From 534eebc433083af4e9c002555e05f9eec3824813 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 17 Jul 2025 09:48:39 -0700 Subject: [PATCH 1/3] selftests/bpf: Introduce task local data Task local data defines an abstract storage type for storing task- specific data (TLD). This patch provides user space and bpf implementation as header-only libraries for accessing task local data. Task local data is a bpf task local storage map with two UPTRs: 1) u_tld_metadata, shared by all tasks of the same process, consists of the total count of TLDs and an array of metadata of TLDs. A metadata of a TLD comprises the size and the name. The name is used to identify a specific TLD in bpf 2) u_tld_data points to a task-specific memory region for storing TLDs. Below are the core task local data API: User space BPF Define TLD TLD_DEFINE_KEY(), tld_create_key() - Get data tld_get_data() tld_get_data() A TLD is first defined by the user space with TLD_DEFINE_KEY() or tld_create_key(). TLD_DEFINE_KEY() defines a TLD statically and allocates just enough memory during initialization. tld_create_key() allows creating TLDs on the fly, but has a fix memory budget, TLD_DYN_DATA_SIZE. Internally, they all go through the metadata array to check if the TLD can be added. The total TLD size needs to fit into a page (limited by UPTR), and no two TLDs can have the same name. It also calculates the offset, the next available space in u_tld_data, by summing sizes of TLDs. If the TLD can be added, it increases the count using cmpxchg as there may be other concurrent tld_create_key(). After a successful cmpxchg, the last metadata slot now belongs to the calling thread and will be updated. tld_create_key() returns the offset encapsulated as a opaque object key to prevent user misuse. Then, user space can pass the key to tld_get_data() to get a pointer to the TLD. The pointer will remain valid for the lifetime of the thread. BPF programs can also locate the TLD by tld_get_data(), but with both name and key. The first time tld_get_data() is called, the name will be used to lookup the metadata. Then, the key will be saved to a task_local_data map, tld_keys_map. Subsequent call to tld_get_data() will use the key to quickly locate the data. User space task local data library uses a light way approach to ensure thread safety (i.e., atomic operation + compiler and memory barriers). While a metadata is being updated, other threads may also try to read it. To prevent them from seeing incomplete data, metadata::size is used to signal the completion of the update, where 0 means the update is still ongoing. Threads will wait until seeing a non-zero size to read a metadata. Signed-off-by: Amery Hung --- .../bpf/prog_tests/task_local_data.h | 388 ++++++++++++++++++ .../selftests/bpf/progs/task_local_data.bpf.h | 227 ++++++++++ 2 files changed, 615 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/task_local_data.h create mode 100644 tools/testing/selftests/bpf/progs/task_local_data.bpf.h diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_data.h b/tools/testing/selftests/bpf/prog_tests/task_local_data.h new file mode 100644 index 0000000000000..73ee122daf819 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/task_local_data.h @@ -0,0 +1,388 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __TASK_LOCAL_DATA_H +#define __TASK_LOCAL_DATA_H + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifdef TLD_FREE_DATA_ON_THREAD_EXIT +#include +#endif + +#include + +/* + * OPTIONS + * + * Define the option before including the header + * + * TLD_FREE_DATA_ON_THREAD_EXIT - Frees memory on thread exit automatically + * + * Thread-specific memory for storing TLD is allocated lazily on the first call to + * tld_get_data(). The thread that calls it must also calls tld_free() on thread exit + * to prevent memory leak. Pthread will be included if the option is defined. A pthread + * key will be registered with a destructor that calls tld_free(). + * + * + * TLD_DYN_DATA_SIZE - The maximum size of memory allocated for TLDs created dynamically + * (default: 64 bytes) + * + * A TLD can be defined statically using TLD_DEFINE_KEY() or created on the fly using + * tld_create_key(). As the total size of TLDs created with tld_create_key() cannot be + * possibly known statically, a