Re: [PATCH v16 07/45] arm64: mm: Handle Granule Protection Faults (GPFs)

If the host attempts to access granules that have been delegated for use
in a realm these accesses will be caught and will trigger a Granule
Protection Fault (GPF).

A fault during a page walk signals a bug in the kernel and is handled by
oopsing the kernel. A non-page walk fault could be caused by user space
having access to a page which has been delegated to the kernel and will
trigger a SIGBUS to allow debugging why user space is trying to access a
delegated page.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Gavin Shan <redacted>
Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes since v10:
 * Don't call arm64_notify_die() in do_gpf() but simply return 1.
Changes since v2:
 * Include missing "Granule Protection Fault at level -1"
---
 arch/arm64/mm/fault.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 85e23388f9bb..ea3ae0ca7dba 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c

@@ -909,6 +909,22 @@ static int do_tag_check_fault(unsigned long far, unsigned long esr,
 	return 0;
 }
 
+static int do_gpf_ptw(unsigned long far, unsigned long esr, struct pt_regs *regs)
+{
+	const struct fault_info *inf = esr_to_fault_info(esr);
+
+	die_kernel_fault(inf->name, far, esr, regs);
+	return 0;
+}
+
+static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs)
+{
+	if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr))
+		return 0;
+
+	return 1;
+}