top,ps: improve /proc/PID/cmdinfo reading code

function                                             old     new   delta
display_status                                         -    1231   +1231
read_cmdline                                           -     101    +101
parse_conf                                          1284    1303     +19
arith                                               2033    2042      +9
collect_blk                                          467     474      +7
fsck_main                                           1909    1911      +2
dhcprelay_main                                      1125    1122      -3
singlemount                                         4555    4547      -8
read_close                                            50      36     -14
get_lcm                                              123     105     -18
ed_main                                             3111    3084     -27
func_args                                             73      28     -45
procps_scan                                          732     658     -74
top_main                                            2187     899   -1288
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 4/8 up/down: 1369/-1477)       Total: -108 bytes
   text    data     bss     dec     hex filename
 676048    2744   13968  692760   a9218 busybox_old
 675940    2744   13968  692652   a91ac busybox_unstripped

5 files changed, 80 insertions, 59 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 6a699a7e6..a95de848b 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -836,7 +836,7 @@ enum { COMM_LEN = 16 };
 typedef struct {
 	DIR *dir;
 /* Fields are set to 0/NULL if failed to determine (or not requested) */
-	char *cmd;
+	/*char *cmd;*/
 	char *argv0;
 	/*char *exe;*/
 	USE_SELINUX(char *context;)
@@ -852,7 +852,9 @@ typedef struct {
 	unsigned gid;
 	unsigned tty_major,tty_minor;
 	char state[4];
-	/* basename of executable in exec(2), read from /proc/N/stat */
+	/* basename of executable in exec(2), read from /proc/N/stat
+	 * (if executable is symlink or script, it is NOT replaced
+	 * by link target or interpreter name) */
 	char comm[COMM_LEN];
 	/* user/group? - use passwd/group parsing functions */
 } procps_status_t;
@@ -863,9 +865,9 @@ enum {
 	PSSCAN_SID      = 1 << 3,
 	PSSCAN_UIDGID   = 1 << 4,
 	PSSCAN_COMM     = 1 << 5,
-	PSSCAN_CMD      = 1 << 6,
+	/* PSSCAN_CMD      = 1 << 6, - use read_cmdline instead */
 	PSSCAN_ARGV0    = 1 << 7,
-	PSSCAN_EXE      = 1 << 8, /* not implemented yet */
+	/* PSSCAN_EXE      = 1 << 8, - not implemented */
 	PSSCAN_STATE    = 1 << 9,
 	PSSCAN_VSZ      = 1 << 10,
 	PSSCAN_RSS      = 1 << 11,
@@ -883,6 +885,9 @@ enum {
 procps_status_t* alloc_procps_scan(int flags);
 void free_procps_scan(procps_status_t* sp);
 procps_status_t* procps_scan(procps_status_t* sp, int flags);
+/* Format cmdline (up to col chars) into char buf[col+1] */
+/* Puts [comm] if cmdline is empty (-> process is a kernel thread) */
+void read_cmdline(char *buf, int col, unsigned pid, const char *comm);
 pid_t *find_pid_by_name(const char* procName);
 pid_t *pidlist_reverse(pid_t *pidList);
 
diff --git a/libbb/procps.c b/libbb/procps.c
index 8413ce8a1..1987e98fd 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -102,7 +102,7 @@ procps_status_t *alloc_procps_scan(int flags)
 void free_procps_scan(procps_status_t* sp)
 {
 	closedir(sp->dir);
-	free(sp->cmd);
+	free(sp->argv0);
 	USE_SELINUX(free(sp->context);)
 	free(sp);
 }
@@ -266,6 +266,7 @@ procps_status_t *procps_scan(procps_status_t* sp, int flags)
 
 		}
 
+#if 0 /* PSSCAN_CMD is not used */
 		if (flags & (PSSCAN_CMD|PSSCAN_ARGV0)) {
 			if (sp->argv0) {
 				free(sp->argv0);
@@ -292,10 +293,42 @@ procps_status_t *procps_scan(procps_status_t* sp, int flags)
 				sp->cmd = xstrdup(buf);
 			}
 		}
+#else
+		if (flags & PSSCAN_ARGV0) {
+			if (sp->argv0) {
+				free(sp->argv0);
+				sp->argv0 = NULL;
+			}
+			strcpy(filename_tail, "/cmdline");
+			n = read_to_buf(filename, buf);
+			if (n <= 0)
+				break;
+			if (flags & PSSCAN_ARGV0)
+				sp->argv0 = xstrdup(buf);
+		}
+#endif
 		break;
 	}
 	return sp;
 }
+
+void read_cmdline(char *buf, int col, unsigned pid, const char *comm)
+{
+	ssize_t sz;
+	char filename[sizeof("/proc//cmdline") + sizeof(int)*3];
+
+	sprintf(filename, "/proc/%u/cmdline", pid);
+	sz = open_read_close(filename, buf, col);
+	if (sz > 0) {
+		buf[sz] = '\0';
+		while (--sz >= 0)
+			if ((unsigned char)(buf[sz]) < ' ')
+				buf[sz] = ' ';
+	} else {
+		snprintf(buf, col, "[%s]", comm);
+	}
+}
+
 /* from kernel:
 	//             pid comm S ppid pgid sid tty_nr tty_pgrp flg
 	sprintf(buffer,"%d (%s) %c %d  %d   %d  %d     %d       %lu %lu \
diff --git a/libbb/read.c b/libbb/read.c
index 05bf754e0..502d407c4 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -124,11 +124,11 @@ char *xmalloc_reads(int fd, char *buf)
 
