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![David Vernet](/assets/img/avatar_default.png)
Currently, a set of core BPF kfuncs (e.g. bpf_task_*, bpf_cgroup_*, bpf_cpumask_*, etc) cannot be invoked from BPF_PROG_TYPE_SYSCALL programs. The whitelist approach taken for enabling kfuncs makes sense: it not safe to call these kfuncs from every program type. For example, it may not be safe to call bpf_task_acquire() in an fentry to free_task(). BPF_PROG_TYPE_SYSCALL, on the other hand, is a perfectly safe program type from which to invoke these kfuncs, as it's a very controlled environment, and we should never be able to run into any of the typical problems such as recursive invoations, acquiring references on freeing kptrs, etc. Being able to invoke these kfuncs would be useful, as BPF_PROG_TYPE_SYSCALL can be invoked with BPF_PROG_RUN, and would therefore enable user space programs to synchronously call into BPF to manipulate these kptrs. This patch therefore enables invoking the aforementioned core kfuncs from BPF_PROG_TYPE_SYSCALL progs. Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/bpf/20240405143041.632519-2-void@manifault.com
484 lines
14 KiB
C
484 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2023 Meta, Inc */
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#include <linux/bpf.h>
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#include <linux/bpf_mem_alloc.h>
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#include <linux/btf.h>
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#include <linux/btf_ids.h>
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#include <linux/cpumask.h>
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/**
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* struct bpf_cpumask - refcounted BPF cpumask wrapper structure
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* @cpumask: The actual cpumask embedded in the struct.
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* @usage: Object reference counter. When the refcount goes to 0, the
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* memory is released back to the BPF allocator, which provides
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* RCU safety.
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*
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* Note that we explicitly embed a cpumask_t rather than a cpumask_var_t. This
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* is done to avoid confusing the verifier due to the typedef of cpumask_var_t
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* changing depending on whether CONFIG_CPUMASK_OFFSTACK is defined or not. See
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* the details in <linux/cpumask.h>. The consequence is that this structure is
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* likely a bit larger than it needs to be when CONFIG_CPUMASK_OFFSTACK is
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* defined due to embedding the whole NR_CPUS-size bitmap, but the extra memory
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* overhead is minimal. For the more typical case of CONFIG_CPUMASK_OFFSTACK
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* not being defined, the structure is the same size regardless.
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*/
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struct bpf_cpumask {
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cpumask_t cpumask;
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refcount_t usage;
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};
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static struct bpf_mem_alloc bpf_cpumask_ma;
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static bool cpu_valid(u32 cpu)
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{
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return cpu < nr_cpu_ids;
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}
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__bpf_kfunc_start_defs();
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/**
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* bpf_cpumask_create() - Create a mutable BPF cpumask.
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*
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* Allocates a cpumask that can be queried, mutated, acquired, and released by
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* a BPF program. The cpumask returned by this function must either be embedded
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* in a map as a kptr, or freed with bpf_cpumask_release().
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*
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* bpf_cpumask_create() allocates memory using the BPF memory allocator, and
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* will not block. It may return NULL if no memory is available.
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*/
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__bpf_kfunc struct bpf_cpumask *bpf_cpumask_create(void)
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{
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struct bpf_cpumask *cpumask;
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/* cpumask must be the first element so struct bpf_cpumask be cast to struct cpumask. */
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BUILD_BUG_ON(offsetof(struct bpf_cpumask, cpumask) != 0);
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cpumask = bpf_mem_cache_alloc(&bpf_cpumask_ma);
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if (!cpumask)
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return NULL;
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memset(cpumask, 0, sizeof(*cpumask));
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refcount_set(&cpumask->usage, 1);
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return cpumask;
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}
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/**
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* bpf_cpumask_acquire() - Acquire a reference to a BPF cpumask.
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* @cpumask: The BPF cpumask being acquired. The cpumask must be a trusted
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* pointer.
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*
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* Acquires a reference to a BPF cpumask. The cpumask returned by this function
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* must either be embedded in a map as a kptr, or freed with
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* bpf_cpumask_release().
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*/
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__bpf_kfunc struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask)
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{
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refcount_inc(&cpumask->usage);
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return cpumask;
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}
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/**
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* bpf_cpumask_release() - Release a previously acquired BPF cpumask.
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* @cpumask: The cpumask being released.
