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d6ea068032
Add macros implementing an 'assert' statement primitive using macros, built on top of the BPF exceptions support introduced in previous patches. The bpf_assert_*_with variants allow supplying a value which can the be inspected within the exception handler to signify the assert statement that led to the program being terminated abruptly, or be returned by the default exception handler. Note that only 64-bit scalar values are supported with these assertion macros, as during testing I found other cases quite unreliable in presence of compiler shifts/manipulations extracting the value of the right width from registers scrubbing the verifier's bounds information and knowledge about the value in the register. Thus, it is easier to reliably support this feature with only the full register width, and support both signed and unsigned variants. The bpf_assert_range is interesting in particular, which clamps the value in the [begin, end] (both inclusive) range within verifier state, and emits a check for the same at runtime. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-17-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
454 lines
15 KiB
C
454 lines
15 KiB
C
#ifndef __BPF_EXPERIMENTAL__
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#define __BPF_EXPERIMENTAL__
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#include <vmlinux.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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#define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node)))
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/* Description
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* Allocates an object of the type represented by 'local_type_id' in
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* program BTF. User may use the bpf_core_type_id_local macro to pass the
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* type ID of a struct in program BTF.
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*
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* The 'local_type_id' parameter must be a known constant.
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* The 'meta' parameter is rewritten by the verifier, no need for BPF
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* program to set it.
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* Returns
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* A pointer to an object of the type corresponding to the passed in
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* 'local_type_id', or NULL on failure.
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*/
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extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
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/* Convenience macro to wrap over bpf_obj_new_impl */
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#define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
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/* Description
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* Free an allocated object. All fields of the object that require
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* destruction will be destructed before the storage is freed.
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*
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* The 'meta' parameter is rewritten by the verifier, no need for BPF
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* program to set it.
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* Returns
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* Void.
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*/
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extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
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/* Convenience macro to wrap over bpf_obj_drop_impl */
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#define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
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/* Description
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* Increment the refcount on a refcounted local kptr, turning the
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* non-owning reference input into an owning reference in the process.
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*
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* The 'meta' parameter is rewritten by the verifier, no need for BPF
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* program to set it.
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* Returns
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* An owning reference to the object pointed to by 'kptr'
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*/
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extern void *bpf_refcount_acquire_impl(void *kptr, void *meta) __ksym;
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/* Convenience macro to wrap over bpf_refcount_acquire_impl */
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#define bpf_refcount_acquire(kptr) bpf_refcount_acquire_impl(kptr, NULL)
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/* Description
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* Add a new entry to the beginning of the BPF linked list.
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*
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* The 'meta' and 'off' parameters are rewritten by the verifier, no need
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* for BPF programs to set them
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* Returns
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* 0 if the node was successfully added
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* -EINVAL if the node wasn't added because it's already in a list
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*/
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extern int bpf_list_push_front_impl(struct bpf_list_head *head,
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struct bpf_list_node *node,
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void *meta, __u64 off) __ksym;
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/* Convenience macro to wrap over bpf_list_push_front_impl */
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#define bpf_list_push_front(head, node) bpf_list_push_front_impl(head, node, NULL, 0)
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/* Description
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* Add a new entry to the end of the BPF linked list.
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*
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* The 'meta' and 'off' parameters are rewritten by the verifier, no need
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* for BPF programs to set them
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* Returns
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* 0 if the node was successfully added
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* -EINVAL if the node wasn't added because it's already in a list
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*/
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extern int bpf_list_push_back_impl(struct bpf_list_head *head,
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struct bpf_list_node *node,
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void *meta, __u64 off) __ksym;
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/* Convenience macro to wrap over bpf_list_push_back_impl */
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#define bpf_list_push_back(head, node) bpf_list_push_back_impl(head, node, NULL, 0)
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/* Description
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* Remove the entry at the beginning of the BPF linked list.
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* Returns
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* Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
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*/
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extern struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head) __ksym;
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/* Description
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* Remove the entry at the end of the BPF linked list.
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* Returns
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* Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
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*/
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extern struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksym;
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/* Description
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* Remove 'node' from rbtree with root 'root'
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* Returns
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* Pointer to the removed node, or NULL if 'root' didn't contain 'node'
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*/
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extern struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
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struct bpf_rb_node *node) __ksym;
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/* Description
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* Add 'node' to rbtree with root 'root' using comparator 'less'
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*
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* The 'meta' and 'off' parameters are rewritten by the verifier, no need
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* for BPF programs to set them
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* Returns
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* 0 if the node was successfully added
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* -EINVAL if the node wasn't added because it's already in a tree
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*/
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extern int bpf_rbtree_add_impl(struct bpf_rb_root *root, struct bpf_rb_node *node,
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bool (less)(struct bpf_rb_node *a, const struct bpf_rb_node *b),
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void *meta, __u64 off) __ksym;
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/* Convenience macro to wrap over bpf_rbtree_add_impl */
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#define bpf_rbtree_add(head, node, less) bpf_rbtree_add_impl(head, node, less, NULL, 0)
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/* Description
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* Return the first (leftmost) node in input tree
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* Returns
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* Pointer to the node, which is _not_ removed from the tree. If the tree
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* contains no nodes, returns NULL.
