processes plugin: Limit the buffer size used for command line matching.

ARG_MAX is quite big on many systems, for example >100 kByte on
GNU/Linux. This is a problem for systems with tight memory constraints,
for example embedded devices.

This patch uses at most 4 kByte for this, which out to be enough for the
vast majority of users. Users with specific requirements can compile
with "CMDLINE_BUFFER_SIZE=${LOTS}" in their CPPFLAGS to override this
default.

Fixes: #652

diff --git a/src/processes.c b/src/processes.c
index 5601d29..aa47f33 100644 (file)
--- a/src/processes.c
+++ b/src/processes.c
@@ -128,8 +128,12 @@
 # include <kstat.h>
 #endif
 
-#ifndef ARG_MAX
-#  define ARG_MAX 4096
+#ifndef CMDLINE_BUFFER_SIZE
+# if defined(ARG_MAX) && (ARG_MAX < 4096)
+#  define CMDLINE_BUFFER_SIZE ARG_MAX
+# else
+#  define CMDLINE_BUFFER_SIZE 4096
+# endif
 #endif
 
 typedef struct procstat_entry_s
@@ -1686,7 +1690,7 @@ static int ps_read (void)
        DIR           *proc;
        int            pid;
 
-       char cmdline[ARG_MAX];
+       char cmdline[CMDLINE_BUFFER_SIZE];
 
        int        status;
        procstat_t ps;
@@ -1824,7 +1828,7 @@ static int ps_read (void)
                 * filter out threads (duplicate PID entries). */
                if ((proc_ptr == NULL) || (proc_ptr->ki_pid != procs[i].ki_pid))
                {
-                       char cmdline[ARG_MAX] = "";
+                       char cmdline[CMDLINE_BUFFER_SIZE] = "";
                        _Bool have_cmdline = 0;
 
                        proc_ptr = &(procs[i]);