Martin:
  Per Andrew comment, this value is the recommended constant. If so, we don't 
need to  add one PCD for it unless someone has the strong request to configure 
it.

Thanks
Liming
From: Olivier Martin [mailto:olivier.mar...@arm.com]
Sent: Tuesday, July 08, 2014 9:26 PM
To: 'Andrew Fish'; Gao, Liming
Cc: Kinney, Michael D; edk2-buildtools-de...@lists.sourceforge.net; 
edk2-devel@lists.sourceforge.net
Subject: RE: [edk2-buildtools] [PATCH 2/3] MdePkg: Introduced BaseStackCheckLib

Actually, I was thinking to replace this canary value by a FixedPcd but I do 
not remember why I have not done it. I might have just forgot it.
Olivier

From: Andrew Fish [mailto:af...@apple.com]
Sent: 08 July 2014 02:14
To: Gao, Liming
Cc: Olivier Martin; Mike Kinney; 
edk2-buildtools-de...@lists.sourceforge.net<mailto:edk2-buildtools-de...@lists.sourceforge.net>;
 edk2-devel@lists.sourceforge.net<mailto:edk2-devel@lists.sourceforge.net>
Subject: Re: [edk2-buildtools] [PATCH 2/3] MdePkg: Introduced BaseStackCheckLib


On Jul 7, 2014, at 5:40 PM, Gao, Liming 
<liming....@intel.com<mailto:liming....@intel.com>> wrote:

Martin:
 What is 0x0AFF for? Is it an address or a value?

This value is the recommended constant if you can not generate a real random 
number for the "canary" value.

It has NULL (will terminate strings), LF, and -1. 
http://wiki.osdev.org/GCC_Stack_Smashing_Protector. So it helps contains read 
based overruns.

__stack_chk_guard is the "canary" placed on the stack by the compiler. 
__stack_check_fail() is called if the "canary" has been over written. These are 
both compiler intrinsics.

Thanks,

Andrew Fish

~/work/Compiler>cat stack.c

void
test (int i, char v)
{
  char test[0x100];

  test[i] = v;
  return;
}

~/work/Compiler>clang -S stack.c
~/work/Compiler>cat stack.S
              .section    __TEXT,__text,regular,pure_instructions
              .globl       _test
              .align        4, 0x90
_test:                                  ## @test
              .cfi_startproc
## BB#0:
              pushq      %rbp
Ltmp2:
              .cfi_def_cfa_offset 16
Ltmp3:
              .cfi_offset %rbp, -16
              movq       %rsp, %rbp
Ltmp4:
              .cfi_def_cfa_register %rbp
              subq        $272, %rsp              ## imm = 0x110
              movb       %sil, %al
              movq       ___stack_chk_guard@GOTPCREL(%rip), %rcx
              movq       (%rcx), %rcx
              movq       %rcx, -8(%rbp)
              movq       ___stack_chk_guard@GOTPCREL(%rip), %rcx
              movl        %edi, -12(%rbp)
              movb       %al, -13(%rbp)
              movb       -13(%rbp), %al
              movslq    -12(%rbp), %rdx
              movb       %al, -272(%rbp,%rdx)
              movq       (%rcx), %rcx
              movq       -8(%rbp), %rdx
              cmpq       %rdx, %rcx
              jne           LBB0_2
## BB#1:                                ## %SP_return
              addq        $272, %rsp              ## imm = 0x110
              popq        %rbp
              ret
LBB0_2:                                 ## %CallStackCheckFailBlk
              callq         ___stack_chk_fail
              .cfi_endproc


.subsections_via_symbols


+/// "canary" value that is inserted by the compiler into the stack frame.
+VOID *__stack_chk_guard = (VOID*)0x0AFF;

 And, this library instance is used as NULL class instance. Its library class 
should be NULL.

Thanks
Liming
-----Original Message-----
From: Olivier Martin [mailto:olivier.mar...@arm.com]
Sent: Monday, July 07, 2014 11:44 PM
To: Kinney, Michael D; 
edk2-buildtools-de...@lists.sourceforge.net<mailto:edk2-buildtools-de...@lists.sourceforge.net>
Cc: andrew.f...@apple.com<mailto:andrew.f...@apple.com>; 
edk2-devel@lists.sourceforge.net<mailto:edk2-devel@lists.sourceforge.net>
Subject: [edk2-buildtools] [PATCH 2/3] MdePkg: Introduced BaseStackCheckLib

