How does softice BPIO work?

NTDEV
1

Hi, all.
As we know in softice we can set breakpoint on I/O port access with the command
BPIO, I wonder how does it work?

best regards
yours brucie

2

> Hi, all.

As we know in softice we can set breakpoint on I/O port access with the command
BPIO, I wonder how does it work?
–
According to it’s manuall, BPIO command uses the debug register support
provided on the Pentium.

best regards
yours brucie

Regards,
Gennady Mayko

3

In TSS you can set trap to IO port you like. See Intel spec.

Bi

-----Original Message-----
From: brucie [mailto:xxxxx@sina.com]
Sent: Wednesday, December 18, 2002 10:38 PM
To: NT Developers Interest List
Subject: [ntdev] How does softice BPIO work?

Hi, all.
As we know in softice we can set breakpoint on I/O port access with the
command
BPIO, I wonder how does it work?

best regards
yours brucie

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4

> Bi Chen wrote:

In TSS you can set trap to IO port you like. See Intel spec.

The I/O permission mask triggers a fault only when the CPL is > the IOPL
in the flags, which will be zero in a Windows system. IOW, an I/O
permission mask setting will not trap accesses from kernel mode. This is
why a debug register trap is needed. FWIW, the device simulator used
with two of the samples in my WDM book relies on exactly this trick to
trap a simulated I/O port.

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