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Re: kern/54486: athn driver panics on arm
The following reply was made to PR kern/54486; it has been noted by GNATS.
From: Andreas Gustafsson <gson%gson.org@localhost>
Cc: gson%gson.org@localhost (Andreas Gustafsson)
Subject: Re: kern/54486: athn driver panics on arm
Date: Fri, 23 Aug 2019 22:57:52 +0300
Looks like gcc is optimizing the memcpy() call on line 2528 of
src/sys/dev/usb/if_athn_usb.c into an unaligned 32-bit store:
txf = (struct ar_tx_frame *)&htc;
memset(txf, 0, sizeof(*txf));
txf->data_type = AR_HTC_NORMAL;
txf->node_idx = sta_index;
txf->vif_idx = 0;
txf->tid = tid;
The fields at the beginning and end of *txf are being assigned to, so
only the middle part really needs the memset()ting, and gcc apparently
figures the way to do that is to store a 32-bit word of zeros there,
at an unaligned address.
I would not be surprised if this optimizaion is also breaking other
parts of the arm kernel. Does anyone know the right way to fix this?
Andreas Gustafsson, gson%gson.org@localhost
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