Re: [PATCH v3] MdePkg/BasePrintLib: avoid absolute addresses for error strings


Ard Biesheuvel
 

On 6/16/20 11:12 PM, Andrew Fish wrote:
I was wondering what would happen if we converted the CHAR8 arrays in to strings with multiple nulls [1]. Looks like it saves space in uncompressed FVs, but not in compressed FVs.
Yeah, those NUL bytes compress really well, so the overhead of the extra code you need to unpack your strings stands out in the compressed FV.


Here are the Xcode numbers for X64 DEBUG Ovmf:
With this Patch:
SECFV [14%Full] 212992 total, 30128 used, 182864 free
PEIFV [29%Full] 917504 total, 273192 used, 644312 free
DXEFV [39%Full] 12582912 total, 4997120 used, 7585792 free
FVMAIN_COMPACT [36%Full] 3440640 total, 1271264 used, 2169376 free
Vs my patch:
SECFV [14%Full] 212992 total, 29872 used, 183120 free
PEIFV [29%Full] 917504 total, 271048 used, 646456 free
DXEFV [39%Full] 12582912 total, 4979552 used, 7603360 free
FVMAIN_COMPACT [36%Full] 3440640 total, 1271824 used, 2168816 free
SEC: -256
PEI: -2,144
Dxe: -17,568
Compact: +560
[1] $ git diff
*diff --git a/MdePkg/Library/BasePrintLib/PrintLibInternal.c b/MdePkg/Library/BasePrintLib/PrintLibInternal.c*
*index 50c6e8559c43..db2533e7affb 100644*
*--- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c*
*+++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c*
@@ -30,53 +30,73 @@GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mHexStr[] = {'0','1','2','3','4','5','
 //
 // Longest string: RETURN_WARN_BUFFER_TOO_SMALL => 24 characters plus NUL byte
 //
-GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mWarningString[][24+1] = {
-  "Success",                      //  RETURN_SUCCESS                = 0
-  "Warning Unknown Glyph",        //  RETURN_WARN_UNKNOWN_GLYPH     = 1
-  "Warning Delete Failure",       //  RETURN_WARN_DELETE_FAILURE    = 2
-  "Warning Write Failure",        //  RETURN_WARN_WRITE_FAILURE     = 3
-  "Warning Buffer Too Small",     //  RETURN_WARN_BUFFER_TOO_SMALL  = 4
-  "Warning Stale Data",           //  RETURN_WARN_STALE_DATA        = 5
-};
+GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 *mWarningString =     \
+  "Success\0"                      /*  RETURN_SUCCESS                = 0 */ \
+  "Warning Unknown Glyph\0"        /*  RETURN_WARN_UNKNOWN_GLYPH     = 1 */ \
+  "Warning Delete Failure\0"       /*  RETURN_WARN_DELETE_FAILURE    = 2 */ \
+  "Warning Write Failure\0"        /*  RETURN_WARN_WRITE_FAILURE     = 3 */ \
+  "Warning Buffer Too Small\0"     /*  RETURN_WARN_BUFFER_TOO_SMALL  = 4 */ \
+  "Warning Stale Data";            /*  RETURN_WARN_STALE_DATA        = 5 */
 //
 // Longest string: RETURN_INCOMPATIBLE_VERSION => 20 characters plus NUL byte
 //
-GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mErrorString[][20+1] = {
-  "Load Error",                   //  RETURN_LOAD_ERROR             = 1  | MAX_BIT
-  "Invalid Parameter",            //  RETURN_INVALID_PARAMETER      = 2  | MAX_BIT
-  "Unsupported",                  //  RETURN_UNSUPPORTED            = 3  | MAX_BIT
-  "Bad Buffer Size",              //  RETURN_BAD_BUFFER_SIZE        = 4  | MAX_BIT
-  "Buffer Too Small",             //  RETURN_BUFFER_TOO_SMALL,      = 5  | MAX_BIT
