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[stackprotector] Added intrinsic llvm.stackprotectorcheck.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188191 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Gottesman 2013-08-12 18:35:32 +00:00
parent 67d135ae40
commit 2a64a639e5
2 changed files with 46 additions and 6 deletions
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50
docs/LangRef.rst
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@ -8641,14 +8641,52 @@ enough space to hold the value of the guard.
Semantics:
""""""""""
This intrinsic causes the prologue/epilogue inserter to force the
position of the ``AllocaInst`` stack slot to be before local variables
on the stack. This is to ensure that if a local variable on the stack is
overwritten, it will destroy the value of the guard. When the function
exits, the guard on the stack is checked against the original guard. If
they are different, then the program aborts by calling the
This intrinsic causes the prologue/epilogue inserter to force the position of
the ``AllocaInst`` stack slot to be before local variables on the stack. This is
to ensure that if a local variable on the stack is overwritten, it will destroy
the value of the guard. When the function exits, the guard on the stack is
checked against the original guard by ``llvm.stackprotectorcheck``. If they are
different, then ``llvm.stackprotectorcheck`` causes the program to abort by
calling the ``__stack_chk_fail()`` function.
'``llvm.stackprotectorcheck``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
declare void @llvm.stackprotectorcheck(i8** <guard>)
Overview:
"""""""""
The ``llvm.stackprotectorcheck`` intrinsic compares ``guard`` against an already
created stack protector and if they do not equal calls the
``__stack_chk_fail()`` function.
Arguments:
""""""""""
The ``llvm.stackprotectorcheck`` intrinsic requires one pointer argument, the
the variable ``@__stack_chk_guard``.
Semantics:
""""""""""
This intrinsic is provided to perform the stack protector check by comparing
``guard`` with the stack slot created by ``llvm.stackprotector`` and if the
values do not match call the ``__stack_chk_fail()`` function.
The reason to provide this as an IR level intrinsic instead of implementing it
via other IR operations is that in order to perform this operation at the IR
level without an intrinsic, one would need to create additional basic blocks to
handle the success/failure cases. This makes it difficult to stop the stack
protector check from disrupting sibling tail calls in Codegen. With this
intrinsic, we are able to generate the stack protector basic blocks late in
codegen after the tail call decision has occured.
'``llvm.objectsize``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

2
include/llvm/IR/Intrinsics.td
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@ -258,6 +258,8 @@ def int_readcyclecounter : Intrinsic<[llvm_i64_ty]>;
// Stack Protector Intrinsic - The stackprotector intrinsic writes the stack
// guard to the correct place on the stack frame.
def int_stackprotector : Intrinsic<[], [llvm_ptr_ty, llvm_ptrptr_ty], []>;
def int_stackprotectorcheck : Intrinsic<[], [llvm_ptrptr_ty],
[IntrReadWriteArgMem]>;
//===------------------- Standard C Library Intrinsics --------------------===//
//