Date: Wed, 9 Aug 2000 16:19:25 +0200 From: "Theo van Klaveren" <t.vanklaveren@student.utwente.nl> To: <freebsd-hackers@freebsd.org> Subject: In-kernel ioctl calls Message-ID: <001e01c0020c$d257b3c0$19e55982@student.utwente.nl>
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I think I've finally figured out why AudioFS isn't working (aside from an
endianess error in v0.1), but I can't think of a solution. The problem I've
found is as follows: The code in atapi-cd.c (from Soren's ATA driver)
assumes the passed buffer (in the ioctl struct) is in user-space. The
following is the offending piece of code from the CDIOCREADAUDIO ioctl call:
--- snip ---
if ((error = atapi_queue_cmd(cdp->atp, ccb, buffer, size,
ATPR_F_READ, 30, NULL,NULL)))
break;
if ((error = copyout(buffer, ubuf, size)))
break;
--- snip ---
The first statement issues the read command to the device, I presume. It
copies the data to an internal (kernel-space) buffer. Next, the internal
buffer is copyout()ed to ubuf (which is my ioctl buffer), which fails
because in the case of AudioFS it's in kernel space.
Boing, break, abort, no data for you. Bad boy.
This, of course, caused the buffer's data not to be initialized, causing
noise and crackles. And AudioFS didn't know the ioctl call failed, because
the driver didn't return an error.
Am I just doing it wrong, or should atapi-cd.c be patched to verify if the
buffer is in user space or in kernel space? If so, what function checks if
an address is in kernel space or in user space? If not, what am I doing
wrong?
Theo van Klaveren
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