-  "Not Ready",                    //  RETURN_NOT_READY              = 6  | MAX_BIT
-  "Device Error",                 //  RETURN_DEVICE_ERROR           = 7  | MAX_BIT
-  "Write Protected",              //  RETURN_WRITE_PROTECTED        = 8  | MAX_BIT
-  "Out of Resources",             //  RETURN_OUT_OF_RESOURCES       = 9  | MAX_BIT
-  "Volume Corrupt",               //  RETURN_VOLUME_CORRUPTED       = 10 | MAX_BIT
-  "Volume Full",                  //  RETURN_VOLUME_FULL            = 11 | MAX_BIT
-  "No Media",                     //  RETURN_NO_MEDIA               = 12 | MAX_BIT
-  "Media changed",                //  RETURN_MEDIA_CHANGED          = 13 | MAX_BIT
-  "Not Found",                    //  RETURN_NOT_FOUND              = 14 | MAX_BIT
-  "Access Denied",                //  RETURN_ACCESS_DENIED          = 15 | MAX_BIT
-  "No Response",                  //  RETURN_NO_RESPONSE            = 16 | MAX_BIT
-  "No mapping",                   //  RETURN_NO_MAPPING             = 17 | MAX_BIT
-  "Time out",                     //  RETURN_TIMEOUT                = 18 | MAX_BIT
-  "Not started",                  //  RETURN_NOT_STARTED            = 19 | MAX_BIT
-  "Already started",              //  RETURN_ALREADY_STARTED        = 20 | MAX_BIT
-  "Aborted",                      //  RETURN_ABORTED                = 21 | MAX_BIT
-  "ICMP Error",                   //  RETURN_ICMP_ERROR             = 22 | MAX_BIT
-  "TFTP Error",                   //  RETURN_TFTP_ERROR             = 23 | MAX_BIT
-  "Protocol Error",               //  RETURN_PROTOCOL_ERROR         = 24 | MAX_BIT
-  "Incompatible Version",         //  RETURN_INCOMPATIBLE_VERSION   = 25 | MAX_BIT
-  "Security Violation",           //  RETURN_SECURITY_VIOLATION     = 26 | MAX_BIT
-  "CRC Error",                    //  RETURN_CRC_ERROR              = 27 | MAX_BIT
-  "End of Media",                 //  RETURN_END_OF_MEDIA           = 28 | MAX_BIT
-  "Reserved (29)",                //  RESERVED                      = 29 | MAX_BIT
-  "Reserved (30)",                //  RESERVED                      = 30 | MAX_BIT
-  "End of File",                  //  RETURN_END_OF_FILE            = 31 | MAX_BIT
-  "Invalid Language",             //  RETURN_INVALID_LANGUAGE       = 32 | MAX_BIT
-  "Compromised Data"              //  RETURN_COMPROMISED_DATA       = 33 | MAX_BIT
-};
+GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 *mErrorString =                 \
+  "Load Error\0"                   /*  RETURN_LOAD_ERROR             = 1  | MAX_BIT */ \
+  "Invalid Parameter\0"            /*  RETURN_INVALID_PARAMETER      = 2  | MAX_BIT */ \
+  "Unsupported\0"                  /*  RETURN_UNSUPPORTED            = 3  | MAX_BIT */ \
+  "Bad Buffer Size\0"              /*  RETURN_BAD_BUFFER_SIZE        = 4  | MAX_BIT */ \
+  "Buffer Too Small\0"             /*  RETURN_BUFFER_TOO_SMALL,      = 5  | MAX_BIT */ \
+  "Not Ready\0"                    /*  RETURN_NOT_READY              = 6  | MAX_BIT */ \
+  "Device Error\0"                 /*  RETURN_DEVICE_ERROR           = 7  | MAX_BIT */ \
+  "Write Protected\0"              /*  RETURN_WRITE_PROTECTED        = 8  | MAX_BIT */ \
