From e31dc4717c75d8e771dfa5c9b1648fa20d88ab0d Mon Sep 17 00:00:00 2001
From: Nhi Pham <nhi@os.amperecomputing.com>
Date: Wed, 6 Jan 2021 23:09:02 +0700
Subject: [PATCH] EmbeddedPkg/TimeBaseLib: Add function to check Timezone and
 Daylight

This adds two functions IsValidTimeZone() and IsValidDaylight() to check
the time zone and daylight value from EFI time. These functions are
retrieved from the RealTimeClockRuntimeDxe module as they reduce
duplicated code in RTC modules.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Nhi Pham <nhi@os.amperecomputing.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>
---
 EmbeddedPkg/Include/Library/TimeBaseLib.h     | 36 ++++++++++++++
 EmbeddedPkg/Library/TimeBaseLib/TimeBaseLib.c | 49 ++++++++++++++++++-
 2 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/EmbeddedPkg/Include/Library/TimeBaseLib.h b/EmbeddedPkg/Include/Library/TimeBaseLib.h
index a9f3c6588b..10700d1a64 100644
--- a/EmbeddedPkg/Include/Library/TimeBaseLib.h
+++ b/EmbeddedPkg/Include/Library/TimeBaseLib.h
@@ -83,6 +83,42 @@ IsDayValid (
   IN  EFI_TIME  *Time
   );
 
+/**
+  Check if the time zone is valid.
+  Valid values are between -1440 and 1440 or 2047 (EFI_UNSPECIFIED_TIMEZONE).
+
+  @param    TimeZone    The time zone to be checked.
+
+  @retval   TRUE    Valid.
+  @retval   FALSE   Invalid.
+
+**/
+BOOLEAN
+EFIAPI
+IsValidTimeZone (
+  IN  INT16  TimeZone
+  );
+
+/**
+  Check if the daylight is valid.
+  Valid values are:
+    0 : Time is not affected.
+    1 : Time is affected, and has not been adjusted for daylight savings.
+    3 : Time is affected, and has been adjusted for daylight savings.
+  All other values are invalid.
+
+  @param    Daylight    The daylight to be checked.
+
+  @retval   TRUE    Valid.
+  @retval   FALSE   Invalid.
+
+**/
+BOOLEAN
+EFIAPI
+IsValidDaylight (
+  IN  INT8  Daylight
+  );
+
 /**
   Check if the UEFI time is valid.
 
diff --git a/EmbeddedPkg/Library/TimeBaseLib/TimeBaseLib.c b/EmbeddedPkg/Library/TimeBaseLib/TimeBaseLib.c
index 17466c1e6c..210d0b2bf1 100644
--- a/EmbeddedPkg/Library/TimeBaseLib/TimeBaseLib.c
+++ b/EmbeddedPkg/Library/TimeBaseLib/TimeBaseLib.c
@@ -210,6 +210,51 @@ IsDayValid (
   return TRUE;
 }
 
+/**
+  Check if the time zone is valid.
+  Valid values are between -1440 and 1440 or 2047 (EFI_UNSPECIFIED_TIMEZONE).
+
+  @param    TimeZone    The time zone to be checked.
+
+  @retval   TRUE    Valid.
+  @retval   FALSE   Invalid.
+
+**/
+BOOLEAN
+EFIAPI
+IsValidTimeZone (
+  IN  INT16  TimeZone
+  )
+{
+  return TimeZone == EFI_UNSPECIFIED_TIMEZONE ||
+         (TimeZone >= -1440 && TimeZone <= 1440);
+}
+
+/**
+  Check if the daylight is valid.
+  Valid values are:
+    0 : Time is not affected.
+    1 : Time is affected, and has not been adjusted for daylight savings.
+    3 : Time is affected, and has been adjusted for daylight savings.
+  All other values are invalid.
+
+  @param    Daylight    The daylight to be checked.
+
+  @retval   TRUE    Valid.
+  @retval   FALSE   Invalid.
+
+**/
+BOOLEAN
+EFIAPI
+IsValidDaylight (
+  IN  INT8  Daylight
+  )
+{
+  return Daylight == 0 ||
+         Daylight == EFI_TIME_ADJUST_DAYLIGHT ||
+         Daylight == (EFI_TIME_ADJUST_DAYLIGHT | EFI_TIME_IN_DAYLIGHT);
+}
+
 /**
   Check if the UEFI time is valid.
 
@@ -235,8 +280,8 @@ IsTimeValid (
      (Time->Minute > 59  )              ||
      (Time->Second > 59  )              ||
      (Time->Nanosecond > 999999999)     ||
-     (!((Time->TimeZone == EFI_UNSPECIFIED_TIMEZONE) || ((Time->TimeZone >= -1440) && (Time->TimeZone <= 1440)))) ||
-     (Time->Daylight & (~(EFI_TIME_ADJUST_DAYLIGHT | EFI_TIME_IN_DAYLIGHT)))) {
+     (!IsValidTimeZone(Time->TimeZone)) ||
+     (!IsValidDaylight(Time->Daylight))) {
     return FALSE;
   }