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6 Commits

Author SHA1 Message Date
Cassio Neri
1d1bb12a8b rtc: Improve performance of rtc_time64_to_tm(). Add tests. 
The current implementation of rtc_time64_to_tm() contains unnecessary
loops, branches and look-up tables. The new one uses an arithmetic-based
algorithm appeared in [1] and is approximately 4.3 times faster (YMMV).

The drawback is that the new code isn't intuitive and contains many 'magic
numbers' (not unusual for this type of algorithm). However, [1] justifies
all those numbers and, given this function's history, the code is unlikely
to need much maintenance, if any at all.

Add a KUnit test case that checks every day in a 160,000 years interval
starting on 1970-01-01 against the expected result. Add a new config
RTC_LIB_KUNIT_TEST symbol to give the option to run this test suite.

[1] Neri, Schneider, "Euclidean Affine Functions and Applications to
Calendar Algorithms". https://arxiv.org/abs/2102.06959

Signed-off-by: Cassio Neri <cassio.neri@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210624201343.85441-1-cassio.neri@gmail.com
 2021-08-10 00:09:21 +02:00
Xuefeng Wang
73f28f714a rtc: lib: check whether tm->tm_year in int32 range 
When setting rtc alarm (RTC_WKALM_SET), the tm_year is not checked if it
is in suiteable range. Use INT_MAX - 1900 to check it.

UBSAN: Undefined behaviour in drivers/rtc/rtc-lib.c:119:30
signed integer overflow:
2147483647 + 1900 cannot be represented in type 'int'
CPU: 1 PID: 20994 Comm: syz-executor0 Not tainted 4.19.18-514.55.6.9.x86_64
+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1
04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xca/0x13e lib/dump_stack.c:113
 ubsan_epilogue+0xe/0x81 lib/ubsan.c:159
 handle_overflow+0x193/0x1e2 lib/ubsan.c:190
 rtc_tm_to_time64+0x267/0x280 drivers/rtc/rtc-lib.c:119
 rtc_tm_to_ktime+0x16/0x70 drivers/rtc/rtc-lib.c:129
 rtc_set_alarm+0x1a9/0x2d0 drivers/rtc/interface.c:466
 rtc_dev_ioctl+0x6db/0x810 drivers/rtc/rtc-dev.c:380
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1a5/0x10b0 fs/ioctl.c:690
 ksys_ioctl+0x89/0xa0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x74/0xb0 fs/ioctl.c:710
 do_syscall_64+0xc8/0x580 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462589
Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89
f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08
0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8
64 89 01 48
RSP: 002b:00007f5348896c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000072bf00 RCX: 0000000000462589
RDX: 0000000020000000 RSI: 000000004028700f RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f53488976bc
R13: 00000000004bf67e R14: 00000000006f96e0 R15: 00000000ffffffff

==========================================================================

Signed-off-by: Xuefeng Wang <wxf.wang@hisilicon.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
 2019-04-06 15:05:31 +02:00
Alexandre Belloni
606cc43c72 rtc: core: correct trivial checkpatch warnings 
Correct trivial checkpatch warnings, mostly whitespace issues and
unbalanced braces.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
 2019-04-04 10:07:08 +02:00
Alexandre Belloni
cdf7545aef rtc: convert core to SPDX identifier 
Use SPDX-License-Identifier instead of a verbose license text. Also fix the
block comment alignment.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
 2019-03-18 03:36:01 +01:00
ZhangXiaoxu
074b01a51d rtc: Fix UBSAN overflow warning 
Users may call 'ioctl' and pass a very big value on 'tm->tm_year'.
It can be overflowed in 'int' after add 1900.
In function 'rtc_month_days' and 'mktime64', also treated it as an
'unsigned' parameter.

UBSAN: Undefined behaviour in drivers/rtc/rtc-lib.c:103:59
signed integer overflow:
2147483647 + 1900 cannot be represented in type 'int'

UBSAN: Undefined behaviour in drivers/rtc/rtc-lib.c:119:30
signed integer overflow:
2147483647 + 1900 cannot be represented in type 'int'

So, covert it to 'unsigned' explicitly.

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
 2019-01-10 22:02:44 +01:00
Alexandre Belloni
36e14f5fdf rtc: rename core files 
Rename core files so there is a clearer separation between the RTC core and
the RTC drivers.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
 2018-12-31 11:36:16 +01:00