mirror of
https://github.com/brain-hackers/u-boot-brain
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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>
48 lines
956 B
C
48 lines
956 B
C
/*
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* cmd_strings.c - just like `strings` command
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*
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* Copyright (c) 2008 Analog Devices Inc.
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*
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* Licensed under the GPL-2 or later.
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*/
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#include <config.h>
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#include <common.h>
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#include <command.h>
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static char *start_addr, *last_addr;
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int do_strings(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
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{
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if (argc == 1) {
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cmd_usage(cmdtp);
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return 1;
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}
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if ((flag & CMD_FLAG_REPEAT) == 0) {
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start_addr = (char *)simple_strtoul(argv[1], NULL, 16);
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if (argc > 2)
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last_addr = (char *)simple_strtoul(argv[2], NULL, 16);
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else
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last_addr = (char *)-1;
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}
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char *addr = start_addr;
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do {
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puts(addr);
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puts("\n");
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addr += strlen(addr) + 1;
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} while (addr[0] && addr < last_addr);
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last_addr = addr + (last_addr - start_addr);
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start_addr = addr;
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return 0;
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}
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U_BOOT_CMD(strings, 3, 1, do_strings,
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"display strings",
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"<addr> [byte count]\n"
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" - display strings at <addr> for at least [byte count] or first double NUL"
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);
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