mirror of
https://github.com/AsahiLinux/u-boot
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54841ab50c
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>
78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
/*
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* (C) Copyright 2005
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* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#include <common.h>
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#include <command.h>
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#undef DEBUG_DISP
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#define DISP_SIZE 8
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#define CWORD_CLEAR 0x80
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#define CLEAR_DELAY (110 * 2)
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int do_display (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
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{
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int i;
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int pos;
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/* Clear display */
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*((volatile char*)(CONFIG_SYS_DISP_CWORD)) = CWORD_CLEAR;
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udelay(1000 * CLEAR_DELAY);
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if (argc < 2)
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return (0);
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for (pos = 0, i = 1; i < argc && pos < DISP_SIZE; i++) {
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char *p = argv[i], c;
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if (i > 1) {
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*((volatile uchar *) (CONFIG_SYS_DISP_CHR_RAM + pos++)) = ' ';
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#ifdef DEBUG_DISP
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putc(' ');
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#endif
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}
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while ((c = *p++) != '\0' && pos < DISP_SIZE) {
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*((volatile uchar *) (CONFIG_SYS_DISP_CHR_RAM + pos++)) = c;
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#ifdef DEBUG_DISP
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putc(c);
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#endif
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}
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}
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#ifdef DEBUG_DISP
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putc('\n');
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#endif
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return (0);
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}
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/***************************************************/
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U_BOOT_CMD(
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display, CONFIG_SYS_MAXARGS, 1, do_display,
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"display string on dot matrix display",
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"[<string>]\n"
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" - with <string> argument: display <string> on dot matrix display\n"
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" - without arguments: clear dot matrix display"
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);
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