Syslinux - Feb 2009 - [PATCH] cmd.c32: new module to just execute a command

Trivial module to execute an arbitrary command.
---
 com32/modules/Makefile |    2 +-
 com32/modules/cmd.c    |   42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletions(-)
 create mode 100644 com32/modules/cmd.c

diff --git a/com32/modules/Makefile b/com32/modules/Makefile
index 2739a39..930e89b 100644
--- a/com32/modules/Makefile
+++ b/com32/modules/Makefile
@@ -20,7 +20,7 @@ include ../MCONFIG
 MODULES	  = chain.c32 config.c32 ethersel.c32 mboot.c32 dmitest.c32 \
 	    cpuidtest.c32 \
 	    pcitest.c32 elf.c32 linux.c32 reboot.c32 pmload.c32 meminfo.c32 \
-	    sdi.c32 sanboot.c32 ifcpu64.c32 vesainfo.c32 kbdmap.c32
+	    sdi.c32 sanboot.c32 ifcpu64.c32 vesainfo.c32 kbdmap.c32 cmd.c32
 
 TESTFILES  
diff --git a/com32/modules/cmd.c b/com32/modules/cmd.c
new file mode 100644
index 0000000..f0b0a96
--- /dev/null
+++ b/com32/modules/cmd.c
@@ -0,0 +1,42 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2008 Michael Brown - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ *   Boston MA 02110-1301, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * cmd.c
+ *
+ * Execute arbitrary commands
+ */
+
+#include <string.h>
+#include <alloca.h>
+#include <console.h>
+#include <com32.h>
+
+int main(int argc, const char *argv[])
+{
+  size_t len = 0;
+  char *cmd;
+  char *tmp;
+  int i;
+
+  openconsole(&dev_stdcon_r, &dev_stdcon_w);
+
+  for (i = 1; i < argc; i++)
+    len += strlen(argv[i]) + 1;
+
+  tmp = cmd = alloca(len);
+
+  for (i = 1; i < argc; i++)
+    tmp += sprintf(tmp, "%s%s", argv[i], (i == argc-1) ? ""
: " ");
+
+  syslinux_run_command(cmd);
+}
-- 
1.5.4.3

On Mon, Feb 16, 2009 at 3:49 AM, Michael Brown <mcb30 at etherboot.org>
wrote:
> Trivial module to execute an arbitrary command.
Similar in function to the alias module I created back in October.
The key differences I notice are that yours appears simpler, mine
could also be tested as a Linux binary, yours uses sprintf versus mine
using memcpy and mine would definitely not pass a command string that
was too long to syslinux_run_command().  I'm not sure if it's even
theoretically possible to even do so though.  It's probably an
unnecessary but paranoid check.

I originally created mine because I often had multiple labels doing
similar tasks with either no or minor variations (short name vs long
name; main vs add an additional parameter) and there's no way for one
label to call another (as far as I could tell).

Including something that provides this functionality into Syslinux
would probably provide benefit for anyone that has multiple similar
labels.

-- 
-Gene

"No one ever says, 'I can't read that ASCII E-mail you sent
me.'"

On Monday 16 February 2009 14:45:36 Gene Cumm wrote:
> On Mon, Feb 16, 2009 at 3:49 AM, Michael Brown <mcb30 at
etherboot.org> wrote:
> > Trivial module to execute an arbitrary command.
>
> Similar in function to the alias module I created back in October.
> The key differences I notice are that yours appears simpler, mine
> could also be tested as a Linux binary, yours uses sprintf versus mine
> using memcpy and mine would definitely not pass a command string that
> was too long to syslinux_run_command().
Is there an upper limit on the length of command strings?

Michael

Michael Brown wrote:
> On Monday 16 February 2009 14:45:36 Gene Cumm wrote:
>> On Mon, Feb 16, 2009 at 3:49 AM, Michael Brown <mcb30 at
etherboot.org> wrote:
>> > Trivial module to execute an arbitrary command.
>>
>> Similar in function to the alias module I created back in October.
>> The key differences I notice are that yours appears simpler, mine
>> could also be tested as a Linux binary, yours uses sprintf versus mine
>> using memcpy and mine would definitely not pass a command string that
>> was too long to syslinux_run_command().
> 
> Is there an upper limit on the length of command strings?
syslinux_run_command() uses INT 22h AX=0003h (com32/lib/syslinux/run_command.c)
which copies the command line from ES:BX to "command_line"
(core/comboot.inc).

parseconfig.inc:command_line    resb max_cmd_len+2      ; Command line buffer
config.inc:max_cmd_len  equ 2047                ; Must be &3; 2047 is the
kernel limit

- Sebastian