- 26 Mar, 2023 6 commits
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Eduard Zingerman authored
Test verifier/and.c automatically converted to use inline assembly. Signed-off-by:
Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20230325025524.144043-7-eddyz87@gmail.comSigned-off-by:
Alexei Starovoitov <ast@kernel.org>
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Eduard Zingerman authored
prog_tests/verifier.c would be used as a host for verifier/*.c tests migrated to use inline assembly and run from test_progs. The run_test_aux() function mimics the test_verifier behavior dropping CAP_SYS_ADMIN upon entry. Signed-off-by:
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Eduard Zingerman authored
Extends test_loader.c:test_loader__run_subtests() by allowing to execute BPF_PROG_TEST_RUN bpf command for selected programs. This is similar to functionality provided by test_verifier. Adds the following new attributes controlling test_loader behavior: __retval(...) __retval_unpriv(...) * If any of these attributes is present, the annotated program would be executed using libbpf's bpf_prog_test_run_opts() function. * If __retval is present, the test run would be done for program loaded in privileged mode. * If __retval_unpriv is present, the test run would be done for program loaded in unprivileged mode. * To mimic test_verifier behavior, the actual run is initiated in privileged mode. * The value returned by a test run is compared against retval parameter. The retval attribute takes one of the following parameters: - a decimal number - a hexadecimal number (must start from '0x') - any of a three special literals (provided for compatibility with test_verifier): - INT_MIN - POINTER_VALUE - TEST_DATA_LEN An example of the attribute usage: SEC("socket") __description("return 42") __success __success_unpriv __retval(42) __naked void the_42_test(void) { asm volatile (" \ r0 = 42; \ exit; \ " ::: __clobber_all); } Signed-off-by: -
Eduard Zingerman authored
Extends test_loader.c:test_loader__run_subtests() by allowing to execute tests in unprivileged mode, similar to test_verifier.c. Adds the following new attributes controlling test_loader behavior: __msg_unpriv __success_unpriv __failure_unpriv * If any of these attributes is present the test would be loaded in unprivileged mode. * If only "privileged" attributes are present the test would be loaded only in privileged mode. * If both "privileged" and "unprivileged" attributes are present the test would be loaded in both modes. * If test has to be executed in both modes, __msg(text) is specified and __msg_unpriv is not specified the behavior is the same as if __msg_unpriv(text) is specified. * For test filtering purposes the name of the program loaded in unprivileged mode is derived from the usual program name by adding `@unpriv' suffix. Also adds attribute '__description'. This attribute specifies text to be used instead of a program name for display and filtering purposes. Signed-off-by:
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Eduard Zingerman authored
Add two convenience macro for BPF test cases, allowing the following usage: #include <linux/filter.h> ... asm volatile ( ... ".8byte %[raw_insn];" ... "r1 += %[st_foo_offset];" ... : : __imm_insn(raw_insn, BPF_RAW_INSN(...)), __imm_const(st_foo_offset, offsetof(struct st, foo)) : __clobber_all); Signed-off-by: -
Eduard Zingerman authored
Change test_loader.c:run_subtest() behavior to show BPF program name when test spec for that program can't be parsed. Signed-off-by:
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- 25 Mar, 2023 4 commits
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Alexei Starovoitov authored