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*/
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extern struct bpf_rb_node *bpf_rbtree_first(struct bpf_rb_root *root) __ksym;
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/* Description
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* Allocates a percpu object of the type represented by 'local_type_id' in
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* program BTF. User may use the bpf_core_type_id_local macro to pass the
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* type ID of a struct in program BTF.
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*
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* The 'local_type_id' parameter must be a known constant.
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* The 'meta' parameter is rewritten by the verifier, no need for BPF
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* program to set it.
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* Returns
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* A pointer to a percpu object of the type corresponding to the passed in
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* 'local_type_id', or NULL on failure.
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*/
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extern void *bpf_percpu_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
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/* Convenience macro to wrap over bpf_percpu_obj_new_impl */
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#define bpf_percpu_obj_new(type) ((type __percpu_kptr *)bpf_percpu_obj_new_impl(bpf_core_type_id_local(type), NULL))
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/* Description
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* Free an allocated percpu object. All fields of the object that require
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* destruction will be destructed before the storage is freed.
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*
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* The 'meta' parameter is rewritten by the verifier, no need for BPF
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* program to set it.
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* Returns
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* Void.
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*/
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extern void bpf_percpu_obj_drop_impl(void *kptr, void *meta) __ksym;
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/* Convenience macro to wrap over bpf_obj_drop_impl */
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#define bpf_percpu_obj_drop(kptr) bpf_percpu_obj_drop_impl(kptr, NULL)
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/* Description
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* Throw a BPF exception from the program, immediately terminating its
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* execution and unwinding the stack. The supplied 'cookie' parameter
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* will be the return value of the program when an exception is thrown,
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* and the default exception callback is used. Otherwise, if an exception
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* callback is set using the '__exception_cb(callback)' declaration tag
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* on the main program, the 'cookie' parameter will be the callback's only
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* input argument.
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*
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* Thus, in case of default exception callback, 'cookie' is subjected to
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* constraints on the program's return value (as with R0 on exit).
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* Otherwise, the return value of the marked exception callback will be
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* subjected to the same checks.
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*
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* Note that throwing an exception with lingering resources (locks,
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* references, etc.) will lead to a verification error.
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*
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* Note that callbacks *cannot* call this helper.
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* Returns
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* Never.
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* Throws
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* An exception with the specified 'cookie' value.
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*/
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extern void bpf_throw(u64 cookie) __ksym;
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/* This macro must be used to mark the exception callback corresponding to the
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* main program. For example:
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*
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* int exception_cb(u64 cookie) {
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* return cookie;
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* }
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*
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* SEC("tc")
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* __exception_cb(exception_cb)
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* int main_prog(struct __sk_buff *ctx) {
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* ...
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* return TC_ACT_OK;
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* }
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*
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* Here, exception callback for the main program will be 'exception_cb'. Note
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* that this attribute can only be used once, and multiple exception callbacks
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* specified for the main program will lead to verification error.
