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monitor: limit the 'm' command response size

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Fixes #5119
This commit is contained in:
Christian Prochaska 2024-02-19 09:07:53 +01:00 committed by Christian Helmuth
parent aa6f99b0a4
commit ea51f1ffda
2 changed files with 18 additions and 20 deletions
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29
repos/os/src/monitor/gdb_stub.h
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@ -642,25 +642,22 @@ struct m : Command_without_separator
gdb_response(out, [&] (Output &out) {
for (size_t pos = 0; pos < len; ) {
/*
* 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] { };
char chunk[16*1024] { };
Byte_range_ptr const dst { buf, min(sizeof(buf), len) };
size_t const remain_len = len - pos;
size_t const num_bytes = min(sizeof(chunk), remain_len);
size_t const read_len =
state.read_memory(Memory_accessor::Virt_addr { addr }, dst);
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;
}
for (unsigned i = 0; i < read_len; i++)
print(out, Gdb_hex(buf[i]));
});
}
};

9
repos/os/src/test/monitor/main.cc
View File

@ -124,16 +124,17 @@ struct Test::Main
/*
* Dimensioning of the buffer for one round trip:
*
* The terminal_crosslink component uses a buffer of 4 KiB.
* The terminal_crosslink component uses a buffer of 4 KiB and
* the debug monitor limits the 'm' command response to 2 KiB to leave
* enough space for asynchronous notifications and protocol overhead.
* GDB's 'm' command encodes memory as hex, two characters per byte.
* Hence, a dump of max. 2 KiB fits into the terminal-crosslink buffer.
* The GDB command, packet header, and checksum also take a few bytes.
* Hence, a dump of max. 1 KiB is currently possible.
*
* The most effective way to optimize the throughput would be to
* increase the terminal-crosslink's buffer size, reducing the number
* of round trips.
*/
char buffer[2*1024 - 16] { };
char buffer[1024] { };
uint64_t const start_us = timer.elapsed_us();
uint64_t now_us = start_us;