libbb/read_cmdline: prepend {comm} if different from argv0. Closes 3835.

function                                             old     new   delta
read_cmdline                                         114     233    +119

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 32 insertions, 3 deletions

diff --git a/libbb/procps.c b/libbb/procps.c
index 9207e9254..1dea61518 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -566,18 +566,47 @@ procps_status_t* FAST_FUNC procps_scan(procps_status_t* sp, int flags)
 void FAST_FUNC read_cmdline(char *buf, int col, unsigned pid, const char *comm)
 {
         int sz;
-        char filename[sizeof("/proc//cmdline") + sizeof(int)*3];
+        char filename[sizeof("/proc/%u/cmdline") + sizeof(int)*3];
 
         sprintf(filename, "/proc/%u/cmdline", pid);
         sz = open_read_close(filename, buf, col - 1);
         if (sz > 0) {
+                const char *base;
+                int comm_len;
+
                 buf[sz] = '\0';
                 while (--sz >= 0 && buf[sz] == '\0')
                         continue;
-                do {
+                base = bb_basename(buf); /* before we replace argv0's NUL with space */
+                while (sz >= 0) {
                         if ((unsigned char)(buf[sz]) < ' ')
                                 buf[sz] = ' ';
-                } while (--sz >= 0);
+                        sz--;
+                }
+
+                /* If comm differs from argv0, prepend "{comm} ".
+                 * It allows to see thread names set by prctl(PR_SET_NAME).
+                 */
+                if (base[0] == '-') /* "-sh" (login shell)? */
+                        base++;
+                comm_len = strlen(comm);
+                /* Why compare up to comm_len, not COMM_LEN-1?
+                 * Well, some processes rewrite argv, and use _spaces_ there
+                 * while rewriting. (KDE is observed to do it).
+                 * I prefer to still treat argv0 "process foo bar"
+                 * as 'equal' to comm "process".
+                 */
+                if (strncmp(base, comm, comm_len) != 0) {
+                        comm_len += 3;
+                        if (col > comm_len)
+                                memmove(buf + comm_len, buf, col - comm_len);
+                        snprintf(buf, col, "{%s}", comm);
+                        if (col <= comm_len)
+                                return;
+                        buf[comm_len - 1] = ' ';
+                        buf[col - 1] = '\0';
+                }
+
         } else {
                 snprintf(buf, col, "[%s]", comm);
         }