fix: use fp unwinding mode when running go test

Go does not produce .eh_frame sections needed for dwarf unwinding.
In dwarf mode, perf captures a stack snapshot that we can use to fall
back to frame pointer unwinding via framehop. However on arm64, the
snapshot is missing a key register (x29/FP) due to Go's non-standard
function calling convention, so the framehop fallback fails.

Using callgraph mode fp avoids this entirely: the kernel performs the
unwinding itself with full access to the stack.

Author: GuillaumeLagrange

src/executor/helpers/env.rs

@@ -50,6 +50,14 @@ pub fn get_base_injected_env(
     env
 }
 
+/// Set the env variable to not warn users about Go's perf unwinding mode when running Go benchmarks
+pub fn suppress_go_perf_unwinding_warning() {
+    // Safety: no multithreading
+    unsafe {
+        std::env::set_var("CODSPEED_GO_SUPPRESS_PERF_UNWINDING_MODE_WARNING", "true");
+    }
+}
+
 pub fn is_codspeed_debug_enabled() -> bool {
     std::env::var("CODSPEED_LOG")
         .ok()

src/executor/helpers/introspected_golang/go.sh

@@ -32,6 +32,11 @@ if [ $# -eq 0 ]; then
     exit $?
 fi
 
+# On arm64, warn about setting CODSPEED_PERF_UNWINDING_MODE to "fp" for correct flamegraphs
+if [ "$(uname -m)" = "aarch64" ] && [ "${CODSPEED_GO_SUPPRESS_PERF_UNWINDING_MODE_WARNING:-}" != "true" ]; then
+    echo "::warning::Go profiling on arm64 require frame pointer unwinding. Set CODSPEED_PERF_UNWINDING_MODE=fp for better profiling." >&2
+fi
+
 # Route command based on first argument
 case "$1" in
     test)

src/executor/wall_time/perf/mod.rs

@@ -4,6 +4,7 @@ use crate::cli::UnwindingMode;
 use crate::executor::ExecutorConfig;
 use crate::executor::helpers::command::CommandBuilder;
 use crate::executor::helpers::env::is_codspeed_debug_enabled;
+use crate::executor::helpers::env::suppress_go_perf_unwinding_warning;
 use crate::executor::helpers::harvest_perf_maps_for_pids::harvest_perf_maps_for_pids;
 use crate::executor::helpers::run_command_with_log_pipe::run_command_with_log_pipe_and_callback;
 use crate::executor::helpers::run_with_sudo::run_with_sudo;
@@ -98,6 +99,8 @@ impl PerfRunner {
             (mode, None)
         } else if config.command.contains("cargo") {
             (UnwindingMode::Dwarf, None)
+        } else if config.command.contains("go test") {
+            (UnwindingMode::FramePointer, None)
         } else if config.command.contains("pytest")
             || config.command.contains("uv")
             || config.command.contains("python")
@@ -112,7 +115,10 @@ impl PerfRunner {
         };
 
         let cg_mode = match cg_mode {
-            UnwindingMode::FramePointer => "fp",
+            UnwindingMode::FramePointer => {
+                suppress_go_perf_unwinding_warning();
+                "fp"
+            }
             UnwindingMode::Dwarf => &format!("dwarf,{}", stack_size.unwrap_or(8192)),
         };
         debug!("Using call graph mode: {cg_mode:?}");