+  "Out of Resources\0"             /*  RETURN_OUT_OF_RESOURCES       = 9  | MAX_BIT */ \
+  "Volume Corrupt\0"               /*  RETURN_VOLUME_CORRUPTED       = 10 | MAX_BIT */ \
+  "Volume Full\0"                  /*  RETURN_VOLUME_FULL            = 11 | MAX_BIT */ \
+  "No Media\0"                     /*  RETURN_NO_MEDIA               = 12 | MAX_BIT */ \
+  "Media changed\0"                /*  RETURN_MEDIA_CHANGED          = 13 | MAX_BIT */ \
+  "Not Found\0"                    /*  RETURN_NOT_FOUND              = 14 | MAX_BIT */ \
+  "Access Denied\0"                /*  RETURN_ACCESS_DENIED          = 15 | MAX_BIT */ \
+  "No Response\0"                  /*  RETURN_NO_RESPONSE            = 16 | MAX_BIT */ \
+  "No mapping\0"                   /*  RETURN_NO_MAPPING             = 17 | MAX_BIT */ \
+  "Time out\0"                     /*  RETURN_TIMEOUT                = 18 | MAX_BIT */ \
+  "Not started\0"                  /*  RETURN_NOT_STARTED            = 19 | MAX_BIT */ \
+  "Already started\0"              /*  RETURN_ALREADY_STARTED        = 20 | MAX_BIT */ \
+  "Aborted\0"                      /*  RETURN_ABORTED                = 21 | MAX_BIT */ \
+  "ICMP Error\0"                   /*  RETURN_ICMP_ERROR             = 22 | MAX_BIT */ \
+  "TFTP Error\0"                   /*  RETURN_TFTP_ERROR             = 23 | MAX_BIT */ \
+  "Protocol Error\0"               /*  RETURN_PROTOCOL_ERROR         = 24 | MAX_BIT */ \
+  "Incompatible Version\0"         /*  RETURN_INCOMPATIBLE_VERSION   = 25 | MAX_BIT */ \
+  "Security Violation\0"           /*  RETURN_SECURITY_VIOLATION     = 26 | MAX_BIT */ \
+  "CRC Error\0"                    /*  RETURN_CRC_ERROR              = 27 | MAX_BIT */ \
+  "End of Media\0"                 /*  RETURN_END_OF_MEDIA           = 28 | MAX_BIT */ \
+  "Reserved (29)\0"                /*  RESERVED                      = 29 | MAX_BIT */ \
+  "Reserved (30)\0"                /*  RESERVED                      = 30 | MAX_BIT */ \
+  "End of File\0"                  /*  RETURN_END_OF_FILE            = 31 | MAX_BIT */ \
+  "Invalid Language\0"             /*  RETURN_INVALID_LANGUAGE       = 32 | MAX_BIT */ \
+  "Compromised Data";              /*  RETURN_COMPROMISED_DATA       = 33 | MAX_BIT */
+
+
+CONST CHAR8 *
+FindNthStr (
+  IN CONST CHAR8 *Start,
+  IN UINTN       Index
+  )
+{
+  CONST CHAR8 *str;
+
+  for (str = Start; Index > 0; str++) {
+    if (*str == '\0') {
+      Index--;
+      if (Index == 0) {
+        str++;
+        break;
+      }
+    }
+  }
+
+  return str;
+}
 /**
@@ -1005,12 +1025,12 @@BasePrintLibSPrintMarker (
           //
           Index = Status & ~MAX_BIT;
           if (Index > 0 && Index <= ERROR_STATUS_NUMBER) {
-            ArgumentString = mErrorString [Index - 1];
+            ArgumentString = FindNthStr (mErrorString, Index - 1);
           }
         } else {
           Index = Status;
           if (Index <= WARNING_STATUS_NUMBER) {
-            ArgumentString = mWarningString [Index];
+            ArgumentString = FindNthStr (mWarningString, Index);
           }
         }
         if (ArgumentString == ValueBuffer) {
Thanks,
Andrew Fish

