u-boot/examples/standalone/interrupt.c
Wolfgang Denk 54841ab50c Make sure that argv[] argument pointers are not modified.
The hush shell dynamically allocates (and re-allocates) memory for the
argument strings in the "char *argv[]" argument vector passed to
commands.  Any code that modifies these pointers will cause serious
corruption of the malloc data structures and crash U-Boot, so make
sure the compiler can check that no such modifications are being done
by changing the code into "char * const argv[]".

This modification is the result of debugging a strange crash caused
after adding a new command, which used the following argument
processing code which has been working perfectly fine in all Unix
systems since version 6 - but not so in U-Boot:

int main (int argc, char **argv)
{
	while (--argc > 0 && **++argv == '-') {
/* ====> */	while (*++*argv) {
			switch (**argv) {
			case 'd':
				debug++;
				break;
			...
			default:
				usage ();
			}
		}
	}
	...
}

The line marked "====>" will corrupt the malloc data structures and
usually cause U-Boot to crash when the next command gets executed by
the shell.  With the modification, the compiler will prevent this with
an
	error: increment of read-only location '*argv'

N.B.: The code above can be trivially rewritten like this:

	while (--argc > 0 && **++argv == '-') {
		char *arg = *argv;
		while (*++arg) {
			switch (*arg) {
			...

Signed-off-by: Wolfgang Denk <wd@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>
2010-07-04 23:55:42 +02:00

81 lines
2.1 KiB
C

/*
* (C) Copyright 2006
* Detlev Zundel, DENX Software Engineering, dzu@denx.de.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* 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; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*
* This is a very simple standalone application demonstrating
* catching IRQs on the MPC52xx architecture.
*
* The interrupt to be intercepted can be specified as an argument
* to the application. Specifying nothing will intercept IRQ1 on the
* MPC5200 platform. On the CR825 carrier board from MicroSys this
* maps to the ABORT switch :)
*
* Note that the specified vector is only a logical number specified
* by the respective header file.
*/
#include <common.h>
#include <exports.h>
#include <config.h>
#if defined(CONFIG_MPC5xxx)
#define DFL_IRQ MPC5XXX_IRQ1
#else
#define DFL_IRQ 0
#endif
static void irq_handler (void *arg);
int interrupt (int argc, char * const argv[])
{
int c, irq = -1;
app_startup (argv);
if (argc > 1)
irq = simple_strtoul (argv[1], NULL, 0);
if ((irq < 0) || (irq > NR_IRQS))
irq = DFL_IRQ;
printf ("Installing handler for irq vector %d and doing busy wait\n",
irq);
printf ("Press 'q' to quit\n");
/* Install interrupt handler */
install_hdlr (irq, irq_handler, NULL);
while ((c = getc ()) != 'q') {
printf ("Ok, ok, I am still alive!\n");
}
free_hdlr (irq);
printf ("\nInterrupt handler has been uninstalled\n");
return (0);
}
/*
* Handler for interrupt
*/
static void irq_handler (void *arg)
{
/* just for demonstration */
printf ("+");
}