Commit Graph

4 Commits

Author SHA1 Message Date
Amilendra Kodithuwakku 1f08b08674 [clang][ARM] Emit warnings when PACBTI-M is used with unsupported architectures
Branch protection in M-class is supported by
 - Armv8.1-M.Main
 - Armv8-M.Main
 - Armv7-M

Attempting to enable this for other architectures, either by
command-line (e.g -mbranch-protection=bti) or by target attribute
in source code (e.g.  __attribute__((target("branch-protection=..."))) )
will generate a warning.

In both cases function attributes related to branch protection will not
be emitted. Regardless of the warning, module level attributes related to
branch protection will be emitted when it is enabled via the command-line.

The following people also contributed to this patch:
- Victor Campos

Reviewed By: chill

Differential Revision: https://reviews.llvm.org/D115501
2022-01-28 09:59:58 +00:00
Ties Stuij 53154a83ae [ARM][clang] Add back branch protection tests
When committing the PACBTI-M frontend support
patch (https://reviews.llvm.org/D112421), the tests in
arm-invalid-branch-protection.c were failing on certain test setups, so it was
removed to make the llvm test suite pass. The fix is to require
arm-registered-target.

This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension

The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:

https://developer.arm.com/documentation/ddi0553/latest

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D115141
2021-12-06 15:03:33 +00:00
Ties Stuij 5b4746f94a [clang][ARM] removing branch protection error cmdline test
This test which was just introduced in the PACBTI-M frontend
patch (https://reviews.llvm.org/D112421) is currently failing on some
platforms. Removing temporarily.
2021-12-01 12:09:08 +00:00
Ties Stuij e3b2f0226b [clang][ARM] PACBTI-M frontend support
Handle branch protection option on the commandline as well as a function
attribute. One patch for both mechanisms, as they use the same underlying
parsing mechanism.

These are recorded in a set of LLVM IR module-level attributes like we do for
AArch64 PAC/BTI (see https://reviews.llvm.org/D85649):

- command-line options are "translated" to module-level LLVM IR
  attributes (metadata).

- functions have PAC/BTI specific attributes iff the
  __attribute__((target("branch-protection=...))) was used in the function
  declaration.

- command-line option -mbranch-protection to armclang targeting Arm,
following this grammar:

branch-protection ::= "-mbranch-protection=" <protection>
protection ::=  "none" | "standard" | "bti" [ "+" <pac-ret-clause> ]
                | <pac-ret-clause> [ "+" "bti"]
pac-ret-clause ::= "pac-ret" [ "+" <pac-ret-option> ]
pac-ret-option ::= "leaf" ["+" "b-key"] | "b-key" ["+" "leaf"]

b-key is simply a placeholder to make it consistent with AArch64's
version. In Arm, however, it triggers a warning informing that b-key is
unsupported and a-key will be selected instead.

- Handle _attribute_((target(("branch-protection=..."))) for AArch32 with the
same grammer as the commandline options.

This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension

The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:

https://developer.arm.com/documentation/ddi0553/latest

The following people contributed to this patch:

- Momchil Velikov
- Victor Campos
- Ties Stuij

Reviewed By: vhscampos

Differential Revision: https://reviews.llvm.org/D112421
2021-12-01 10:37:16 +00:00