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

Pedro Alves
2012-02-09T20:09:45Z

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That page is obsolete.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 (é½å°§)
>
>
> 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