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![Yonghong Song](/assets/img/avatar_default.png)
Similar to sk/inode/task storage, implement similar cgroup local storage. There already exists a local storage implementation for cgroup-attached bpf programs. See map type BPF_MAP_TYPE_CGROUP_STORAGE and helper bpf_get_local_storage(). But there are use cases such that non-cgroup attached bpf progs wants to access cgroup local storage data. For example, tc egress prog has access to sk and cgroup. It is possible to use sk local storage to emulate cgroup local storage by storing data in socket. But this is a waste as it could be lots of sockets belonging to a particular cgroup. Alternatively, a separate map can be created with cgroup id as the key. But this will introduce additional overhead to manipulate the new map. A cgroup local storage, similar to existing sk/inode/task storage, should help for this use case. The life-cycle of storage is managed with the life-cycle of the cgroup struct. i.e. the storage is destroyed along with the owning cgroup with a call to bpf_cgrp_storage_free() when cgroup itself is deleted. The userspace map operations can be done by using a cgroup fd as a key passed to the lookup, update and delete operations. Typically, the following code is used to get the current cgroup: struct task_struct *task = bpf_get_current_task_btf(); ... task->cgroups->dfl_cgrp ... and in structure task_struct definition: struct task_struct { .... struct css_set __rcu *cgroups; .... } With sleepable program, accessing task->cgroups is not protected by rcu_read_lock. So the current implementation only supports non-sleepable program and supporting sleepable program will be the next step together with adding rcu_read_lock protection for rcu tagged structures. Since map name BPF_MAP_TYPE_CGROUP_STORAGE has been used for old cgroup local storage support, the new map name BPF_MAP_TYPE_CGRP_STORAGE is used for cgroup storage available to non-cgroup-attached bpf programs. The old cgroup storage supports bpf_get_local_storage() helper to get the cgroup data. The new cgroup storage helper bpf_cgrp_storage_get() can provide similar functionality. While old cgroup storage pre-allocates storage memory, the new mechanism can also pre-allocate with a user space bpf_map_update_elem() call to avoid potential run-time memory allocation failure. Therefore, the new cgroup storage can provide all functionality w.r.t. the old one. So in uapi bpf.h, the old BPF_MAP_TYPE_CGROUP_STORAGE is alias to BPF_MAP_TYPE_CGROUP_STORAGE_DEPRECATED to indicate the old cgroup storage can be deprecated since the new one can provide the same functionality. Acked-by: David Vernet <void@manifault.com> Signed-off-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20221026042850.673791-1-yhs@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
45 lines
1.7 KiB
Makefile
45 lines
1.7 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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obj-y := core.o
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ifneq ($(CONFIG_BPF_JIT_ALWAYS_ON),y)
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# ___bpf_prog_run() needs GCSE disabled on x86; see 3193c0836f203 for details
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cflags-nogcse-$(CONFIG_X86)$(CONFIG_CC_IS_GCC) := -fno-gcse
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endif
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CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-nogcse-yy)
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obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o
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obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o
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obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
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obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
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obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o
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obj-$(CONFIG_BPF_SYSCALL) += disasm.o
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obj-$(CONFIG_BPF_JIT) += trampoline.o
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obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o
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obj-$(CONFIG_BPF_JIT) += dispatcher.o
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ifeq ($(CONFIG_NET),y)
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obj-$(CONFIG_BPF_SYSCALL) += devmap.o
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obj-$(CONFIG_BPF_SYSCALL) += cpumap.o
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obj-$(CONFIG_BPF_SYSCALL) += offload.o
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obj-$(CONFIG_BPF_SYSCALL) += net_namespace.o
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endif
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ifeq ($(CONFIG_PERF_EVENTS),y)
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obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
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endif
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ifeq ($(CONFIG_CGROUPS),y)
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obj-$(CONFIG_BPF_SYSCALL) += cgroup_iter.o bpf_cgrp_storage.o
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endif
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obj-$(CONFIG_CGROUP_BPF) += cgroup.o
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ifeq ($(CONFIG_INET),y)
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obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o
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endif
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ifeq ($(CONFIG_SYSFS),y)
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obj-$(CONFIG_DEBUG_INFO_BTF) += sysfs_btf.o
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endif
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ifeq ($(CONFIG_BPF_JIT),y)
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obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
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obj-${CONFIG_BPF_LSM} += bpf_lsm.o
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endif
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obj-$(CONFIG_BPF_PRELOAD) += preload/
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obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
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$(obj)/relo_core.o: $(srctree)/tools/lib/bpf/relo_core.c FORCE
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$(call if_changed_rule,cc_o_c)
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