[PATCH v17 1/1] arm64: mm: Handle Granule Protection Faults (GPFs)

[Suzuki K Poulose]

From: Steven Price <steven.price at arm.com>

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.

Also, until we unmap the "private" memory pages from the linear map, we could
get spurious GPFs from within the kernel, e.g., load_unaligned_zeropad(). So,
try to fix them up for now.

Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Reviewed-by: Gavin Shan <gshan at redhat.com>
Signed-off-by: Steven Price <steven.price at arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---
Changes since v16:
 * Update the commit description to indicate why we try to fixup GPFs
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 0b52557652be6..ad00997b1a873 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -910,6 +910,22 @@ 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"	},
@@ -946,12 +962,12 @@ 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,	"level -1 granule protection fault (translation table walk)" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 0 granule protection fault (translation table walk)" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 1 granule protection fault (translation table walk)" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 2 granule protection fault (translation table walk)" },
+	{ do_gpf_ptw,		SIGKILL, SI_KERNEL,	"level 3 granule protection fault (translation table walk)" },
+	{ do_gpf,		SIGBUS,  SI_KERNEL,	"granule protection fault" },
 	{ 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