test_printf: test printf family at runtime

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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Martin Kletzander <mkletzan@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 366 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1d1521c26302..16bf3bc25e3e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1686,6 +1686,9 @@ 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 8de3b012eac7..7f1de26613d2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -42,6 +42,7 @@ 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 ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/test_printf.c b/lib/test_printf.c
new file mode 100644
index 000000000000..c5a666af9ba5
--- /dev/null
+++ b/lib/test_printf.c
@@ -0,0 +1,362 @@
+/*
+ * Test cases for printf facility.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include <linux/socket.h>
+#include <linux/in.h>
+
+#define BUF_SIZE 256
+#define FILL_CHAR '$'
+
+#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("vsnprintf(buf, %d, \"%s\", ...) returned %d, expected %d\n",
+                        bufsize, fmt, ret, elen);
+                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)
+{
+        /* Work around annoying "warning: zero-length gnu_printf format string". */
+        char nul = '\0';
+
+        test("", &nul);
+        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 precision 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 failed_tests ? -EINVAL : 0;
+}
+
+module_init(test_printf_init);
+
+MODULE_AUTHOR("Rasmus Villemoes <linux@rasmusvillemoes.dk>");
+MODULE_LICENSE("GPL");