[StackProtector] Fix computation of GSCookieOffset and EHCookieOffset with SEH4

Summary:
Fix the computation of the offsets present in the scopetable when using the
SEH (__except_handler4).

This patch added an intrinsic to track the position of the allocation on the
stack of the EHGuard. This position is needed when producing the ScopeTable.

```
    struct _EH4_SCOPETABLE {
        DWORD GSCookieOffset;
        DWORD GSCookieXOROffset;
        DWORD EHCookieOffset;
        DWORD EHCookieXOROffset;
        _EH4_SCOPETABLE_RECORD ScopeRecord[1];
    };

    struct _EH4_SCOPETABLE_RECORD {
        DWORD EnclosingLevel;
        long (*FilterFunc)();
            union {
            void (*HandlerAddress)();
            void (*FinallyFunc)();
        };
    };
```

The code to generate the EHCookie is added in `X86WinEHState.cpp`.
Which is adding these instructions when using SEH4.

```
Lfunc_begin0:
# BB#0:                                 # %entry
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx
	pushl	%edi
	pushl	%esi
	subl	$28, %esp
	movl	%ebp, %eax                <<-- Loading FramePtr
	movl	%esp, -36(%ebp)
	movl	$-2, -16(%ebp)
	movl	$L__ehtable$use_except_handler4_ssp, %ecx
	xorl	___security_cookie, %ecx
	movl	%ecx, -20(%ebp)
	xorl	___security_cookie, %eax  <<-- XOR FramePtr and Cookie
	movl	%eax, -40(%ebp)           <<-- Storing EHGuard
	leal	-28(%ebp), %eax
	movl	$__except_handler4, -24(%ebp)
	movl	%fs:0, %ecx
	movl	%ecx, -28(%ebp)
	movl	%eax, %fs:0
	movl	$0, -16(%ebp)
	calll	_may_throw_or_crash
LBB1_1:                                 # %cont
	movl	-28(%ebp), %eax
	movl	%eax, %fs:0
	addl	$28, %esp
	popl	%esi
	popl	%edi
	popl	%ebx
	popl	%ebp
	retl

```

And the corresponding offset is computed:
```
Luse_except_handler4_ssp$parent_frame_offset = -36
	.p2align	2
L__ehtable$use_except_handler4_ssp:
	.long	-2                      # GSCookieOffset
	.long	0                       # GSCookieXOROffset
	.long	-40                     # EHCookieOffset    <<----
	.long	0                       # EHCookieXOROffset
	.long	-2                      # ToState
	.long	_catchall_filt          # FilterFunction
	.long	LBB1_2                  # ExceptionHandler

```

Clang is not yet producing function using SEH4, but it's a work in progress.
This patch is a step toward having a valid implementation of SEH4.
Unfortunately, it is not yet fully working. The EH registration block is not
allocated at the right offset on the stack.

Reviewers: rnk, majnemer

Subscribers: llvm-commits, chrisha

Differential Revision: http://reviews.llvm.org/D21231

llvm-svn: 273281

1 files changed, 47 insertions, 1 deletions

diff --git a/llvm/test/CodeGen/X86/win32-eh.ll b/llvm/test/CodeGen/X86/win32-eh.ll
index 9c43264f1b4..88403c68740 100644
--- a/llvm/test/CodeGen/X86/win32-eh.ll
+++ b/llvm/test/CodeGen/X86/win32-eh.ll
@@ -88,12 +88,58 @@ catch:
 ; CHECK-LABEL: L__ehtable$use_except_handler4:
 ; CHECK-NEXT:  .long   -2
 ; CHECK-NEXT:  .long   0
-; CHECK-NEXT:  .long   9999
+; CHECK-NEXT:  .long   -40
 ; CHECK-NEXT:  .long   0
 ; CHECK-NEXT:  .long   -2
 ; CHECK-NEXT:  .long   _catchall_filt
 ; CHECK-NEXT:  .long   LBB2_2
 
+define void @use_except_handler4_ssp() sspstrong personality i32 (...)* @_except_handler4 {
+entry:
+  invoke void @may_throw_or_crash()
+      to label %cont unwind label %lpad
+cont:
+  ret void
+lpad:
+  %cs = catchswitch within none [label %catch] unwind to caller
+catch:
+  %p = catchpad within %cs [i8* bitcast (i32 ()* @catchall_filt to i8*)]
+  catchret from %p to label %cont
+}
+
+; CHECK-LABEL: _use_except_handler4_ssp:
+; CHECK: pushl %ebp
+; CHECK: movl %esp, %ebp
+; CHECK: subl ${{[0-9]+}}, %esp
+; CHECK: movl %ebp, %[[ehguard:[^ ,]*]]
+; CHECK: movl %esp, -36(%ebp)
+; CHECK: movl $-2, -16(%ebp)
+; CHECK: movl $L__ehtable$use_except_handler4_ssp, %[[lsda:[^ ,]*]]
+; CHECK: xorl ___security_cookie, %[[lsda]]
+; CHECK: movl %[[lsda]], -20(%ebp)
+; CHECK: xorl ___security_cookie, %[[ehguard]]
+; CHECK: movl %[[ehguard]], -40(%ebp)
+; CHECK: leal -28(%ebp), %[[node:[^ ,]*]]
+; CHECK: movl $__except_handler4, -24(%ebp)
+; CHECK: movl %fs:0, %[[next:[^ ,]*]]
+; CHECK: movl %[[next]], -28(%ebp)
+; CHECK: movl %[[node]], %fs:0
+; CHECK: calll _may_throw_or_crash
+; CHECK: movl -28(%ebp), %[[next:[^ ,]*]]
+; CHECK: movl %[[next]], %fs:0   
+; CHECK: retl
+; CHECK: [[catch:[^ ,]*]]: # %catch{{$}}
+
+; CHECK: .section .xdata,"dr"
+; CHECK-LABEL: L__ehtable$use_except_handler4_ssp:
+; CHECK-NEXT:  .long   -2
+; CHECK-NEXT:  .long   0
+; CHECK-NEXT:  .long   -40  
+; CHECK-NEXT:  .long   0
+; CHECK-NEXT:  .long   -2
+; CHECK-NEXT:  .long   _catchall_filt
+; CHECK-NEXT:  .long   [[catch]]
+
 define void @use_CxxFrameHandler3() personality i32 (...)* @__CxxFrameHandler3 {
   invoke void @may_throw_or_crash()
       to label %cont unwind label %catchall