2016-03-22 22:16:19

by Tina Ruchandani

Subject: [PATCH v2] prism54: isl_38xx: Replace 'struct timeval'

'struct timeval' uses a 32-bit seconds field which will overflow in
year 2038 and beyond. This patch is part of a larger effort to remove
all instances of 'struct timeval' from the kernel and replace them
with 64-bit timekeeping variables.
The correctness of the code isn't affected by this patch - the seconds
value being printed would earlier be wrong due to overflow in timeval,
and now it gets truncated to 32-bit due to the 'long' cast used on
tv.sec field to prevent compiler warnings. Truly fixing this would
require changing the debug print to print more than 8 digits and
use a different specifier from %li.
The patch was build-tested / debugged by removing the
"if VERBOSE > SHOW_ERROR_MESSAGES" guards.

Signed-off-by: Tina Ruchandani <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
--
Changes in v2:
- Changed printf specifier as suggested by Arnd Bergmann to
avoid truncation.
---
drivers/net/wireless/intersil/prism54/isl_38xx.c | 35 ++++++++++++------------
1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/net/wireless/intersil/prism54/isl_38xx.c b/drivers/net/wireless/intersil/prism54/isl_38xx.c
index 333c1a2..6700387 100644
--- a/drivers/net/wireless/intersil/prism54/isl_38xx.c
+++ b/drivers/net/wireless/intersil/prism54/isl_38xx.c
@@ -19,6 +19,7 @@
#include <linux/module.h>
#include <linux/types.h>
#include <linux/delay.h>
+#include <linux/ktime.h>

#include <asm/uaccess.h>
#include <asm/io.h>
@@ -113,7 +114,7 @@ isl38xx_trigger_device(int asleep, void __iomem *device_base)

#if VERBOSE > SHOW_ERROR_MESSAGES
u32 counter = 0;
- struct timeval current_time;
+ struct timespec64 current_ts64;
DEBUG(SHOW_FUNCTION_CALLS, "isl38xx trigger device\n");
#endif

@@ -121,22 +122,22 @@ isl38xx_trigger_device(int asleep, void __iomem *device_base)
if (asleep) {
/* device is in powersave, trigger the device for wakeup */
#if VERBOSE > SHOW_ERROR_MESSAGES
- do_gettimeofday(&current_time);
- DEBUG(SHOW_TRACING, "%08li.%08li Device wakeup triggered\n",
- current_time.tv_sec, (long)current_time.tv_usec);
+ ktime_get_real_ts64(&current_ts64);
+ DEBUG(SHOW_TRACING, "%lld.%09ld Device wakeup triggered\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec);

- DEBUG(SHOW_TRACING, "%08li.%08li Device register read %08x\n",
- current_time.tv_sec, (long)current_time.tv_usec,
+ DEBUG(SHOW_TRACING, "%lld.%09ld Device register read %08x\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec,
readl(device_base + ISL38XX_CTRL_STAT_REG));
#endif

reg = readl(device_base + ISL38XX_INT_IDENT_REG);
if (reg == 0xabadface) {
#if VERBOSE > SHOW_ERROR_MESSAGES
- do_gettimeofday(&current_time);
+ ktime_get_real_ts64(&current_ts64);
DEBUG(SHOW_TRACING,
- "%08li.%08li Device register abadface\n",
- current_time.tv_sec, (long)current_time.tv_usec);
+ "%lld.%09ld Device register abadface\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec);
#endif
/* read the Device Status Register until Sleepmode bit is set */
while (reg = readl(device_base + ISL38XX_CTRL_STAT_REG),
@@ -149,13 +150,13 @@ isl38xx_trigger_device(int asleep, void __iomem *device_base)

#if VERBOSE > SHOW_ERROR_MESSAGES
DEBUG(SHOW_TRACING,
- "%08li.%08li Device register read %08x\n",
- current_time.tv_sec, (long)current_time.tv_usec,
+ "%lld.%09ld Device register read %08x\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec,
readl(device_base + ISL38XX_CTRL_STAT_REG));
- do_gettimeofday(&current_time);
+ ktime_get_real_ts64(&current_ts64);
DEBUG(SHOW_TRACING,
- "%08li.%08li Device asleep counter %i\n",
- current_time.tv_sec, (long)current_time.tv_usec,
+ "%lld.%09ld Device asleep counter %i\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec,
counter);
#endif
}
@@ -168,9 +169,9 @@ isl38xx_trigger_device(int asleep, void __iomem *device_base)

/* perform another read on the Device Status Register */
reg = readl(device_base + ISL38XX_CTRL_STAT_REG);
- do_gettimeofday(&current_time);
- DEBUG(SHOW_TRACING, "%08li.%08li Device register read %08x\n",
- current_time.tv_sec, (long)current_time.tv_usec, reg);
+ ktime_get_real_ts64(&current_ts64);
+ DEBUG(SHOW_TRACING, "%lld.%00ld Device register read %08x\n",
+ (s64)current_ts64.tv_sec, current_ts64.tv_nsec, reg);
#endif
} else {
/* device is (still) awake */
--
2.8.0.rc3.226.g39d4020

2016-03-23 13:28:18

by Arnd Bergmann

Subject: Re: [Y2038] [PATCH v2] prism54: isl_38xx: Replace 'struct timeval'

On Tuesday 22 March 2016 15:16:15 Tina Ruchandani wrote:
> 'struct timeval' uses a 32-bit seconds field which will overflow in
> year 2038 and beyond. This patch is part of a larger effort to remove
> all instances of 'struct timeval' from the kernel and replace them
> with 64-bit timekeeping variables.
> The correctness of the code isn't affected by this patch - the seconds
> value being printed would earlier be wrong due to overflow in timeval,
> and now it gets truncated to 32-bit due to the 'long' cast used on
> tv.sec field to prevent compiler warnings. Truly fixing this would
> require changing the debug print to print more than 8 digits and
> use a different specifier from %li.
> The patch was build-tested / debugged by removing the
> "if VERBOSE > SHOW_ERROR_MESSAGES" guards.
>
> Signed-off-by: Tina Ruchandani <[email protected]>
> Suggested-by: Arnd Bergmann <[email protected]>
> --
> Changes in v2:
> - Changed printf specifier as suggested by Arnd Bergmann to
> avoid truncation.
>

The patch looks great now, but it no longer matches the description,
as you actually fix the correctness.

Arnd