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Subject[PATCH v2 0/7] KVM: selftests: Fix "fix hypercall test" build errors
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After a toolchain upgrade, the x86 fix_hypercall_test started throwing
warnings due to -Werror=array-bounds rightly complaining that the test is
generating an out-of-bounds array access.

The "obvious" fix is to replace the memcpy() with a memcmp() and compare
only the exact size of the hypercall instruction. That worked, until I
fiddled with the code a bit more and suddenly the test started jumping into
the weeds due to gcc generating a call to the external memcmp() through the
PLT, which isn't supported in the selftests.

To fix that mess, which has been a pitfall for quite some time, provide
implementations of memcmp(), memcpy(), and memset() to effectively override
the compiler built-ins. My thought is to start with the helpers that are
most likely to be used in guest code, and then add more as needed.

v2:
- Revert a patch that avoided memset(). [Jim]
- Collect reviews. [Oliver]
- Rename kvm_string.c => string_overrides.c. [David]
- Tweak the "fix hypercall" test to verify that the original opcode
is preserved exactly. [Oliver]
- Further dedup code in the "fix hypercall" test.

v1: https://lore.kernel.org/all/20220908233134.3523339-1-seanjc@google.com

Sean Christopherson (7):
KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest
use
KVM: selftests: Compare insn opcodes directly in fix_hypercall_test
KVM: selftests: Remove unnecessary register shuffling in
fix_hypercall_test
KVM: selftests: Hardcode VMCALL/VMMCALL opcodes in "fix hypercall"
test
KVM: selftests: Explicitly verify KVM doesn't patch hypercall if
quirk==off
KVM: selftests: Dedup subtests of fix_hypercall_test
Revert "KVM: selftests: Fix nested SVM tests when built with clang"

tools/testing/selftests/kvm/Makefile | 11 +-
.../selftests/kvm/lib/string_override.c | 39 +++++
tools/testing/selftests/kvm/lib/x86_64/svm.c | 14 +-
.../selftests/kvm/x86_64/fix_hypercall_test.c | 134 +++++++-----------
4 files changed, 103 insertions(+), 95 deletions(-)
create mode 100644 tools/testing/selftests/kvm/lib/string_override.c


base-commit: c59fb127583869350256656b7ed848c398bef879
--
2.37.3.998.g577e59143f-goog

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