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efi_loader: correctly implement 100ns conversion

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In efi_set_timer we receive the trigger time in intervals of 100 ns.
We should convert it to intervals of 1000 ns by 64bit division.

The patch supplies function efi_div10 that uses multiplication to
implement the missing 64 bit division.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
xypron.glpk@gmx.de 2017-07-18 20:17:23 +02:00 committed by Alexander Graf
parent 91be9a77b7
commit 8787b02e32
1 changed files with 40 additions and 9 deletions
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49
lib/efi_loader/efi_boottime.c
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@ -81,6 +81,39 @@ efi_status_t efi_exit_func(efi_status_t ret)
return ret;
}
/* Low 32 bit */
#define EFI_LOW32(a) (a & 0xFFFFFFFFULL)
/* High 32 bit */
#define EFI_HIGH32(a) (a >> 32)
/*
* 64bit division by 10 implemented as multiplication by 1 / 10
*
* Decimals of one tenth: 0x1 / 0xA = 0x0.19999...
*/
#define EFI_TENTH 0x199999999999999A
static u64 efi_div10(u64 a)
{
u64 prod;
u64 rem;
u64 ret;
ret = EFI_HIGH32(a) * EFI_HIGH32(EFI_TENTH);
prod = EFI_HIGH32(a) * EFI_LOW32(EFI_TENTH);
rem = EFI_LOW32(prod);
ret += EFI_HIGH32(prod);
prod = EFI_LOW32(a) * EFI_HIGH32(EFI_TENTH);
rem += EFI_LOW32(prod);
ret += EFI_HIGH32(prod);
prod = EFI_LOW32(a) * EFI_LOW32(EFI_TENTH);
rem += EFI_HIGH32(prod);
ret += EFI_HIGH32(rem);
/* Round to nearest integer */
if (rem >= (1 << 31))
++ret;
return ret;
}
void efi_signal_event(struct efi_event *event)
{
if (event->signaled)
@ -244,7 +277,7 @@ void efi_timer_check(void)
continue;
if (efi_events[i].trigger_type == EFI_TIMER_PERIODIC) {
efi_events[i].trigger_next +=
efi_events[i].trigger_time / 10;
efi_events[i].trigger_time;
efi_events[i].signaled = 0;
}
efi_signal_event(&efi_events[i]);
@ -255,15 +288,13 @@ void efi_timer_check(void)
efi_status_t efi_set_timer(struct efi_event *event, int type,
uint64_t trigger_time)
{
/* We don't have 64bit division available everywhere, so limit timer
* distances to 32bit bits. */
u32 trigger32 = trigger_time;
int i;
if (trigger32 < trigger_time) {
printf("WARNING: Truncating timer from %"PRIx64" to %x\n",
trigger_time, trigger32);
}
/*
* The parameter defines a multiple of 100ns.
* We use multiples of 1000ns. So divide by 10.
*/
trigger_time = efi_div10(trigger_time);
for (i = 0; i < ARRAY_SIZE(efi_events); ++i) {
if (event != &efi_events[i])
@ -278,7 +309,7 @@ efi_status_t efi_set_timer(struct efi_event *event, int type,
case EFI_TIMER_PERIODIC:
case EFI_TIMER_RELATIVE:
event->trigger_next =
timer_get_us() + (trigger32 / 10);
timer_get_us() + trigger_time;
break;
default:
return EFI_INVALID_PARAMETER;