David Vernet says: ==================== When a map value is being freed, we loop over all of the fields of the corresponding BPF object and issue the appropriate cleanup calls corresponding to the field's type. If the field is a referenced kptr, we atomically xchg the value out of the map, and invoke the kptr's destructor on whatever was there before. Currently, we always invoke the destructor (or bpf_obj_drop() for a local kptr) on any kptr, including if no value was xchg'd out of the map. This means that any function serving as the kptr's KF_RELEASE destructor must always treat the argument as possibly NULL, and we invoke unnecessary (and seemingly unsafe) cleanup logic for the local kptr path as well. This is an odd requirement -- KF_RELEASE kfuncs that are invoked by BPF programs do not have this restriction, and the verifier will fail to load the program if the register containing the to-be-released type has any untrusted modifiers (e.g. PTR_UNTRUSTED or PTR_MAYBE_NULL). So as to simplify the expectations required for a KF_RELEASE kfunc, this patch set updates the KPTR_REF destructor logic to only be invoked when a non-NULL value is xchg'd out of the map. Additionally, the patch removes now-unnecessary KF_RELEASE calls from several kfuncs, and finally, updates the verifier to have KF_RELEASE automatically imply KF_TRUSTED_ARGS. This restriction was already implicitly happening because of the aforementioned logic in the verifier to reject any regs with untrusted modifiers, and to enforce that KF_RELEASE args are passed with a 0 offset. This change just updates the behavior to match that of other trusted args. This patch is left to the end of the series in case it happens to be controversial, as it arguably is slightly orthogonal to the purpose of the rest of the series. ==================== Signed-off-by: -
David Vernet authored
KF_RELEASE kfuncs are not currently treated as having KF_TRUSTED_ARGS, even though they have a superset of the requirements of KF_TRUSTED_ARGS. Like KF_TRUSTED_ARGS, KF_RELEASE kfuncs require a 0-offset argument, and don't allow NULL-able arguments. Unlike KF_TRUSTED_ARGS which require _either_ an argument with ref_obj_id > 0, _or_ (ref->type & BPF_REG_TRUSTED_MODIFIERS) (and no unsafe modifiers allowed), KF_RELEASE only allows for ref_obj_id > 0. Because KF_RELEASE today doesn't automatically imply KF_TRUSTED_ARGS, some of these requirements are enforced in different ways that can make the behavior of the verifier feel unpredictable. For example, a KF_RELEASE kfunc with a NULL-able argument will currently fail in the verifier with a message like, "arg#0 is ptr_or_null_ expected ptr_ or socket" rather than "Possibly NULL pointer passed to trusted arg0". Our intention is the same, but the semantics are different due to implemenetation details that kfunc authors and BPF program writers should not need to care about. Let's make the behavior of the verifier more consistent and intuitive by having KF_RELEASE kfuncs imply the presence of KF_TRUSTED_ARGS. Our eventual goal is to have all kfuncs assume KF_TRUSTED_ARGS by default anyways, so this takes us a step in that direction. Note that it does not make sense to assume KF_TRUSTED_ARGS for all KF_ACQUIRE kfuncs. KF_ACQUIRE kfuncs can have looser semantics than KF_RELEASE, with e.g. KF_RCU | KF_RET_NULL. We may want to have KF_ACQUIRE imply KF_TRUSTED_ARGS _unless_ KF_RCU is specified, but that can be left to another patch set, and there are no such subtleties to address for KF_RELEASE. Signed-off-by:
David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230325213144.486885-4-void@manifault.comSigned-off-by:
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David Vernet authored
Now that we're not invoking kfunc destructors when the kptr in a map was NULL, we no longer require NULL checks in many of our KF_RELEASE kfuncs. This patch removes those NULL checks. Signed-off-by:
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David Vernet authored
