On Tue, 2018-11-13 at 19:43 +0100, Borislav Petkov wrote: > On Thu, Oct 11, 2018 at 08:15:01AM -0700, Yu-cheng Yu wrote: > > Explain how CET works and the no_cet_shstk/no_cet_ibt kernel > > parameters. > > > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> > > --- > > .../admin-guide/kernel-parameters.txt | 6 + > > Documentation/index.rst | 1 + > > Documentation/x86/index.rst | 11 + > > Documentation/x86/intel_cet.rst | 266 ++++++++++++++++++ > > 4 files changed, 284 insertions(+) > > create mode 100644 Documentation/x86/index.rst > > create mode 100644 Documentation/x86/intel_cet.rst > > So this patch should probably come first in the series so that a reader > can know what to expect... > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > b/Documentation/admin-guide/kernel-parameters.txt > > index 92eb1f42240d..3854423f7c86 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2764,6 +2764,12 @@ > > noexec=on: enable non-executable mappings (default) > > noexec=off: disable non-executable mappings > > > > + no_cet_ibt [X86-64] Disable indirect branch tracking for > > user-mode > > + applications > > + > > + no_cet_shstk [X86-64] Disable shadow stack support for user- > > mode > > + applications > > + > > nosmap [X86] > > Disable SMAP (Supervisor Mode Access Prevention) > > even if it is supported by processor. > > diff --git a/Documentation/index.rst b/Documentation/index.rst > > index 5db7e87c7cb1..1cdc139adb40 100644 > > --- a/Documentation/index.rst > > +++ b/Documentation/index.rst > > Please integrate scripts/checkpatch.pl into your patch creation > workflow. Some of the warnings/errors *actually* make sense: > > WARNING: Missing or malformed SPDX-License-Identifier tag in line 1 > #76: FILE: Documentation/x86/index.rst:1: > +======================= > > WARNING: Missing or malformed SPDX-License-Identifier tag in line 1 > #93: FILE: Documentation/x86/intel_cet.rst:1: > +========================================= > > > @@ -104,6 +104,7 @@ implementation. > > :maxdepth: 2 > > > > sh/index > > + x86/index > > > > Filesystem Documentation > > ------------------------ > > diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst > > new file mode 100644 > > index 000000000000..9c34d8cbc8f0 > > --- /dev/null > > +++ b/Documentation/x86/index.rst > > @@ -0,0 +1,11 @@ > > +======================= > > +X86 Documentation > > +======================= > > + > > +Control Flow Enforcement > > +======================== > > + > > +.. toctree:: > > + :maxdepth: 1 > > + > > + intel_cet > > diff --git a/Documentation/x86/intel_cet.rst > > b/Documentation/x86/intel_cet.rst > > new file mode 100644 > > index 000000000000..946f4802a51f > > --- /dev/null > > +++ b/Documentation/x86/intel_cet.rst > > @@ -0,0 +1,266 @@ > > +========================================= > > +Control Flow Enforcement Technology (CET) > > +========================================= > > + > > +[1] Overview > > +============ > > + > > +Control Flow Enforcement Technology (CET) provides protection against > > +return/jump-oriented programming (ROP) attacks. It can be implemented > > +to protect both the kernel and applications. In the first phase, > > +only the user-mode protection is implemented on the 64-bit kernel. > > s/the// is implemented in 64-bit mode. > > > +However, 32-bit applications are supported under the compatibility > > +mode. > > Drop "However": > > "32-bit applications are, of course, supported in compatibility mode." > > > + > > +CET includes shadow stack (SHSTK) and indirect branch tracking (IBT). > > "CET introduces two a shadow stack and an indirect branch tracking mechanism." > > > +The SHSTK is a secondary stack allocated from memory. The processor > > s/The// > > > +automatically pushes/pops a secure copy to the SHSTK every return > > +address and, > > that reads funny - pls reorganize. Also, what is a "secure copy"? > > You mean a copy of every return address which software cannot access? > > > by comparing the secure copy to the program stack copy, > > +verifies function returns are as intended. > > ... have not been corrupted/modified." > > > The IBT verifies all > > +indirect CALL/JMP targets are intended and marked by the compiler with > > +'ENDBR' op codes. > > "opcode" - one word. And before you use "ENDBR" you need to explain it > above what it is. > > /me reads further... encounters ENDBR's definition... > > ah, ok, so you should say something like > > "... and marked by the compiler with the ENDBR opcode (see below)." I will work on it. Thanks! Yu-cheng