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*
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* Releases a previously acquired reference to a BPF cpumask. When the final
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* reference of the BPF cpumask has been released, it is subsequently freed in
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* an RCU callback in the BPF memory allocator.
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*/
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__bpf_kfunc void bpf_cpumask_release(struct bpf_cpumask *cpumask)
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{
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if (!refcount_dec_and_test(&cpumask->usage))
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return;
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migrate_disable();
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bpf_mem_cache_free_rcu(&bpf_cpumask_ma, cpumask);
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migrate_enable();
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}
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__bpf_kfunc void bpf_cpumask_release_dtor(void *cpumask)
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{
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bpf_cpumask_release(cpumask);
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}
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CFI_NOSEAL(bpf_cpumask_release_dtor);
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/**
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* bpf_cpumask_first() - Get the index of the first nonzero bit in the cpumask.
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* @cpumask: The cpumask being queried.
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*
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* Find the index of the first nonzero bit of the cpumask. A struct bpf_cpumask
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* pointer may be safely passed to this function.
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*/
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__bpf_kfunc u32 bpf_cpumask_first(const struct cpumask *cpumask)
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{
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return cpumask_first(cpumask);
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}
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/**
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* bpf_cpumask_first_zero() - Get the index of the first unset bit in the
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* cpumask.
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* @cpumask: The cpumask being queried.
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*
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* Find the index of the first unset bit of the cpumask. A struct bpf_cpumask
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* pointer may be safely passed to this function.
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*/
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__bpf_kfunc u32 bpf_cpumask_first_zero(const struct cpumask *cpumask)
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{
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return cpumask_first_zero(cpumask);
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}
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/**
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* bpf_cpumask_first_and() - Return the index of the first nonzero bit from the
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* AND of two cpumasks.
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* @src1: The first cpumask.
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* @src2: The second cpumask.
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*
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* Find the index of the first nonzero bit of the AND of two cpumasks.
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc u32 bpf_cpumask_first_and(const struct cpumask *src1,
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const struct cpumask *src2)
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{
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return cpumask_first_and(src1, src2);
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}
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/**
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* bpf_cpumask_set_cpu() - Set a bit for a CPU in a BPF cpumask.
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* @cpu: The CPU to be set in the cpumask.
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* @cpumask: The BPF cpumask in which a bit is being set.
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*/
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__bpf_kfunc void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
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{
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if (!cpu_valid(cpu))
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return;
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cpumask_set_cpu(cpu, (struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_clear_cpu() - Clear a bit for a CPU in a BPF cpumask.
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* @cpu: The CPU to be cleared from the cpumask.
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* @cpumask: The BPF cpumask in which a bit is being cleared.
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*/
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__bpf_kfunc void bpf_cpumask_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
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{
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if (!cpu_valid(cpu))
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return;
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cpumask_clear_cpu(cpu, (struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_test_cpu() - Test whether a CPU is set in a cpumask.
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* @cpu: The CPU being queried for.
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* @cpumask: The cpumask being queried for containing a CPU.
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*
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* Return:
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* * true - @cpu is set in the cpumask
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* * false - @cpu was not set in the cpumask, or @cpu is an invalid cpu.
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*/
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__bpf_kfunc bool bpf_cpumask_test_cpu(u32 cpu, const struct cpumask *cpumask)
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{
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if (!cpu_valid(cpu))
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return false;
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return cpumask_test_cpu(cpu, (struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_test_and_set_cpu() - Atomically test and set a CPU in a BPF cpumask.
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* @cpu: The CPU being set and queried for.
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* @cpumask: The BPF cpumask being set and queried for containing a CPU.
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*
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* Return:
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* * true - @cpu is set in the cpumask
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* * false - @cpu was not set in the cpumask, or @cpu is invalid.
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*/
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__bpf_kfunc bool bpf_cpumask_test_and_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
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{
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if (!cpu_valid(cpu))
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return false;
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return cpumask_test_and_set_cpu(cpu, (struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_test_and_clear_cpu() - Atomically test and clear a CPU in a BPF
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* cpumask.
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* @cpu: The CPU being cleared and queried for.
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* @cpumask: The BPF cpumask being cleared and queried for containing a CPU.
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*
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* Return:
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* * true - @cpu is set in the cpumask
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* * false - @cpu was not set in the cpumask, or @cpu is invalid.
