On Mon, Jun 18, 2018 at 4:07 PM Arnd Bergmann arnd@arndb.de wrote:
As Mathieu pointed out, my conversion to time64_t was incorrect and resulted in negative times to be read from the RTC. The problem is that during the conversion from a byte array to a time64_t, the 'unsigned char' variable holding the top byte gets turned into a negative signed 32-bit integer before being assigned to the 64-bit variable for any times after 1972.
This changes the logic to cast to an unsigned 32-bit number first for the Macintosh time and then convert that to the Unix time, which then gives us a time in the documented 1904..2040 year range. I decided not to use the longer 1970..2106 range that other drivers use, for consistency with the literal interpretation of the register, but that could be easily changed if we decide we want to support any Mac after 2040.
Just to be on the safe side, I'm also adding a WARN_ON that will trigger if either the year 2040 has come and is observed by this driver, or we run into an RTC that got set back to a pre-1970 date for some reason (the two are indistinguishable).
The same code exists in arch/m68k/ and is patched in an identical way now in a separate patch.
Fixes: 5bfd643583b2 ("powerpc: use time64_t in read_persistent_clock") Reported-by: Mathieu Malaterre malat@debian.org Signed-off-by: Arnd Bergmann arnd@arndb.de
arch/powerpc/platforms/powermac/time.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/platforms/powermac/time.c b/arch/powerpc/platforms/powermac/time.c index 7c968e46736f..173a80630169 100644 --- a/arch/powerpc/platforms/powermac/time.c +++ b/arch/powerpc/platforms/powermac/time.c @@ -42,7 +42,11 @@ #define DBG(x...) #endif
-/* Apparently the RTC stores seconds since 1 Jan 1904 */ +/*
- Offset between Unix time (1970-based) and Mac time (1904-based). Cuda and PMU
- times wrap in 2040. If we need to handle later times, the read_time functions
- need to be changed to interpret wrapped times as post-2040.
- */
#define RTC_OFFSET 2082844800
/* @@ -97,8 +101,11 @@ static time64_t cuda_get_time(void) if (req.reply_len != 7) printk(KERN_ERR "cuda_get_time: got %d byte reply\n", req.reply_len);
now = (req.reply[3] << 24) + (req.reply[4] << 16)+ (req.reply[5] << 8) + req.reply[6];
now = (u32)((req.reply[3] << 24) + (req.reply[4] << 16) +(req.reply[5] << 8) + req.reply[6]);/* it's either after year 2040, or the RTC has gone backwards */WARN_ON(now < RTC_OFFSET);return now - RTC_OFFSET;}
@@ -140,8 +147,12 @@ static time64_t pmu_get_time(void) if (req.reply_len != 4) printk(KERN_ERR "pmu_get_time: got %d byte reply from PMU\n", req.reply_len);
now = (req.reply[0] << 24) + (req.reply[1] << 16)+ (req.reply[2] << 8) + req.reply[3];
now = (u32)((req.reply[0] << 24) + (req.reply[1] << 16) +(req.reply[2] << 8) + req.reply[3]);/* it's either after year 2040, or the RTC has gone backwards */WARN_ON(now < RTC_OFFSET);return now - RTC_OFFSET;}
Sadly, trying again today does not work anymore. Adding some printk just before WARN_ON:
