Subject: [PATCH v14 03/44] arm64: RME: Handle Granule Protection Faults (GPFs)

From: Steven Price <[email-masked]>
Date: Wed, 13 May 2026 14:17:11 +0100

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 <[email-masked]>
Reviewed-by: Gavin Shan <[email-masked]>
Signed-off-by: Steven Price <[email-masked]>
---
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 0f3c5c7ca054..6358ea4787ba 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -905,6 +905,22 @@ 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;
+}
+
 static const struct fault_info fault_info[] = {
 	{ do_bad,		SIGKILL, SI_KERNEL,	"ttbr address size fault"	},
 	{ do_bad,		SIGKILL, SI_KERNEL,	"level 1 address size fault"	},
@@ -941,12 +957,12 @@ static const struct fault_info fault_info[] = {
 	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 32"			},
 	{ do_alignment_fault,	SIGBUS,  BUS_ADRALN,	"alignment fault"		},
 	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 34"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 35"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 36"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 37"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 38"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 39"			},
-	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 40"			},
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level -1" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 0" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 1" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 2" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"Granule Protection Fault at level 3" },
+	{ do_gpf,		SIGBUS,  SI_KERNEL,	"Granule Protection Fault not on table walk" },
 	{ do_bad,		SIGKILL, SI_KERNEL,	"level -1 address size fault"	},
 	{ do_bad,		SIGKILL, SI_KERNEL,	"unknown 42"			},
 	{ do_translation_fault,	SIGSEGV, SEGV_MAPERR,	"level -1 translation fault"	},
-- 
2.43.0