When a map value is being freed, we loop over all of the fields of the corresponding BPF object and issue the appropriate cleanup calls corresponding to the field's type. If the field is a referenced kptr, we atomically xchg the value out of the map, and invoke the kptr's destructor on whatever was there before (or bpf_obj_drop() it if it was a local kptr). Currently, we always invoke the destructor (either bpf_obj_drop() or the kptr's registered destructor) on any KPTR_REF-type field in a map, even if there wasn't a value in the map. This means that any function serving as the kptr's KF_RELEASE destructor must always treat the argument as possibly NULL, as the following can and regularly does happen: void *xchgd_field; /* No value was in the map, so xchgd_field is NULL */ xchgd_field = (void *)xchg(unsigned long *field_ptr, 0); field->kptr.dtor(xchgd_field); These are odd semantics to impose on KF_RELEASE kfuncs -- BPF programs are prohibited by the verifier from passing NULL pointers to KF_RELEASE kfuncs, so it doesn't make sense to require this of BPF programs, but not the main kernel destructor path. It's also unnecessary to invoke any cleanup logic for local kptrs. If there is no object there, there's nothing to drop. So as to allow KF_RELEASE kfuncs to fully assume that an argument is non-NULL, this patch updates a KPTR_REF's destructor to only be invoked when a non-NULL value is xchg'd out of the kptr map field. Signed-off-by:
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- 24 Mar, 2023 1 commit
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Martin KaFai Lau authored
This patch fixes a mistake in checking NULL instead of checking IS_ERR for the bpf_map_get() return value. It also fixes the return value in link_update_map() from -EINVAL to PTR_ERR(*_map). Reported-by: syzbot+71ccc0fe37abb458406b@syzkaller.appspotmail.com Fixes: 68b04864 ("bpf: Create links for BPF struct_ops maps.") Fixes: aef56f2e ("bpf: Update the struct_ops of a bpf_link.") Signed-off-by:
Martin KaFai Lau <martin.lau@kernel.org> Acked-by:
Kui-Feng Lee <kuifeng@meta.com> Acked-by:
Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/r/20230324184241.1387437-1-martin.lau@linux.devSigned-off-by:
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- 23 Mar, 2023 10 commits
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Martin KaFai Lau authored
Kui-Feng Lee says: ==================== Major changes: - Create bpf_links in the kernel for BPF struct_ops to register and unregister it. - Enables switching between implementations of bpf-tcp-cc under a name instantly by replacing the backing struct_ops map of a bpf_link. Previously, BPF struct_ops didn't go off, as even when the user program creating it was terminated, none of these ever were pinned. For instance, the TCP congestion control subsystem indirectly maintains a reference count on the struct_ops of any registered BPF implemented algorithm. Thus, the algorithm won't be deactivated until someone deliberately unregisters it. For compatibility with other BPF programs, bpf_links have been created to work in coordination with struct_ops maps. This ensures that the registration and unregistration of these respective maps is carried out at the start and end of the bpf_link. We also faced complications when attempting to replace an existing TCP congestion control algorithm with a new implementation on the fly. A struct_ops map was used to register a TCP congestion control algorithm with a unique name. We had to either register the alternative implementation with a new name and move over or unregister the current one before being able to reregistration with the same name. To fix this problem, we can an option to migrate the registration of the algorithm from struct_ops maps to bpf_links. By modifying the backing map of a bpf_link, it suddenly becomes possible to replace an existing TCP congestion control algorithm with ease. --- The major differences from v11: - Fix incorrectly setting both old_prog_fd and old_map_fd. The major differences from v10: - Add old_map_fd as an additional field instead of an union in bpf_link_update_opts. The major differences from v9: - Add test case for BPF_F_LINK. Includes adding old_map_fd to struct bpf_link_update_opts in patch 6. - Return -EPERM instead of -EINVAL when the old map fd doesn't match with BPF_F_LINK. - Fix -EBUSY case in bpf_map__attach_struct_ops(). The major differences form v8: - Check bpf_struct_ops::{validate,update} in bpf_struct_ops_map_alloc() The major differences from v7: - Use synchronize_rcu_mult(call_rcu, call_rcu_tasks) to replace synchronize_rcu() and synchronize_rcu_tasks(). - Call synchronize_rcu() in tcp_update_congestion_control(). - Handle -EBUSY in bpf_map__attach_struct_ops() to