memory area of size TLD_DYN_DATA_SIZE will be allocated + * for these TLDs. This additional memory is allocated for every thread that calls + * tld_get_data() even if no tld_create_key are actually called, so be mindful of + * potential memory wastage. Use TLD_DEFINE_KEY() whenever possible as just enough memory + * will be allocated for TLDs created with it. + * + * + * TLD_NAME_LEN - The maximum length of the name of a TLD (default: 62) + * + * Setting TLD_NAME_LEN will affect the maximum number of TLDs a process can store, + * TLD_MAX_DATA_CNT. + * + * + * TLD_DATA_USE_ALIGNED_ALLOC - Always use aligned_alloc() instead of malloc() + * + * When allocating the memory for storing TLDs, we need to make sure there is a memory + * region of the X bytes within a page. This is due to the limit posed by UPTR: memory + * pinned to the kernel cannot exceed a page nor can it cross the page boundary. The + * library normally calls malloc(2*X) given X bytes of total TLDs, and only uses + * aligned_alloc(PAGE_SIZE, X) when X >= PAGE_SIZE / 2. This is to reduce memory wastage + * as not all memory allocator can use the exact amount of memory requested to fulfill + * aligned_alloc(). For example, some may round the size up to the alignment. Enable the + * option to always use aligned_alloc() if the implementation has low memory overhead. + */ + +#define TLD_PIDFD_THREAD O_EXCL + +#define TLD_PAGE_SIZE getpagesize() +#define TLD_PAGE_MASK (~(TLD_PAGE_SIZE - 1)) + +#define TLD_ROUND_MASK(x, y) ((__typeof__(x))((y) - 1)) +#define TLD_ROUND_UP(x, y) ((((x) - 1) | TLD_ROUND_MASK(x, y)) + 1) + +#define TLD_READ_ONCE(x) (*(volatile typeof(x) *)&(x)) + +#ifndef TLD_DYN_DATA_SIZE +#define TLD_DYN_DATA_SIZE 64 +#endif + +#define TLD_MAX_DATA_CNT (TLD_PAGE_SIZE / sizeof(struct tld_metadata) - 1) + +#ifndef TLD_NAME_LEN +#define TLD_NAME_LEN 62 +#endif + +#ifdef __cplusplus +extern "C" { +#endif + +typedef struct { + __s16 off; +} tld_key_t; + +struct tld_metadata { + char name[TLD_NAME_LEN]; + _Atomic __u16 size; +}; + +struct u_tld_metadata { + _Atomic __u8 cnt; + __u16 size; + struct tld_metadata metadata[]; +}; + +struct u_tld_data { + __u64 start; /* offset of u_tld_data->data in a page */ + char data[]; +}; + +struct tld_map_value { + void *data; + struct u_tld_metadata *metadata; +}; + +struct u_tld_metadata * _Atomic tld_metadata_p __attribute__((weak)); +__thread struct u_tld_data *tld_data_p __attribute__((weak)); +__thread void *tld_data_alloc_p __attribute__((weak)); + +#ifdef TLD_FREE_DATA_ON_THREAD_EXIT +pthread_key_t tld_pthread_key __attribute__((weak)); + +static void tld_free(void); + +static void __tld_thread_exit_handler(void *unused) +{ + tld_free(); +} +#endif + +static int __tld_init_metadata(void) +{ + struct u_tld_metadata *meta, *uninit = NULL; + int err = 0; + + meta = (struct u_tld_metadata *)aligned_alloc(TLD_PAGE_SIZE, TLD_PAGE_SIZE); + if (!meta) { + err = -ENOMEM; + goto out; + } + + memset(meta, 0, TLD_PAGE_SIZE); + meta->size = TLD_DYN_DATA_SIZE; + + if (!atomic_compare_exchange_strong(&tld_metadata_p, &uninit, meta)) { + free(meta); + goto out; + } + +#ifdef TLD_FREE_DATA_ON_THREAD_EXIT + pthread_key_create(&tld_pthread_key, __tld_thread_exit_handler); +#endif +out: + return err; +} + +static int __tld_init_data(int map_fd) +{ + bool use_aligned_alloc = false; + struct tld_map_value map_val; + struct u_tld_data *data; + int err, tid_fd = -1; + void *d = NULL; + + tid_fd = syscall(SYS_pidfd_open, gettid(), TLD_PIDFD_THREAD); + if (tid_fd < 0) { + err = -errno; + goto out; + } + +#ifdef TLD_DATA_USE_ALIGNED_ALLOC + use_aligned_alloc = true; +#endif + + /* + * tld_metadata_p->size = TLD_DYN_DATA_SIZE + + * total size of TLDs defined via TLD_DEFINE_KEY() + */ + if (use_aligned_alloc || tld_metadata_p->size >= TLD_PAGE_SIZE / 2) + d = aligned_alloc(TLD_PAGE_SIZE, tld_metadata_p->size); + else + d = malloc(tld_metadata_p->size * 2); + if (!d) { + err = -ENOMEM; + goto out; + } + + /* + * Always pass a page-aligned address to UPTR since the size of tld_map_value::data + * is a page in BTF. If d spans across two pages, use the page that contains large + * enough memory. + */ + if (TLD_PAGE_SIZE - (~TLD_PAGE_MASK & (intptr_t)d) >= tld_metadata_p->size) { + map_val.data = (void *)(TLD_PAGE_MASK & (intptr_t)d); + data = d; + data->start = (~TLD_PAGE_MASK & (intptr_t)d) + offsetof(struct u_tld_data, data); + } else { + map_val.data = (void *)(TLD_ROUND_UP((intptr_t)d, TLD_PAGE_SIZE)); + data = (void *)(TLD_ROUND_UP((intptr_t)d, TLD_PAGE_SIZE)); + data->start = offsetof(struct u_tld_data, data); + } + map_val.metadata = TLD_READ_ONCE(tld_metadata_p); + + err = bpf_map_update_elem(map_fd, &tid_fd, &map_val, 0); + if (err) { + free(d); + goto out; + } + + tld_data_p = (struct u_tld_data *)data; + tld_data_alloc_p = d; +#ifdef TLD_FREE_DATA_ON_THREAD_EXIT + pthread_setspecific(tld_pthread_key, (void *)1); +#endif +out: + if (tid_fd >= 0) + close(tid_fd); + return err; +} + +static tld_key_t __tld_create_key(const char *name, size_t size, bool dyn_data) +{ + int err, i, sz, off = 0; + __u8 cnt; + + if (!TLD_READ_ONCE(tld_metadata_p)) { + err = __tld_init_metadata(); + if (err) + return (tld_key_t){err}; + } + + for (i = 0; i < TLD_MAX_DATA_CNT; i++) { +retry: + cnt = atomic_load(&tld_metadata_p->cnt); + if (i < cnt) { + /* A metadata is not ready until size is updated with a non-zero value */ + while (!(sz = atomic_load(&tld_metadata_p->metadata[i].size))) + sched_yield(); + + if (!strncmp(tld_metadata_p->metadata[i].name, name, TLD_NAME_LEN)) + return (tld_key_t){-EEXIST}; + + off += TLD_ROUND_UP(sz, 8); + continue; + } + + /* + * TLD_DEFINE_KEY() is given memory upto a page while at most + * TLD_DYN_DATA_SIZE is allocated for tld_create_key() + */ + if (dyn_data) { + if (off + TLD_ROUND_UP(size, 8) > tld_metadata_p->size) + return (tld_key_t){-E2BIG}; + } else { + if (off + TLD_ROUND_UP(size, 8) > TLD_PAGE_SIZE - sizeof(struct u_tld_data)) + return (tld_key_t){-E2BIG}; + tld_metadata_p->size += TLD_ROUND_UP(size, 8); + } + + /* + * Only one tld_create_key() can increase the current cnt by one and + * takes the latest available slot. Other threads will check again if a new + * TLD can still be added, and then compete for the new slot after the + * succeeding thread update the size. + */ + if (!atomic_compare_exchange_strong(&tld_metadata_p->cnt, &cnt, cnt + 1)) + goto retry; + + strncpy(tld_metadata_p->metadata[i].name, name, TLD_NAME_LEN); + atomic_store(&tld_metadata_p->metadata[i].size, size); + return (tld_key_t){(__s16)off}; + } + + return (tld_key_t){-ENOSPC}; +} + +/** + * TLD_DEFINE_KEY() - Define a TLD and a global variable key associated with the TLD. + * + * @name: The name of the TLD + * @size: The size of the TLD + * @key: The variable name of the key. Cannot exceed TLD_NAME_LEN + * + * The macro can only be used in file scope. + * + * A global variable key of opaque type, tld_key_t, will be declared and initialized before + * main() starts. Use tld_key_is_err() or tld_key_err_or_zero() later to check if the key + * creation succeeded. Pass the key to tld_get_data() to get a pointer to the TLD. + * bpf programs can also fetch the same key by name. + * + * The total size of TLDs created using TLD_DEFINE_KEY() cannot exceed a page. Just + * enough memory will be allocated for each thread on the first call to tld_get_data(). + */ +#define TLD_DEFINE_KEY(key, name, size) \ +tld_key_t key; \ + \ +__attribute__((constructor)) \ +void __tld_define_key_##key(void) \ +{ \ + key = __tld_create_key(name, size, false); \ +} + +/** + * tld_create_key() - Create a TLD and return a key associated with the TLD. + * + * @name: The name the TLD + * @size: The size of the TLD + * + * Return an opaque object key. Use tld_key_is_err() or tld_key_err_or_zero() to check + * if the key creation succeeded. Pass the key to tld_get_data() to get a pointer to + * locate the TLD. bpf programs can also fetch the same key by name. + * + * Use tld_create_key() only when a TLD needs to be created dynamically (e.g., @name is + * not known statically or a TLD needs to be created conditionally) + * + * An additional TLD_DYN_DATA_SIZE bytes are allocated per-thread to accommodate TLDs + * created dynamically with tld_create_key(). Since only a user page is pinned to the + * kernel, when TLDs created with TLD_DEFINE_KEY() uses more than TLD_PAGE_SIZE - + * TLD_DYN_DATA_SIZE, the buffer size will be limited to the rest of the page. + */ +__attribute__((unused)) +static tld_key_t tld_create_key(const char *name, size_t size) +{ + return __tld_create_key(name, size, true); +} + +__attribute__((unused)) +static inline bool tld_key_is_err(tld_key_t key) +{ + return key.off < 0; +} + +__attribute__((unused)) +static inline int tld_key_err_or_zero(tld_key_t key) +{ + return tld_key_is_err(key) ? key.off : 0; +} + +/** + * tld_get_data() - Get a pointer to the TLD associated with the given key of the + * calling thread. + * + * @map_fd: A file descriptor of tld_data_map, the underlying BPF task local storage map + * of task local data. + * @key: A key object created by TLD_DEFINE_KEY() or tld_create_key(). + * + * Return a pointer to the TLD if the key is valid; NULL if not enough memory for TLD + * for this thread, or the key is invalid. The returned pointer is guaranteed to be 8-byte + * aligned. + * + * Threads that call tld_get_data() must call tld_free() on exit to prevent + * memory leak if TLD_FREE_DATA_ON_THREAD_EXIT is not defined. + */ +__attribute__((unused)) +static void *tld_get_data(int map_fd, tld_key_t key) +{ + if (!TLD_READ_ONCE(tld_metadata_p)) + return NULL; + + /* tld_data_p is allocated on the first invocation of tld_get_data() */ + if (!tld_data_p && __tld_init_data(map_fd)) + return NULL; + + return tld_data_p->data + key.off; +} + +/** + * tld_free() - Free task local data memory of the calling thread + * + * For the calling thread, all pointers to TLDs acquired before will become invalid. + * + * Users must call tld_free() on thread exit to prevent memory leak. Alternatively, + * define TLD_FREE_DATA_ON_THREAD_EXIT and a thread exit handler will be registered + * to free the memory automatically. + */ +__attribute__((unused)) +static void tld_free(void) +{ + if (tld_data_alloc_p) { + free(tld_data_alloc_p); + tld_data_alloc_p = NULL; + tld_data_p = NULL; + } +} + +#ifdef __cplusplus +} /* extern "C" */ +#endif + +#endif /* __TASK_LOCAL_DATA_H */ diff --git a/tools/testing/selftests/bpf/progs/task_local_data.bpf.h b/tools/testing/selftests/bpf/progs/task_local_data.bpf.h new file mode 100644 index 0000000000000..2f919fa87a666 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/task_local_data.bpf.h @@ -0,0 +1,227 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __TASK_LOCAL_DATA_BPF_H +#define __TASK_LOCAL_DATA_BPF_H + +/* + * Task local data is a library that facilitates sharing per-task data + * between user space and bpf programs. + * + * + * USAGE + * + * A TLD, an entry of data in task local data, first needs to be created by the + * user space. This is done by calling user space API, TLD_DEFINE_KEY() or + * tld_create_key(), with the name of the TLD and the size. + * + * TLD_DEFINE_KEY(prio, "priority", sizeof(int)); + * + * or + * + * void func_call(...) { + * tld_key_t prio, in_cs; + * + * prio = tld_create_key("priority", sizeof(int)); + * in_cs = tld_create_key("in_critical_section", sizeof(bool)); + * ... + * + * A key associated with the TLD, which has an opaque type tld_key_t, will be + * initialized or returned. It can be used to get a pointer to the TLD in the + * user space by calling tld_get_data(). + * + * In a bpf program, tld_object_init() first needs to be called to initialized a + * tld_object on the stack. Then, TLDs can be accessed by calling tld_get_data(). + * The API will try to fetch the key by the name and use it to locate the data. + * A pointer to the TLD will be returned. It also caches the key in a task local + * storage map, tld_key_map, whose value type, struct tld_keys, must be defined + * by the developer. + * + * struct tld_keys { + * tld_key_t prio; + * tld_key_t in_cs; + * }; + * + * SEC("struct_ops") + * void prog(struct task_struct task, ...) + * { + * struct tld_object tld_obj; + * int err, *p; + * + * err = tld_object_init(task, &tld_obj); + * if (err) + * return; + * + * p = tld_get_data(&tld_obj, prio, "priority", sizeof(int)); + * if (p) + * // do something depending on *p + */ +#include +#include + +#define TLD_ROUND_MASK(x, y) ((__typeof__(x))((y) - 1)) +#define TLD_ROUND_UP(x, y) ((((x) - 1) | TLD_ROUND_MASK(x, y)) + 1) + +#define TLD_MAX_DATA_CNT (__PAGE_SIZE / sizeof(struct tld_metadata) - 1) + +#ifndef TLD_NAME_LEN +#define TLD_NAME_LEN 62 +#endif + +typedef struct { + __s16 off; +} tld_key_t; + +struct tld_metadata { + char name[TLD_NAME_LEN]; + __u16 size; +}; + +struct u_tld_metadata { + __u8 cnt; + __u16 