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*/
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__bpf_kfunc bool bpf_cpumask_test_and_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
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{
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if (!cpu_valid(cpu))
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return false;
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return cpumask_test_and_clear_cpu(cpu, (struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_setall() - Set all of the bits in a BPF cpumask.
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* @cpumask: The BPF cpumask having all of its bits set.
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*/
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__bpf_kfunc void bpf_cpumask_setall(struct bpf_cpumask *cpumask)
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{
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cpumask_setall((struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_clear() - Clear all of the bits in a BPF cpumask.
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* @cpumask: The BPF cpumask being cleared.
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*/
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__bpf_kfunc void bpf_cpumask_clear(struct bpf_cpumask *cpumask)
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{
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cpumask_clear((struct cpumask *)cpumask);
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}
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/**
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* bpf_cpumask_and() - AND two cpumasks and store the result.
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* @dst: The BPF cpumask where the result is being stored.
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* @src1: The first input.
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* @src2: The second input.
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*
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* Return:
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* * true - @dst has at least one bit set following the operation
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* * false - @dst is empty following the operation
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc bool bpf_cpumask_and(struct bpf_cpumask *dst,
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const struct cpumask *src1,
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const struct cpumask *src2)
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{
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return cpumask_and((struct cpumask *)dst, src1, src2);
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}
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/**
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* bpf_cpumask_or() - OR two cpumasks and store the result.
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* @dst: The BPF cpumask where the result is being stored.
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* @src1: The first input.
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* @src2: The second input.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc void bpf_cpumask_or(struct bpf_cpumask *dst,
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const struct cpumask *src1,
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const struct cpumask *src2)
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{
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cpumask_or((struct cpumask *)dst, src1, src2);
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}
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/**
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* bpf_cpumask_xor() - XOR two cpumasks and store the result.
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* @dst: The BPF cpumask where the result is being stored.
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* @src1: The first input.
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* @src2: The second input.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc void bpf_cpumask_xor(struct bpf_cpumask *dst,
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const struct cpumask *src1,
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const struct cpumask *src2)
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{
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cpumask_xor((struct cpumask *)dst, src1, src2);
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}
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/**
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* bpf_cpumask_equal() - Check two cpumasks for equality.
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* @src1: The first input.
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* @src2: The second input.
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*
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* Return:
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* * true - @src1 and @src2 have the same bits set.
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* * false - @src1 and @src2 differ in at least one bit.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc bool bpf_cpumask_equal(const struct cpumask *src1, const struct cpumask *src2)
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{
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return cpumask_equal(src1, src2);
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}
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/**
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* bpf_cpumask_intersects() - Check two cpumasks for overlap.
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* @src1: The first input.
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* @src2: The second input.
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*
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* Return:
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* * true - @src1 and @src2 have at least one of the same bits set.
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* * false - @src1 and @src2 don't have any of the same bits set.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc bool bpf_cpumask_intersects(const struct cpumask *src1, const struct cpumask *src2)
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{
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return cpumask_intersects(src1, src2);
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}
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/**
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* bpf_cpumask_subset() - Check if a cpumask is a subset of another.
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* @src1: The first cpumask being checked as a subset.
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* @src2: The second cpumask being checked as a superset.
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*
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* Return:
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* * true - All of the bits of @src1 are set in @src2.
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* * false - At least one bit in @src1 is not set in @src2.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc bool bpf_cpumask_subset(const struct cpumask *src1, const struct cpumask *src2)
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{
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return cpumask_subset(src1, src2);
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}
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/**
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* bpf_cpumask_empty() - Check if a cpumask is empty.
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* @cpumask: The cpumask being checked.
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*
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* Return:
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* * true - None of the bits in @cpumask are set.
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* * false - At least one bit in @cpumask is set.
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*
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* A struct bpf_cpumask pointer may be safely passed to @cpumask.
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*/
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__bpf_kfunc bool bpf_cpumask_empty(const struct cpumask *cpumask)
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{
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return cpumask_empty(cpumask);
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}
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/**
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* bpf_cpumask_full() - Check if a cpumask has all bits set.
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* @cpumask: The cpumask being checked.
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*
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* Return:
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* * true - All of the bits in @cpumask are set.
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* * false - At least one bit in @cpumask is cleared.
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*
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* A struct bpf_cpumask pointer may be safely passed to @cpumask.
