Fix our handling of process groups for job control, working around a couple GNO bugs.

*Most significantly, we avoid using setpgid(), because it doesn't work and in fact corrupts the kernel's process group table.
*Also, work around tctpgrp() returning garbage instead of 0 on success.

This adds an implementation of tcsetpgrp that works by reading the process tables to find a process in the appropriate group. This isn't used for the main job control operations, though, since it might be relatively slow.

At this point, basic job control seems to work.

Makefile

@@ -51,7 +51,8 @@ LIBBB_C_SRC = \
 	libbb/s.gethostname.c \
 	libbb/safe.poll.c \
 	libbb/parse.mode.c \
-	libbb/poll.c 
+	libbb/poll.c \
+	libbb/pgrp.c
 
 LIBBB_D_SRC = \
 	libbb/xfuncs.printf.c \

Makefile.gmake

@@ -51,7 +51,8 @@ SRCS = \
 	libbb/mempcpy.c \
 	libbb/vfork.and.run.c \
 	libbb/poll.c \
-	libbb/get.exec.path.c
+	libbb/get.exec.path.c \
+	libbb/pgrp.c
 OBJS = $(SRCS:.c=.o)
 
 INCLUDES = -I include -I shell -I libbb

include/libbb.h

@@ -481,6 +481,8 @@ off_t xlseek(int fd, off_t offset, int whence) FAST_FUNC;
 int xmkstemp(char *template) FAST_FUNC;
 off_t fdlength(int fd) FAST_FUNC;
 
+int tc_set_to_my_pgrp(int fd);
+
 #ifdef __GNO__
 void unsetenv_wrapper(const char *var);
 int putenv_wrapper(char *string);

libbb/pgrp.c

@@ -0,0 +1,56 @@
+#include <unistd.h>
+#include <errno.h>
+#ifdef __GNO__
+# include <gno/gno.h>
+# include <gno/kvm.h>
+#endif
+
+#ifndef __GNO__
+
+int tc_set_to_my_pgrp(int fd)
+{
+	return tcsetpgrp(fd, getpgrp());
+}
+
+#else
+
+int tc_set_to_my_pgrp(int fd)
+{
+	return tctpgrp(fd, getpid());
+}
+
+/* We implement tcsetpgrp by searching the process table for a process
+ * in the right pgrp and calling tctpgrp using that process.
+ */
+int tcsetpgrp(int fd, pid_t pgrp)
+{
+	kvmt *kvm_context;
+	struct pentry *proc_entry;
+	int result = 1;
+
+	kvm_context = kvm_open();
+	if (kvm_context == NULL)
+		return -1;
+		
+	while ((proc_entry = kvmnextproc(kvm_context)) != NULL) {
+		if (proc_entry->pgrp == pgrp) {
+			if (tctpgrp(fd, kvm_context->pid) != -1) {
+				result = 0;
+				break;
+			} else {
+				result = -1;
+			}
+		}
+	}
+	
+	kvm_close(kvm_context);
+	
+	if (result == 1) {	/* if we didn't find a matching process */
+		result = -1;
+		errno = ESRCH;
+	}
+	
+	return result;
+}
+
+#endif

shell/hush.c

@@ -109,6 +109,18 @@
 # define PIPE_BUF 4096  /* amount of buffering in a pipe */
 #endif
 
+#ifdef __GNO__
+# define setpgid setpgid_is_broken_on_gno_206
+/* setpgid is broken in GNO 2.0.6: It doesn't actually change the pgrp for 
+ * the process (but it does update the pgrp reference counts, effectively
+ * corrupting them).  Don't use it.
+ *
+ * Another bug related to pgrp functions:
+ * tctpgrp() and settpgrp() don't set a return value on success, so they
+ * may return random garbage instead of 0.  Hopefully it can't be -1...
+ */
+#endif
+
 //config:config HUSH
 //config:	bool "hush"
 //config:	default y
@@ -1639,12 +1651,7 @@ static void sigexit(int sig)
 		 * Mostly paranoid measure, to prevent infinite SIGTTOU.
 		 */
 		sigprocmask_allsigs(SIG_BLOCK);
-# ifndef __GNO__
 		tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
-# else
-		setpgid(getpid(), G_saved_tty_pgrp);
-		tctpgrp(G_interactive_fd, getpid());
-# endif
 	}
 
 	/* Not a signal, just exit */
@@ -7145,11 +7152,7 @@ static int checkjobs_and_fg_shell(struct pipe *fg_pipe)
 		/* Job finished, move the shell to the foreground */
 		p = getpgrp(); /* our process group id */
 		debug_printf_jobs(("fg'ing ourself: getpgrp()=%d\n", (int)p));
-#ifndef __GNO__
-		tcsetpgrp(G_interactive_fd, p);
-#else
-		tctpgrp(G_interactive_fd, getpid());
-#endif
+		tc_set_to_my_pgrp(G_interactive_fd);
 	}
 	return rcode;
 }
@@ -7531,11 +7534,12 @@ static NOINLINE int run_pipe(struct pipe *pi)
 		} else {
 			pi->alive_cmds++;
 #if ENABLE_HUSH_JOB
+# ifndef __GNO__
 			/* Second and next children need to know pid of first one */
 			if (pi->pgrp < 0)
-# ifndef __GNO__
 				pi->pgrp = command->pid;
 # else
+			if (pi->pgrp != _getpgrp(command->pid))
 				pi->pgrp = _getpgrp(command->pid);
 # endif
 #endif
@@ -7559,37 +7563,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
 	debug_printf_exec(("run_pipe return -1 (%u children started)\n", pi->alive_cmds));
 	return -1;
 }
-	
 
