[AArch64] Add SEH_Nop opcodes for BTI hints

These are harmless for the unwinder - the unwinder doesn't need to
handle them for being able to unwind correctly.

Only add the opcodes when the branch t

[AArch64] Add SEH_Nop opcodes for BTI hints

These are harmless for the unwinder - the unwinder doesn't need to
handle them for being able to unwind correctly.

Only add the opcodes when the branch target is in a SEH prologue;
for jumptables e.g. within a function, we shouldn't add any SEH
opcodes.

Differential Revision: https://reviews.llvm.org/D135277

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[AArch64] Fix for BTI landing pad insertion with PAC-RET+bkey.

EMITBKEY is emitted for PAC-RET+bkey, which is a non machine instructions.

PR: 49957

Reviewed By: eugenis

Differential Revision: htt

[AArch64] Fix for BTI landing pad insertion with PAC-RET+bkey.

EMITBKEY is emitted for PAC-RET+bkey, which is a non machine instructions.

PR: 49957

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D100996

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[AArch64][v8.5A] Add BTI to all function starts

The existing BTI placement pass avoids inserting "BTI c" when the
function has local linkage and is only directly called. However,
even in this case,

[AArch64][v8.5A] Add BTI to all function starts

The existing BTI placement pass avoids inserting "BTI c" when the
function has local linkage and is only directly called. However,
even in this case, there is a (small) chance that the linker later
adds a hunk with an indirect call to the function, e.g. if the
function is placed in a separate section and moved far away from
its callers. Make sure to add BTI for these functions too.

Differential Revision: https://reviews.llvm.org/D99417

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[AArch64] PAC/BTI code generation for LLVM generated functions

PAC/BTI-related codegen in the AArch64 backend is controlled by a set
of LLVM IR function attributes, added to the function by Clang, b

[AArch64] PAC/BTI code generation for LLVM generated functions

PAC/BTI-related codegen in the AArch64 backend is controlled by a set
of LLVM IR function attributes, added to the function by Clang, based
on command-line options and GCC-style function attributes. However,
functions, generated in the LLVM middle end (for example,
asan.module.ctor or __llvm_gcov_write_out) do not get any attributes
and the backend incorrectly does not do any PAC/BTI code generation.

This patch record the default state of PAC/BTI codegen in a set of
LLVM IR module-level attributes, based on command-line options:

* "sign-return-address", with non-zero value means generate code to
sign return addresses (PAC-RET), zero value means disable PAC-RET.

* "sign-return-address-all", with non-zero value means enable PAC-RET
for all functions, zero value means enable PAC-RET only for
functions, which spill LR.

* "sign-return-address-with-bkey", with non-zero value means use B-key
for signing, zero value mean use A-key.

This set of attributes are always added for AArch64 targets (as
opposed, for example, to interpreting a missing attribute as having a
value 0) in order to be able to check for conflicts when combining
module attributed during LTO.

Module-level attributes are overridden by function level attributes.
All the decision making about whether to not to generate PAC and/or
BTI code is factored out into AArch64FunctionInfo, there shouldn't be
any places left, other than AArch64FunctionInfo, which directly
examine PAC/BTI attributes, except AArch64AsmPrinter.cpp, which
is/will-be handled by a separate patch.

Differential Revision: https://reviews.llvm.org/D85649

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[AArch64] Fix BTI instruction emission.

Summary:
SCTLR_EL1.BT[01] controls the PACI[AB]SP compatibility with PBYTE 11
(see [1])
This bit will be set to zero so PACI[AB]SP are equal to BTI C
instruct

[AArch64] Fix BTI instruction emission.

Summary:
SCTLR_EL1.BT[01] controls the PACI[AB]SP compatibility with PBYTE 11
(see [1])
This bit will be set to zero so PACI[AB]SP are equal to BTI C
instruction only.

[1] https://developer.arm.com/docs/ddi0595/b/aarch64-system-registers/sctlr_el1

Reviewers: chill, tamas.petz, pbarrio, ostannard

Reviewed By: tamas.petz, ostannard

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81746

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[AArch64] Fix BTI landing pad generation.

In some cases BTI landing pad is inserted even compatible instruction
was there already. Meta instruction does not count in this case
therefore skip them in

[AArch64] Fix BTI landing pad generation.

In some cases BTI landing pad is inserted even compatible instruction
was there already. Meta instruction does not count in this case
therefore skip them in the check for first instructions in the function.

Differential revision: https://reviews.llvm.org/D74492

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Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the ne

Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636

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[AArch64][v8.5A] Branch Target Identification code-generation pass

The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark val

[AArch64][v8.5A] Branch Target Identification code-generation pass

The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.

There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.

Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).

This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).

We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.

Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.

Differential revision: https://reviews.llvm.org/D52867

llvm-svn: 343967

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