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;
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> 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
Cc: andrew.f...@apple.com; 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>
Signed-off-by: Olivier Martin <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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Open source business process management suite built on Java and Eclipse
Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
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------------------------------------------------------------------------------
Open source business process management suite built on Java and Eclipse
Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
_______________________________________________
edk2-devel mailing list
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