On 09/27/2017 09:17 AM, Tsimbalist, Igor V wrote:
Updated version #3.
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index e52a1ea..accba40 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -5655,6 +5655,14 @@ compiled with the @option{-fcf-protection=branch}
option. The
compiler assumes that the function's address is a valid target for a
control-flow transfer.
+@emph{x86 implementation:} when @option{-fcf-protection} option is
+specified the compiler inserts an @code{endbr} instruction at function's
+prologue if the function's type does not have the @code{nocf_check}
+attribute and addresses to which indirect control-flow transfer can
+happen. The instruction triggers the HW check if a control-flow
+transfer to the address where @code{endbr} instruction was inserted
+is valid.
+
I think the consensus among Joseph, Jeff, and I is that this doesn't
belong in the GCC manual at all, but in the ABI documentation. So
please delete the implementation note.
@@ -5662,7 +5670,9 @@ not be instrumented when compiled with the
that the function's address from the pointer is a valid target for
a control-flow transfer. A direct function call through a function
name is assumed to be a safe call thus direct calls are not
-instrumented by the compiler.
+instrumented by the compiler. For @emph{x86 implementation} the
+compiler inserts a @code{notrack} prefix before an indirect call
+instruction.
Ditto with this implementation note.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c4faa23..189130b 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1203,6 +1203,7 @@ See RS/6000 and PowerPC Options.
-msse4a -m3dnow -m3dnowa -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop @gol
-mlzcnt -mbmi2 -mfxsr -mxsave -mxsaveopt -mrtm -mlwp -mmpx @gol
-mmwaitx -mclzero -mpku -mthreads @gol
+-mcet -mibt -mshstk @gol
-mms-bitfields -mno-align-stringops -minline-all-stringops @gol
-minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol
-mmemcpy-strategy=@var{strategy} -mmemset-strategy=@var{strategy} @gol
@@ -11374,6 +11375,14 @@ You can also use the @code{nocf_check} attribute to
identify
which functions and calls should be skipped from instrumentation
(@pxref{Function Attributes}).
+Currently the x86 GNU/Linux target provides an implementation based
+on Intel Control-flow Enforcement Technology (CET). Instrumentation
+for x86 is controlled by target-specific options @option{-mcet},
+@option{-mibt} and @option{-mshstk} (@pxref{x86 Options}).
This part is OK.
+The compiler also provides a number of built-in functions for
+fine-grained control in a CET-based application.
+See @xref{x86 Built-in Functions}, for more information.
I think these builtins emit instructions in the CET extension explicitly
and don't affect the GCC's code generation for the -fcf-protection
option. So please move this to the discussion of -mcet in the x86
options section instead....
@@ -25779,6 +25792,11 @@ supported architecture, using the appropriate flags.
In particular,
the file containing the CPU detection code should be compiled without
these options.
+The @option{-mcet} option turns on the @option{-mibt} and @option{-mshstk}
+options. The @option{-mibt} option enables indirect branch tracking support
+and the @option{-mshstk} option enables shadow stack support from
+Intel Control-flow Enforcement Technology (CET).
+
...here.
The patch is OK with those changes.
-Sandra