size; + struct tld_metadata metadata[TLD_MAX_DATA_CNT]; +}; + +struct u_tld_data { + __u64 start; /* offset of u_tld_data->data in a page */ + char data[__PAGE_SIZE - sizeof(__u64)]; +}; + +struct tld_map_value { + struct u_tld_data __uptr *data; + struct u_tld_metadata __uptr *metadata; +}; + +typedef struct tld_uptr_dummy { + struct u_tld_data data[0]; + struct u_tld_metadata metadata[0]; +} *tld_uptr_dummy_t; + +struct tld_object { + struct tld_map_value *data_map; + struct tld_keys *key_map; + /* + * Force the compiler to generate the actual definition of u_tld_metadata + * and u_tld_data in BTF. Without it, u_tld_metadata and u_tld_data will + * be BTF_KIND_FWD. + */ + tld_uptr_dummy_t dummy[0]; +}; + +/* + * Map value of tld_key_map for caching keys. Must be defined by the developer. + * Members should be tld_key_t and passed to the 3rd argument of tld_fetch_key(). + */ +struct tld_keys; + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, struct tld_map_value); +} tld_data_map SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_TASK_STORAGE); + __uint(map_flags, BPF_F_NO_PREALLOC); + __type(key, int); + __type(value, struct tld_keys); +} tld_key_map SEC(".maps"); + +/** + * tld_object_init() - Initialize a tld_object. + * + * @task: The task_struct of the target task + * @tld_obj: A pointer to a tld_object to be initialized + * + * Return 0 on success; -ENODATA if the user space did not initialize task local data + * for the current task through tld_get_data(); -ENOMEM if the creation of tld_key_map + * fails + */ +__attribute__((unused)) +static int tld_object_init(struct task_struct *task, struct tld_object *tld_obj) +{ + tld_obj->data_map = bpf_task_storage_get(&tld_data_map, task, 0, 0); + if (!tld_obj->data_map) + return -ENODATA; + + tld_obj->key_map = bpf_task_storage_get(&tld_key_map, task, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + if (!tld_obj->key_map) + return -ENOMEM; + + return 0; +} + +/* + * Return the offset of TLD if @name is found. Otherwise, return the current TLD count + * using the nonpositive range so that the next tld_get_data() can skip fetching key if + * no new TLD is added or start comparing name from the first newly added TLD. + */ +__attribute__((unused)) +static int __tld_fetch_key(struct tld_object *tld_obj, const char *name, int i_start) +{ + struct tld_metadata *metadata; + int i, cnt, start, off = 0; + + if (!tld_obj->data_map || !tld_obj->data_map->data || !tld_obj->data_map->metadata) + return 0; + + start = tld_obj->data_map->data->start; + cnt = tld_obj->data_map->metadata->cnt; + metadata = tld_obj->data_map->metadata->metadata; + + bpf_for(i, 0, cnt) { + if (i >= TLD_MAX_DATA_CNT) + break; + + if (i >= i_start && !bpf_strncmp(metadata[i].name, TLD_NAME_LEN, name)) + return start + off; + + off += TLD_ROUND_UP(metadata[i].size, 8); + } + + return -cnt; +} + +/** + * tld_get_data() - Retrieve a pointer to the TLD associated with the name. + * + * @tld_obj: A pointer to a valid tld_object initialized by tld_object_init() + * @key: The cached key of the TLD in tld_key_map + * @name: The name of the key associated with a TLD + * @size: The size of the TLD. Must be a known constant value + * + * Return a pointer to the TLD associated with @name; NULL if not found or @size is too + * big. @key is used to cache the key if the TLD is found to speed up subsequent calls. + * It should be defined as an member of tld_keys of tld_key_t type by the developer. + */ +#define tld_get_data(tld_obj, key, name, size) \ + ({ \ + void *data = NULL, *_data = (tld_obj)->data_map->data; \ + long off = (tld_obj)->key_map->key.off; \ + int cnt; \ + \ + if (likely(_data)) { \ + if (likely(off > 0)) { \ + barrier_var(off); \ + if (likely(off < __PAGE_SIZE - size)) \ + data = _data + off; \ + } else { \ + cnt = -(off); \ + if (likely((tld_obj)->data_map->metadata) && \ + cnt < (tld_obj)->data_map->metadata->cnt) { \ + off = __tld_fetch_key(tld_obj, name, cnt); \ + (tld_obj)->key_map->key.off = off; \ + \ + if (likely(off < __PAGE_SIZE - size)) { \ + barrier_var(off); \ + if (off > 0) \ + data = _data + off; \ + } \ + } \ + } \ + } \ + data; \ + }) + +#endif From a0e6e5e0dfb33dce0048a53f95b45b3fe279d611 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 17 Jul 2025 09:48:40 -0700 