On Thu, 2018-08-30 at 22:39 +0200, Pavel Machek wrote:

Hi!

quoted

diff --git a/Documentation/admin-guide/kernel-parameters.txt

b/Documentation/admin-guide/kernel-parameters.txt
index 9871e649ffef..b090787188b4 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

Hmm, not too consistent with "nosmap" below. Would it make sense to
have cet=on/off/ibt/shstk instead?

quoted

+++ b/Documentation/x86/intel_cet.rst

@@ -0,0 +1,252 @@
+=========================================
+Control Flow Enforcement Technology (CET)
+=========================================
+
+[1] Overview
+============
+
+Control Flow Enforcement Technology (CET) provides protection

against
+return/jump-oriented programing (ROP) attacks.

Can you add something like "It attempts to protect process from
running arbitrary code even after attacker has control of its stack"
-- for people that don't know what ROP is, and perhaps link to
wikipedia explaining ROP or something...

quoted

It can be implemented
+to protect both the kernel and applications.  In the first phase,
+only the user-mode protection is implemented for the 64-bit
kernel.
+Thirty-two bit applications are supported under the compatibility

32-bit (for consistency).

Ok, so CET stops execution of malicious code before architectural
effects are visible, correct? Does it prevent micro-architectural
effects of the malicious code? (cache content would be one example;
see Spectre).

quoted

+[3] Application Enabling
+========================

"Enabling CET in applications" ?

quoted

+Signal
+------
+
+The main program and its signal handlers use the same
SHSTK.  Because
+the SHSTK stores only return addresses, we can estimate a large
+enough SHSTK to cover the condition that both the program stack
and
+the sigaltstack run out.

English? Is it estimate or is it large enough? "a large" -- "a"
should
be deleted AFAICT.
 

I will work on these, thanks!