linux-kernel - [PATCH 08/14] KVM: arm64: Enable UBsan check for unreachable code inside hyp/nVHE code

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Message-Id: <20200914172750.852684-9-georgepope@google.com>
Date:   Mon, 14 Sep 2020 17:27:44 +0000
From:   George-Aurelian Popescu <georgepope@...gle.com>
To:     maz@...nel.org, catalin.marinas@....com, will@...nel.org,
        masahiroy@...nel.org, michal.lkml@...kovi.net
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        clang-built-linux@...glegroups.com, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        natechancellor@...il.com, ndesaulniers@...gle.com,
        dbrazdil@...gle.com, broonie@...nel.org, maskray@...gle.com,
        ascull@...gle.com, keescook@...omium.org,
        akpm@...ux-foundation.org, dvyukov@...gle.com, elver@...gle.com,
        tglx@...utronix.de, arnd@...db.de,
        George Popescu <georgepope@...gle.com>
Subject: [PATCH 08/14] KVM: arm64: Enable UBsan check for unreachable code inside hyp/nVHE code

From: George Popescu <georgepope@...gle.com>

The data from __ubsan_handle_builtin_unreachable is passed to the buffer
and printed inside the kernel by its symmetric handler.

Signed-off-by: George Popescu <georgepope@...gle.com>
---
 arch/arm64/include/asm/kvm_ubsan.h |  5 ++++-
 arch/arm64/kvm/hyp/nvhe/ubsan.c    | 12 +++++++++++-
 arch/arm64/kvm/kvm_ubsan_buffer.c  |  3 +++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index 575881e0bd5f..7fd0d0dfbd82 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -20,10 +20,12 @@ struct ubsan_values {
 struct kvm_ubsan_info {
 	enum {
 		UBSAN_NONE,
-		UBSAN_OUT_OF_BOUNDS
+		UBSAN_OUT_OF_BOUNDS,
+		UBSAN_UNREACHABLE_DATA
 	} type;
 	union {
 		struct out_of_bounds_data out_of_bounds_data;
+		struct unreachable_data unreachable_data;
 	};
 	union {
 		struct ubsan_values u_val;
@@ -32,3 +34,4 @@ struct kvm_ubsan_info {
 #endif
 
 void __ubsan_handle_out_of_bounds(void *_data, void *index);
+void __ubsan_handle_builtin_unreachable(void *_data);
diff --git a/arch/arm64/kvm/hyp/nvhe/ubsan.c b/arch/arm64/kvm/hyp/nvhe/ubsan.c
index b2d3404f6215..9497e7f7f397 100644
--- a/arch/arm64/kvm/hyp/nvhe/ubsan.c
+++ b/arch/arm64/kvm/hyp/nvhe/ubsan.c
@@ -58,6 +58,16 @@ void __ubsan_handle_out_of_bounds(void *_data, void *index)
 
 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs) {}
 
-void __ubsan_handle_builtin_unreachable(void *_data) {}
+void __ubsan_handle_builtin_unreachable(void *_data)
+{
+	struct kvm_ubsan_info *slot;
+	struct unreachable_data *data = _data;
+
+	slot = kvm_ubsan_buffer_next_slot();
+	if (slot) {
+		slot->type = UBSAN_UNREACHABLE_DATA;
+		slot->unreachable_data = *data;
+	}
+}
 
 void __ubsan_handle_load_invalid_value(void *_data, void *val) {}
diff --git a/arch/arm64/kvm/kvm_ubsan_buffer.c b/arch/arm64/kvm/kvm_ubsan_buffer.c
index ce796bdd027e..f66cc5f7878e 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -25,6 +25,9 @@ void __kvm_check_ubsan_data(struct kvm_ubsan_info *slot)
 		__ubsan_handle_out_of_bounds(&slot->out_of_bounds_data,
 				slot->u_val.lval);
 		break;
+	case UBSAN_UNREACHABLE_DATA:
+		__ubsan_handle_builtin_unreachable(&slot->unreachable_data);
+		break;
 	}
 }
 
-- 
2.28.0.618.gf4bc123cb7-goog