[PATCH 18/19] ArmPkg/DefaultExceptionHandlerLib: replace AsciiStrCat() with AsciiStrCatS()

[Laszlo Ersek <lersek@redhat.com>]

AsciiStrCat() is deprecated / disabled under the
DISABLE_NEW_DEPRECATED_INTERFACES feature test macro.

The caller of CpsrString() is required to pass in "ReturnStr" with 32
CHAR8 elements. (DefaultExceptionHandler() complies with this.) "Str" is
used to build "ReturnStr" gradually. Just before calling AsciiStrCat(),
"Str" points to the then-terminating NUL character in "ReturnStr".

The difference (Str - ReturnStr) gives the number of non-NUL characters
we've written thus far, hence (32 - (Str - ReturnStr)) yields the number
of remaining bytes in ReturnStr, including the ultimately terminating NUL
character.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Michael Zimmermann <sigmaepsilon92@gmail.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=164
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=165
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    - build-tested only
    
    - Michael (CC'd) had posted a patch earlier for this:
      <https://lists.01.org/pipermail/edk2-devel/2016-August/000489.html>,
      but I only noticed that now that he pointed it out, in
      <https://lists.01.org/pipermail/edk2-devel/2016-October/003121.html>.
      I'll leave it to the ArmPkg maintainers to choose one; I don't feel
      strongly either way.

 ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
index aece26355e2e..4b2ee9a9acf7 100644
--- a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
+++ b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
@@ -116,7 +116,10 @@ CpsrString (
     break;
   }
 
-  AsciiStrCat (Str, ModeStr);
+  //
+  // See the interface contract in the leading comment block.
+  //
+  AsciiStrCatS (Str, 32 - (Str - ReturnStr), ModeStr);
   return;
 }
 
-- 
2.9.2