allow a struct_ops can be used to create links more than once. Include a test case. - Add old_map_fd to bpf_attr and handle BPF_F_REPLACE in bpf_struct_ops_map_link_update(). - Remove changes in bpf_dummy_struct_ops.c and add a check of .update function pointer of bpf_struct_ops. The major differences from v6: - Reword commit logs of the patch 1, 2, and 8. - Call synchronize_rcu_tasks() as well in bpf_struct_ops_map_free(). - Refactor bpf_struct_ops_map_free() so that bpf_struct_ops_map_alloc() can free a struct_ops without waiting for a RCU grace period. The major differences from v5: - Add a new step to bpf_object__load() to prepare vdata. - Accept BPF_F_REPLACE. - Check section IDs in find_struct_ops_map_by_offset() - Add a test case to check mixing w/ and w/o link struct_ops. - Add a test case of using struct_ops w/o link to update a link. - Improve bpf_link__detach_struct_ops() to handle the w/ link case. The major differences from v4: - Rebase. - Reorder patches and merge part 4 to part 2 of the v4. The major differences from v3: - Remove bpf_struct_ops_map_free_rcu(), and use synchronize_rcu(). - Improve the commit log of the part 1. - Before transitioning to the READY state, we conduct a value check to ensure that struct_ops can be successfully utilized and links created later. The major differences from v2: - Simplify states - Remove TOBEUNREG. - Rename UNREG to READY. - Stop using the refcnt of the kvalue of a struct_ops. Explicitly increase and decrease the refcount of struct_ops. - Prepare kernel vdata during the load phase of libbpf. The major differences from v1: - Added bpf_struct_ops_link to replace the previous union-based approach. - Added UNREG and TOBEUNREG to the state of bpf_struct_ops_map. - bpf_struct_ops_transit_state() maintains state transitions. - Fixed synchronization issue. - Prepare kernel vdata of struct_ops during the loading phase of bpf_object. - Merged previous patch 3 to patch 1. v11: https://lore.kernel.org/all/20230323010409.2265383-1-kuifeng@meta.com/ v10: https://lore.kernel.org/all/20230321232813.3376064-1-kuifeng@meta.com/ v9: https://lore.kernel.org/all/20230320195644.1953096-1-kuifeng@meta.com/ v8: https://lore.kernel.org/all/20230318053144.1180301-1-kuifeng@meta.com/ v7: https://lore.kernel.org/all/20230316023641.2092778-1-kuifeng@meta.com/ v6: https://lore.kernel.org/all/20230310043812.3087672-1-kuifeng@meta.com/ v5: https://lore.kernel.org/all/20230308005050.255859-1-kuifeng@meta.com/ v4: https://lore.kernel.org/all/20230307232913.576893-1-andrii@kernel.org/ v3: https://lore.kernel.org/all/20230303012122.852654-1-kuifeng@meta.com/ v2: https://lore.kernel.org/bpf/20230223011238.12313-1-kuifeng@meta.com/ v1: https://lore.kernel.org/bpf/20230214221718.503964-1-kuifeng@meta.com/ ==================== Signed-off-by: -
Kui-Feng Lee authored
Create a pair of sockets that utilize the congestion control algorithm under a particular name. Then switch up this congestion control algorithm to another implementation and check whether newly created connections using the same cc name now run the new implementation. Also, try to update a link with a struct_ops that is without BPF_F_LINK or with a wrong or different name. These cases should fail due to the violation of assumptions. To update a bpf_link of a struct_ops, it must be replaced with another struct_ops that is identical in type and name and has the BPF_F_LINK flag. The other test case is to create links from the same struct_ops more than once. It makes sure a struct_ops can be used repeatly. Signed-off-by:
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Kui-Feng Lee authored
Flags a struct_ops is to back a bpf_link by putting it to the ".struct_ops.link" section. Once it is flagged, the created struct_ops can be used to create a bpf_link or update a bpf_link that has been backed by another struct_ops. Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230323032405.3735486-8-kuifeng@meta.comSigned-off-by:
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Kui-Feng Lee authored
Introduce bpf_link__update_map(), which allows to atomically update underlying struct_ops implementation for given struct_ops BPF link. Also add old_map_fd to struct bpf_link_update_opts to handle BPF_F_REPLACE feature. Signed-off-by:
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Kui-Feng Lee authored
By improving the BPF_LINK_UPDATE command of bpf(), it should allow you to conveniently switch between different struct_ops on a single bpf_link. This would enable smoother transitions from one struct_ops to another. The struct_ops maps passing along with BPF_LINK_UPDATE should have the BPF_F_LINK flag. Signed-off-by:
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Kui-Feng Lee authored
bpf_map__attach_struct_ops() was creating a dummy bpf_link as a placeholder, but now it is constructing an authentic one by calling bpf_link_create() if the map has the BPF_F_LINK flag. You can flag a struct_ops map with BPF_F_LINK by calling bpf_map__set_map_flags(). Signed-off-by:
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Kui-Feng Lee authored
Make bpf_link support struct_ops. Previously, struct_ops were always used alone without any associated links. Upon updating its value, a struct_ops would be activated automatically. Yet other BPF program types required to make a bpf_link with their instances before they could become active. Now, however, you can create an inactive struct_ops, and create a link to activate it later. With bpf_links, struct_ops has a behavior similar to other BPF program types. You can pin/unpin them from their links and the struct_ops will be deactivated when its link is removed while previously need someone to delete the value for it to be deactivated. bpf_links are responsible for registering their associated struct_ops. You can only use a struct_ops that has the BPF_F_LINK flag set to create a bpf_link, while a structs without this flag behaves in the same manner as before and is registered upon updating its value. The BPF_LINK_TYPE_STRUCT_OPS serves a dual purpose. Not only is it used to craft the links for BPF struct_ops programs, but also to create links for BPF struct_ops them-self. Since the links of BPF struct_ops programs are only used to create trampolines internally, they are never seen in other contexts. Thus, they can be reused for struct_ops themself. To maintain a reference to the map supporting this link, we add bpf_struct_ops_link as an additional type. The pointer of the map is RCU and won't be necessary until later in the patchset. Signed-off-by:
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Kui-Feng Lee authored
This feature lets you immediately transition to another congestion control algorithm or implementation with the same name. Once a name is updated, new connections will apply this new algorithm. The purpose is to update a customized algorithm implemented in BPF struct_ops with a new version on the flight. The following is an example of using the userspace API implemented in later BPF patches. link = bpf_map__attach_struct_ops(skel->maps.ca_update_1); ....... err = bpf_link__update_map(link, skel->maps.ca_update_2); We first load and register an algorithm implemented in BPF struct_ops, then swap it out with a new one using the same name. After that, newly created connections will apply the updated algorithm, while older ones retain the previous version already applied. This patch also takes this chance to refactor the ca validation into the new tcp_validate_congestion_control() function. Cc: netdev@vger.kernel.org, Eric Dumazet <edumazet@google.com> Signed-off-by:
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Kui-Feng Lee authored