 ssize_t read_close(int fd, void *buf, size_t size)
 {
-	int e;
+	/*int e;*/
 	size = full_read(fd, buf, size);
-	e = errno;
+	/*e = errno;*/
 	close(fd);
-	errno = e;
+	/*errno = e;*/
 	return size;
 }
 
diff --git a/procps/ps.c b/procps/ps.c
index 003e8eacd..c6bffc60d 100644
--- a/procps/ps.c
+++ b/procps/ps.c
@@ -27,11 +27,7 @@ static void func_comm(char *buf, int size, const procps_status_t *ps)
 
 static void func_args(char *buf, int size, const procps_status_t *ps)
 {
-	buf[0] = '\0';
-	if (ps->cmd)
-		safe_strncpy(buf, ps->cmd, size+1);
-	else if (size >= 2)
-		sprintf(buf, "[%.*s]", size-2, ps->comm);
+	read_cmdline(buf, size, ps->pid, ps->comm);
 }
 
 static void func_pid(char *buf, int size, const procps_status_t *ps)
@@ -112,25 +108,25 @@ typedef struct {
 
 static const ps_out_t out_spec[] = {
 // Mandated by POSIX:
-	{ 8                  , "user"  ,"USER"   ,func_user  ,PSSCAN_UIDGID          },
-	{ 16                 , "comm"  ,"COMMAND",func_comm  ,PSSCAN_COMM            },
-	{ 256                , "args"  ,"COMMAND",func_args  ,PSSCAN_CMD|PSSCAN_COMM },
-	{ 5                  , "pid"   ,"PID"    ,func_pid   ,PSSCAN_PID             },
-	{ 5                  , "ppid"  ,"PPID"   ,func_ppid  ,PSSCAN_PPID            },
-	{ 5                  , "pgid"  ,"PGID"   ,func_pgid  ,PSSCAN_PGID            },
-//	{ sizeof("ELAPSED")-1, "etime" ,"ELAPSED",func_etime ,PSSCAN_                },
-//	{ sizeof("GROUP"  )-1, "group" ,"GROUP"  ,func_group ,PSSCAN_UIDGID          },
-//	{ sizeof("NI"     )-1, "nice"  ,"NI"     ,func_nice  ,PSSCAN_                },
-//	{ sizeof("%CPU"   )-1, "pcpu"  ,"%CPU"   ,func_pcpu  ,PSSCAN_                },
-//	{ sizeof("RGROUP" )-1, "rgroup","RGROUP" ,func_rgroup,PSSCAN_UIDGID          },
-//	{ sizeof("RUSER"  )-1, "ruser" ,"RUSER"  ,func_ruser ,PSSCAN_UIDGID          },
-//	{ sizeof("TIME"   )-1, "time"  ,"TIME"   ,func_time  ,PSSCAN_                },
-	{ 6                  , "tty"   ,"TT"     ,func_tty   ,PSSCAN_TTY             },
-	{ 4                  , "vsz"   ,"VSZ"    ,func_vsz   ,PSSCAN_VSZ             },
+	{ 8                  , "user"  ,"USER"   ,func_user  ,PSSCAN_UIDGID  },
+	{ 16                 , "comm"  ,"COMMAND",func_comm  ,PSSCAN_COMM    },
+	{ 256                , "args"  ,"COMMAND",func_args  ,PSSCAN_COMM    },
+	{ 5                  , "pid"   ,"PID"    ,func_pid   ,PSSCAN_PID     },
+	{ 5                  , "ppid"  ,"PPID"   ,func_ppid  ,PSSCAN_PPID    },
+	{ 5                  , "pgid"  ,"PGID"   ,func_pgid  ,PSSCAN_PGID    },
+//	{ sizeof("ELAPSED")-1, "etime" ,"ELAPSED",func_etime ,PSSCAN_        },
+//	{ sizeof("GROUP"  )-1, "group" ,"GROUP"  ,func_group ,PSSCAN_UIDGID  },
+//	{ sizeof("NI"     )-1, "nice"  ,"NI"     ,func_nice  ,PSSCAN_        },
+//	{ sizeof("%CPU"   )-1, "pcpu"  ,"%CPU"   ,func_pcpu  ,PSSCAN_        },
+//	{ sizeof("RGROUP" )-1, "rgroup","RGROUP" ,func_rgroup,PSSCAN_UIDGID  },
+//	{ sizeof("RUSER"  )-1, "ruser" ,"RUSER"  ,func_ruser ,PSSCAN_UIDGID  },
+//	{ sizeof("TIME"   )-1, "time"  ,"TIME"   ,func_time  ,PSSCAN_        },
+	{ 6                  , "tty"   ,"TT"     ,func_tty   ,PSSCAN_TTY     },
+	{ 4                  , "vsz"   ,"VSZ"    ,func_vsz   ,PSSCAN_VSZ     },
 // Not mandated by POSIX, but useful:
-	{ 4                  , "rss"   ,"RSS"    ,func_rss   ,PSSCAN_RSS             },
+	{ 4                  , "rss"   ,"RSS"    ,func_rss   ,PSSCAN_RSS     },
 #if ENABLE_SELINUX
-	{ 35                 , "label" ,"LABEL"  ,func_label ,PSSCAN_CONTEXT         },
+	{ 35                 , "label" ,"LABEL"  ,func_label ,PSSCAN_CONTEXT },
 #endif
 };
 
