Allow attaching to the sidecar via gdb (#687)

It worked when DD_SPAWN_WORKER_USE_EXEC=1 was set, but not generally. Having a /proc/<pid>/X path will tell gdb exactly where to find it, instead of a /proc/self/fd/X which is pointing into gdbs own process from the perspective of gdb.

This also prevented sidecar core dumps from being opened with gdb, which was rather ugly.

Signed-off-by: Bob Weinand <[email protected]>

Author: bwoebi

spawn_worker/src/trampoline.c

@@ -67,6 +67,16 @@ int main(int argc, char *argv[]) {
           unlink_next = true;
           continue;
       }
+#ifndef _WIN32
+      char buf[30];
+      // Redirect the symlinked /proc/self/X to the actual /proc/<pid>/X - as otherwise debugging tooling may try to read it
+      // And reading /proc/self from the debugging tooling will usually lead to it reading from itself, which may be flatly wrong
+      // E.g. gdb will just hang up for e.g. /proc/self/fd/4, which is an open pipe...
+      if (strncmp(lib_path, "/proc/self/", strlen("/proc/self/")) == 0 && strlen(lib_path) < 20) {
+        sprintf(buf, "/proc/%d/%s", getpid(), lib_path + strlen("/proc/self/"));
+        lib_path = buf;
+      }
+#endif
       if (!(handles[additional_shared_libraries_count++] = dlopen(lib_path, RTLD_LAZY | RTLD_GLOBAL))) {
           fputs(dlerror(), error_fd());
           return 9;

trace-utils/Cargo.toml

@@ -16,7 +16,7 @@ path = "benches/main.rs"
 
 [dependencies]
 anyhow = "1.0"
-hyper = { version = "0.14", features = ["client", "server", "backports", "deprecated"] }
+hyper = { version = "0.14", features = ["client", "server", "runtime", "backports", "deprecated"] }
 hyper-proxy = { version = "0.9.1", default-features = false, features = ["rustls"], optional = true }
 hyper-rustls = {version = "0.27", default-features = false, features = ["native-tokio", "http1", "tls12"]}
 serde = { version = "1.0.145", features = ["derive"] }