+printk(KERN_ERR " rtc DBG pmu_get_time1: %lld %d %lld \n", now, RTC_OFFSET, now - RTC_OFFSET ); +printk(KERN_ERR " rtc DBG pmu_get_time2: %x %x %x %x %d \n", req.reply[0], req.reply[1], req.reply[2], req.reply[3] , req.reply_len);
leads to:
[ 0.000000] rtc DBG pmu_get_time1: 14096662 2082844800 -2068748138 [ 0.000000] rtc DBG pmu_get_time2: 0 d7 19 16 4 [ 0.000000] WARNING: CPU: 0 PID: 0 at ../arch/powerpc/platforms/powermac/time.c:158 pmu_get_time+0x11c/0x16c [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.17.0+ #8 [ 0.000000] NIP: c0035658 LR: c0035640 CTR: c00d4a5c [ 0.000000] REGS: c0cf7da0 TRAP: 0700 Not tainted (4.17.0+) [ 0.000000] MSR: 00021032 <ME,IR,DR,RI> CR: 84000848 XER: 00000000 [ 0.000000] GPR00: c0035640 c0cf7e50 c0a41bd0 00000025 00000001 00000051 c0d56430 00000000 GPR08: 00000051 00000001 c0aa4b38 00000004 24000842 00000000 ffbbf4c0 0013da1c GPR16: 0013da18 0013da20 00000000 00000000 00b81044 01696028 01697e02 40140000 GPR24: 00000000 00d71000 c09debec dfff1120 000001a4 00d71916 ffffffff 84b16896 [ 0.000000] NIP [c0035658] pmu_get_time+0x11c/0x16c [ 0.000000] LR [c0035640] pmu_get_time+0x104/0x16c [ 0.000000] Call Trace: [ 0.000000] [c0cf7e50] [c0035640] pmu_get_time+0x104/0x16c (unreliable) [ 0.000000] [c0cf7ed0] [c00113fc] read_persistent_clock64+0x78/0x1ac [ 0.000000] [c0cf7f30] [c09ad470] timekeeping_init+0x24/0x2f4 [ 0.000000] [c0cf7fc0] [c09986f0] start_kernel+0x34c/0x490 [ 0.000000] [c0cf7ff0] [00003444] 0x3444 [ 0.000000] Instruction dump: [ 0.000000] 88e1002f 3863404c 88c1002e 88a1002d 8881002c 4809baf1 3d207c25 6129b07f [ 0.000000] 7f9d4840 39200001 409d0008 39200000 <0f090000> 4bffff20 3c60c0c1 7fe4fb78 [ 0.000000] random: get_random_bytes called from print_oops_end_marker+0x6c/0x90 with crng_init=0 [ 0.000000] ---[ end trace 93a1b37c50fb7a33 ]---
and then later on :
[ 5.535354] rtc DBG pmu_get_time1: 14096667 2082844800 -2068748133 [ 5.539988] rtc DBG pmu_get_time2: 0 d7 19 1b 4 [ 5.544477] WARNING: CPU: 0 PID: 1 at ../arch/powerpc/platforms/powermac/time.c:158 pmu_get_time+0x11c/0x16c [ 5.553536] Modules linked in: [ 5.558076] CPU: 0 PID: 1 Comm: swapper Tainted: G W 4.17.0+ #8 [ 5.562769] NIP: c0035658 LR: c0035640 CTR: c00d4a5c [ 5.567437] REGS: df4e7a90 TRAP: 0700 Tainted: G W (4.17.0+) [ 5.572201] MSR: 00029032 <EE,ME,IR,DR,RI> CR: 88008288 XER: 00000000 [ 5.577028] GPR00: c0035640 df4e7b40 df4e8000 00000025 00000001 00000344 00000400 00000000 GPR08: 00000003 00000001 c0aa4b38 00000000 28008282 00000000 c09dfc4c c09dfc28 GPR16: 00000690 c0aedae0 c0aee64c c0aecf50 00000054 c0ae7488 c0aea0f4 00000000 GPR24: c0d70000 c0a85850 c086fc74 df4e7c5c df4e7ce8 00d7191b ffffffff 84b1689b [ 5.601871] NIP [c0035658] pmu_get_time+0x11c/0x16c [ 5.606952] LR [c0035640] pmu_get_time+0x104/0x16c [ 5.612042] Call Trace: [ 5.617079] [df4e7b40] [c0035640] pmu_get_time+0x104/0x16c (unreliable) [ 5.622297] [df4e7bc0] [c003572c] pmac_get_rtc_time+0x34/0x4c [ 5.627509] [df4e7bd0] [c001076c] rtc_generic_get_time+0x2c/0x40 [ 5.632740] [df4e7be0] [c0611fb8] __rtc_read_time+0x70/0x13c [ 5.637977] [df4e7c00] [c06120f0] rtc_read_time+0x6c/0x130 [ 5.643230] [df4e7c30] [c0613324] __rtc_read_alarm+0x34/0x684 [ 5.648503] [df4e7ce0] [c060fe18] rtc_device_register+0x88/0x218 [ 5.653804] [df4e7d40] [c061000c] devm_rtc_device_register+0x64/0xc4 [ 5.659127] [df4e7d60] [c09d2630] generic_rtc_probe+0x50/0x78 [ 5.664457] [df4e7d70] [c055eefc] platform_drv_probe+0xa8/0x128 [ 5.669735] [df4e7d90] [c055a780] driver_probe_device+0x354/0x6fc [ 5.674905] [df4e7dd0] [c055acc8] __driver_attach+0x1a0/0x22c [ 5.679971] [df4e7df0] [c05565c8] bus_for_each_dev+0x84/0xdc [ 5.685017] [df4e7e20] [c0558e78] bus_add_driver+0x188/0x348 [ 5.690021] [df4e7e40] [c055c20c] driver_register+0xa0/0x18c [ 5.694982] [df4e7e50] [c055f3a8] __platform_driver_probe+0x8c/0x198 [ 5.699918] [df4e7e70] [c0005800] do_one_initcall+0x64/0x280 [ 5.704726] [df4e7ee0] [c0998bd8] kernel_init_freeable+0x3a4/0x444 [ 5.709433] [df4e7f30] [c00049f8] kernel_init+0x24/0x118 [ 5.713995] [df4e7f40] [c001b1c4] ret_from_kernel_thread+0x14/0x1c [ 5.718536] Instruction dump: [ 5.723041] 88e1002f 3863404c 88c1002e 88a1002d 8881002c 4809baf1 3d207c25 6129b07f [ 5.727651] 7f9d4840 39200001 409d0008 39200000 <0f090000> 4bffff20 3c60c0c1 7fe4fb78 [ 5.732196] ---[ end trace 93a1b37c50fb7a34 ]--- [ 5.736768] ================================================================================ [ 5.741519] UBSAN: Undefined behaviour in ../drivers/rtc/rtc-lib.c:87:22 [ 5.746295] signed integer overflow: [ 5.751002] 1193026 * 3600 cannot be represented in type 'int' [ 5.755739] CPU: 0 PID: 1 Comm: swapper Tainted: G W 4.17.0+ #8 [ 5.760529] Call Trace: [ 5.765124] [df4e7b00] [c04817ec] ubsan_epilogue+0x18/0x4c (unreliable) [ 5.769871] [df4e7b10] [c048218c] handle_overflow+0xbc/0xdc [ 5.774580] [df4e7b90] [c060e27c] rtc_time64_to_tm+0x344/0x388 [ 5.779264] [df4e7bd0] [c001076c] rtc_generic_get_time+0x2c/0x40 [ 5.783841] [df4e7be0] [c0611fb8] __rtc_read_time+0x70/0x13c [ 5.788395] [df4e7c00] [c06120f0] rtc_read_time+0x6c/0x130 [ 5.792929] [df4e7c30] [c0613324] __rtc_read_alarm+0x34/0x684 [ 5.797415] [df4e7ce0] [c060fe18] rtc_device_register+0x88/0x218 [ 5.801895] [df4e7d40] [c061000c] devm_rtc_device_register+0x64/0xc4 [ 5.806395] [df4e7d60] [c09d2630] generic_rtc_probe+0x50/0x78 [ 5.810889] [df4e7d70] [c055eefc] platform_drv_probe+0xa8/0x128 [ 5.815405] [df4e7d90] [c055a780] driver_probe_device+0x354/0x6fc [ 5.819929] [df4e7dd0] [c055acc8] __driver_attach+0x1a0/0x22c [ 5.824440] [df4e7df0] [c05565c8] bus_for_each_dev+0x84/0xdc [ 5.828922] [df4e7e20] [c0558e78] bus_add_driver+0x188/0x348 [ 5.833366] [df4e7e40] [c055c20c] driver_register+0xa0/0x18c [ 5.837789] [df4e7e50] [c055f3a8] __platform_driver_probe+0x8c/0x198 [ 5.842244] [df4e7e70] [c0005800] do_one_initcall+0x64/0x280 [ 5.846700] [df4e7ee0] [c0998bd8] kernel_init_freeable+0x3a4/0x444 [ 5.851186] [df4e7f30] [c00049f8] kernel_init+0x24/0x118 [ 5.855656] [df4e7f40] [c001b1c4] ret_from_kernel_thread+0x14/0x1c [ 5.860171] ================================================================================ [ 5.864998] device: 'rtc0': device_add
-- 2.9.0