string of the specified size at most
* (the trailing NUL byte does count towards the length here!), abbreviated with a "..." ellipsis. If
* comm_fallback is true and the process has no command line set (the case for kernel threads), or has a
* command line that resolves to the empty string will return the "comm" name of the process instead.
*
* Returns -ESRCH if the process doesn't exist, and -ENOENT if the process has no command line (and
* comm_fallback is false). */
p = procfs_file_alloca(pid, "cmdline");
f = fopen(p, "re");
@@ -119,12 +128,22 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
return -errno;
}
if (max_length == 0) {
if (max_length == 1) {
/* If there's only room for one byte, return the empty string */
r = new0(char, 1);
if (!r)
return -ENOMEM;
*line = r;
return 0;
} else if (max_length == 0) {
size_t len = 0, allocated = 0;
while ((c = getc(f)) != EOF) {
if (!GREEDY_REALLOC(r, allocated, len+2)) {
if (!GREEDY_REALLOC(r, allocated, len+3)) {
free(r);
return -ENOMEM;
}
@@ -136,7 +155,7 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
}
r[len++] = c;
} else
} else if (len > 0)
space = true;
}
@@ -144,6 +163,7 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
r[len] = 0;
} else {
bool dotdotdot = false;
size_t left;
r = new(char, max_length);
@@ -155,28 +175,46 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
while ((c = getc(f)) != EOF) {
if (isprint(c)) {
if (space) {
if (left <= 4)
if (left <= 2) {
dotdotdot = true;
break;
}
*(k++) = ' ';
left--;
space = false;
}
if (left <= 4)
if (left <= 1) {
dotdotdot = true;
break;
}
*(k++) = (char) c;
left--;
} else
} else if (k > r)
space = true;
}
if (left <= 4) {
size_t n = MIN(left-1, 3U);
memcpy(k, "...", n);
k[n] = 0;
if (dotdotdot) {
if (max_length <= 4) {
k = r;
left = max_length;
} else {
k = r + max_length - 4;
left = 4;
/* Eat up final spaces */
while (k > r && isspace(k[-1])) {
k--;
left++;
}
}
strncpy(k, "...", left-1);
k[left] = 0;
} else
*k = 0;
}
@@ -195,7 +233,37 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
if (h < 0)
return h;
r = strjoin("[", t, "]", NULL);
if (max_length == 0)
r = strjoin("[", t, "]", NULL);
else {
size_t l;
l = strlen(t);
if (l + 3 <= max_length)
r = strjoin("[", t, "]", NULL);
else if (max_length <= 6) {
r = new(char, max_length);
if (!r)
return -ENOMEM;
memcpy(r, "[...]", max_length-1);
r[max_length-1] = 0;
} else {
char *e;
t[max_length - 6] = 0;
/* Chop off final spaces */
e = strchr(t, 0);
while (e > t && isspace(e[-1]))
e--;
*e = 0;
r = strjoin("[", t, "...]", NULL);
}
}
if (!r)
return -ENOMEM;
}