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linux-next/lib/test_hexdump.c
Jason A. Donenfeld 81895a65ec treewide: use prandom_u32_max() when possible, part 1 
Rather than incurring a division or requesting too many random bytes for
the given range, use the prandom_u32_max() function, which only takes
the minimum required bytes from the RNG and avoids divisions. This was
done mechanically with this coccinelle script:

@basic@
expression E;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
(
- ((T)get_random_u32() % (E))
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
|
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ~PAGE_MASK)
+ prandom_u32_max(PAGE_SIZE)
)

@multi_line@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
identifier RAND;
expression E;
@@

-       RAND = get_random_u32();
        ... when != RAND
-       RAND %= (E);
+       RAND = prandom_u32_max(E);

// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@

        ((T)get_random_u32()@p & (LITERAL))

// Add one to the literal.
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@

value = None
if literal.startswith('0x'):
        value = int(literal, 16)
elif literal[0] in '123456789':
        value = int(literal, 10)
if value is None:
        print("I don't know how to handle %s" % (literal))
        cocci.include_match(False)
elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1:
        print("Skipping 0x%x for cleanup elsewhere" % (value))
        cocci.include_match(False)
elif value & (value + 1) != 0:
        print("Skipping 0x%x because it's not a power of two minus one" % (value))
        cocci.include_match(False)
elif literal.startswith('0x'):
        coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1))
else:
        coccinelle.RESULT = cocci.make_expr("%d" % (value + 1))

// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
expression add_one.RESULT;
identifier FUNC;
@@

-       (FUNC()@p & (LITERAL))
+       prandom_u32_max(RESULT)

