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Subject[PATCH 4/4] test_printf: test printf family at runtime
Date
This adds a simple module for testing the kernel's printf
facilities. Previously, some %p extensions have caused a wrong return
value in case the entire output didn't fit and/or been unusable in
kasprintf(). This should help catch such issues. Also, it should help
ensure that changes to the formatting algorithms don't break anything.

I'm not sure if we have a struct dentry or struct file lying around at
boot time or if we can fake one, but most %p extensions should be
testable, as should the ordinary number and string formatting.

The nature of vararg functions means we can't use a more conventional
table-driven approach.

For now, this is mostly a skeleton; contributions are very
welcome. Some tests are/will be slightly annoying to write, since the
expected output depends on stuff like CONFIG_*, sizeof(long), runtime
values etc.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
lib/Kconfig.debug | 3 +
lib/Makefile | 1 +
lib/test_printf.c | 364 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 368 insertions(+)
create mode 100644 lib/test_printf.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ab76b99adc85..c23fc42dc659 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1685,6 +1685,9 @@ config TEST_STRING_HELPERS
config TEST_KSTRTOX
tristate "Test kstrto*() family of functions at runtime"

+config TEST_PRINTF
+ tristate "Test printf() family of functions at runtime"
+
config TEST_RHASHTABLE
tristate "Perform selftest on resizable hash table"
default n
diff --git a/lib/Makefile b/lib/Makefile
index 13a7c6ae3fec..775de427ea92 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o
obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
+obj-$(CONFIG_TEST_PRINTF) += test_printf.o