Subject: [PATCH 2/3] selftests/bpf: Test basic task local data operations Test basic operations of task local data with valid and invalid tld_create_key(). For invalid calls, make sure they return the right error code and check that the TLDs are not inserted by running tld_get_data(" value_not_exists") on the bpf side. The call should a null pointer. For valid calls, first make sure the TLDs are created by calling tld_get_data() on the bpf side. The call should return a valid pointer. Finally, verify that the TLDs are indeed task-specific (i.e., their addresses do not overlap) with multiple user threads. This done by writing values unique to each thread, reading them from both user space and bpf, and checking if the value read back matches the value written. Signed-off-by: Amery Hung --- .../bpf/prog_tests/test_task_local_data.c | 192 ++++++++++++++++++ .../bpf/progs/test_task_local_data.c | 65 ++++++ 2 files changed, 257 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_task_local_data.c create mode 100644 tools/testing/selftests/bpf/progs/test_task_local_data.c diff --git a/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c b/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c new file mode 100644 index 0000000000000..fde4a030ab42c --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c @@ -0,0 +1,192 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include + +#define TLD_FREE_DATA_ON_THREAD_EXIT +#define TLD_DYN_DATA_SIZE 4096 +#include "task_local_data.h" + +struct test_tld_struct { + __u64 a; + __u64 b; + __u64 c; + __u64 d; +}; + +#include "test_task_local_data.skel.h" + +TLD_DEFINE_KEY(value0_key, "value0", sizeof(int)); + +/* + * Reset task local data between subtests by clearing metadata other + * than the statically defined value0. This is safe as subtests run + * sequentially. Users of task local data library should not touch + * library internal. + */ +static void reset_tld(void) +{ + if (TLD_READ_ONCE(tld_metadata_p)) { + /* Remove TLDs created by tld_create_key() */ + tld_metadata_p->cnt = 1; + tld_metadata_p->size = TLD_DYN_DATA_SIZE; + memset(&tld_metadata_p->metadata[1], 0, + (TLD_MAX_DATA_CNT - 1) * sizeof(struct tld_metadata)); + } +} + +/* Serialize access to bpf program's global variables */ +static pthread_mutex_t global_mutex; + +static tld_key_t *tld_keys; + +#define TEST_BASIC_THREAD_NUM 32 + +void *test_task_local_data_basic_thread(void *arg) +{ + LIBBPF_OPTS(bpf_test_run_opts, opts); + struct test_task_local_data *skel = (struct test_task_local_data *)arg; + int fd, err, tid, *value0, *value1; + struct test_tld_struct *value2; + + fd = bpf_map__fd(skel->maps.tld_data_map); + + value0 = tld_get_data(fd, value0_key); + if (!ASSERT_OK_PTR(value0, "tld_get_data")) + goto out; + + value1 = tld_get_data(fd, tld_keys[1]); + if (!ASSERT_OK_PTR(value1, "tld_get_data")) + goto out; + + value2 = tld_get_data(fd, tld_keys[2]); + if (!ASSERT_OK_PTR(value2, "tld_get_data")) + goto out; + + tid = gettid(); + + *value0 = tid + 0; + *value1 = tid + 1; + value2->a = tid + 2; + value2->b = tid + 3; + value2->c = tid + 4; + value2->d = tid + 5; + + pthread_mutex_lock(&global_mutex); + /* Run task_main that read task local data and save to global variables */ + err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.task_main), &opts); + ASSERT_OK(err, "run task_main"); + ASSERT_OK(opts.retval, "task_main retval"); + + ASSERT_EQ(skel->bss->test_value0, tid + 0, "tld_get_data value0"); + ASSERT_EQ(skel->bss->test_value1, tid + 1, "tld_get_data value1"); + ASSERT_EQ(skel->bss->test_value2.a, tid + 2, "tld_get_data value2.a"); + ASSERT_EQ(skel->bss->test_value2.b, tid + 3, "tld_get_data value2.b"); + ASSERT_EQ(skel->bss->test_value2.c, tid + 4, "tld_get_data value2.c"); + ASSERT_EQ(skel->bss->test_value2.d, tid + 5, "tld_get_data value2.d"); + pthread_mutex_unlock(&global_mutex); + + /* Make sure valueX are indeed local to threads */ + ASSERT_EQ(*value0, tid + 0, "value0"); + ASSERT_EQ(*value1, tid + 1, "value1"); + ASSERT_EQ(value2->a, tid + 2, "value2.a"); + ASSERT_EQ(value2->b, tid + 3, "value2.b"); + ASSERT_EQ(value2->c, tid + 4, "value2.c"); + ASSERT_EQ(value2->d, tid + 5, "value2.d"); + + *value0 = tid + 5; + *value1 = tid + 4; + value2->a = tid + 3; + value2->b = tid + 2; + value2->c = tid + 