Messages in this thread | | | Date | Wed, 21 Feb 2007 21:57:50 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Serial related oops |
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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?
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