@@ -386,10 +382,9 @@ int ps_main(int argc, char **argv)
 			| PSSCAN_UIDGID
 			| PSSCAN_STATE
 			| PSSCAN_VSZ
-			| PSSCAN_CMD
+			| PSSCAN_COMM
 			| use_selinux
 	))) {
-		char *namecmd = p->cmd;
 #if ENABLE_SELINUX
 		if (use_selinux) {
 			len = printf("%5u %-32s %s ",
@@ -408,21 +403,11 @@ int ps_main(int argc, char **argv)
 					p->pid, user, p->vsz, p->state);
 		}
 
-		i = terminal_width-len;
-
-		if (namecmd && namecmd[0]) {
-			if (i < 0)
-				i = 0;
-			if (strlen(namecmd) > (size_t)i)
-				namecmd[i] = '\0';
-			puts(namecmd);
-		} else {
-			namecmd = p->comm;
-			if (i < 2)
-				i = 2;
-			if (strlen(namecmd) > ((size_t)i-2))
-				namecmd[i-2] = '\0';
-			printf("[%s]\n", namecmd);
+		{
+			char sz = terminal_width - len;
+			char buf[sz + 1];
+			read_cmdline(buf, sz, p->pid, p->comm);
+			puts(buf);
 		}
 	}
 	if (ENABLE_FEATURE_CLEAN_UP)
diff --git a/procps/top.c b/procps/top.c
index 136f1404a..a37a0d07f 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -40,11 +40,10 @@ typedef struct top_status_t {
 	unsigned pid, ppid;
 	unsigned uid;
 	char state[4];
-/* TODO: read /proc/$PID/cmdline only for processes which are displayed */
-	char cmd[64];
+	char comm[COMM_LEN];
 } top_status_t;
 
-typedef struct jiffy_counts_t{
+typedef struct jiffy_counts_t {
 	unsigned long long usr,nic,sys,idle,iowait,irq,softirq,steal;
 	unsigned long long total;
 	unsigned long long busy;
@@ -421,7 +420,7 @@ static void display_status(int count, int scr_width)
 
 	/* Ok, all prelim data is ready, go thru the list */
 	while (count-- > 0) {
-		int col = scr_width+1;
+		int col = scr_width;
 		CALC_STAT(pmem, (s->vsz*pmem_scale + pmem_half) >> pmem_shift);
 #if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
 		CALC_STAT(pcpu, (s->pcpu*pcpu_scale + pcpu_half) >> pcpu_shift);
@@ -444,8 +443,11 @@ static void display_status(int count, int scr_width)
 				, SHOW_STAT(pcpu)
 #endif
 		);
-		if (col > 0)
-			printf("%.*s", col, s->cmd);
+		if (col > 0) {
+			char buf[col + 1];
+			read_cmdline(buf, col, s->pid, s->comm);
+			fputs(buf, stdout);
+		}
 		/* printf(" %d/%d %lld/%lld", s->pcpu, total_pcpu,
 			jif.busy - prev_jif.busy, jif.total - prev_jif.total); */
 		s++;
@@ -560,12 +562,11 @@ int top_main(int argc, char **argv)
 				| PSSCAN_UTIME
 				| PSSCAN_STATE
 				| PSSCAN_COMM
-				| PSSCAN_CMD
 				| PSSCAN_SID
 				| PSSCAN_UIDGID
 		))) {
 			int n = ntop;
-			top = xrealloc(top, (++ntop)*sizeof(top_status_t));
+			top = xrealloc(top, (++ntop) * sizeof(*top));
 			top[n].pid = p->pid;
 			top[n].ppid = p->ppid;
 			top[n].vsz = p->vsz;
@@ -574,10 +575,7 @@ int top_main(int argc, char **argv)
 #endif
 			top[n].uid = p->uid;
 			strcpy(top[n].state, p->state);
-			if (p->cmd)
-				safe_strncpy(top[n].cmd, p->cmd, sizeof(top[n].cmd));
-			else /* mimic ps */
-				sprintf(top[n].cmd, "[%s]", p->comm);
+			strcpy(top[n].comm, p->comm);
 		}
 		if (ntop == 0) {
 			bb_error_msg_and_die("no process info in /proc");