linux/kernel/bpf/bpf_task_storage.c, branch v6.3

bpf: Fix a compilation failure with clang lto build

2022-12-01T01:13:25Z

When building the kernel with clang lto (CONFIG_LTO_CLANG_FULL=y), the following compilation error will appear: $ make LLVM=1 LLVM_IAS=1 -j ... ld.lld: error: ld-temp.o :26889:1: symbol 'cgroup_storage_map_btf_ids' is already defined cgroup_storage_map_btf_ids:; ^ make[1]: *** [/.../bpf-next/scripts/Makefile.vmlinux_o:61: vmlinux.o] Error 1 In local_storage.c, we have BTF_ID_LIST_SINGLE(cgroup_storage_map_btf_ids, struct, bpf_local_storage_map) Commit c4bcfb38a95e ("bpf: Implement cgroup storage available to non-cgroup-attached bpf progs") added the above identical BTF_ID_LIST_SINGLE definition in bpf_cgrp_storage.c. With duplicated definitions, llvm linker complains with lto build. Also, extracting btf_id of 'struct bpf_local_storage_map' is defined four times for sk, inode, task and cgrp local storages. Let us define a single global one with a different name than cgroup_storage_map_btf_ids, which also fixed the lto compilation error. Fixes: c4bcfb38a95e ("bpf: Implement cgroup storage available to non-cgroup-attached bpf progs") Signed-off-by: Yonghong Song Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221130052147.1591625-1-yhs@fb.com

bpf: Refactor some inode/task/sk storage functions for reuse

2022-10-26T06:19:19Z

Refactor codes so that inode/task/sk storage implementation can maximally share the same code. I also added some comments in new function bpf_local_storage_unlink_nolock() to make codes easy to understand. There is no functionality change. Acked-by: David Vernet Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20221026042845.672944-1-yhs@fb.com Signed-off-by: Alexei Starovoitov

bpf: Add new bpf_task_storage_delete proto with no deadlock detection

2022-10-26T06:11:46Z

The bpf_lsm and bpf_iter do not recur that will cause a deadlock. The situation is similar to the bpf_pid_task_storage_delete_elem() which is called from the syscall map_delete_elem. It does not need deadlock detection. Otherwise, it will cause unnecessary failure when calling the bpf_task_storage_delete() helper. This patch adds bpf_task_storage_delete proto that does not do deadlock detection. It will be used by bpf_lsm and bpf_iter program. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-8-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check

2022-10-26T06:11:46Z

Similar to the earlier change in bpf_task_storage_get_recur. This patch changes bpf_task_storage_delete_recur such that it does the lookup first. It only returns -EBUSY if it needs to take the spinlock to do the deletion when potential deadlock is detected. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-7-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Add new bpf_task_storage_get proto with no deadlock detection

2022-10-26T06:11:46Z

The bpf_lsm and bpf_iter do not recur that will cause a deadlock. The situation is similar to the bpf_pid_task_storage_lookup_elem() which is called from the syscall map_lookup_elem. It does not need deadlock detection. Otherwise, it will cause unnecessary failure when calling the bpf_task_storage_get() helper. This patch adds bpf_task_storage_get proto that does not do deadlock detection. It will be used by bpf_lsm and bpf_iter programs. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-6-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Avoid taking spinlock in bpf_task_storage_get if potential deadlock is detected

2022-10-26T06:11:46Z

bpf_task_storage_get() does a lookup and optionally inserts new data if BPF_LOCAL_STORAGE_GET_F_CREATE is present. During lookup, it will cache the lookup result and caching requires to acquire a spinlock. When potential deadlock is detected (by the bpf_task_storage_busy pcpu-counter added in commit bc235cdb423a ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]")), the current behavior is returning NULL immediately to avoid deadlock. It is too pessimistic. This patch will go ahead to do a lookup (which is a lockless operation) but it will avoid caching it in order to avoid acquiring the spinlock. When lookup fails to find the data and BPF_LOCAL_STORAGE_GET_F_CREATE is set, an insertion is needed and this requires acquiring a spinlock. This patch will still return NULL when a potential deadlock is detected. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-5-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Refactor the core bpf_task_storage_get logic into a new function

2022-10-26T06:11:46Z

This patch creates a new function __bpf_task_storage_get() and moves the core logic of the existing bpf_task_storage_get() into this new function. This new function will be shared by another new helper proto in the latter patch. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-4-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Append _recur naming to the bpf_task_storage helper proto

2022-10-26T06:11:46Z

This patch adds the "_recur" naming to the bpf_task_storage_{get,delete} proto. In a latter patch, they will only be used by the tracing programs that requires a deadlock detection because a tracing prog may use bpf_task_storage_{get,delete} recursively and cause a deadlock. Another following patch will add a different helper proto for the non tracing programs because they do not need the deadlock prevention. This patch does this rename to prepare for this future proto additions. Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20221025184524.3526117-3-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Use this_cpu_{inc|dec|inc_return} for bpf_task_storage_busy

2022-09-01T19:16:12Z

Now migrate_disable() does not disable preemption and under some architectures (e.g. arm64) __this_cpu_{inc|dec|inc_return} are neither preemption-safe nor IRQ-safe, so for fully preemptible kernel concurrent lookups or updates on the same task local storage and on the same CPU may make bpf_task_storage_busy be imbalanced, and bpf_task_storage_trylock() on the specific cpu will always fail. Fixing it by using this_cpu_{inc|dec|inc_return} when manipulating bpf_task_storage_busy. Fixes: bc235cdb423a ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]") Signed-off-by: Hou Tao Acked-by: Alexei Starovoitov Link: https://lore.kernel.org/r/20220901061938.3789460-2-houtao@huaweicloud.com Signed-off-by: Martin KaFai Lau

bpf: Compute map_btf_id during build time

2022-04-26T18:35:21Z

For now, the field 'map_btf_id' in 'struct bpf_map_ops' for all map types are computed during vmlinux-btf init: btf_parse_vmlinux() -> btf_vmlinux_map_ids_init() It will lookup the btf_type according to the 'map_btf_name' field in 'struct bpf_map_ops'. This process can be done during build time, thanks to Jiri's resolve_btfids. selftest of map_ptr has passed: $96 map_ptr:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Reported-by: kernel test robot Signed-off-by: Menglong Dong Signed-off-by: Alexei Starovoitov