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Treat cache write as a read in arm64 data faults

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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
This commit is contained in:
Andrew Turner 2022-03-26 15:59:34 +00:00
parent 7afec5182a
commit 029c1c4828
1 changed files with 10 additions and 2 deletions
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12
sys/arm64/arm64/trap.c
View file

@ -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;
}