Date: Thu, 31 May 2007 14:36:48 +0200 From: Raoul MEGELAS <rmgls@orange.fr> To: freebsd-hackers@freebsd.org Subject: Re: direct I/O access Message-ID: <20070531123650.2DB081C000AB@mwinf2332.orange.fr>
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On Thu, 31 May 2007 08:44:33 +0400
Eygene Ryabinkin <rea-fbsd@codelabs.ru> wrote,
Wed, May 30, 2007 at 02:43:07AM -0400, Mike Meyer wrote:
>> I believe this should be $0x4, as you want to *set* the values, not
>> get them.
> Right.
>> You also need to open the file "/dev/io". I believe that leaving this
>> file open for anything more than a handful of instructions would be a
>> bad thing, but I'm not going to verify it.
> I feel that the i386_set_ioperm directly manipulates the task's I/O
> bitmap referenced by the task state segment (TSS), so you don't
> need to mangle with /dev/io. /dev/io itself is the higher-level
> semi machine-indenepdent abstraction. Opening /dev/io grants the
> global access to all ports, while using i386_set_ioperm gives the
> fine-grained access. When you closing /dev/io, the port I/O access
> is revoked.
> To summarise: either you open /dev/io and do all your port I/O as
> in the good old days of the real-mode programs, or you're using
> i386_set_ioperm to obtain the access permissions to the I/O port
> range and again, do all port I/O as usual.
i rewrote my code and this time, all works fine.
thanks to Mike and Eygene.
here is the code as a proof of the above explanation:
# test_io.S
.include "system.inc"
BUFSIZE = 0x80
.data
params: .long 0x70,2,1,0
path: .asciz "/dev/io"
.bss
buffer: .fill BUFSIZE, 0
.text
.global _start
err:
pushl $0x1 # return failure
SysExit
_start:
addl $8,%esp # discard argc and argv[0]
leal params,%eax
pushl %eax
pushl $4
movl $0xa5,%eax
call bsd_kernel
addl $12,%esp
movl $0X330,%edx
inb %dx,%al
# if i try to read or write another port than 0x70/0x71, i have a segbus fault.
leal path,%ecx
pushl $0 # O_RDONLY
pushl %ecx
SysOpen
jc err # open failed
addl $8,%esp
movl $0X330,%edx
inb %dx,%al
# all is ok!
pushl $0 # return success
SysExit
Thanks again.
Raoul
rmgls@wanadoo.fr
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