From 029c1c4828aab451ba262cd4e2e1d9362cf18b76 Mon Sep 17 00:00:00 2001 From: Andrew Turner Date: Sat, 26 Mar 2022 15:59:34 +0000 Subject: [PATCH] Treat cache write as a read in arm64 data faults On arm64 we can ask the hardware to perform cache operations from userspace. These require read permission however when the memory is unmapped the kernel will receive a write exception. Add a check to see if the cause of the exception is from the cache and pass a memory read fault type to the vm subsystem. PR: 262836 Reported by: dch Sponsored by: The FreeBSD Foundation --- sys/arm64/arm64/trap.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c index fa921e39b84..226f6959295 100644 --- a/sys/arm64/arm64/trap.c +++ b/sys/arm64/arm64/trap.c @@ -318,8 +318,16 @@ data_abort(struct thread *td, struct trapframe *frame, uint64_t esr, ftype = VM_PROT_EXECUTE; break; default: - ftype = (esr & ISS_DATA_WnR) == 0 ? VM_PROT_READ : - VM_PROT_WRITE; + /* + * If the exception was because of a read or cache operation + * pass a read fault type into the vm code. Cache operations + * need read permission but will set the WnR flag when the + * memory is unmapped. + */ + if ((esr & ISS_DATA_WnR) == 0 || (esr & ISS_DATA_CM) != 0) + ftype = VM_PROT_READ; + else + ftype = VM_PROT_WRITE; break; }