linux-kernel - [PATCH v2] lib/test_printf.c: call wait_for_random

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Date:   Wed, 13 Jun 2018 11:29:19 +0200
From:   Thierry Escande <thierry.escande@...aro.org>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Petr Mladek <pmladek@...e.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Tobin C . Harding" <me@...in.cc>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] lib/test_printf.c: call wait_for_random_bytes() before plain %p tests

If the test_printf module is loaded before the crng is initialized, the
plain 'p' tests will fail because the printed address will not be hashed
and the buffer will contain "(ptrval)" instead.
Since we cannot wait for the crng to be initialized for an undefined
time, both plain 'p' tests now accept the string "(ptrval)" as a valid
result and print a warning message.

Signed-off-by: Thierry Escande <thierry.escande@...aro.org>

---

Change in v2:
- Remove wait_for_random_bytes() usage
- Removed Acked-by from Tobin as the proposed solution is not the same
  anymore.

 lib/test_printf.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/lib/test_printf.c b/lib/test_printf.c
index 71ebfa43ad05..a625e3749566 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -206,6 +206,7 @@ test_string(void)
 #define PTR_WIDTH 16
 #define PTR ((void *)0xffff0123456789ab)
 #define PTR_STR "ffff0123456789ab"
+#define PTR_VAL_NO_CRNG "        (ptrval)"
 #define ZEROS "00000000"	/* hex 32 zero bits */
 
 static int __init
@@ -216,7 +217,16 @@ plain_format(void)
 
 	nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
 
-	if (nchars != PTR_WIDTH || strncmp(buf, ZEROS, strlen(ZEROS)) != 0)
+	if (nchars != PTR_WIDTH)
+		return -1;
+
+	if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) {
+		pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"",
+			PTR_VAL_NO_CRNG);
+		return 0;
+	}
+
+	if (strncmp(buf, ZEROS, strlen(ZEROS)) != 0)
 		return -1;
 
 	return 0;
@@ -227,6 +237,7 @@ plain_format(void)
 #define PTR_WIDTH 8
 #define PTR ((void *)0x456789ab)
 #define PTR_STR "456789ab"
+#define PTR_VAL_NO_CRNG "(ptrval)"
 
 static int __init
 plain_format(void)
@@ -245,7 +256,16 @@ plain_hash(void)
 
 	nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
 
-	if (nchars != PTR_WIDTH || strncmp(buf, PTR_STR, PTR_WIDTH) == 0)
+	if (nchars != PTR_WIDTH)
+		return -1;
+
+	if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) {
+		pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"",
+			PTR_VAL_NO_CRNG);
+		return 0;
+	}
+
+	if (strncmp(buf, PTR_STR, PTR_WIDTH) == 0)
 		return -1;
 
 	return 0;
-- 
2.14.1