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[Qemu-devel] [PATCH 0/5]

From: Liu Yu
Subject: [Qemu-devel] [PATCH 0/5]
Date: Sat, 25 Jul 2009 16:40:12 +0800

The whole patchset includes:
patch 1: fix kvmppc build error
patch 2: fix kvmppc init error
patch 3~5: add kvmppc guest debug support

The guest debug still have some problems I haven't solved.

1. gdb 'next' command uses software breakpoint
software breakpoint is implemented via modify guest's code.
In most case it works well,
but when used by 'next' it's easy to make trouble on powerpc booke.

For example booke has a code template for
jumping to and returning from interrupt handlers:

        bl transfer
        .long handler_addr
        .long ret_addr

when call transfer, it never return but
in transfer assembly code it will read the handler_addr
and ultimately call the handler.
Gdb doesn't know that and treat it as a normal function call.
so gdb put a software breakpoint instruction at handler_addr,
in order to get trap there when return from transfer.

Then guest will read software breakpoint as handler_addr and jump to there..

I'm not sure if x86 suffer this kind of issue.
Is there any way to avoid this?

2. gdb 'watch' command
Jan told me gdb>6.8 can issue hardware watchpoint request via command 'watch',
my gdb is and our toolchain provider confirm that it 
supports hardware watch
However when I use 'watch', I can only see single step from gdbstub side.
Did I miss anything?

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