1; + value2->d = tid + 0; + + /* Run task_main again */ + pthread_mutex_lock(&global_mutex); + err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.task_main), &opts); + ASSERT_OK(err, "run task_main"); + ASSERT_OK(opts.retval, "task_main retval"); + + ASSERT_EQ(skel->bss->test_value0, tid + 5, "tld_get_data value0"); + ASSERT_EQ(skel->bss->test_value1, tid + 4, "tld_get_data value1"); + ASSERT_EQ(skel->bss->test_value2.a, tid + 3, "tld_get_data value2.a"); + ASSERT_EQ(skel->bss->test_value2.b, tid + 2, "tld_get_data value2.b"); + ASSERT_EQ(skel->bss->test_value2.c, tid + 1, "tld_get_data value2.c"); + ASSERT_EQ(skel->bss->test_value2.d, tid + 0, "tld_get_data value2.d"); + pthread_mutex_unlock(&global_mutex); + +out: + pthread_exit(NULL); +} + +static void test_task_local_data_basic(void) +{ + struct test_task_local_data *skel; + pthread_t thread[TEST_BASIC_THREAD_NUM]; + char dummy_key_name[TLD_NAME_LEN]; + tld_key_t key; + int i, err; + + reset_tld(); + + ASSERT_OK(pthread_mutex_init(&global_mutex, NULL), "pthread_mutex_init"); + + skel = test_task_local_data__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_and_load")) + return; + + tld_keys = calloc(TLD_MAX_DATA_CNT, sizeof(tld_key_t)); + if (!ASSERT_OK_PTR(tld_keys, "calloc tld_keys")) + goto out; + + ASSERT_FALSE(tld_key_is_err(value0_key), "TLD_DEFINE_KEY"); + tld_keys[1] = tld_create_key("value1", sizeof(int)); + ASSERT_FALSE(tld_key_is_err(tld_keys[1]), "tld_create_key"); + tld_keys[2] = tld_create_key("value2", sizeof(struct test_tld_struct)); + ASSERT_FALSE(tld_key_is_err(tld_keys[2]), "tld_create_key"); + + /* + * Shouldn't be able to store data exceed a page. Create a TLD just big + * enough to exceed a page. TLDs already created are int value0, int + * value1, and struct test_tld_struct value2. + */ + key = tld_create_key("value_not_exist", + TLD_PAGE_SIZE - 2 * sizeof(int) - sizeof(struct test_tld_struct) + 1); + ASSERT_EQ(tld_key_err_or_zero(key), -E2BIG, "tld_create_key"); + + key = tld_create_key("value2", sizeof(struct test_tld_struct)); + ASSERT_EQ(tld_key_err_or_zero(key), -EEXIST, "tld_create_key"); + + /* Shouldn't be able to create the (TLD_MAX_DATA_CNT+1)-th TLD */ + for (i = 3; i < TLD_MAX_DATA_CNT; i++) { + snprintf(dummy_key_name, TLD_NAME_LEN, "dummy_value%d", i); + tld_keys[i] = tld_create_key(dummy_key_name, sizeof(int)); + ASSERT_FALSE(tld_key_is_err(tld_keys[i]), "tld_create_key"); + } + key = tld_create_key("value_not_exist", sizeof(struct test_tld_struct)); + ASSERT_EQ(tld_key_err_or_zero(key), -ENOSPC, "tld_create_key"); + + /* Access TLDs from multiple threads and check if they are thread-specific */ + for (i = 0; i < TEST_BASIC_THREAD_NUM; i++) { + err = pthread_create(&thread[i], NULL, test_task_local_data_basic_thread, skel); + if (!ASSERT_OK(err, "pthread_create")) + goto out; + } + +out: + for (i = 0; i < TEST_BASIC_THREAD_NUM; i++) + pthread_join(thread[i], NULL); + + if (tld_keys) { + free(tld_keys); + tld_keys = NULL; + } + tld_free(); + test_task_local_data__destroy(skel); +} + +void test_task_local_data(void) +{ + if (test__start_subtest("task_local_data_basic")) + test_task_local_data_basic(); +} diff --git a/tools/testing/selftests/bpf/progs/test_task_local_data.c b/tools/testing/selftests/bpf/progs/test_task_local_data.c new file mode 100644 index 0000000000000..fffafc0130449 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_task_local_data.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include + +#include "task_local_data.bpf.h" + +struct tld_keys { + tld_key_t value0; + tld_key_t value1; + tld_key_t value2; + tld_key_t value_not_exist; +}; + +struct test_tld_struct { + __u64 a; + __u64 b; + __u64 c; + __u64 d; +}; + +int test_value0; +int test_value1; +struct test_tld_struct test_value2; + +SEC("syscall") +int task_main(void *ctx) +{ + struct tld_object tld_obj; + struct test_tld_struct *struct_p; + struct task_struct *task; + int err, *int_p; + + task = bpf_get_current_task_btf(); + err = tld_object_init(task, &tld_obj); + if (err) + return 1; + + int_p = tld_get_data(&tld_obj, value0, "value0", sizeof(int)); + if (int_p) + test_value0 = *int_p; + else + return 2; + + int_p = tld_get_data(&tld_obj, value1, "value1", sizeof(int)); + if (int_p) + test_value1 = *int_p; + else + return 3; + + struct_p = tld_get_data(&tld_obj, value2, "value2", sizeof(struct test_tld_struct)); + if (struct_p) + test_value2 = *struct_p; + else + return 4; + + int_p = tld_get_data(&tld_obj, value_not_exist, "value_not_exist", sizeof(int)); + if (int_p) + return 5; + + return 0; +} + +char _license[] SEC("license") = "GPL"; From 87a21dd2d38b6f0f92f0fe0e84c1efd963f9c220 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 17 Jul 2025 09:48:41 -0700 Subject: [PATCH 3/3] selftests/bpf: Test concurrent task local data key creation Test thread-safety of tld_create_key(). Since tld_create_key() does not rely on locks but memory barriers and atomic operations to protect the shared metadata, the thread-safety of the function is non-trivial. Make sure concurrent tld_key_create(), both valid and invalid, can not race and corrupt metatada, which may leads to TLDs not being thread- specific or duplicate TLDs with the same name. Signed-off-by: Amery Hung --- .../bpf/prog_tests/test_task_local_data.c | 105 ++++++++++++++++++ 1 file changed, 105 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c b/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c index fde4a030ab42c..1d3ccb98b5db5 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c +++ b/tools/testing/selftests/bpf/prog_tests/test_task_local_data.c @@ -185,8 +185,113 @@ static void test_task_local_data_basic(void) test_task_local_data__destroy(skel); } +#define TEST_RACE_THREAD_NUM (TLD_MAX_DATA_CNT - 3) + +void *test_task_local_data_race_thread(void *arg) +{ + int err = 0, id = (intptr_t)arg; + char key_name[32]; + tld_key_t key; + + key = tld_create_key("value_not_exist", TLD_PAGE_SIZE + 1); + if (tld_key_err_or_zero(key) != -E2BIG) { + err = 1; + goto out; + } + + /* Only one thread will succeed in creating value1 */ + key = tld_create_key("value1", sizeof(int)); + if (!tld_key_is_err(key)) + tld_keys[1] = key; + + /* Only one thread will succeed in creating value2 */ + key = tld_create_key("value2", sizeof(struct test_tld_struct)); + if (!tld_key_is_err(key)) + tld_keys[2] = key; + + snprintf(key_name, 32, "thread_%d", id); + tld_keys[id] = tld_create_key(key_name, sizeof(int)); + if (tld_key_is_err(tld_keys[id])) + err = 2; +out: + return (void *)(intptr_t)err; +} + +static void test_task_local_data_race(void) +{ + LIBBPF_OPTS(bpf_test_run_opts, opts); + pthread_t thread[TEST_RACE_THREAD_NUM]; + struct test_task_local_data *skel; + int fd, i, j, err, *data; + void *ret = NULL; + + skel = test_task_local_data__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_and_load")) + return; + + tld_keys = calloc(TLD_MAX_DATA_CNT, sizeof(tld_key_t)); + if (!ASSERT_OK_PTR(tld_keys, "calloc tld_keys")) + goto out; + + fd = bpf_map__fd(skel->maps.tld_data_map); + + ASSERT_FALSE(tld_key_is_err(value0_key), "TLD_DEFINE_KEY"); + tld_keys[0] = value0_key; + + for (j = 0; j < 100; j++) { + reset_tld(); + + for (i = 0; i < TEST_RACE_THREAD_NUM; i++) { + /* + * Try to make tld_create_key() race with each other. Call + * tld_create_key(), both valid and invalid, from different threads. + */ + err = pthread_create(&thread[i], NULL, test_task_local_data_race_thread, + (void *)(intptr_t)(i + 3)); + if (CHECK_FAIL(err)) + break; + } + + /* Wait for all tld_create_key() to return */ + for (i = 0; i < TEST_RACE_THREAD_NUM; i++) { + pthread_join(thread[i], &ret); + if (CHECK_FAIL(ret)) + break; + } + + /* Write a unique number to each TLD */ + for (i = 0; i < TLD_MAX_DATA_CNT; i++) { + data = tld_get_data(fd, tld_keys[i]); + if (CHECK_FAIL(!data)) + break; + *data = i; + } + + /* Read TLDs and check the value to see if any address collides with another */ + for (i = 0; i < TLD_MAX_DATA_CNT; i++) { + data = tld_get_data(fd, tld_keys[i]); + if (CHECK_FAIL(*data != i)) + break; + } + + /* Run task_main to make sure no invalid TLDs are added */ + err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.task_main), &opts); + ASSERT_OK(err, "run task_main"); + ASSERT_OK(opts.retval, "task_main retval"); + } +out: + if (tld_keys) { + free(tld_keys); + tld_keys = NULL; + } + tld_free(); + test_task_local_data__destroy(skel); +} + void test_task_local_data(void) { if (test__start_subtest("task_local_data_basic")) test_task_local_data_basic(); + if (test__start_subtest("task_local_data_race")) + test_task_local_data_race(); }