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SubjectRe: 2.5.45 odd deref in serial_in
On Mon, Nov 04, 2002 at 11:27:28PM -0500, Zwane Mwaikambo wrote:
> 0xc023b428 <serial_in+24>: je 0xc023b461 <serial_in+81>
> 0xc023b42a <serial_in+26>: cmp $0x2,%eax
> 0xc023b42d <serial_in+29>: je 0xc023b440 <serial_in+48>
> 0xc023b42f <serial_in+31>: mov 0x8(%ebx),%eax
> 0xc023b432 <serial_in+34>: add %eax,%edx
> 0xc023b434 <serial_in+36>: in (%dx),%al
> eax: 00000000 ebx: 81acc5f0 ecx: 00000000 edx: 00000005
> ...
> default:
> return inb(up->port.iobase + offset); <--
> }

Ok, if I'm reading this correctly:

offset = %edx
up->port.iobase = 0x8(%ebx)
up = %ebx

To get to this return statement, we would have had to execute:

static _INLINE_ unsigned int serial_in(struct uart_8250_port *up, int offset)
offset <<= up->port.regshift;

switch (up->port.iotype) {

which also dereferences "up". So something may have corrupted %ebx
between executing that switch statement and executing the inb().

Could the NMI handler be corrupting %ebx ?

Russell King ( The developer of ARM Linux

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