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monitor: make maximum GDB response size configurable

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Fixes #5137
This commit is contained in:
Christian Prochaska 2024-03-08 11:12:34 +01:00 committed by Christian Helmuth
parent 011a521968
commit d1a750c528
3 changed files with 45 additions and 26 deletions
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7
repos/os/src/monitor/README
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@ -45,7 +45,7 @@ GDB commands are useful:
The <monitor> configuration can host optional <policy> nodes referring to
inferiors by their respective labels. For example:
! <monitor>
! <monitor max_response="2K">
! <policy label="first-test-log" wait="no" stop="yes" wx="no"/>
! </monitor>
@ -67,6 +67,11 @@ The enabling of the 'wx' attribute prompts the monitor to map the executable
code of the monitored component as writeable memory, allowing the patching of
text segment by GDB, which is needed for using breakpoints.
The "max_response" attribute of the <monitor> node specifies the
maximum payload size of a GDB command response packet. The default value
is 2048 bytes. It can be increased for higher memory dump throughput, provided
that the terminal session component has the capacity to receive the configured
amount plus GDB protocol overhead and potential asynchronous notifications.
RAM wiping
----------

57
repos/os/src/monitor/gdb_stub.h
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@ -153,6 +153,10 @@ struct Monitor::Gdb::State : Noncopyable
bool gdb_connected { false };
struct Max_response { size_t num_bytes; };
Max_response max_response;
void flush(Inferior_pd &pd)
{
if (_current.constructed() && _current->pd.id() == pd.id())
@ -266,9 +270,12 @@ struct Monitor::Gdb::State : Noncopyable
return false;
}
State(Inferiors &inferiors, Memory_accessor &memory_accessor)
State(Inferiors &inferiors, Memory_accessor &memory_accessor,
Xml_node const &config)
:
inferiors(inferiors), _memory_accessor(memory_accessor)
inferiors(inferiors), _memory_accessor(memory_accessor),
max_response(config.sub_node("monitor").attribute_value("max_response",
Number_of_bytes(2048)))
{ }
};
@ -343,12 +350,12 @@ struct qXfer : Command_with_separator
{
size_t offset, len;
static Window from_args(Const_byte_range_ptr const &args)
static Window from_args(Const_byte_range_ptr const &args,
State::Max_response max_response)
{
return { .offset = comma_separated_hex_value(args, 0, 0UL),
/* terminal_crosslink currently buffers 4096 bytes */
.len = min(comma_separated_hex_value(args, 1, 0UL),
2048UL) };
max_response.num_bytes) };
}
};
@ -368,14 +375,14 @@ struct qXfer : Command_with_separator
with_skipped_prefix(args, "features:read:target.xml:", [&] (Const_byte_range_ptr const &args) {
Raw_data_ptr const total_bytes { _binary_gdb_target_xml_start, _binary_gdb_target_xml_end };
_send_window(out, total_bytes, Window::from_args(args));
_send_window(out, total_bytes, Window::from_args(args, state.max_response));
handled = true;
});
with_skipped_prefix(args, "threads:read::", [&] (Const_byte_range_ptr const &args) {
State::Thread_list const thread_list(state.inferiors);
thread_list.with_bytes([&] (Const_byte_range_ptr const &bytes) {
_send_window(out, bytes, Window::from_args(args)); });
_send_window(out, bytes, Window::from_args(args, state.max_response)); });
handled = true;
});
@ -383,7 +390,7 @@ struct qXfer : Command_with_separator
if (state.current_defined()) {
State::Memory_map const memory_map(state._current->pd);
memory_map.with_bytes([&] (Const_byte_range_ptr const &bytes) {
_send_window(out, bytes, Window::from_args(args)); });
_send_window(out, bytes, Window::from_args(args, state.max_response)); });
} else
gdb_response(out, [&] (Output &out) {
print(out, "l"); });
@ -638,26 +645,32 @@ struct m : Command_without_separator
void execute(State &state, Const_byte_range_ptr const &args, Output &out) const override
{
addr_t const addr = comma_separated_hex_value(args, 0, addr_t(0));
size_t const len = comma_separated_hex_value(args, 1, 0UL);
/* GDB's 'm' command encodes memory as hex, two characters per byte. */
size_t const len = min(comma_separated_hex_value(args, 1, 0UL),
state.max_response.num_bytes / 2);
gdb_response(out, [&] (Output &out) {
/*
* The terminal_crosslink component uses a buffer of 4 KiB and
* some space is needed for asynchronous notifications and
* protocol overhead. GDB's 'm' command encodes memory as hex,
* two characters per byte. Hence, a dump of max. 1 KiB is
* currently possible.
*/
char buf[1024] { };
for (size_t pos = 0; pos < len; ) {
Byte_range_ptr const dst { buf, min(sizeof(buf), len) };
char chunk[min(16*1024UL, len)] { };
size_t const read_len =
state.read_memory(Memory_accessor::Virt_addr { addr }, dst);
size_t const remain_len = len - pos;
size_t const num_bytes = min(sizeof(chunk), remain_len);
for (unsigned i = 0; i < read_len; i++)
print(out, Gdb_hex(buf[i]));
size_t const read_len =
state.read_memory(Memory_accessor::Virt_addr { addr + pos },
Byte_range_ptr(chunk, num_bytes));
for (unsigned i = 0; i < read_len; i++)
print(out, Gdb_hex(chunk[i]));
pos += read_len;
if (read_len < num_bytes)
break;
}
});
}
};

7
repos/os/src/monitor/main.cc
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@ -197,9 +197,9 @@ struct Monitor::Main : Sandbox::State_handler,
}
}
Gdb_stub(Env &env, Inferiors &inferiors)
Gdb_stub(Env &env, Inferiors &inferiors, Xml_node const &config)
:
_env(env), _state(inferiors, _memory_accessor)
_env(env), _state(inferiors, _memory_accessor, config)
{
_terminal.read_avail_sigh(_terminal_read_avail_handler);
_handle_terminal_read_avail();
@ -342,7 +342,8 @@ struct Monitor::Main : Sandbox::State_handler,
if (_reporter.constructed())
_reporter->enabled(reporter_enabled);
_gdb_stub.conditional(config.has_sub_node("monitor"), _env, _inferiors);
_gdb_stub.conditional(config.has_sub_node("monitor"), _env, _inferiors,
config);
_apply_monitor_config_to_inferiors();