bin/146916: [patch] sh(1) uses dumb terminal in single-user mode

[Guy Yur]

>Number:         146916
>Category:       bin
>Synopsis:       [patch] sh(1) uses dumb terminal in single-user mode
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon May 24 11:50:01 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Guy Yur
>Release:        8.0-RELEASE-p2
>Organization:
>Environment:
FreeBSD samwise.localdomain 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #0: Sat Mar 27 00:32:42 IDT 2010     root at samwise.localdomain:/usr/obj/usr/src/sys/SAMWISE  i386
>Description:
1. sh doesn't call setenv() for "TERM" so getenv("TERM") will return NULL
   in single-user mode when used as the first shell.
   libedit el_init() passes "dumb" to ncurses if getenv("TERM") returns NULL.
   "dumb" isn't in /usr/src/etc/termcap.small

2. sh doesn't call el_set(el, EL_TERMINAL, term) when TERM changes.
   so libedit will keep thinking it has a "dumb" terminal.

3. rev 206182 changed 'bin/sh/options.c' to set -o emacs if interactive shell.
   this is done before /.profile can set TERM= in single-user mode
   so el_init() is called without TERM env var
>How-To-Repeat:
create /etc/termcap.small.db taken from /usr/src/etc/termcap.small
it should have cons25 (or xterm on CURRENT)
it should not have a "dumb" entry

in /.profile have
  export TERM=${TERM:-cons25}    # xterm on CURRENT
or any terminal found in /etc/termcap.small.db

boot into single-user mode and use the default /bin/sh
/usr shouldn't be not mounted
or have /usr/share/misc/termcap.db not accessible.

run `set -o emacs`

see
  Cannot read termcap database;
  using dumb terminal settings.
even though /etc/termcap.small.db is readable and cons25/xterm entry exists
>Fix:
looking in NetBSD, /bin/sh calls setenv/unsetenv for "TERM" before el_init()
and calls el_set(el, EL_TERMINAL, term) when TERM changes.

I have made patches using the changes against bin/sh in NetBSD.
Only the TERM support changes are included in the patches.
The patches are against head, svn revision 208452

cd /usr/src/bin/sh
patch < /patch/to/sh.patch

possible fixes to revision 206182 'bin/sh/options.c'
1. add the "dumb" entry to etc/termcap.small to silence el_init()

2. instead of enabling -o emacs in 'bin/sh/options.c',
   create /usr/src/etc/root/dot.shrc with
     set -o emacs
   add to /usr/src/etc/root/dot.profile
     ENV=$HOME/.shrc
     export ENV
   this way -o emacs will be called after /.profile has set a valid TERM

Patch attached with submission follows:

--- histedit.c.orig	2010-05-24 02:43:10.000000000 +0300
+++ histedit.c	2010-05-24 11:55:22.000000000 +0300
@@ -98,6 +98,8 @@
 			/*
 			 * turn editing on
 			 */
+			char *term;
+
 			INTOFF;
 			if (el_in == NULL)
 				el_in = fdopen(0, "r");
@@ -107,6 +109,11 @@
 				el_out = fdopen(2, "w");
 			if (el_in == NULL || el_err == NULL || el_out == NULL)
 				goto bad;
+			term = lookupvar("TERM");
+			if (term)
+				setenv("TERM", term, 1);
+			else
+				unsetenv("TERM");
 			el = el_init(arg0, el_in, el_out, el_err);
 			if (el != NULL) {
 				if (hist)
@@ -160,6 +167,13 @@
 	}
 }
 
+void
+setterm(const char *term)
+{
+	if (el != NULL && term != NULL)
+		el_set(el, EL_TERMINAL, term);
+}
+
 int
 histcmd(int argc, char **argv)
 {
--- myhistedit.h.orig	2010-05-24 02:43:10.000000000 +0300
+++ myhistedit.h	2010-05-24 11:55:45.000000000 +0300
@@ -38,6 +38,7 @@
 
 void histedit(void);
 void sethistsize(const char *);
+void setterm(const char *);
 int histcmd(int, char **);
 int not_fcnumber(const char *);
 int str_to_event(const char *, int);
--- var.c.orig	2010-05-24 02:43:10.000000000 +0300
+++ var.c	2010-05-24 12:03:07.000000000 +0300
@@ -80,6 +80,7 @@
 
 #ifndef NO_HISTORY
 struct var vhistsize;
+struct var vterm;
 #endif
 struct var vifs;
 struct var vmail;
@@ -114,6 +115,10 @@
 	  NULL },
 	{ &vps4,	0,				"PS4=+ ",
 	  NULL },
+#ifndef NO_HISTORY
+	{ &vterm,	VUNSET,				"TERM=",
+	  setterm },
+#endif
 	{ &voptind,	0,				"OPTIND=1",
 	  getoptsreset },
 	{ NULL,	0,				NULL,
--- var.h.orig	2010-05-24 02:43:10.000000000 +0300
+++ var.h	2010-05-24 11:57:07.000000000 +0300
@@ -77,6 +77,7 @@
 extern struct var vps4;
 #ifndef NO_HISTORY
 extern struct var vhistsize;
+extern struct var vterm;
 #endif
 
 /*
@@ -96,6 +97,7 @@
 #define optindval()	(voptind.text + 7)
 #ifndef NO_HISTORY
 #define histsizeval()	(vhistsize.text + 9)
+#define termval()	(vterm.text + 5)
 #endif
 
 #define mpathset()	((vmpath.flags & VUNSET) == 0)


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