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fat: Support file modification times 

This allows comparing file ages on EFI system partitions.

Signed-off-by: David Michael <fedora.dm0@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
David Michael 2020-03-07 00:59:52 -05:00 committed by Daniel Kiper
parent 8ad7c23864
commit 20def1a3c3
1 changed files with 60 additions and 0 deletions
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60
grub-core/fs/fat.c
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@ -26,6 +26,7 @@
#include <grub/err.h>
#include <grub/dl.h>
#include <grub/charset.h>
#include <grub/datetime.h>
#ifndef MODE_EXFAT
#include <grub/fat.h>
#else
@ -730,6 +731,33 @@ grub_fat_iterate_dir_next (grub_fshelp_node_t node,
return grub_errno ? : GRUB_ERR_EOF;
}
/*
* Convert a timestamp in exFAT format to seconds since the UNIX epoch
* according to sections 7.4.8 and 7.4.9 in the exFAT specification.
* https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
*/
static int
grub_exfat_timestamp (grub_uint32_t field, grub_uint8_t msec, grub_int32_t *nix) {
struct grub_datetime datetime = {
.year = (field >> 25) + 1980,
.month = (field & 0x01E00000) >> 21,
.day = (field & 0x001F0000) >> 16,
.hour = (field & 0x0000F800) >> 11,
.minute = (field & 0x000007E0) >> 5,
.second = (field & 0x0000001F) * 2 + (msec >= 100 ? 1 : 0),
};
/* The conversion below allows seconds=60, so don't trust its validation. */
if ((field & 0x1F) > 29)
return 0;
/* Validate the 10-msec field even though it is rounded down to seconds. */
if (msec > 199)
return 0;
return grub_datetime2unixtime (&datetime, nix);
}
#else
static grub_err_t
@ -857,6 +885,29 @@ grub_fat_iterate_dir_next (grub_fshelp_node_t node,
return grub_errno ? : GRUB_ERR_EOF;
}
/*
* Convert a date and time in FAT format to seconds since the UNIX epoch
* according to sections 11.3.5 and 11.3.6 in ECMA-107.
* https://www.ecma-international.org/publications/files/ECMA-ST/Ecma-107.pdf
*/
static int
grub_fat_timestamp (grub_uint16_t time, grub_uint16_t date, grub_int32_t *nix) {
struct grub_datetime datetime = {
.year = (date >> 9) + 1980,
.month = (date & 0x01E0) >> 5,
.day = (date & 0x001F),
.hour = (time >> 11),
.minute = (time & 0x07E0) >> 5,
.second = (time & 0x001F) * 2,
};
/* The conversion below allows seconds=60, so don't trust its validation. */
if ((time & 0x1F) > 29)
return 0;
return grub_datetime2unixtime (&datetime, nix);
}
#endif
static grub_err_t lookup_file (grub_fshelp_node_t node,
@ -966,10 +1017,19 @@ grub_fat_dir (grub_device_t device, const char *path, grub_fs_dir_hook_t hook,
#ifdef MODE_EXFAT
if (!ctxt.dir.have_stream)
continue;
info.mtimeset = grub_exfat_timestamp (grub_le_to_cpu32 (ctxt.entry.type_specific.file.m_time),
ctxt.entry.type_specific.file.m_time_tenth,
&info.mtime);
#else
if (ctxt.dir.attr & GRUB_FAT_ATTR_VOLUME_ID)
continue;
info.mtimeset = grub_fat_timestamp (grub_le_to_cpu16 (ctxt.dir.w_time),
grub_le_to_cpu16 (ctxt.dir.w_date),
&info.mtime);
#endif
if (info.mtimeset == 0)
grub_error (GRUB_ERR_OUT_OF_RANGE,
"invalid modification timestamp for %s", path);
if (hook (ctxt.filename, &info, hook_data))
break;