Re: [patch 6/8] Agent's capability

[Pedro Alves <palves@redhat.com>]

On 01/23/2012 02:03 PM, Yao Qi wrote:
> GDB/GDBserver could be able to talk with different agents, if they
> follow the same protocol.  However, different agents may have different
> capabilities, say, one agent can install fast tracepoint, while the
> other agent can't.  Agent capability is to present what agent can do.
> 
> In agent side, we use an interger bit map, and each bit represents a
> corresponding capability.
> 
> This piece of work is different from this, which is about target capability,
> 
> http://sourceware.org/gdb/current/onlinedocs/gdb/Varying-Target-Capabilities.html

That page is obsolete.  We've been addressing those kinds of things with
qSupported features.  I won't stand in the way of this change, but I do
wonder whether we shouldn't instead ask the agent about its features with
a similar (or exactly the same) mechanism.

> 
> -- Yao (齐尧)
> 
> 
> 0006-agent-capability.patch
> 
> 
> 2012-01-23  Yao Qi  <yao@codesourcery.com>
> 
> 	* common/agent.c (struct ipa_sym_addresses) <addr_capability>: New.
> 	(agent_check_capability): New.
> 	(symbol_list): New array element.
> 	* common/agent.h (enum agent_capa): New.
> ---
>  gdb/common/agent.c |   31 +++++++++++++++++++++++++++++++
>  gdb/common/agent.h |   15 +++++++++++++++
>  2 files changed, 46 insertions(+), 0 deletions(-)
> 
> diff --git a/gdb/common/agent.c b/gdb/common/agent.c
> index 5c66071..f4ff08c 100644
> --- a/gdb/common/agent.c
> +++ b/gdb/common/agent.c
> @@ -44,6 +44,7 @@ struct ipa_sym_addresses
>  {
>    CORE_ADDR addr_helper_thread_id;
>    CORE_ADDR addr_cmd_buf;
> +  CORE_ADDR addr_capability;
>  };
>  
>  /* Cache of the helper thread id.  */
> @@ -57,6 +58,7 @@ static struct
>  } symbol_list[] = {
>    IPA_SYM(helper_thread_id),
>    IPA_SYM(cmd_buf),
> +  IPA_SYM(capability),
>  };
>  
>  static struct ipa_sym_addresses ipa_sym_addrs;
> @@ -114,6 +116,9 @@ agent_get_helper_thread_id (void)
>    return helper_thread_id;
>  }
>  
> +/* Each bit of it stands for a capability of agent.  */
> +static unsigned int agent_capability = 0;

Something should be clearing these fields whenever you launch a
new program, or reconnect.

> +
>  /* Connects to synchronization socket.  PID is the pid of inferior, which is
>     used to set up connection socket.  */
>  
> @@ -260,3 +265,29 @@ agent_run_command (int pid, const char *cmd, int len)
>  	}
>      }
>  }
> +
> +/* Return true if agent has capability AGENT_CAP, otherwise return false.  */
> +
> +int
> +agent_check_capability (enum agent_capa agent_capa)
> +{
> +  if  (agent_capability == 0)

Spurious space.

> +    {
> +#ifdef GDBSERVER
> +      if (read_inferior_memory (ipa_sym_addrs.addr_capability,
> +				(unsigned char *) &agent_capability,
> +				sizeof agent_capability))
> +#else
> +      enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
> +      gdb_byte buf[4];
> +
> +      if (target_read_memory (ipa_sym_addrs.addr_capability,
> +			      buf, sizeof buf) == 0)
> +	agent_capability = extract_unsigned_integer (buf, sizeof buf,
> +						     byte_order);
> +      else
> +#endif

#endif seems misplaced.

> +	warning ("Error reading helper thread's id in lib");

Wrong warning?

> +    }
> +  return agent_capability & agent_capa;
> +}
> diff --git a/gdb/common/agent.h b/gdb/common/agent.h
> index 079b65e..cf3fab1 100644
> --- a/gdb/common/agent.h
> +++ b/gdb/common/agent.h
> @@ -36,3 +36,18 @@ void agent_look_up_symbols (void);
>  extern int debug_agent ;
>  
>  extern int use_agent;
> +
> +/* Capability of agent.  Different agents may have different capabilities,
> +   such as installing fast tracepoint or evaluating breakpoint conditions.
> +   Capabilities are represented by bit-maps, and each capability occupy one
> +   bit.  */
> +
> +enum agent_capa
> +{
> +  /* Capability to install fast tracepoint.  */
> +  AGENT_CAPA_FAST_TRACE = 0x1,
> +  /* Capability to install static tracepoint.  */
> +  AGENT_CAPA_STATIC_TRACE = (0x1 << 1),
> +};
> +
> +int agent_check_capability (enum agent_capa);

-- 
Pedro Alves