ifeq ($(CONFIG_DEBUG_KOBJECT),y)
CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/test_printf.c b/lib/test_printf.c
new file mode 100644
index 000000000000..d9a2741c2909
--- /dev/null
+++ b/lib/test_printf.c
@@ -0,0 +1,364 @@
+/*
+ * Test cases for printf facility.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include <linux/socket.h>
+#include <linux/in.h>
+
+#define BUF_SIZE 256
+#define FILL_CHAR '$'
+
+#define PTR1 ((void*)0x01234567)
+#define PTR2 ((void*)(long)(int)0xfedcba98)
+
+#if BITS_PER_LONG == 64
+#define PTR1_ZEROES "000000000"
+#define PTR1_SPACES " "
+#define PTR1_STR "1234567"
+#define PTR2_STR "fffffffffedcba98"
+#define PTR_WIDTH 16
+#else
+#define PTR1_ZEROES "0"
+#define PTR1_SPACES " "
+#define PTR1_STR "1234567"
+#define PTR2_STR "fedcba98"
+#define PTR_WIDTH 8
+#endif
+#define PTR_WIDTH_STR stringify(PTR_WIDTH)
+
+static unsigned total_tests __initdata;
+static unsigned failed_tests __initdata;
+static char *test_buffer __initdata;
+
+static int __printf(4, 0) __init
+do_test(int bufsize, const char *expect, int elen,
+ const char *fmt, va_list ap)
+{
+ va_list aq;
+ int ret, written;
+
+ total_tests++;
+
+ memset(test_buffer, FILL_CHAR, BUF_SIZE);
+ va_copy(aq, ap);
+ ret = vsnprintf(test_buffer, bufsize, fmt, aq);
+ va_end(aq);
+
+ if (ret != elen) {
+ pr_warn("bad return value, expected %d, got %d, format was '%s'\n",
+ elen, ret, fmt);
+ return 1;
+ }
+
+ if (!bufsize) {
+ if (memchr_inv(test_buffer, FILL_CHAR, BUF_SIZE)) {
+ pr_warn("vsnprintf(buf, 0, \"%s\", ...) wrote to buffer\n",
+ fmt);
+ return 1;
+ }
+ return 0;
+ }
+
+ written = min(bufsize-1, elen);
+ if (test_buffer[written]) {
+ pr_warn("vsnprintf(buf, %d, \"%s\", ...) did not nul-terminate buffer\n",
+ bufsize, fmt);
+ return 1;
+ }
+
+ if (memcmp(test_buffer, expect, written)) {
+ pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote '%s', expected '%.*s'\n",
+ bufsize, fmt, test_buffer, written, expect);
+ return 1;
+ }
+ return 0;
+}
+
+
+static void __printf(3, 4) __init
+__test(const char *expect, int elen, const char *fmt, ...)
+{
+ va_list ap;
+ int rand;
+ char *p;
+
+ BUG_ON(elen >= BUF_SIZE);
+
+ va_start(ap, fmt);
+
+ /*
+ * Every fmt+args is subjected to four tests: Three where we
+ * tell vsnprintf varying buffer sizes (plenty, not quite
+ * enough and 0), and then we also test that kvasprintf would
+ * be able to print it as expected.
+ */
+ failed_tests += do_test(BUF_SIZE, expect, elen, fmt, ap);
+ rand = 1 + prandom_u32_max(elen+1);
+ /* Since elen < BUF_SIZE, we have 1 <= rand <= BUF_SIZE. */
+ failed_tests += do_test(rand, expect, elen, fmt, ap);
+ failed_tests += do_test(0, expect, elen, fmt, ap);
+
+ p = kvasprintf(GFP_KERNEL, fmt, ap);
+ if (p) {
+ if (memcmp(p, expect, elen+1)) {
+ pr_warn("kvasprintf(..., \"%s\", ...) returned '%s', expected '%s'\n",
+ fmt, p, expect);
+ failed_tests++;
+ }
+ kfree(p);
+ }
+ va_end(ap);
+}
+
+#define test(expect, fmt, ...) \
+ __test(expect, strlen(expect), fmt, ##__VA_ARGS__)
+
+
+static void __init
+test_basic(void)
+{
+ test("", "");
+ test("100%", "100%%");
+ test("xxx%yyy", "xxx%cyyy", '%');
+ __test("xxx\0yyy", 7, "xxx%cyyy", '\0');
+}
+
+static void __init
+test_number(void)
+{
+ test("0x1234abcd ", "%#-12x", 0x1234abcd);
+ test(" 0x1234abcd", "%#12x", 0x1234abcd);
+ test("0|001| 12|+123| 1234|-123|-1234", "%d|%03d|%3d|%+d|% d|%+d|% d", 0, 1, 12, 123, 1234, -123, -1234);
+}
+
+static void __init
+test_string(void)
+{
+ test("", "%s%.0s", "", "123");
+ test("ABCD|abc|123", "%s|%.3s|%.*s", "ABCD", "abcdef", 3, "123456");
+ test("1 | 2|3 | 4|5 ", "%-3s|%3s|%-*s|%*s|%*s", "1", "2", 3, "3", 3, "4", -3, "5");
+ /*
+ * POSIX and C99 say that a missing precision should be
+ * treated as a precision of 0. However, the kernel's printf
+ * implementation treats this case as if the . wasn't
+ * present. Let's add a test case documenting the current
+ * behaviour; should anyone ever feel the need to follow the
+ * standards more closely, this can be revisited.
+ */
+ test("a||", "%.s|%.0s|%.*s", "a", "b", 0, "c");
+ test("a | | ", "%-3.s|%-3.0s|%-3.*s", "a", "b", 0, "c");
+}
+
+
+static void __init
+plain(void)
+{
+ test(PTR1_ZEROES PTR1_STR " " PTR2_STR, "%p %p", PTR1, PTR2);
+ /*