On Jun 15, 2020, at 6:57 PM, Liming Gao <liming.gao@... <mailto:liming.gao@...>> wrote:

This data is great. The change is good. Reviewed-by: Liming Gao <liming.gao@... <mailto:liming.gao@...>>
*From:*Liu, Zhiguang <zhiguang.liu@... <mailto:zhiguang.liu@...>>
*Sent:*2020年6月15日15:34
*To:*Ard Biesheuvel <ard.biesheuvel@... <mailto:ard.biesheuvel@...>>; Gao, Liming <liming.gao@... <mailto:liming.gao@...>>;devel@edk2.groups.io <mailto:devel@edk2.groups.io>
*Cc:*Kinney, Michael D <michael.d.kinney@... <mailto:michael.d.kinney@...>>
*Subject:*RE: [edk2-devel] [PATCH v3] MdePkg/BasePrintLib: avoid absolute addresses for error strings
Hi Ard,
I also collected the image size of OVMFX64 size building with VS2015x86.

Debug

Release

before

after

After-before

before

after

after-before
sec

27664

27409

-255

13968

13968

0
pei

223016

221000

-2016

107208

106984

-224
dxe

4507000

4481336

-25664

2987064

2979384

-7680
compact

1179776

1172528

-7248

922664

920304

-2360

It can reduce the image size in X64.
Reviewed-by: Zhiguang Liu <zhiguang.liu@... <mailto:zhiguang.liu@...>>
-----Original Message-----
From: Ard Biesheuvel <ard.biesheuvel@... <mailto:ard.biesheuvel@...>>
Sent: Friday, June 12, 2020 11:11 PM
To: Gao, Liming <liming.gao@...
<mailto:liming.gao@...>>;devel@edk2.groups.io <mailto:devel@edk2.groups.io>
Cc: Kinney, Michael D <michael.d.kinney@... <mailto:michael.d.kinney@...>>; Liu,
Zhiguang
<zhiguang.liu@... <mailto:zhiguang.liu@...>>
Subject: Re: [edk2-devel] [PATCH v3] MdePkg/BasePrintLib: avoid absolute
addresses for error strings

On 6/12/20 4:33 PM, Gao, Liming wrote:
Ard:
    I will collect the image size on OVMF X64 platform with this patch.
Building OvmfPkgX64.dsc in RELEASE mode using GCC5 profile gives me


Before:
SECFV [5%Full] 212992 total, 11760 used, 201232 free PEIFV [9%Full] 917504
total, 89384 used, 828120 free DXEFV [22%Full] 12582912 total, 2806320 used,
9776592 free FVMAIN_COMPACT [26%Full] 3440640 total, 918760 used,
2521880 free

After:
SECFV [5%Full] 212992 total, 11760 used, 201232 free PEIFV [9%Full] 917504
total, 89192 used, 828312 free DXEFV [22%Full] 12582912 total, 2802928 used,
9779984 free FVMAIN_COMPACT [26%Full] 3440640 total, 916784 used,
2523856 free

So no change for SECFV, -192 bytes for PEIFV, -3392 bytes for DXEFV and
-1976 bytes for the resulting outer FV image.



-----Original Message-----
From:devel@edk2.groups.io
<mailto:devel@edk2.groups.io><devel@edk2.groups.io <mailto:devel@edk2.groups.io>> On Behalf Of Ard
Biesheuvel
Sent: Friday, June 12, 2020 6:35 AM
To:devel@edk2.groups.io <mailto:devel@edk2.groups.io>
Cc: Ard Biesheuvel <ard.biesheuvel@... <mailto:ard.biesheuvel@...>>; Kinney, Michael D
<michael.d.kinney@... <mailto:michael.d.kinney@...>>; Gao,
Liming <liming.gao@... <mailto:liming.gao@...>>
Subject: [edk2-devel] [PATCH v3] MdePkg/BasePrintLib: avoid absolute
addresses for error strings

The mStatusString[] array 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 extra work needs to
be done at runtime to process these relocations, every time a module is
loaded that incorporates this library.

