gh-96143: Allow Linux perf profiler to see Python calls (GH-96123)

:warning:  :warning: Note for reviewers, hackers and fellow systems/low-level/compiler engineers :warning: :warning: 

If you have a lot of experience with this kind of shenanigans and want to improve the **first** version, **please make a PR against my branch** or **reach out by email** or **suggest code changes directly on GitHub**. 

If you have any **refinements or optimizations** please, wait until the first version is merged before starting hacking or proposing those so we can keep this PR productive.

1 files changed, 39 insertions, 0 deletions

diff --git a/Python/initconfig.c b/Python/initconfig.c
index 70f0363..33a8f27 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -118,6 +118,11 @@ The following implementation-specific options are available:\n\
    files are desired as well as suppressing the extra visual location indicators \n\
    when the interpreter displays tracebacks.\n\
 \n\
+-X perf: activate support for the Linux \"perf\" profiler by activating the \"perf\"\n\
+    trampoline. When this option is activated, the Linux \"perf\" profiler will be \n\
+    able to report Python calls. This option is only available on some platforms and will \n\
+    do nothing if is not supported on the current system. The default value is \"off\".\n\
+\n\
 -X frozen_modules=[on|off]: whether or not frozen modules should be used.\n\
    The default is \"on\" (or \"off\" if you are running a local build).";
 
@@ -745,6 +750,7 @@ _PyConfig_InitCompatConfig(PyConfig *config)
     config->use_hash_seed = -1;
     config->faulthandler = -1;
     config->tracemalloc = -1;
+    config->perf_profiling = -1;
     config->module_search_paths_set = 0;
     config->parse_argv = 0;
     config->site_import = -1;
@@ -829,6 +835,7 @@ PyConfig_InitIsolatedConfig(PyConfig *config)
     config->use_hash_seed = 0;
     config->faulthandler = 0;
     config->tracemalloc = 0;
+    config->perf_profiling = 0;
     config->safe_path = 1;
     config->pathconfig_warnings = 0;
 #ifdef MS_WINDOWS
@@ -940,6 +947,7 @@ _PyConfig_Copy(PyConfig *config, const PyConfig *config2)
     COPY_ATTR(_install_importlib);
     COPY_ATTR(faulthandler);
     COPY_ATTR(tracemalloc);
+    COPY_ATTR(perf_profiling);
     COPY_ATTR(import_time);
     COPY_ATTR(code_debug_ranges);
     COPY_ATTR(show_ref_count);
@@ -1050,6 +1058,7 @@ _PyConfig_AsDict(const PyConfig *config)
     SET_ITEM_UINT(hash_seed);
     SET_ITEM_INT(faulthandler);
     SET_ITEM_INT(tracemalloc);
+    SET_ITEM_INT(perf_profiling);
     SET_ITEM_INT(import_time);
     SET_ITEM_INT(code_debug_ranges);
     SET_ITEM_INT(show_ref_count);
@@ -1331,6 +1340,7 @@ _PyConfig_FromDict(PyConfig *config, PyObject *dict)
     CHECK_VALUE("hash_seed", config->hash_seed <= MAX_HASH_SEED);
     GET_UINT(faulthandler);
     GET_UINT(tracemalloc);
+    GET_UINT(perf_profiling);
     GET_UINT(import_time);
     GET_UINT(code_debug_ranges);
     GET_UINT(show_ref_count);
@@ -1687,6 +1697,26 @@ config_read_env_vars(PyConfig *config)
     return _PyStatus_OK();
 }
 
+static PyStatus
+config_init_perf_profiling(PyConfig *config)
+{
+    int active = 0;
+    const char *env = config_get_env(config, "PYTHONPERFSUPPORT");
+    if (env) {
+        if (_Py_str_to_int(env, &active) != 0) {
+            active = 0;
+        }
+        if (active) {
+            config->perf_profiling = 1;
+        }
+    }
+    const wchar_t *xoption = config_get_xoption(config, L"perf");
+    if (xoption) {
+        config->perf_profiling = 1;
+    }
+    return _PyStatus_OK();
+
+}
 
 static PyStatus
 config_init_tracemalloc(PyConfig *config)
@@ -1788,6 +1818,12 @@ config_read_complex_options(PyConfig *config)
             return status;
         }
     }
+    if (config->perf_profiling < 0) {
+        status = config_init_perf_profiling(config);
+        if (_PyStatus_EXCEPTION(status)) {
+            return status;
+        }
+    }
 
     if (config->pycache_prefix == NULL) {
         status = config_init_pycache_prefix(config);
@@ -2104,6 +2140,9 @@ config_read(PyConfig *config, int compute_path_config)
     if (config->tracemalloc < 0) {
         config->tracemalloc = 0;
     }
+    if (config->perf_profiling < 0) {
+        config->perf_profiling = 0;
+    }
     if (config->use_hash_seed < 0) {
         config->use_hash_seed = 0;
         config->hash_seed = 0;