gh-141770: Annotate anonymous mmap usage in debug builds only

Include/internal/pycore_pymem.h

@@ -11,6 +11,11 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#if defined(Py_DEBUG) && defined(HAVE_PR_SET_VMA_ANON_NAME) && defined(__linux__)
+#include <linux/prctl.h>
+#include <sys/prctl.h>
+#endif
+
 // Try to get the allocators name set by _PyMem_SetupAllocators().
 // Return NULL if unknown.
 // Export for '_testinternalcapi' shared extension.
@@ -91,6 +96,18 @@ static inline int _PyMem_IsULongFreed(unsigned long value)
 #endif
 }
 
+static inline int
+_PyAnnotateMemoryMap(void *addr, size_t size, const char *name)
+{
+#if defined(Py_DEBUG) && defined(HAVE_PR_SET_VMA_ANON_NAME) && defined(__linux__)
+   prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, (unsigned long)addr, size, name);
+   // Ignore errno from prctl
+   // See: https://bugzilla.redhat.com/show_bug.cgi?id=2302746
+   errno = 0;
+#endif
+   return 0;
+}
+
 extern int _PyMem_GetAllocatorName(
     const char *name,
     PyMemAllocatorName *allocator);

Misc/NEWS.d/next/Core_and_Builtins/2025-11-29-18-14-28.gh-issue-141770.JURnvg.rst

@@ -0,0 +1,2 @@
+Annotate anonymous mmap usage in debug builds only when supported by the
+Linux kernel. Patch by Donghee Na.

Modules/_ctypes/malloc_closure.c

@@ -14,6 +14,7 @@
 #  endif
 #endif
 #include "ctypes.h"
+#include "pycore_obmalloc.h"      // _PyAnnotateMemoryMap()
 
 /* BLOCKSIZE can be adjusted.  Larger blocksize will take a larger memory
    overhead, but allocate less blocks from the system.  It may be that some
@@ -74,14 +75,16 @@ static void more_core(void)
     if (item == NULL)
         return;
 #else
+    size_t mem_size = count * sizeof(ITEM);
     item = (ITEM *)mmap(NULL,
-                        count * sizeof(ITEM),
+                        mem_size,
                         PROT_READ | PROT_WRITE | PROT_EXEC,
                         MAP_PRIVATE | MAP_ANONYMOUS,
                         -1,
                         0);
     if (item == (void *)MAP_FAILED)
         return;
+    _PyAnnotateMemoryMap(item, mem_size, "cpython:more_core");
 #endif
 
 #ifdef MALLOC_CLOSURE_DEBUG

Modules/mmapmodule.c

@@ -26,6 +26,7 @@
 #include "pycore_abstract.h"      // _Py_convert_optional_to_ssize_t()
 #include "pycore_bytesobject.h"   // _PyBytes_Find()
 #include "pycore_fileutils.h"     // _Py_stat_struct
+#include "pycore_obmalloc.h"      // _PyAnnotateMemoryMap()
 #include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 
 #include <stddef.h>               // offsetof()
@@ -1951,6 +1952,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }
+    _PyAnnotateMemoryMap(m_obj->data, map_size, "cpython:new_mmap_object");
     m_obj->access = (access_mode)access;
     return (PyObject *)m_obj;
 }

Objects/obmalloc.c

@@ -467,6 +467,7 @@ _PyMem_ArenaAlloc(void *Py_UNUSED(ctx), size_t size)
     if (ptr == MAP_FAILED)
         return NULL;
     assert(ptr != NULL);
+    _PyAnnotateMemoryMap(ptr, size, "cpython:PyMem_ArenaAlloc");
     return ptr;
 #else
     return malloc(size);

Python/jit.c

@@ -71,6 +71,9 @@ jit_alloc(size_t size)
     int prot = PROT_READ | PROT_WRITE;
     unsigned char *memory = mmap(NULL, size, prot, flags, -1, 0);
     int failed = memory == MAP_FAILED;
+    if (!failed) {
+        _PyAnnotateMemoryMap(memory, size, "cpython:jit_alloc");
+    }
 #endif
     if (failed) {
         jit_error("unable to allocate memory");

Python/perf_jit_trampoline.c

@@ -61,6 +61,7 @@
 #include "pycore_ceval.h"         // _PyPerf_Callbacks
 #include "pycore_frame.h"
 #include "pycore_interp.h"
+#include "pycore_obmalloc.h"      // _PyAnnotateMemoryMap()
 #include "pycore_runtime.h"       // _PyRuntime
 
 #ifdef PY_HAVE_PERF_TRAMPOLINE
@@ -1085,6 +1086,7 @@ static void* perf_map_jit_init(void) {
         close(fd);
         return NULL;  // Memory mapping failed
     }
+    _PyAnnotateMemoryMap(perf_jit_map_state.mapped_buffer, page_size, "cpython:perf_map_jit_init");
 #endif
 
     perf_jit_map_state.mapped_size = page_size;

Python/perf_trampoline.c

@@ -132,6 +132,7 @@ any DWARF information available for them).
 #include "Python.h"
 #include "pycore_ceval.h"         // _PyPerf_Callbacks
 #include "pycore_interpframe.h"   // _PyFrame_GetCode()
+#include "pycore_obmalloc.h"      // _PyAnnotateMemoryMap()
 #include "pycore_runtime.h"       // _PyRuntime
 
 
@@ -290,6 +291,7 @@ new_code_arena(void)
         perf_status = PERF_STATUS_FAILED;
         return -1;
     }
+    _PyAnnotateMemoryMap(memory, mem_size, "cpython:new_code_arena");
     void *start = &_Py_trampoline_func_start;
     void *end = &_Py_trampoline_func_end;
     size_t code_size = end - start;

configure.ac

@@ -5578,6 +5578,13 @@ AC_CHECK_DECLS([UT_NAMESIZE],
               [],
               [@%:@include <utmp.h>])
 
+AC_CHECK_DECLS([PR_SET_VMA_ANON_NAME],
+              [AC_DEFINE([HAVE_PR_SET_VMA_ANON_NAME], [1],
+                         [Define if you have the 'PR_SET_VMA_ANON_NAME' constant.])],
+              [],
+              [@%:@include <linux/prctl.h>
+               @%:@include <sys/prctl.h>])
+
 # check for openpty, login_tty, and forkpty
 
 AC_CHECK_FUNCS([openpty], [],

pyconfig.h.in

@@ -228,6 +228,10 @@
 /* Define to 1 if you have the <db.h> header file. */
 #undef HAVE_DB_H
 
+/* Define to 1 if you have the declaration of 'PR_SET_VMA_ANON_NAME', and to 0
+   if you don't. */
+#undef HAVE_DECL_PR_SET_VMA_ANON_NAME
+
 /* Define to 1 if you have the declaration of 'RTLD_DEEPBIND', and to 0 if you
    don't. */
 #undef HAVE_DECL_RTLD_DEEPBIND
@@ -996,6 +1000,9 @@
 /* Define if your compiler supports function prototype */
 #undef HAVE_PROTOTYPES
 
+/* Define if you have the 'PR_SET_VMA_ANON_NAME' constant. */
+#undef HAVE_PR_SET_VMA_ANON_NAME
+
 /* Define to 1 if you have the 'pthread_condattr_setclock' function. */
 #undef HAVE_PTHREAD_CONDATTR_SETCLOCK