-/* Get a new process group ID and set our pgrp to it. */
-#ifndef __GNO__
-static pid_t new_pgrp(int fdtty)
-{
-	pid_t pgrp = getpid();
-	setpgid(0, pgrp);
-	return pgrp;
-}
-#else
-/* On GNO we can't just use our pid--pgrps have a separate, smaller range
- * and need to be explicitly allocated with tcnewpgrp. */
-static pid_t new_pgrp(int fdtty)
-{
-	int result;
-	
-	result = tcnewpgrp(fdtty);
-	if (result != 0)
-		return -1;
-	
-	settpgrp(fdtty);
-	
-	/* Set tty back to parent's pgrp for now. This may be what we want if
-	 * this job is backgrounded.  Otherwise, we'll re-set it to the new
-	 * pgrp later. */
-	tctpgrp(fdtty, getppid());
-	
-	return getpgrp();
-}
-#endif
 
 #ifdef __ORCAC__
 # pragma databank 1
@@ -7607,20 +7581,41 @@ static void forked_child(void *args_struct)
 	if (G.run_list_level == 1 && G_interactive_fd) {
 		pid_t pgrp;
 		pgrp = (*args->pi_p)->pgrp;
+# ifndef __GNO__
 		if (pgrp < 0) /* true for 1st process only */
-			pgrp = new_pgrp(G_interactive_fd);
+			pgrp = getpid();
 		if (setpgid(0, pgrp) == 0
 		 && (*args->pi_p)->followup != PIPE_BG
 		 && G_saved_tty_pgrp /* we have ctty */
 		) {
 			/* We do it in *every* child, not just first,
 			 * to avoid races */
-# ifndef __GNO__
-			tcsetpgrp(G_interactive_fd, pgrp);
-# else
-			tctpgrp(G_interactive_fd, getpid());
-# endif
+			tc_set_to_my_pgrp(G_interactive_fd);
 		}
+# else
+		if (pgrp < 0) {
+			tcnewpgrp(G_interactive_fd);
+		} else {
+			int i;
+			for (i = 0; i < (*args->pi_p)->num_cmds; i++) {
+				pid_t pid = (*args->pi_p)->cmds[i].pid;
+				if (pid != 0 && _getpgrp(pid) == pgrp && tctpgrp(G_interactive_fd, pid) != -1)
+					goto tty_has_pgrp;
+			}
+			/* If none of the other processes in the pipe has the right pgrp,
+			 * (because they exited or changed their pgrp), allocate a new one. */
+			if (getpgrp() != pgrp)
+				tcnewpgrp(G_interactive_fd);
+		}
+
+ tty_has_pgrp:
+		settpgrp(G_interactive_fd);
+		
+		/* If the terminal shouldn't really be set to the new pgrp 
+		 * (e.g. because the pipe is backgrounded), set it back to the parent. */
+		if ((*args->pi_p)->followup == PIPE_BG || !G_saved_tty_pgrp)
+			tctpgrp(G_interactive_fd, getppid());
+# endif
 	}
 #endif
 	if ((*args->pi_p)->alive_cmds == 0 && (*args->pi_p)->followup == PIPE_BG) {
@@ -8508,7 +8503,7 @@ int hush_main(int argc, char **argv)
 		if (G_saved_tty_pgrp) {
 			/* tcnewpgrp() should generate SIGTTOU if we're not in the
 			 * foreground, having an effect similar to the loop in the
-			 * original code. */
+			 * original code (but I think it actually doesn't). */
 			tcnewpgrp(G_interactive_fd);
 			install_fatal_sighandlers();
 			install_special_sighandlers();
@@ -8694,12 +8689,7 @@ static int FAST_FUNC builtin_exec(char **argv)
 	/* Careful: we can end up here after [v]fork. Do not restore
 	 * tty pgrp then, only top-level shell process does that */
 	if (G_saved_tty_pgrp && getpid() == G.root_pid) {
-#ifndef __GNO__
 		tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
-#else
-		setpgid(getpid(), G_saved_tty_pgrp);
-		tctpgrp(G_interactive_fd, getpid());
-#endif
 	}
 
 	/* TODO: if exec fails, bash does NOT exit! We do.
@@ -9037,7 +9027,7 @@ static int FAST_FUNC builtin_fg_bg(char **argv)
 		 */
 		for (i = 0; i < pi->num_cmds; i++) {
 			pid_t pid = pi->cmds[i].pid;
-			if (pid != 0 && tctpgrp(G_interactive_fd, pid) == 0)
+			if (pid != 0 && tctpgrp(G_interactive_fd, pid) != -1)
 				break;
 		}
 # endif