linux-kernel - [PATCH v2 4/9] KVM: arm64: Enable UBsan check for unreachable code inside hyp/nVHE code

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Date:   Thu, 14 Jan 2021 17:23:34 +0000
From:   Elena Petrova <lenaptr@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Elena Petrova <lenaptr@...gle.com>,
        linux-arm-kernel@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        George Popescu <george.apopescu97@...il.com>,
        George Popescu <georgepope@...gle.com>
Subject: [PATCH v2 4/9] 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 simetric handler.

Signed-off-by: George Popescu <georgepope@...gle.com>
Change-Id: I71d789b7f4ec3d4c787012a061b7f5d7952cee19
Signed-off-by: Elena Petrova <lenaptr@...gle.com>
---
 arch/arm64/include/asm/kvm_ubsan.h |  3 +++
 arch/arm64/kvm/hyp/nvhe/ubsan.c    | 12 +++++++++++-
 arch/arm64/kvm/kvm_ubsan_buffer.c  |  3 +++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_ubsan.h b/arch/arm64/include/asm/kvm_ubsan.h
index 4f471acb88b0..70c6f2541d07 100644
--- a/arch/arm64/include/asm/kvm_ubsan.h
+++ b/arch/arm64/include/asm/kvm_ubsan.h
@@ -19,9 +19,11 @@ struct ubsan_values {
 struct kvm_ubsan_info {
 	enum {
 		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;
@@ -29,3 +31,4 @@ struct kvm_ubsan_info {
 };
 
 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 55a8f6db8555..5e55897b2d72 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 a1523f86be3c..e51949c275aa 100644
--- a/arch/arm64/kvm/kvm_ubsan_buffer.c
+++ b/arch/arm64/kvm/kvm_ubsan_buffer.c
@@ -24,6 +24,9 @@ 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;
 	}
 }
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog