Sergei Barannikov
2d0137dd64
[clang] Differentiate between identifier and string EnumArgument ( #68550 )
...
EnumArgument may be a string or an identifier. If it is a string, it
should be parsed as unevaluated string literal. Add IsString flag to
EnumArgument so that the parser can choose the correct parsing method.
Target-specific attributes that share spelling may have different
attribute "prototypes". For example, ARM's version of "interrupt"
attribute accepts a string enum, while MSP430's version accepts an
unsigned integer. Adjust ClangAttrEmitter so that the generated
`attributeStringLiteralListArg` returns the correct mask depending on
target triple.
It is worth noting that even after this change some string arguments are
still parsed as identifiers or, worse, as expressions. This is because
of some special logic in `ParseAttributeArgsCommon`. Fixing it is out of
scope of this patch.
2024-02-18 17:44:19 +03:00
Nick Desaulniers
2240d72f15
[X86] initial -mfunction-return=thunk-extern support
...
Adds support for:
* `-mfunction-return=<value>` command line flag, and
* `__attribute__((function_return("<value>")))` function attribute
Where the supported <value>s are:
* keep (disable)
* thunk-extern (enable)
thunk-extern enables clang to change ret instructions into jmps to an
external symbol named __x86_return_thunk, implemented as a new
MachineFunctionPass named "x86-return-thunks", keyed off the new IR
attribute fn_ret_thunk_extern.
The symbol __x86_return_thunk is expected to be provided by the runtime
the compiled code is linked against and is not defined by the compiler.
Enabling this option alone doesn't provide mitigations without
corresponding definitions of __x86_return_thunk!
This new MachineFunctionPass is very similar to "x86-lvi-ret".
The <value>s "thunk" and "thunk-inline" are currently unsupported. It's
not clear yet that they are necessary: whether the thunk pattern they
would emit is beneficial or used anywhere.
Should the <value>s "thunk" and "thunk-inline" become necessary,
x86-return-thunks could probably be merged into x86-retpoline-thunks
which has pre-existing machinery for emitting thunks (which could be
used to implement the <value> "thunk").
Has been found to build+boot with corresponding Linux
kernel patches. This helps the Linux kernel mitigate RETBLEED.
* CVE-2022-23816
* CVE-2022-28693
* CVE-2022-29901
See also:
* "RETBLEED: Arbitrary Speculative Code Execution with Return
Instructions."
* AMD SECURITY NOTICE AMD-SN-1037: AMD CPU Branch Type Confusion
* TECHNICAL GUIDANCE FOR MITIGATING BRANCH TYPE CONFUSION REVISION 1.0
2022-07-12
* Return Stack Buffer Underflow / Return Stack Buffer Underflow /
CVE-2022-29901, CVE-2022-28693 / INTEL-SA-00702
SystemZ may eventually want to support "thunk-extern" and "thunk"; both
options are used by the Linux kernel's CONFIG_EXPOLINE.
This functionality has been available in GCC since the 8.1 release, and
was backported to the 7.3 release.
Many thanks for folks that provided discrete review off list due to the
embargoed nature of this hardware vulnerability. Many Bothans died to
bring us this information.
Link: https://www.youtube.com/watch?v=IF6HbCKQHK8
Link: https://github.com/llvm/llvm-project/issues/54404
Link: https://gcc.gnu.org/legacy-ml/gcc-patches/2018-01/msg01197.html
Link: https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/advisory-guidance/return-stack-buffer-underflow.html
Link: https://arstechnica.com/information-technology/2022/07/intel-and-amd-cpus-vulnerable-to-a-new-speculative-execution-attack/?comments=1
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce114c866860aa9eae3f50974efc68241186ba60
Link: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00702.html
Link: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00707.html
Reviewed By: aaron.ballman, craig.topper
Differential Revision: https://reviews.llvm.org/D129572
2022-07-12 09:17:54 -07:00
