gh-118518: Allow perf to work without frame pointers (#112254)

Python/perf_trampoline.c

@@ -143,6 +143,8 @@ any DWARF information available for them).
 #include <sys/mman.h>             // mmap()
 #include <sys/types.h>
 #include <unistd.h>               // sysconf()
+#include <sys/time.h>           // gettimeofday()
+
 
 #if defined(__arm__) || defined(__arm64__) || defined(__aarch64__)
 #define PY_HAVE_INVALIDATE_ICACHE
@@ -187,12 +189,19 @@ struct code_arena_st {
 typedef struct code_arena_st code_arena_t;
 typedef struct trampoline_api_st trampoline_api_t;
 
+enum perf_trampoline_type {
+    PERF_TRAMPOLINE_UNSET = 0,
+    PERF_TRAMPOLINE_TYPE_MAP = 1,
+    PERF_TRAMPOLINE_TYPE_JITDUMP = 2,
+};
+
 #define perf_status _PyRuntime.ceval.perf.status
 #define extra_code_index _PyRuntime.ceval.perf.extra_code_index
 #define perf_code_arena _PyRuntime.ceval.perf.code_arena
 #define trampoline_api _PyRuntime.ceval.perf.trampoline_api
 #define perf_map_file _PyRuntime.ceval.perf.map_file
 #define persist_after_fork _PyRuntime.ceval.perf.persist_after_fork
+#define perf_trampoline_type _PyRuntime.ceval.perf.perf_trampoline_type
 
 static void
 perf_map_write_entry(void *state, const void *code_addr,
@@ -220,6 +229,8 @@ static void*
 perf_map_init_state(void)
 {
     PyUnstable_PerfMapState_Init();
+    trampoline_api.code_padding = 0;
+    perf_trampoline_type = PERF_TRAMPOLINE_TYPE_MAP;
     return NULL;
 }
 
@@ -236,6 +247,30 @@ _PyPerf_Callbacks _Py_perfmap_callbacks = {
     &perf_map_free_state,
 };
 
+
+static size_t round_up(int64_t value, int64_t multiple) {
+    if (multiple == 0) {
+        // Avoid division by zero
+        return value;
+    }
+
+    int64_t remainder = value % multiple;
+    if (remainder == 0) {
+        // Value is already a multiple of 'multiple'
+        return value;
+    }
+
+    // Calculate the difference to the next multiple
+    int64_t difference = multiple - remainder;
+
+    // Add the difference to the value
+    int64_t rounded_up_value = value + difference;
+
+    return rounded_up_value;
+}
+
+// TRAMPOLINE MANAGEMENT API
+
 static int
 new_code_arena(void)
 {
@@ -256,6 +291,7 @@ new_code_arena(void)
     void *start = &_Py_trampoline_func_start;
     void *end = &_Py_trampoline_func_end;
     size_t code_size = end - start;
+    size_t chunk_size = round_up(code_size + trampoline_api.code_padding, 16);
     // TODO: Check the effect of alignment of the code chunks. Initial investigation
     // showed that this has no effect on performance in x86-64 or aarch64 and the current
     // version has the advantage that the unwinder in GDB can unwind across JIT-ed code.
@@ -264,9 +300,9 @@ new_code_arena(void)
     // measurable performance improvement by rounding trampolines up to 32-bit
     // or 64-bit alignment.
 
-    size_t n_copies = mem_size / code_size;
+    size_t n_copies = mem_size / chunk_size;
     for (size_t i = 0; i < n_copies; i++) {
-        memcpy(memory + i * code_size, start, code_size * sizeof(char));
+        memcpy(memory + i * chunk_size, start, code_size * sizeof(char));
     }
     // Some systems may prevent us from creating executable code on the fly.
     int res = mprotect(memory, mem_size, PROT_READ | PROT_EXEC);
@@ -320,16 +356,18 @@ static inline py_trampoline
 code_arena_new_code(code_arena_t *code_arena)
 {
     py_trampoline trampoline = (py_trampoline)code_arena->current_addr;
-    code_arena->size_left -= code_arena->code_size;
-    code_arena->current_addr += code_arena->code_size;
+    size_t total_code_size = round_up(code_arena->code_size + trampoline_api.code_padding, 16);
+    code_arena->size_left -= total_code_size;
+    code_arena->current_addr += total_code_size;
     return trampoline;
 }
 
 static inline py_trampoline
 compile_trampoline(void)
 {
+    size_t total_code_size = round_up(perf_code_arena->code_size + trampoline_api.code_padding, 16);
     if ((perf_code_arena == NULL) ||
-        (perf_code_arena->size_left <= perf_code_arena->code_size)) {
+        (perf_code_arena->size_left <= total_code_size)) {
         if (new_code_arena() < 0) {
             return NULL;
         }
@@ -480,6 +518,7 @@ _PyPerfTrampoline_Fini(void)
     }
     if (perf_status == PERF_STATUS_OK) {
         trampoline_api.free_state(trampoline_api.state);
+        perf_trampoline_type = PERF_TRAMPOLINE_UNSET;
     }
     extra_code_index = -1;
     perf_status = PERF_STATUS_NO_INIT;
@@ -508,6 +547,9 @@ _PyPerfTrampoline_AfterFork_Child(void)
 {
 #ifdef PY_HAVE_PERF_TRAMPOLINE
     if (persist_after_fork) {
+        if (perf_trampoline_type != PERF_TRAMPOLINE_TYPE_MAP) {
+            return PyStatus_Error("Failed to copy perf map file as perf trampoline type is not type map.");
+        }
         _PyPerfTrampoline_Fini();
         char filename[256];
         pid_t parent_pid = getppid();