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*/
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#define __exception_cb(name) __attribute__((btf_decl_tag("exception_callback:" #name)))
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#define __bpf_assert_signed(x) _Generic((x), \
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unsigned long: 0, \
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unsigned long long: 0, \
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signed long: 1, \
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signed long long: 1 \
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)
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#define __bpf_assert_check(LHS, op, RHS) \
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_Static_assert(sizeof(&(LHS)), "1st argument must be an lvalue expression"); \
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_Static_assert(sizeof(LHS) == 8, "Only 8-byte integers are supported\n"); \
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_Static_assert(__builtin_constant_p(__bpf_assert_signed(LHS)), "internal static assert"); \
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_Static_assert(__builtin_constant_p((RHS)), "2nd argument must be a constant expression")
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#define __bpf_assert(LHS, op, cons, RHS, VAL) \
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({ \
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(void)bpf_throw; \
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asm volatile ("if %[lhs] " op " %[rhs] goto +2; r1 = %[value]; call bpf_throw" \
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: : [lhs] "r"(LHS), [rhs] cons(RHS), [value] "ri"(VAL) : ); \
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})
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#define __bpf_assert_op_sign(LHS, op, cons, RHS, VAL, supp_sign) \
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({ \
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__bpf_assert_check(LHS, op, RHS); \
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if (__bpf_assert_signed(LHS) && !(supp_sign)) \
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__bpf_assert(LHS, "s" #op, cons, RHS, VAL); \
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else \
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__bpf_assert(LHS, #op, cons, RHS, VAL); \
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})
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#define __bpf_assert_op(LHS, op, RHS, VAL, supp_sign) \
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({ \
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if (sizeof(typeof(RHS)) == 8) { \
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const typeof(RHS) rhs_var = (RHS); \
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__bpf_assert_op_sign(LHS, op, "r", rhs_var, VAL, supp_sign); \
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} else { \
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__bpf_assert_op_sign(LHS, op, "i", RHS, VAL, supp_sign); \
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} \
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})
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/* Description
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* Assert that a conditional expression is true.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert(cond) if (!(cond)) bpf_throw(0);
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/* Description
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* Assert that a conditional expression is true.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_with(cond, value) if (!(cond)) bpf_throw(value);
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/* Description
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* Assert that LHS is equal to RHS. This statement updates the known value
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* of LHS during verification. Note that RHS must be a constant value, and
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* must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_eq(LHS, RHS) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, ==, RHS, 0, true); \
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})
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/* Description
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* Assert that LHS is equal to RHS. This statement updates the known value
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* of LHS during verification. Note that RHS must be a constant value, and
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* must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_eq_with(LHS, RHS, value) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, ==, RHS, value, true); \
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})
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/* Description
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* Assert that LHS is less than RHS. This statement updates the known
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* bounds of LHS during verification. Note that RHS must be a constant
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* value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_lt(LHS, RHS) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, <, RHS, 0, false); \
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})
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/* Description
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* Assert that LHS is less than RHS. This statement updates the known
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* bounds of LHS during verification. Note that RHS must be a constant
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* value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_lt_with(LHS, RHS, value) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, <, RHS, value, false); \
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})
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/* Description
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* Assert that LHS is greater than RHS. This statement updates the known
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* bounds of LHS during verification. Note that RHS must be a constant
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* value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_gt(LHS, RHS) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >, RHS, 0, false); \
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})
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/* Description
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* Assert that LHS is greater than RHS. This statement updates the known
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* bounds of LHS during verification. Note that RHS must be a constant
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* value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_gt_with(LHS, RHS, value) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >, RHS, value, false); \
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})
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/* Description
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* Assert that LHS is less than or equal to RHS. This statement updates the
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* known bounds of LHS during verification. Note that RHS must be a
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* constant value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_le(LHS, RHS) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, <=, RHS, 0, false); \
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})
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/* Description
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* Assert that LHS is less than or equal to RHS. This statement updates the
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* known bounds of LHS during verification. Note that RHS must be a
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* constant value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_le_with(LHS, RHS, value) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, <=, RHS, value, false); \
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})
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/* Description
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* Assert that LHS is greater than or equal to RHS. This statement updates
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* the known bounds of LHS during verification. Note that RHS must be a
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* constant value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_ge(LHS, RHS) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >=, RHS, 0, false); \
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})
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/* Description
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* Assert that LHS is greater than or equal to RHS. This statement updates
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* the known bounds of LHS during verification. Note that RHS must be a
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* constant value, and must fit within the data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_ge_with(LHS, RHS, value) \
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({ \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >=, RHS, value, false); \
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})
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/* Description
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* Assert that LHS is in the range [BEG, END] (inclusive of both). This
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* statement updates the known bounds of LHS during verification. Note
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* that both BEG and END must be constant values, and must fit within the
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* data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the value zero when the assertion fails.
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*/
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#define bpf_assert_range(LHS, BEG, END) \
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({ \
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_Static_assert(BEG <= END, "BEG must be <= END"); \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >=, BEG, 0, false); \
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__bpf_assert_op(LHS, <=, END, 0, false); \
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})
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/* Description
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* Assert that LHS is in the range [BEG, END] (inclusive of both). This
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* statement updates the known bounds of LHS during verification. Note
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* that both BEG and END must be constant values, and must fit within the
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* data type of LHS.
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* Returns
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* Void.
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* Throws
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* An exception with the specified value when the assertion fails.
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*/
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#define bpf_assert_range_with(LHS, BEG, END, value) \
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({ \
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_Static_assert(BEG <= END, "BEG must be <= END"); \
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barrier_var(LHS); \
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__bpf_assert_op(LHS, >=, BEG, value, false); \
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__bpf_assert_op(LHS, <=, END, value, false); \
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})
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#endif
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