This library only support GCC and XCode for now.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Andrew Fish <andrew.f...@apple.com<mailto:andrew.f...@apple.com>>
Signed-off-by: Olivier Martin 
<olivier.mar...@arm.com<mailto:olivier.mar...@arm.com>

Change-Id: Ib51239b7d315637fd22c34a9a78a7a830f2ffdc7
---
.../Library/BaseStackCheckLib/BaseStackCheckGcc.c  | 62 ++++++++++++++++++++++
.../BaseStackCheckLib/BaseStackCheckLib.inf        | 41 ++++++++++++++
2 files changed, 103 insertions(+)
create mode 100644 MdePkg/Library/BaseStackCheckLib/BaseStackCheckGcc.c
create mode 100644 MdePkg/Library/BaseStackCheckLib/BaseStackCheckLib.inf

diff --git a/MdePkg/Library/BaseStackCheckLib/BaseStackCheckGcc.c 
b/MdePkg/Library/BaseStackCheckLib/BaseStackCheckGcc.c
new file mode 100644
index 0000000..9ec76d8
--- /dev/null
+++ b/MdePkg/Library/BaseStackCheckLib/BaseStackCheckGcc.c
@@ -0,0 +1,62 @@
+/** @file
+ Base Stack Check library for GCC/clang.
+
+ Use -fstack-protector-all compiler flag to make the compiler insert
+ the __stack_chk_guard "canary" value into the stack and check the
+ value prior to exiting the function. If the "canary" is overwritten
+ __stack_chk_fail() is called. This is GCC specific code.
+
+ Copyright (c) 2012, Apple Inc. All rights reserved.<BR> This program
+ and the accompanying materials are licensed and made available under
+ the terms and conditions of the BSD License which accompanies this
+ distribution.  The full text of the license may be found at
+ http://opensource.org/licenses/bsd-license.php.
+
+ THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <Base.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/PcdLib.h>
+
+VOID
+__stack_chk_fail (
+ VOID
+ );
+
+
+/// "canary" value that is inserted by the compiler into the stack frame.
+VOID *__stack_chk_guard = (VOID*)0x0AFF;
+
+// If ASLR was enabled we could use
+//void (*__stack_chk_guard)(void) = __stack_chk_fail;
+
+/**
+ Error path for compiler generated stack "canary" value check code. If
+the  stack canary has been overwritten this function gets called on
+exit of the  function.
+**/
+VOID
+__stack_chk_fail (
+ VOID
+ )
+{
+  UINT8 DebugPropertyMask;
+
+  DEBUG ((DEBUG_ERROR, "STACK FAULT: Buffer Overflow in function
+ %a.\n", __builtin_return_address(0)));
+
+  //
+  // Generate a Breakpoint, DeadLoop, or NOP based on PCD settings even
+if
+  // BaseDebugLibNull is in use.
+  //
+  DebugPropertyMask = PcdGet8 (PcdDebugPropertyMask);
+  if ((DebugPropertyMask & DEBUG_PROPERTY_ASSERT_BREAKPOINT_ENABLED) != 0) {
+    CpuBreakpoint ();
+  } else if ((DebugPropertyMask & DEBUG_PROPERTY_ASSERT_DEADLOOP_ENABLED) != 
0) {
+   CpuDeadLoop ();
+  }
+}
+
diff --git a/MdePkg/Library/BaseStackCheckLib/BaseStackCheckLib.inf 
b/MdePkg/Library/BaseStackCheckLib/BaseStackCheckLib.inf
new file mode 100644
index 0000000..4e2285d
--- /dev/null
+++ b/MdePkg/Library/BaseStackCheckLib/BaseStackCheckLib.inf
@@ -0,0 +1,41 @@
+## @file
+#  Stack Check Library
+#
+#  Copyright (c) 2014, ARM Ltd. All rights reserved.<BR> # #  This
+program and the accompanying materials #  are licensed and made
+available under the terms and conditions of the BSD License #  which
+accompanies this distribution. The full text of the license may be
+found at #  http://opensource.org/licenses/bsd-license.php.
+#  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS"
+BASIS, #  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR 
IMPLIED.
+#
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = BaseStackCheckLib
+  FILE_GUID                      = 5f6579f7-b648-4fdb-9f19-4c17e27e8eff
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = BaseStackCheckLib
+
+
+#
+#  VALID_ARCHITECTURES           = ARM AARCH64
+#
+
+[Sources]
+  BaseStackCheckGcc.c | GCC
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  BaseLib
+  DebugLib
+
+[Pcd]
+  gEfiMdePkgTokenSpaceGuid.PcdDebugPropertyMask
+
--
1.8.5


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Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
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