linux-kernel - [PATCH] pstore: Remove bogus format string definition

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Date:   Wed, 30 May 2018 22:30:09 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     y2038@...ts.linaro.org, deepa.kernel@...il.com
Cc:     Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Geliang Tang <geliangtang@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] pstore: Remove bogus format string definition

The pstore conversion to timespec64 introduces its own method of passing
seconds into sscanf() and sprintf() type functions to work around the
timespec64 definition on 64-bit systems that redefine it to 'timespec'.

That hack is now finally getting removed, but that means we get a (harmless)
warning once both patches are merged:

fs/pstore/ram.c: In function 'ramoops_read_kmsg_hdr':
fs/pstore/ram.c:39:29: error: format '%ld' expects argument of type 'long int *', but argument 3 has type 'time64_t *' {aka 'long long int *'} [-Werror=format=]
 #define RAMOOPS_KERNMSG_HDR "===="
                             ^~~~~~
fs/pstore/ram.c:167:21: note: in expansion of macro 'RAMOOPS_KERNMSG_HDR'

This removes the pstore specific workaround and uses the same method that
we have in place for all other functions that print a timespec64.

Related to this, I found that the kasprintf() output contains an incorrect
nanosecond values for any number starting with zeroes, and I adapt the
format string accordingly.

Link: https://lkml.org/lkml/2018/5/19/115
Link: https://lkml.org/lkml/2018/5/16/1080
Fixes: 0f0d83b99ef7 ("pstore: Convert internal records to timespec64")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/pstore/ram.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 69e893076ab7..bbd1e357c23d 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -38,11 +38,6 @@
 
 #define RAMOOPS_KERNMSG_HDR "===="
 #define MIN_MEM_SIZE 4096UL
-#if __BITS_PER_LONG == 64
-# define TVSEC_FMT "%ld"
-#else
-# define TVSEC_FMT "%lld"
-#endif
 
 static ulong record_size = MIN_MEM_SIZE;
 module_param(record_size, ulong, 0400);
@@ -164,15 +159,15 @@ static int ramoops_read_kmsg_hdr(char *buffer, struct timespec64 *time,
 	char data_type;
 	int header_length = 0;
 
-	if (sscanf(buffer, RAMOOPS_KERNMSG_HDR TVSEC_FMT ".%lu-%c\n%n",
-		   &time->tv_sec, &time->tv_nsec, &data_type,
+	if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lld.%lu-%c\n%n",
+		   (time64_t *)&time->tv_sec, &time->tv_nsec, &data_type,
 		   &header_length) == 3) {
 		if (data_type == 'C')
 			*compressed = true;
 		else
 			*compressed = false;
-	} else if (sscanf(buffer, RAMOOPS_KERNMSG_HDR TVSEC_FMT ".%lu\n%n",
-			  &time->tv_sec, &time->tv_nsec,
+	} else if (sscanf(buffer, RAMOOPS_KERNMSG_HDR "%lld.%lu\n%n",
+			  (time64_t *)&time->tv_sec, &time->tv_nsec,
 			  &header_length) == 2) {
 		*compressed = false;
 	} else {
@@ -367,8 +362,8 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz,
 	char *hdr;
 	size_t len;
 
-	hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR TVSEC_FMT ".%lu-%c\n",
-		record->time.tv_sec,
+	hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lld.%06lu-%c\n",
+		(time64_t)record->time.tv_sec,
 		record->time.tv_nsec / 1000,
 		record->compressed ? 'C' : 'D');
 	WARN_ON_ONCE(!hdr);
-- 
2.9.0