[PATCH 1/5] MdePkg/BasePrintLib: avoid absolute addresses for error strings

["Ard Biesheuvel" <ard.biesheuvel@arm.com>]

The mStatusString[] is constructed as an array of pointer-to-char, which
means that on X64 or AARCH64, it is emitted as a single linear list of
64-bit quantities, each containing the absolute address of one of the
string literals in memory.

This means that each string takes up 8 bytes of additional space, along
with 2 bytes of relocation data. It also means that the array cannot be
used until PE/COFF relocation has completed, and so the following
invocation

    Status = PeCoffLoaderRelocateImage (&ImageContext);
    ASSERT_EFI_ERROR (Status);

that we will be introducing into StandaloneMmCore entrypoint for AARCH64
to relocate the executable on the fly is guaranteed to return bogus output
or crash, which is less than helpful.

So fix both issues, by emitting mStatusString as an array of char arrays
instead. The memory footprint increases from 955 to 975 bytes, but given
that in the latter case, the overhead consists of 410 NUL characters
rather than 390 bytes worth of absolute addresses and relocation records,
the impact on a compressed image is actually positive. For example, when
building ArmVirtQemu.dsc in RELEASE mode for AARCH64 with the GCC5 profile,
I get:

  Before

  FV Space Information
  FVMAIN [99%Full] 4784768 total, 4784720 used, 48 free
  FVMAIN_COMPACT [38%Full] 2093056 total, 811560 used, 1281496 free

  After

  FV Space Information
  FVMAIN [99%Full] 4780672 total, 4780624 used, 48 free
  FVMAIN_COMPACT [38%Full] 2093056 total, 813488 used, 1279568 free

So the compressed image is 4 KB smaller, whereas the entire image is
< 2 KB larger, which is in the order of 0.2 %

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
---
 MdePkg/Library/BasePrintLib/PrintLibInternal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MdePkg/Library/BasePrintLib/PrintLibInternal.c b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
index b6ec5ac4fbb9..c8b932c7e07a 100644
--- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
+++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
@@ -27,7 +27,7 @@
 
 GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mHexStr[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
 
-GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 * CONST mStatusString[] = {
+GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mStatusString[][25] = {
   "Success",                      //  RETURN_SUCCESS                = 0
   "Warning Unknown Glyph",        //  RETURN_WARN_UNKNOWN_GLYPH     = 1
   "Warning Delete Failure",       //  RETURN_WARN_DELETE_FAILURE    = 2
-- 
2.26.2