This is a note to let you know that I've just added the patch titled
parisc: Clear stale IIR value on instruction access rights trap
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-clear-stale-iir-value-on-instruction-access-r.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0896c841802374350db1d2a827cb1aceb4b3ccc7
Author: Helge Deller <deller@xxxxxx>
Date: Wed Dec 8 11:06:52 2021 +0100
parisc: Clear stale IIR value on instruction access rights trap
[ Upstream commit 484730e5862f6b872dca13840bed40fd7c60fa26 ]
When a trap 7 (Instruction access rights) occurs, this means the CPU
couldn't execute an instruction due to missing execute permissions on
the memory region. In this case it seems the CPU didn't even fetched
the instruction from memory and thus did not store it in the cr19 (IIR)
register before calling the trap handler. So, the trap handler will find
some random old stale value in cr19.
This patch simply overwrites the stale IIR value with a constant magic
"bad food" value (0xbaadf00d), in the hope people don't start to try to
understand the various random IIR values in trap 7 dumps.
Noticed-by: John David Anglin <dave.anglin@xxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index a52c7abf2ca49..43f56335759a4 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -729,6 +729,8 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
}
mmap_read_unlock(current->mm);
}
+ /* CPU could not fetch instruction, so clear stale IIR value. */
+ regs->iir = 0xbaadf00d;
fallthrough;
case 27:
/* Data memory protection ID trap */
