Do not scan ram to find RTT block, instead use elf to find exact address

probe-plotter-tools/src/bin/custom-viewer.rs

@@ -6,7 +6,8 @@ use std::{env, io::Read, sync::mpsc, thread, time::Duration};
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let help = "Usage: \nprobe-plotter /path/to/elf [chip] [update_rate_ms=10] [channel_mode=no change]";
+    let help =
+        "Usage: \nprobe-plotter /path/to/elf [chip] [update_rate_ms=10] [channel_mode=no change]";
 
     let elf_path = env::args().nth(1).expect(help);
 
@@ -39,7 +40,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .read_to_end(&mut elf_bytes)
         .unwrap();
 
-    let (metrics, settings) = parse(&elf_bytes);
+    let (metrics, settings, scan_region) = parse(&elf_bytes);
 
     let main_thread_token = rerun::MainThreadToken::i_promise_i_am_on_the_main_thread();
 
@@ -78,6 +79,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             &elf_bytes,
             settings,
             metrics,
+            scan_region,
             settings_update_receiver,
             initial_settings_sender,
         )

probe-plotter-tools/src/bin/minimal.rs

@@ -16,7 +16,7 @@ fn main() {
     let mut session = probe_rs::Session::auto_attach(target, Default::default()).unwrap();
     let mut core = session.core(0).unwrap();
 
-    let (mut metrics, _settings) = parse_elf_file(&elf_path);
+    let (mut metrics, _settings, _) = parse_elf_file(&elf_path);
     for m in &metrics {
         println!("{}: {}", m.name, m.address);
     }

probe-plotter-tools/src/lib.rs

@@ -10,7 +10,7 @@ use defmt_parser::Level;
 use object::{Object, ObjectSymbol};
 use probe_rs::{
     Core, MemoryInterface,
-    rtt::{ChannelMode, Rtt},
+    rtt::{self, ChannelMode, Rtt},
 };
 use rerun::TextLogLevel;
 use serde::Deserialize;
@@ -47,17 +47,24 @@ pub enum Type {
 }
 
 // Most of this is taken from https://github.com/knurling-rs/defmt/blob/8e517f8d7224237893e39337a61de8ef98b341f2/decoder/src/elf2table/mod.rs and modified
-pub fn parse(elf_bytes: &[u8]) -> (Vec<Metric>, Vec<Setting>) {
+pub fn parse(elf_bytes: &[u8]) -> (Vec<Metric>, Vec<Setting>, rtt::ScanRegion) {
     let elf = object::File::parse(elf_bytes).unwrap();
 
     let mut metrics = Vec::new();
     let mut settings = Vec::new();
 
+    let mut scan_region = rtt::ScanRegion::Ram;
+
     for entry in elf.symbols() {
         let Ok(name) = entry.name() else {
             continue;
         };
 
+        if name == "_SEGGER_RTT" {
+            scan_region = rtt::ScanRegion::Exact(entry.address());
+            continue;
+        }
+
         let Ok(sym) = Symbol::demangle(name) else {
             continue;
         };
@@ -98,20 +105,18 @@ pub fn parse(elf_bytes: &[u8]) -> (Vec<Metric>, Vec<Setting>) {
         }
     }
 
-    (metrics, settings)
+    (metrics, settings, scan_region)
 }
 
 /// Parse elf file into a set of Metrics and Settings
-pub fn parse_elf_file(elf_path: &str) -> (Vec<Metric>, Vec<Setting>) {
+pub fn parse_elf_file(elf_path: &str) -> (Vec<Metric>, Vec<Setting>, rtt::ScanRegion) {
     let mut buffer = Vec::new();
     std::fs::File::open(elf_path)
         .unwrap()
         .read_to_end(&mut buffer)
         .unwrap();
 
-    let (metrics, settings) = parse(&buffer);
-
-    (metrics, settings)
+    parse(&buffer)
 }
 
 /// A background task which communicates with the probe
@@ -129,12 +134,13 @@ pub fn probe_background_thread(
     elf_bytes: &[u8],
     mut settings: Vec<Setting>,
     mut metrics: Vec<Metric>,
+    scan_region: rtt::ScanRegion,
     settings_update_receiver: mpsc::Receiver<Setting>,
     initial_settings_sender: mpsc::Sender<Vec<Setting>>,
 ) {
     let mut session = probe_rs::Session::auto_attach(target, Default::default()).unwrap();
     let mut core = session.core(0).unwrap();
-    let mut rtt = Rtt::attach(&mut core).unwrap();
+    let mut rtt = Rtt::attach_region(&mut core, &scan_region).unwrap();
     let table = defmt_decoder::Table::parse(elf_bytes).unwrap().unwrap();
 
     // TODO: Get this to work