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*/
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__bpf_kfunc bool bpf_cpumask_full(const struct cpumask *cpumask)
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{
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return cpumask_full(cpumask);
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}
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/**
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* bpf_cpumask_copy() - Copy the contents of a cpumask into a BPF cpumask.
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* @dst: The BPF cpumask being copied into.
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* @src: The cpumask being copied.
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*
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* A struct bpf_cpumask pointer may be safely passed to @src.
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*/
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__bpf_kfunc void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src)
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{
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cpumask_copy((struct cpumask *)dst, src);
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}
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/**
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* bpf_cpumask_any_distribute() - Return a random set CPU from a cpumask.
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* @cpumask: The cpumask being queried.
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*
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* Return:
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* * A random set bit within [0, num_cpus) if at least one bit is set.
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* * >= num_cpus if no bit is set.
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*
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* A struct bpf_cpumask pointer may be safely passed to @src.
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*/
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__bpf_kfunc u32 bpf_cpumask_any_distribute(const struct cpumask *cpumask)
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{
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return cpumask_any_distribute(cpumask);
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}
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/**
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* bpf_cpumask_any_and_distribute() - Return a random set CPU from the AND of
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* two cpumasks.
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* @src1: The first cpumask.
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* @src2: The second cpumask.
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*
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* Return:
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* * A random set bit within [0, num_cpus) from the AND of two cpumasks, if at
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* least one bit is set.
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* * >= num_cpus if no bit is set.
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*
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* struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
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*/
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__bpf_kfunc u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1,
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const struct cpumask *src2)
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{
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return cpumask_any_and_distribute(src1, src2);
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}
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/**
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* bpf_cpumask_weight() - Return the number of bits in @cpumask.
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* @cpumask: The cpumask being queried.
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*
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* Count the number of set bits in the given cpumask.
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*/
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__bpf_kfunc u32 bpf_cpumask_weight(const struct cpumask *cpumask)
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{
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return cpumask_weight(cpumask);
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}
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__bpf_kfunc_end_defs();
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BTF_KFUNCS_START(cpumask_kfunc_btf_ids)
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BTF_ID_FLAGS(func, bpf_cpumask_create, KF_ACQUIRE | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_cpumask_release, KF_RELEASE)
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BTF_ID_FLAGS(func, bpf_cpumask_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
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BTF_ID_FLAGS(func, bpf_cpumask_first, KF_RCU)
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BTF_ID_FLAGS(func, bpf_cpumask_first_zero, KF_RCU)
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BTF_ID_FLAGS(func, bpf_cpumask_first_and, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_set_cpu, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_clear_cpu, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_test_cpu, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_test_and_set_cpu, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_test_and_clear_cpu, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_setall, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_clear, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_and, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_or, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_xor, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_equal, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_intersects, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_subset, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_empty, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_full, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU)
|
|
BTF_ID_FLAGS(func, bpf_cpumask_weight, KF_RCU)
|
|
BTF_KFUNCS_END(cpumask_kfunc_btf_ids)
|
|
|
|
static const struct btf_kfunc_id_set cpumask_kfunc_set = {
|
|
.owner = THIS_MODULE,
|
|
.set = &cpumask_kfunc_btf_ids,
|
|
};
|
|
|
|
BTF_ID_LIST(cpumask_dtor_ids)
|
|
BTF_ID(struct, bpf_cpumask)
|
|
BTF_ID(func, bpf_cpumask_release_dtor)
|
|
|
|
static int __init cpumask_kfunc_init(void)
|
|
{
|
|
int ret;
|
|
const struct btf_id_dtor_kfunc cpumask_dtors[] = {
|
|
{
|
|
.btf_id = cpumask_dtor_ids[0],
|
|
.kfunc_btf_id = cpumask_dtor_ids[1]
|
|
},
|
|
};
|
|
|
|
ret = bpf_mem_alloc_init(&bpf_cpumask_ma, sizeof(struct bpf_cpumask), false);
|
|
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &cpumask_kfunc_set);
|
|
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &cpumask_kfunc_set);
|
|
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &cpumask_kfunc_set);
|
|
return ret ?: register_btf_id_dtor_kfuncs(cpumask_dtors,
|
|
ARRAY_SIZE(cpumask_dtors),
|
|
THIS_MODULE);
|
|
}
|
|
|
|
late_initcall(cpumask_kfunc_init);
|