@collapse_ret@
type T;
identifier VAR;
expression E;
@@

 {
-       T VAR;
-       VAR = (E);
-       return VAR;
+       return E;
 }

@drop_var@
type T;
identifier VAR;
@@

 {
-       T VAR;
        ... when != VAR
 }

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-10-11 17:42:55 -06:00

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/*
* Test cases for lib/hexdump.c module.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/string.h>
static const unsigned char data_b[] = {
'\xbe', '\x32', '\xdb', '\x7b', '\x0a', '\x18', '\x93', '\xb2', /* 00 - 07 */
'\x70', '\xba', '\xc4', '\x24', '\x7d', '\x83', '\x34', '\x9b', /* 08 - 0f */
'\xa6', '\x9c', '\x31', '\xad', '\x9c', '\x0f', '\xac', '\xe9', /* 10 - 17 */
'\x4c', '\xd1', '\x19', '\x99', '\x43', '\xb1', '\xaf', '\x0c', /* 18 - 1f */
};
static const unsigned char data_a[] = ".2.{....p..$}.4...1.....L...C...";
static const char * const test_data_1[] __initconst = {
"be", "32", "db", "7b", "0a", "18", "93", "b2",
"70", "ba", "c4", "24", "7d", "83", "34", "9b",
"a6", "9c", "31", "ad", "9c", "0f", "ac", "e9",
"4c", "d1", "19", "99", "43", "b1", "af", "0c",
};
static const char * const test_data_2_le[] __initconst = {
"32be", "7bdb", "180a", "b293",
"ba70", "24c4", "837d", "9b34",
"9ca6", "ad31", "0f9c", "e9ac",
"d14c", "9919", "b143", "0caf",
};
static const char * const test_data_2_be[] __initconst = {
"be32", "db7b", "0a18", "93b2",
"70ba", "c424", "7d83", "349b",
"a69c", "31ad", "9c0f", "ace9",
"4cd1", "1999", "43b1", "af0c",
};
static const char * const test_data_4_le[] __initconst = {
"7bdb32be", "b293180a", "24c4ba70", "9b34837d",
"ad319ca6", "e9ac0f9c", "9919d14c", "0cafb143",
};
static const char * const test_data_4_be[] __initconst = {
"be32db7b", "0a1893b2", "70bac424", "7d83349b",
"a69c31ad", "9c0face9", "4cd11999", "43b1af0c",
};
static const char * const test_data_8_le[] __initconst = {
"b293180a7bdb32be", "9b34837d24c4ba70",
"e9ac0f9cad319ca6", "0cafb1439919d14c",
};
static const char * const test_data_8_be[] __initconst = {
"be32db7b0a1893b2", "70bac4247d83349b",
"a69c31ad9c0face9", "4cd1199943b1af0c",
};
#define FILL_CHAR '#'
static unsigned total_tests __initdata;
static unsigned failed_tests __initdata;
static void __init test_hexdump_prepare_test(size_t len, int rowsize,
int groupsize, char *test,
size_t testlen, bool ascii)
{
char *p;
const char * const *result;
size_t l = len;
int gs = groupsize, rs = rowsize;
unsigned int i;
const bool is_be = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
if (rs != 16 && rs != 32)
rs = 16;
if (l > rs)
l = rs;
if (!is_power_of_2(gs) || gs > 8 || (len % gs != 0))
gs = 1;
if (gs == 8)
result = is_be ? test_data_8_be : test_data_8_le;
else if (gs == 4)
result = is_be ? test_data_4_be : test_data_4_le;
else if (gs == 2)
result = is_be ? test_data_2_be : test_data_2_le;
else
result = test_data_1;
/* hex dump */
p = test;
for (i = 0; i < l / gs; i++) {
const char *q = *result++;
size_t amount = strlen(q);
memcpy(p, q, amount);
p += amount;
*p++ = ' ';
}
if (i)
p--;
/* ASCII part */
if (ascii) {
do {
*p++ = ' ';
} while (p < test + rs * 2 + rs / gs + 1);
strncpy(p, data_a, l);
p += l;
}
*p = '\0';
}
#define TEST_HEXDUMP_BUF_SIZE (32 * 3 + 2 + 32 + 1)
static void __init test_hexdump(size_t len, int rowsize, int groupsize,
bool ascii)
{
char test[TEST_HEXDUMP_BUF_SIZE];
char real[TEST_HEXDUMP_BUF_SIZE];
total_tests++;
memset(real, FILL_CHAR, sizeof(real));
hex_dump_to_buffer(data_b, len, rowsize, groupsize, real, sizeof(real),
ascii);
memset(test, FILL_CHAR, sizeof(test));
test_hexdump_prepare_test(len, rowsize, groupsize, test, sizeof(test),
ascii);
if (memcmp(test, real, TEST_HEXDUMP_BUF_SIZE)) {
pr_err("Len: %zu row: %d group: %d\n", len, rowsize, groupsize);
pr_err("Result: '%s'\n", real);
pr_err("Expect: '%s'\n", test);
failed_tests++;
}
}
static void __init test_hexdump_set(int rowsize, bool ascii)
{
size_t d = min_t(size_t, sizeof(data_b), rowsize);
size_t len = prandom_u32_max(d) + 1;
test_hexdump(len, rowsize, 4, ascii);
test_hexdump(len, rowsize, 2, ascii);
test_hexdump(len, rowsize, 8, ascii);
test_hexdump(len, rowsize, 1, ascii);
}
static void __init test_hexdump_overflow(size_t buflen, size_t len,
int rowsize, int groupsize,
bool ascii)
{
char test[TEST_HEXDUMP_BUF_SIZE];
char buf[TEST_HEXDUMP_BUF_SIZE];
int rs = rowsize, gs = groupsize;
int ae, he, e, f, r;
bool a;
total_tests++;
memset(buf, FILL_CHAR, sizeof(buf));
r = hex_dump_to_buffer(data_b, len, rs, gs, buf, buflen, ascii);
/*
* Caller must provide the data length multiple of groupsize. The
* calculations below are made with that assumption in mind.
*/
ae = rs * 2 /* hex */ + rs / gs /* spaces */ + 1 /* space */ + len /* ascii */;
he = (gs * 2 /* hex */ + 1 /* space */) * len / gs - 1 /* no trailing space */;
if (ascii)
e = ae;
else
e = he;
f = min_t(int, e + 1, buflen);
if (buflen) {
test_hexdump_prepare_test(len, rs, gs, test, sizeof(test), ascii);
test[f - 1] = '\0';
}
memset(test + f, FILL_CHAR, sizeof(test) - f);
a = r == e && !memcmp(test, buf, TEST_HEXDUMP_BUF_SIZE);
buf[sizeof(buf) - 1] = '\0';
if (!a) {
pr_err("Len: %zu buflen: %zu strlen: %zu\n",
len, buflen, strnlen(buf, sizeof(buf)));
pr_err("Result: %d '%s'\n", r, buf);
pr_err("Expect: %d '%s'\n", e, test);
failed_tests++;
}
}
static void __init test_hexdump_overflow_set(size_t buflen, bool ascii)
{
unsigned int i = 0;
int rs = (prandom_u32_max(2) + 1) * 16;
do {
int gs = 1 << i;
size_t len = prandom_u32_max(rs) + gs;
test_hexdump_overflow(buflen, rounddown(len, gs), rs, gs, ascii);
} while (i++ < 3);
}
static int __init test_hexdump_init(void)
{
unsigned int i;
int rowsize;
rowsize = (prandom_u32_max(2) + 1) * 16;
for (i = 0; i < 16; i++)
test_hexdump_set(rowsize, false);
rowsize = (prandom_u32_max(2) + 1) * 16;
for (i = 0; i < 16; i++)
test_hexdump_set(rowsize, true);
for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
test_hexdump_overflow_set(i, false);
for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
test_hexdump_overflow_set(i, true);
if (failed_tests == 0)
pr_info("all %u tests passed\n", total_tests);
else
pr_err("failed %u out of %u tests\n", failed_tests, total_tests);
return failed_tests ? -EINVAL : 0;
}
module_init(test_hexdump_init);
static void __exit test_hexdump_exit(void)
{
/* do nothing */
}
module_exit(test_hexdump_exit);
MODULE_AUTHOR("Andy Shevchenko <andriy.shevchenko@linux.intel.com>");
MODULE_LICENSE("Dual BSD/GPL");
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