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added a comment on year 2038 and nano seconds file times

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Bo Branten
2024-09-03 00:57:48 +02:00
parent 0eb2f4ed1c
commit 1062de3fa4
1 changed files with 23 additions and 6 deletions
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29
Ext4Fsd/misc.c
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@@ -36,6 +36,21 @@ Ext2Log2(ULONG Value)
return (Order - 1); return (Order - 1);
} }
/* The built in functions RtlTimeToSecondsSince1970 and RtlSecondsSince1970ToTime is
* not "year 2038 safe" because they use 32-bit seconds. The new functions
* Ext2TimeToSecondsSince1970 and Ext2SecondsSince1970ToTime is a reimplementation
* that uses 64-bit seconds.
*
* The superblock has new time fields ending in "_hi" containing the high 8-bit of
* the seconds and the existing time fields contain the lower 32-bit.
*
* The inodes has new time fields ending in "_extra". They contain both the high
* 2-bit of the seconds, that is bit 33 and 34 and also the nano seconds encoded
* as (nsec << 2 | epoch) The existing fields contain the low 32-bit of the seconds.
*
* Windows system time is in number of 100 nano seconds.
*/
VOID VOID
Ext2TimeToSecondsSince1970( Ext2TimeToSecondsSince1970(
IN PLARGE_INTEGER SysTime, IN PLARGE_INTEGER SysTime,
@@ -66,13 +81,14 @@ Ext2SetInodeTime(
OUT PULONG i_time_extra) OUT PULONG i_time_extra)
{ {
LARGE_INTEGER LinuxTime; LARGE_INTEGER LinuxTime;
ULONG epoc, nano_sec; ULONG epoch, nano_sec;
Ext2TimeToSecondsSince1970(SysTime, &LinuxTime.LowPart, &LinuxTime.HighPart); Ext2TimeToSecondsSince1970(SysTime, &LinuxTime.LowPart, &LinuxTime.HighPart);
epoc = ((LinuxTime.QuadPart - (signed int)LinuxTime.QuadPart) >> 32) & EXT4_EPOCH_MASK; epoch = ((LinuxTime.QuadPart - (signed int)LinuxTime.QuadPart) >> 32) & EXT4_EPOCH_MASK;
nano_sec = (SysTime->QuadPart % (ULONGLONG)TICKSPERSEC) * 100; nano_sec = (SysTime->QuadPart % (ULONGLONG)TICKSPERSEC) * 100;
/* i_time is lower 32-bit and i_time_extra is (nsec << 2 | epoch) */
*i_time = LinuxTime.LowPart; *i_time = LinuxTime.LowPart;
*i_time_extra = (epoc | (nano_sec << EXT4_EPOCH_BITS)); *i_time_extra = (epoch | (nano_sec << EXT4_EPOCH_BITS));
} }
LARGE_INTEGER LARGE_INTEGER
@@ -81,11 +97,12 @@ Ext2GetInodeTime(
IN ULONG i_time_extra) IN ULONG i_time_extra)
{ {
LARGE_INTEGER LinuxTime, SysTime; LARGE_INTEGER LinuxTime, SysTime;
ULONG epoc, nano_sec; ULONG epoch, nano_sec;
epoc = i_time_extra & EXT4_EPOCH_MASK; /* i_time is lower 32-bit and i_time_extra is (nsec << 2 | epoch) */
epoch = i_time_extra & EXT4_EPOCH_MASK;
nano_sec = (i_time_extra & EXT4_NSEC_MASK) >> EXT4_EPOCH_BITS; nano_sec = (i_time_extra & EXT4_NSEC_MASK) >> EXT4_EPOCH_BITS;
LinuxTime.QuadPart = (signed)i_time + ((ULONGLONG)epoc << 32); LinuxTime.QuadPart = (signed)i_time + ((ULONGLONG)epoch << 32);
Ext2SecondsSince1970ToTime(LinuxTime.LowPart, LinuxTime.HighPart, &SysTime); Ext2SecondsSince1970ToTime(LinuxTime.LowPart, LinuxTime.HighPart, &SysTime);
SysTime.QuadPart += nano_sec / 100; SysTime.QuadPart += nano_sec / 100;