[PATCH 00/14] UBSan Enablement for hyp/nVHE code

George-Aurelian Popescu georgepope at google.com
Mon Sep 14 13:27:36 EDT 2020

The main problem solved is logging from hyp/nVHE. Because the nVHE code is
independent from the Linux kernel the logging mechanisms aren’t working.
For this purpose a generic kvm_debug_buffer is designed. It is composed
from a statically allocated array and a writing index and comes with a set
of macros to facilitate it’s usage. To avoid concurrency problems between
cores, the kvm_debug_buffer is defined per_cpu. The buffer is checked every
time when the code returns from an hvc call, by modifying the kvm_call_hyp
and kvm_call_hyp_ret macros. The buffer’s writing index is reseted to zero
inside of the el1_sync entry.

Since UBSan’s handlers are living inside the kernel, they can not be called
inside hyp/nVHE. To enable UBSan new handlers had to be defined there. To
store the data from the handler, the kvm_ubsan_buff is defined. It can store
logging data from the handlers in a new defined struct called struct
kvm_ubsan_info. Each handler has to encapsulate it’s data inside the new
struct and write it into the buffer. The kvm_debug_buffer.c file is
responsible for decapsulating the data and calling the kernel handlers.
To check if UBSan works correctly inside hyp/nVHE the last patch comes
with a test mechanism, that calls UBSan when the hyp is initialized.

George Popescu (14):
  KVM: arm64: Enable UBSan instrumentation in nVHE hyp code
  KVM: arm64: Define a macro for storing a value inside a per_cpu
  KVM: arm64: Add support for creating and checking a logging buffer
    inside hyp/nVHE
  KVM: arm64: Add support for buffer usage
  KVM: arm64: Define a buffer that can pass UBSan data from hyp/nVHE to
  Fix CFLAGS for UBSAN_BOUNDS on Clang
  KVM: arm64: Enable UBSAN_BOUNDS for the both the kernel and hyp/nVHE
  KVM: arm64: Enable UBsan check for unreachable code inside hyp/nVHE
  KVM: arm64: Enable shift out of bounds undefined behaviour check for
  KVM: arm64: __ubsan_handle_load_invalid_value hyp/nVHE implementation.
  KVM: arm64: Detect type mismatch undefined behaviour from hyp/nVHE
  KVM: arm64: Detect arithmetic overflow is inside hyp/nVHE.
  KVM: arm64: Enable the CONFIG_TEST UBSan for PKVM.
  DO NOT MERGE: Enable configs to test the patch series

 arch/arm64/include/asm/kvm_asm.h          |   8 ++
 arch/arm64/include/asm/kvm_debug_buffer.h |  61 ++++++++
 arch/arm64/include/asm/kvm_host.h         |  12 ++
 arch/arm64/include/asm/kvm_ubsan.h        |  53 +++++++
 arch/arm64/kvm/Kconfig                    |   3 +
 arch/arm64/kvm/Makefile                   |   4 +
 arch/arm64/kvm/arm.c                      |  46 +++++-
 arch/arm64/kvm/hyp/hyp-entry.S            |   6 +-
 arch/arm64/kvm/hyp/nvhe/Makefile          |   5 +-
 arch/arm64/kvm/hyp/nvhe/ubsan.c           | 164 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/ubsan_test.c      | 115 +++++++++++++++
 arch/arm64/kvm/kvm_ubsan_buffer.c         |  75 ++++++++++
 lib/Kconfig.ubsan                         |   5 +-
 scripts/Makefile.ubsan                    |   9 +-
 14 files changed, 561 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/kvm_debug_buffer.h
 create mode 100644 arch/arm64/include/asm/kvm_ubsan.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/ubsan.c
 create mode 100644 arch/arm64/kvm/hyp/nvhe/ubsan_test.c
 create mode 100644 arch/arm64/kvm/kvm_ubsan_buffer.c


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