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    SubjectRe: Serial related oops
    Russell King wrote:

    >
    > Plainly, %ebx changed across the call to serial_in() at c01c0f7b.
    > First thing to notice is this violates the C code - "up" can not
    > change.
    >
    > Now let's look at serial_in:
    >
    > c01bfa70: 55 push %ebp
    > c01bfa71: 89 e5 mov %esp,%ebp
    > c01bfa73: 53 push %ebx
    > ...
    > c01bfab7: 5b pop %ebx
    > c01bfab8: 5d pop %ebp
    > c01bfab9: c3 ret
    >
    > This code tells the CPU to preserves %ebx and %ebp. But we know %ebx
    > _wasn't_ preserved. Ergo, your CPU is plainly not doing what the code
    > told it to do.
    >

    ... assuming nothing else clobbered the stack slot (which would be a
    compiler error, or a wild pointer.)

    Got a disassembly of the whole function?

    -hpa
    -
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