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Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection |
Date: |
Wed, 5 Jun 2019 09:36:27 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
On 6/5/19 2:20 AM, Michael Rolnik wrote:
> Hi Richard.
>
> I am still struggling with this one.
>
> The spec says.
> The BREAK instruction is used by the On-chip Debug system, and is normally not
> used in the application software.
> When the BREAK instruction is executed, the AVR CPU is set in the Stopped
> Mode.
> This gives the On-chip Debugger access to internal resources.
> If any Lock bits are set, or either the JTAGEN or OCDEN Fuses are
> unprogrammed,
> the CPU will treat the BREAK instruction as a NOP and will not enter the
> Stopped mode.
Yep.
> I read is as follows
> - If user has an intention of using debugger, BREAK should be translated to
> QEMU debug breakpoint
> - If user has no intention of using debugger, BREAK should be translated into
> NOP.
I do not read it that way. The spec is talking about a specific implementation
of debugging -- fuses, jtag and all. We do not need to implement breakpoints
using any of those mechanisms, because we can insert breakpoints via
on-the-side data structures and re-translation.
r~
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/01
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Richard Henderson, 2019/06/03
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/03
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Richard Henderson, 2019/06/03
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/03
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/05
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection,
Richard Henderson <=
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/05
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Richard Henderson, 2019/06/05
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Alex Bennée, 2019/06/05
- Re: [Qemu-devel] [PATCH RFC v20 3/8] target/avr: Add mechanism to check for active debugger connection, Michael Rolnik, 2019/06/05