We have replaced kvalue-refcnt with synchronize_rcu() to wait for an RCU grace period. Maintenance of kvalue->refcnt was a complicated task, as we had to simultaneously keep track of two reference counts: one for the reference count of bpf_map. When the kvalue->refcnt reaches zero, we also have to reduce the reference count on bpf_map - yet these steps are not performed in an atomic manner and require us to be vigilant when managing them. By eliminating kvalue->refcnt, we can make our maintenance more straightforward as the refcount of bpf_map is now solely managed! To prevent the trampoline image of a struct_ops from being released while it is still in use, we wait for an RCU grace period. The setsockopt(TCP_CONGESTION, "...") command allows you to change your socket's congestion control algorithm and can result in releasing the old struct_ops implementation. It is fine. However, this function is exposed through bpf_setsockopt(), it may be accessed by BPF programs as well. To ensure that the trampoline image belonging to struct_op can be safely called while its method is in use, the trampoline safeguarde the BPF program with rcu_read_lock(). Doing so prevents any destruction of the associated images before returning from a trampoline and requires us to wait for an RCU grace period. Signed-off-by:
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Andrii Nakryiko authored
For iter_new() functions iterator state's slot might not be yet initialized, in which case iter_get_spi() will return -ERANGE. This is expected and is handled properly. But for iter_next() and iter_destroy() cases iter slot is supposed to be initialized and correct, so -ERANGE is not possible. Move meta->iter.{spi,frameno} initialization into iter_next/iter_destroy handling branch to make it more explicit that valid information will be remembered in meta->iter block for subsequent use in process_iter_next_call(), avoiding confusingly looking -ERANGE assignment for meta->iter.spi. Reported-by:Dan Carpenter <error27@gmail.com> Signed-off-by:
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- 22 Mar, 2023 11 commits
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Xu Kuohai authored
Add cases to check if bound is updated correctly when 64-bit value is not in the 32-bit range. Signed-off-by:
Xu Kuohai <xukuohai@huawei.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:
John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20230322213056.2470-2-daniel@iogearbox.net
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Daniel Borkmann authored
Xu reports that after commit 3f50f132 ("bpf: Verifier, do explicit ALU32 bounds tracking"), the following BPF program is rejected by the verifier: 0: (61) r2 = *(u32 *)(r1 +0) ; R2_w=pkt(off=0,r=0,imm=0) 1: (61) r3 = *(u32 *)(r1 +4) ; R3_w=pkt_end(off=0,imm=0) 2: (bf) r1 = r2 3: (07) r1 += 1 4: (2d) if r1 > r3 goto pc+8 5: (71) r1 = *(u8 *)(r2 +0) ; R1_w=scalar(umax=255,var_off=(0x0; 0xff)) 6: (18) r0 = 0x7fffffffffffff10 8: (0f) r1 += r0 ; R1_w=scalar(umin=0x7fffffffffffff10,umax=0x800000000000000f) 9: (18) r0 = 0x8000000000000000 11: (07) r0 += 1 12: (ad) if r0 < r1 goto pc-2 13: (b7) r0 = 0 14: (95) exit And the verifier log says: func#0 @0 0: R1=ctx(off=0,imm=0) R10=fp0 0: (61) r2 = *(u32 *)(r1 +0) ; R1=ctx(off=0,imm=0) R2_w=pkt(off=0,r=0,imm=0) 1: (61) r3 = *(u32 *)(r1 +4) ; R1=ctx(off=0,imm=0) R3_w=pkt_end(off=0,imm=0) 2: (bf) r1 = r2 ; R1_w=pkt(off=0,r=0,imm=0) R2_w=pkt(off=0,r=0,imm=0) 3: (07) r1 += 1 ; R1_w=pkt(off=1,r=0,imm=0) 4: (2d) if r1 > r3 goto pc+8 ; R1_w=pkt(off=1,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) 5: (71) r1 = *(u8 *)(r2 +0) ; R1_w=scalar(umax=255,var_off=(0x0; 0xff)) R2_w=pkt(off=0,r=1,imm=0) 6: (18) r0 = 0x7fffffffffffff10 ; R0_w=9223372036854775568 8: (0f) r1 += r0 ; R0_w=9223372036854775568 R1_w=scalar(umin=9223372036854775568,umax=9223372036854775823,s32_min=-240,s32_max=15) 9: (18) r0 = 0x8000000000000000 ; R0_w=-9223372036854775808 11: (07) r0 += 1 ; R0_w=-9223372036854775807 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775807 R1_w=scalar(umin=9223372036854775568,umax=9223372036854775809) 13: (b7) r0 = 0 ; R0_w=0 14: (95) exit from 12 to 11: R0_w=-9223372036854775807 R1_w=scalar(umin=9223372036854775810,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) R2_w=pkt(off=0,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775806 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775806 R1_w=scalar(umin=9223372036854775810,umax=9223372036854775810,var_off=(0x8000000000000000; 0xffffffff)) 13: safe [...] from 12 to 11: R0_w=-9223372036854775795 R1=scalar(umin=9223372036854775822,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775794 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775794 