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Re: breakpoint extension for remote protocol, take II
- To: Toshiyasu Morita <tm@netcom.com>
- Subject: Re: breakpoint extension for remote protocol, take II
- From: jtc@redback.com (J.T. Conklin)
- Date: 14 Jun 1999 17:42:02 -0700
- Cc: gdb@sourceware.cygnus.com
- References: <199906150023.RAA14961@netcom16.netcom.com>
- Reply-To: jtc@redback.com
>>>>> "Toshiyasu" == Toshiyasu Morita <tm@netcom.com> writes:
>> I was unaware processors with multiple software breakpoints
>> existed. I assume that the 2 byte breakpoint instructions have to
>> be inserted in "high-density" code segments and 4 byte breakpoints
>> insns have to be inserted in "low-density" segments.
Toshiyasu> Is there a four-byte sequence which is an illegal
Toshiyasu> instruction in both MIPS16 and MIPS32 modes?
Even if there were, I don't think it would work.
If you installed this four byte sequence in a 16 bit code segment at
0x1000, it would also overwrite the instruction at 0x1002. If that
instruction is a branch target, bad things are likely to happen. A
bit of compiler support to insert a nop before branch targets could
possibly make this work, but that would diminish any benefit high
density instructions are supposed to offer.
--jtc
--
J.T. Conklin
RedBack Networks