+ * The field width is overloaded for some %p extensions to
+ * pass another piece of information. For plain pointers, the
+ * behaviour is slightly odd: One cannot pass either the 0
+ * flag nor a precition to %p without gcc complaining, and if
+ * one explicitly gives a field width, the number is no longer
+ * zero-padded.
+ */
+ test("|" PTR1_STR PTR1_SPACES " | " PTR1_SPACES PTR1_STR "|",
+ "|%-*p|%*p|", PTR_WIDTH+2, PTR1, PTR_WIDTH+2, PTR1);
+ test("|" PTR2_STR " | " PTR2_STR "|",
+ "|%-*p|%*p|", PTR_WIDTH+2, PTR2, PTR_WIDTH+2, PTR2);
+
+ /*
+ * Unrecognized %p extensions are treated as plain %p, but the
+ * alphanumeric suffix is ignored (that is, does not occur in
+ * the output.)
+ */
+ test("|"PTR1_ZEROES PTR1_STR"|", "|%p0y|", PTR1);
+ test("|"PTR2_STR"|", "|%p0y|", PTR2);
+}
+
+static void __init
+symbol_ptr(void)
+{
+}
+
+static void __init
+kernel_ptr(void)
+{
+}
+
+static void __init
+struct_resource(void)
+{
+}
+
+static void __init
+addr(void)
+{
+}
+
+static void __init
+escaped_str(void)
+{
+}
+
+static void __init
+hex_string(void)
+{
+ const char buf[3] = {0xc0, 0xff, 0xee};
+
+ test("c0 ff ee|c0:ff:ee|c0-ff-ee|c0ffee",
+ "%3ph|%3phC|%3phD|%3phN", buf, buf, buf, buf);
+ test("c0 ff ee|c0:ff:ee|c0-ff-ee|c0ffee",
+ "%*ph|%*phC|%*phD|%*phN", 3, buf, 3, buf, 3, buf, 3, buf);
+}
+
+static void __init
+mac(void)
+{
+ const u8 addr[6] = {0x2d, 0x48, 0xd6, 0xfc, 0x7a, 0x05};
+
+ test("2d:48:d6:fc:7a:05", "%pM", addr);
+ test("05:7a:fc:d6:48:2d", "%pMR", addr);
+ test("2d-48-d6-fc-7a-05", "%pMF", addr);
+ test("2d48d6fc7a05", "%pm", addr);
+ test("057afcd6482d", "%pmR", addr);
+}
+
+static void __init
+ip4(void)
+{
+ struct sockaddr_in sa;
+
+ sa.sin_family = AF_INET;
+ sa.sin_port = cpu_to_be16(12345);
+ sa.sin_addr.s_addr = cpu_to_be32(0x7f000001);
+
+ test("127.000.000.001|127.0.0.1", "%pi4|%pI4", &sa.sin_addr, &sa.sin_addr);
+ test("127.000.000.001|127.0.0.1", "%piS|%pIS", &sa, &sa);
+ sa.sin_addr.s_addr = cpu_to_be32(0x01020304);
+ test("001.002.003.004:12345|1.2.3.4:12345", "%piSp|%pISp", &sa, &sa);
+}
+
+static void __init
+ip6(void)
+{
+}
+
+static void __init
+ip(void)
+{
+ ip4();
+ ip6();
+}
+
+static void __init
+uuid(void)
+{
+ const char uuid[16] = {0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7,
+ 0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf};
+
+ test("00010203-0405-0607-0809-0a0b0c0d0e0f", "%pUb", uuid);
+ test("00010203-0405-0607-0809-0A0B0C0D0E0F", "%pUB", uuid);
+ test("03020100-0504-0706-0809-0a0b0c0d0e0f", "%pUl", uuid);
+ test("03020100-0504-0706-0809-0A0B0C0D0E0F", "%pUL", uuid);
+}
+
+static void __init
+dentry(void)
+{
+}
+
+static void __init
+struct_va_format(void)
+{
+}
+
+static void __init
+struct_clk(void)
+{
+}
+
+static void __init
+bitmap(void)
+{
+ DECLARE_BITMAP(bits, 20);
+ const int primes[] = {2,3,5,7,11,13,17,19};
+ int i;
+
+ bitmap_zero(bits, 20);
+ test("00000|00000", "%20pb|%*pb", bits, 20, bits);
+ test("|", "%20pbl|%*pbl", bits, 20, bits);
+
+ for (i = 0; i < ARRAY_SIZE(primes); ++i)
+ set_bit(primes[i], bits);
+ test("a28ac|a28ac", "%20pb|%*pb", bits, 20, bits);
+ test("2-3,5,7,11,13,17,19|2-3,5,7,11,13,17,19", "%20pbl|%*pbl", bits, 20, bits);
+
+ bitmap_fill(bits, 20);
+ test("fffff|fffff", "%20pb|%*pb", bits, 20, bits);
+ test("0-19|0-19", "%20pbl|%*pbl", bits, 20, bits);
+}
+
+static void __init
+netdev_features(void)
+{
+}
+
+
+static void __init
+test_pointer(void)
+{
+ plain();
+ symbol_ptr();
+ kernel_ptr();
+ struct_resource();
+ addr();
+ escaped_str();
+ hex_string();
+ mac();
+ ip();
+ uuid();
+ dentry();
+ struct_va_format();
+ struct_clk();
+ bitmap();
+ netdev_features();
+}
+
+static int __init
+test_printf_init(void)
+{
+ test_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
+ if (!test_buffer)
+ return -ENOMEM;
+
+ test_basic();
+ test_number();
+ test_string();
+ test_pointer();
+
+ kfree(test_buffer);
+
+ if (failed_tests == 0)
+ pr_info("all %u tests passed\n", total_tests);
+ else
+ pr_warn("failed %u out of %u tests\n", failed_tests, total_tests);
+
+ return 0;
+}
+
+module_init(test_printf_init);
+
+
+MODULE_AUTHOR("Rasmus Villemoes <linux@rasmusvillemoes.dk>");
+MODULE_LICENSE("GPL");
--
2.1.3


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