Merge pull request #5245 from jepler/pool-fix-circuitpython

 gc.c: Ensure a gap of one byte before the finaliser table.

Author: tannewt

py/gc.c

@@ -32,6 +32,10 @@
 #include "py/gc.h"
 #include "py/runtime.h"
 
+#if MICROPY_DEBUG_VALGRIND
+#include <valgrind/memcheck.h>
+#endif
+
 #include "supervisor/shared/safe_mode.h"
 
 #if CIRCUITPY_MEMORYMONITOR
@@ -126,7 +130,7 @@ void gc_init(void *start, void *end) {
     // => T = A * (1 + BLOCKS_PER_ATB / BLOCKS_PER_FTB + BLOCKS_PER_ATB * BYTES_PER_BLOCK)
     size_t total_byte_len = (byte *)end - (byte *)start;
     #if MICROPY_ENABLE_FINALISER
-    MP_STATE_MEM(gc_alloc_table_byte_len) = total_byte_len * MP_BITS_PER_BYTE / (MP_BITS_PER_BYTE + MP_BITS_PER_BYTE * BLOCKS_PER_ATB / BLOCKS_PER_FTB + MP_BITS_PER_BYTE * BLOCKS_PER_ATB * BYTES_PER_BLOCK);
+    MP_STATE_MEM(gc_alloc_table_byte_len) = (total_byte_len - 1) * MP_BITS_PER_BYTE / (MP_BITS_PER_BYTE + MP_BITS_PER_BYTE * BLOCKS_PER_ATB / BLOCKS_PER_FTB + MP_BITS_PER_BYTE * BLOCKS_PER_ATB * BYTES_PER_BLOCK);
     #else
     MP_STATE_MEM(gc_alloc_table_byte_len) = total_byte_len / (1 + MP_BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
     #endif
@@ -135,7 +139,7 @@ void gc_init(void *start, void *end) {
 
     #if MICROPY_ENABLE_FINALISER
     size_t gc_finaliser_table_byte_len = (MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB + BLOCKS_PER_FTB - 1) / BLOCKS_PER_FTB;
-    MP_STATE_MEM(gc_finaliser_table_start) = MP_STATE_MEM(gc_alloc_table_start) + MP_STATE_MEM(gc_alloc_table_byte_len);
+    MP_STATE_MEM(gc_finaliser_table_start) = MP_STATE_MEM(gc_alloc_table_start) + MP_STATE_MEM(gc_alloc_table_byte_len) + 1;
     #endif
 
     size_t gc_pool_block_len = MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB;
@@ -391,6 +395,11 @@ void gc_collect_ptr(void *ptr) {
 __attribute__((no_sanitize_address))
 #endif
 static void *gc_get_ptr(void **ptrs, int i) {
+    #if MICROPY_DEBUG_VALGRIND
+    if (!VALGRIND_CHECK_MEM_IS_ADDRESSABLE(&ptrs[i], sizeof(*ptrs))) {
+        return NULL;
+    }
+    #endif
     return ptrs[i];
 }
 

py/mpconfig.h

@@ -486,6 +486,11 @@
 #define MICROPY_DEBUG_VM_STACK_OVERFLOW (0)
 #endif
 
+// Whether to enable extra instrumentation for valgrind
+#ifndef MICROPY_DEBUG_VALGRIND
+#define MICROPY_DEBUG_VALGRIND (0)
+#endif
+
 /*****************************************************************************/
 /* Optimisations                                                             */