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[3.14] gh-91048: Revert the memory cache removal for remote debugging (GH-136440) (#136443)

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gh-91048: Revert the memory cache removal for remote debugging (GH-136440)
(cherry picked from commit 77d25e5b16)


gh-91048: Reintroduce the memory cache for remote debugging

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
This commit is contained in:
Miss Islington (bot) 2025-07-09 03:21:56 +02:00 • committed by GitHub
parent 6a2a2906f8
commit 9a79c5128f
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GPG key ID: B5690EEEBB952194
2 changed files with 88 additions and 0 deletions
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78
Python/remote_debug.h
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@ -110,6 +110,14 @@ get_page_size(void) {
return page_size;
}
typedef struct page_cache_entry {
uintptr_t page_addr; // page-aligned base address
char *data;
int valid;
struct page_cache_entry *next;
} page_cache_entry_t;
#define MAX_PAGES 1024
// Define a platform-independent process handle structure
typedef struct {
@ -121,9 +129,27 @@ typedef struct {
#elif defined(__linux__)
int memfd;
#endif
page_cache_entry_t pages[MAX_PAGES];
Py_ssize_t page_size;
} proc_handle_t;
static void
_Py_RemoteDebug_FreePageCache(proc_handle_t *handle)
{
for (int i = 0; i < MAX_PAGES; i++) {
PyMem_RawFree(handle->pages[i].data);
handle->pages[i].data = NULL;
handle->pages[i].valid = 0;
}
}
UNUSED static void
_Py_RemoteDebug_ClearCache(proc_handle_t *handle)
{
for (int i = 0; i < MAX_PAGES; i++) {
handle->pages[i].valid = 0;
}
}
#if defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX
static mach_port_t pid_to_task(pid_t pid);
@ -152,6 +178,10 @@ _Py_RemoteDebug_InitProcHandle(proc_handle_t *handle, pid_t pid) {
handle->memfd = -1;
#endif
handle->page_size = get_page_size();
for (int i = 0; i < MAX_PAGES; i++) {
handle->pages[i].data = NULL;
handle->pages[i].valid = 0;
}
return 0;
}
@ -170,6 +200,7 @@ _Py_RemoteDebug_CleanupProcHandle(proc_handle_t *handle) {
}
#endif
handle->pid = 0;
_Py_RemoteDebug_FreePageCache(handle);
}
#if defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX
@ -1035,6 +1066,53 @@ _Py_RemoteDebug_PagedReadRemoteMemory(proc_handle_t *handle,
size_t size,
void *out)
{
size_t page_size = handle->page_size;
uintptr_t page_base = addr & ~(page_size - 1);
size_t offset_in_page = addr - page_base;
if (offset_in_page + size > page_size) {
return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out);
}
// Search for valid cached page
for (int i = 0; i < MAX_PAGES; i++) {
page_cache_entry_t *entry = &handle->pages[i];
if (entry->valid && entry->page_addr == page_base) {
memcpy(out, entry->data + offset_in_page, size);
return 0;
}
}
// Find reusable slot
for (int i = 0; i < MAX_PAGES; i++) {
page_cache_entry_t *entry = &handle->pages[i];
if (!entry->valid) {
if (entry->data == NULL) {
entry->data = PyMem_RawMalloc(page_size);
if (entry->data == NULL) {
_set_debug_exception_cause(PyExc_MemoryError,
"Cannot allocate %zu bytes for page cache entry "
"during read from PID %d at address 0x%lx",
page_size, handle->pid, addr);
return -1;
}
}
if (_Py_RemoteDebug_ReadRemoteMemory(handle, page_base, page_size, entry->data) < 0) {
// Try to just copy the exact ammount as a fallback
PyErr_Clear();
goto fallback;
}
entry->page_addr = page_base;
entry->valid = 1;
memcpy(out, entry->data + offset_in_page, size);
return 0;
}
}
fallback:
// Cache full — fallback to uncached read
return _Py_RemoteDebug_ReadRemoteMemory(handle, addr, size, out);
}