On Tuesday 02 Feb 2021 at 10:00:29 (+0000), Will Deacon wrote:

On Tue, Feb 02, 2021 at 09:57:36AM +0000, Quentin Perret wrote:

quoted

On Monday 01 Feb 2021 at 19:06:20 (+0000), Will Deacon wrote:

quoted

On Fri, Jan 08, 2021 at 12:15:09PM +0000, Quentin Perret wrote:

quoted

In order to use the kernel list library at EL2, introduce stubs for the
CONFIG_DEBUG_LIST out-of-lines calls.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/kvm/hyp/nvhe/Makefile |  2 +-
 arch/arm64/kvm/hyp/nvhe/stub.c   | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kvm/hyp/nvhe/stub.c

diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index 1fc0684a7678..33bd381d8f73 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile

@@ -10,7 +10,7 @@ lib-objs := clear_page.o copy_page.o memcpy.o memset.o
 lib-objs := $(addprefix ../../../lib/, $(lib-objs))
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
-	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o
+	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o
 obj-y += $(lib-objs)

diff --git a/arch/arm64/kvm/hyp/nvhe/stub.c b/arch/arm64/kvm/hyp/nvhe/stub.c
new file mode 100644
index 000000000000..c0aa6bbfd79d
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/stub.c

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Stubs for out-of-line function calls caused by re-using kernel
+ * infrastructure at EL2.
+ *
+ * Copyright (C) 2020 - Google LLC
+ */
+
+#include <linux/list.h>
+
+#ifdef CONFIG_DEBUG_LIST
+bool __list_add_valid(struct list_head *new, struct list_head *prev,
+		      struct list_head *next)
+{
+		return true;
+}
+
+bool __list_del_entry_valid(struct list_head *entry)
+{
+		return true;
+}
+#endif

Can we get away with defining our own CHECK_DATA_CORRUPTION macro instead?

Yes I think eventually it'd be nice to get there, but that has other
implications (e.g. how do you report something in dmesg from EL2?) so
perhaps we can keep that a separate series?

We wouldn't necessarily have to report anything, but having the return value
of these functions be based off the generic checks would be great if we can
do it (i.e. we'd avoid corrupting the list).

Ah, I see what you mean. Happy to have a go a it, there are a few other
small things that make that it a bit annoying e.g. CHECK_DATA_CORRUPTION
is unconditionally defined in bug.h, and I'll need to stub EXPORT_SYMBOL
as well, which may both require changing core files, but maybe that's
fine. And if that is too painful I think it would make sense to keep
this a separate and self-contained series which would be a nice
incremental improvement over the simple approach I have here :)

Cheers,
Quentin

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