The only difference between them is that OptionalBool's third state
is "unknown" and LazyBool's is "calculate". We don't need to tell
the difference in a single context, so I've made a new eLazyBoolDontKnow
which is an alias of eLazyBoolCalculate.
By turning SetMemoryTagged into a builder method (returns a reference to
self). Then only using that in the tests that need to change the default
of "don't know".
Nothing passes anything but the default value here. Code that wants to
set it is starting with a default constructed info, and filling in the
fields one by one (the gdb-remote client for example).
Meaning a method on an object, which returns a reference to self.
I am doing this because it was pointed out to me that MemoryRegionInfo
has lots of construction paramaters, and most of the time, we want the
default value for most of the things.
So now we can do:
MemoryRegionInfo(...); // Shadow stack is "don't know".
MemoryRegionInfo(...).SetIsShadowStack(eNo) // Shadow stack is "no".
Which removes one parameter from every use of the constructor.
Along the way I realised that the shadow stack "ss" flag is only tested
by the Guarded Control Stack tests, which only run on specific Arm
hardware. I've added a new "ss" test to LinuxProcMapsTest, which will
run on any system.
This is intended for use with Arm's Guarded Control Stack extension
(GCS). Which reuses some existing shadow stack support in Linux. It
should also work with the x86 equivalent.
A "ss" flag is added to the "VmFlags" line of shadow stack memory
regions in `/proc/<pid>/smaps`. To keep the naming generic I've called
it shadow stack instead of guarded control stack.
Also the wording is "shadow stack: yes" because the shadow stack region
is just where it's stored. It's enabled for the whole process or it
isn't. As opposed to memory tagging which can be enabled per region, so
"memory tagging: enabled" fits better for that.
I've added a test case that is also intended to be the start of a set of
tests for GCS. This should help me avoid duplicating the inline assembly
needed.
Note that no special compiler support is needed for the test. However,
for the intial enabling of GCS (assuming the libc isn't doing it) we do
need to use an inline assembly version of prctl.
This is because as soon as you enable GCS, all returns are checked
against the GCS. If the GCS is empty, the program will fault. In other
words, you can never return from the function that enabled GCS, unless
you push values onto it (which is possible but not needed here).
So you cannot use the libc's prctl wrapper for this reason. You can use
that wrapper for anything else, as we do to check if GCS is enabled.
This extends the "memory region" command to
show tagged regions on AArch64 Linux when the MTE
extension is enabled.
(lldb) memory region the_page
[0x0000fffff7ff8000-0x0000fffff7ff9000) rw-
memory tagging: enabled
This is done by adding an optional "flags" field to
the qMemoryRegion packet. The only supported flag is
"mt" but this can be extended.
This "mt" flag is read from /proc/{pid}/smaps on Linux,
other platforms will leave out the "flags" field.
Where this "mt" flag is received "memory region" will
show that it is enabled. If it is not or the target
doesn't support memory tagging, the line is not shown.
(since majority of the time tagging will not be enabled)
Testing is added for the existing /proc/{pid}/maps
parsing and the new smaps parsing.
Minidump parsing has been updated where needed,
though it only uses maps not smaps.
Target specific tests can be run with QEMU and I have
added MTE flags to the existing helper scripts.
Reviewed By: labath
Differential Revision: https://reviews.llvm.org/D87442