So fix both issues, by splitting mStatusString into two arrays of char
arrays. The memory footprint decreases from 955 to 843 bytes, and given
that in the latter case, the overhead consists of 278 NUL characters rather
than 390 bytes worth of absolute addresses and relocation records, the
size
of a compressed image is reduced even further. For example, when
building
ArmVirtQemu.dsc in RELEASE mode for AARCH64 with the GCC5 profile, I
get:

    Before

    FV Space Information
    FVMAIN [100%Full] 5329920 total, 5329920 used, 0 free
    FVMAIN_COMPACT [38%Full] 2093056 total, 811840 used, 1281216 free

    After

    FV Space Information
    FVMAIN [100%Full] 5321728 total, 5321728 used, 0 free
    FVMAIN_COMPACT [38%Full] 2093056 total, 809696 used, 1283360 free

So the uncompressed contents of the compressed image are 8 KB smaller,
whereas the resulting flash image (consisting of the compressed image
along with SEC, PEI_CORE and a set of PEIMs that execute in place) is
2 KB smaller.

Cc: "Kinney, Michael D" <michael.d.kinney@... <mailto:michael.d.kinney@...>>
Cc: "Gao, Liming" <liming.gao@... <mailto:liming.gao@...>>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@... <mailto:ard.biesheuvel@...>>
---
v3:
- add code comments to explain what the inner dimension of each array is
    based on

v2:
- split off this patch from the StandaloneMmPkg series, since they are not
    interdependent anyway, and so they can be discussed separately
- remove mention of StandaloneMmPkg from the commit log - the space
savings
    by themselves are sufficient justification
- update the before/after numbers with the current results
- split the warnings and errors into a separate array, so that the latter
    can use smaller entries
- clarify the commit log to explain the effect on compressed as well as
    XIP images (which both get smaller)

   MdePkg/Library/BasePrintLib/PrintLibInternal.c | 15 ++++++++++++---
   1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
index b6ec5ac4fbb9..50c6e8559c43 100644
--- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
+++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
@@ -27,13 +27,22 @@


   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[] = {

+//

+// Longest string: RETURN_WARN_BUFFER_TOO_SMALL => 24
characters plus NUL byte

+//

+GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8
mWarningString[][24+1] = {

     "Success",                      //  RETURN_SUCCESS                = 0

     "Warning Unknown Glyph",        //  RETURN_WARN_UNKNOWN_GLYPH
= 1

     "Warning Delete Failure",       //  RETURN_WARN_DELETE_FAILURE    = 2

     "Warning Write Failure",        //  RETURN_WARN_WRITE_FAILURE     = 3

     "Warning Buffer Too Small",     //
RETURN_WARN_BUFFER_TOO_SMALL  = 4

     "Warning Stale Data",           //  RETURN_WARN_STALE_DATA        = 5

+};

+

+//

+// Longest string: RETURN_INCOMPATIBLE_VERSION => 20 characters
plus NUL byte

+//

+GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8
mErrorString[][20+1] = {

     "Load Error",                   //  RETURN_LOAD_ERROR             = 1  | MAX_BIT

     "Invalid Parameter",            //  RETURN_INVALID_PARAMETER      = 2  |
MAX_BIT

     "Unsupported",                  //  RETURN_UNSUPPORTED            = 3  |
MAX_BIT

@@ -996,12 +1005,12 @@ BasePrintLibSPrintMarker (
             //

             Index = Status & ~MAX_BIT;

             if (Index > 0 && Index <= ERROR_STATUS_NUMBER) {

-            ArgumentString = mStatusString [Index +
WARNING_STATUS_NUMBER];

+            ArgumentString = mErrorString [Index - 1];

             }

           } else {

             Index = Status;

             if (Index <= WARNING_STATUS_NUMBER) {

-            ArgumentString = mStatusString [Index];

+            ArgumentString = mWarningString [Index];

             }

           }

           if (ArgumentString == ValueBuffer) {

--
2.26.2


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