R1=scalar(umin=9223372036854775822,umax=9223372036854775822,var_off=(0x8000000000000000; 0xffffffff)) 13: safe from 12 to 11: R0_w=-9223372036854775794 R1=scalar(umin=9223372036854775823,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775793 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775793 R1=scalar(umin=9223372036854775823,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) 13: safe from 12 to 11: R0_w=-9223372036854775793 R1=scalar(umin=9223372036854775824,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775792 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775792 R1=scalar(umin=9223372036854775824,umax=9223372036854775823,var_off=(0x8000000000000000; 0xffffffff)) 13: safe [...] The 64bit umin=9223372036854775810 bound continuously bumps by +1 while umax=9223372036854775823 stays as-is until the verifier complexity limit is reached and the program gets finally rejected. During this simulation, the umin also eventually surpasses umax. Looking at the first 'from 12 to 11' output line from the loop, R1 has the following state: R1_w=scalar(umin=0x8000000000000002 (9223372036854775810), umax=0x800000000000000f (9223372036854775823), var_off=(0x8000000000000000; 0xffffffff)) The var_off has technically not an inconsistent state but it's very imprecise and far off surpassing 64bit umax bounds whereas the expected output with refined known bits in var_off should have been like: R1_w=scalar(umin=0x8000000000000002 (9223372036854775810), umax=0x800000000000000f (9223372036854775823), var_off=(0x8000000000000000; 0xf)) In the above log, var_off stays as var_off=(0x8000000000000000; 0xffffffff) and does not converge into a narrower mask where more bits become known, eventually transforming R1 into a constant upon umin=9223372036854775823, umax=9223372036854775823 case where the verifier would have terminated and let the program pass. The __reg_combine_64_into_32() marks the subregister unknown and propagates 64bit {s,u}min/{s,u}max bounds to their 32bit equivalents iff they are within the 32bit universe. The question came up whether __reg_combine_64_into_32() should special case the situation that when 64bit {s,u}min bounds have the same value as 64bit {s,u}max bounds to then assign the latter as well to the 32bit reg->{s,u}32_{min,max}_value. As can be seen from the above example however, that is just /one/ special case and not a /generic/ solution given above example would still not be addressed this way and remain at an imprecise var_off=(0x8000000000000000; 0xffffffff). The improvement is needed in __reg_bound_offset() to refine var32_off with the updated var64_off instead of the prior reg->var_off. The reg_bounds_sync() code first refines information about the register's min/max bounds via __update_reg_bounds() from the current var_off, then in __reg_deduce_bounds() from sign bit and with the potentially learned bits from bounds it'll update the var_off tnum in __reg_bound_offset(). For example, intersecting with the old var_off might have improved bounds slightly, e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc), then new var_off will then result in (0; 0x7f...fc). The intersected var64_off holds then the universe which is a superset of var32_off. The point for the latter is not to broaden, but to further refine known bits based on the intersection of var_off with 32 bit bounds, so that we later construct the final var_off from upper and lower 32 bits. The final __update_reg_bounds() can then potentially still slightly refine bounds if more bits became known from the new var_off. After the improvement, we can see R1 converging successively: func#0 @0 0: R1=ctx(off=0,imm=0) R10=fp0 0: (61) r2 = *(u32 *)(r1 +0) ; R1=ctx(off=0,imm=0) R2_w=pkt(off=0,r=0,imm=0) 1: (61) r3 = *(u32 *)(r1 +4) ; R1=ctx(off=0,imm=0) R3_w=pkt_end(off=0,imm=0) 2: (bf) r1 = r2 ; R1_w=pkt(off=0,r=0,imm=0) R2_w=pkt(off=0,r=0,imm=0) 3: (07) r1 += 1 ; R1_w=pkt(off=1,r=0,imm=0) 4: (2d) if r1 > r3 goto pc+8 ; R1_w=pkt(off=1,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) 5: (71) r1 = *(u8 *)(r2 +0) ; R1_w=scalar(umax=255,var_off=(0x0; 0xff)) R2_w=pkt(off=0,r=1,imm=0) 6: (18) r0 = 0x7fffffffffffff10 ; R0_w=9223372036854775568 8: (0f) r1 += r0 ; R0_w=9223372036854775568 R1_w=scalar(umin=9223372036854775568,umax=9223372036854775823,s32_min=-240,s32_max=15) 9: (18) r0 = 0x8000000000000000 ; R0_w=-9223372036854775808 11: (07) r0 += 1 ; R0_w=-9223372036854775807 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775807 R1_w=scalar(umin=9223372036854775568,umax=9223372036854775809) 13: (b7) r0 = 0 ; R0_w=0 14: (95) exit from 12 to 11: R0_w=-9223372036854775807 R1_w=scalar(umin=9223372036854775810,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2_w=pkt(off=0,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775806 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775806 R1_w=-9223372036854775806 13: safe from 12 to 11: R0_w=-9223372036854775806 R1_w=scalar(umin=9223372036854775811,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2_w=pkt(off=0,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775805 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775805 R1_w=-9223372036854775805 13: safe [...] from 12 to 11: R0_w=-9223372036854775798 R1=scalar(umin=9223372036854775819,umax=9223372036854775823,var_off=(0x8000000000000008; 0x7),s32_min=8,s32_max=15,u32_min=8,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775797 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775797 R1=-9223372036854775797 13: safe from 12 to 11: R0_w=-9223372036854775797 R1=scalar(umin=9223372036854775820,umax=9223372036854775823,var_off=(0x800000000000000c; 0x3),s32_min=12,s32_max=15,u32_min=12,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775796 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775796 R1=-9223372036854775796 13: safe from 12 to 11: R0_w=-9223372036854775796 R1=scalar(umin=9223372036854775821,umax=9223372036854775823,var_off=(0x800000000000000c; 0x3),s32_min=12,s32_max=15,u32_min=12,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775795 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775795 R1=-9223372036854775795 13: safe from 12 to 11: R0_w=-9223372036854775795 R1=scalar(umin=9223372036854775822,umax=9223372036854775823,var_off=(0x800000000000000e; 0x1),s32_min=14,s32_max=15,u32_min=14,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775794 12: (ad) if r0 < r1 goto pc-2 ; R0_w=-9223372036854775794 R1=-9223372036854775794 13: safe from 12 to 11: R0_w=-9223372036854775794 R1=-9223372036854775793 R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 11: (07) r0 += 1 ; R0_w=-9223372036854775793 12: (ad) if r0 < r1 goto pc-2 last_idx 12 first_idx 12 parent didn't have regs=1 stack=0 marks: R0_rw=P-9223372036854775801 R1_r=scalar(umin=9223372036854775815,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 last_idx 11 first_idx 11 regs=1 stack=0 before 11: (07) r0 += 1 parent didn't have regs=1 stack=0 marks: R0_rw=P-9223372036854775805 R1_rw=scalar(umin=9223372036854775812,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2_w=pkt(off=0,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) R10=fp0 last_idx 12 first_idx 0 regs=1 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=1 stack=0 before 11: (07) r0 += 1 regs=1 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=1 stack=0 before 11: (07) r0 += 1 regs=1 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=1 stack=0 before 11: (07) r0 += 1 regs=1 stack=0 before 9: (18) r0 = 0x8000000000000000 last_idx 12 first_idx 12 parent didn't have regs=2 stack=0 marks: R0_rw=P-9223372036854775801 R1_r=Pscalar(umin=9223372036854775815,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2=pkt(off=0,r=1,imm=0) R3=pkt_end(off=0,imm=0) R10=fp0 last_idx 11 first_idx 11 regs=2 stack=0 before 11: (07) r0 += 1 parent didn't have regs=2 stack=0 marks: R0_rw=P-9223372036854775805 R1_rw=Pscalar(umin=9223372036854775812,umax=9223372036854775823,var_off=(0x8000000000000000; 0xf),s32_min=0,s32_max=15,u32_max=15) R2_w=pkt(off=0,r=1,imm=0) R3_w=pkt_end(off=0,imm=0) R10=fp0 last_idx 12 first_idx 0 regs=2 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=2 stack=0 before 11: (07) r0 += 1 regs=2 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=2 stack=0 before 11: (07) r0 += 1 regs=2 stack=0 before 12: (ad) if r0 < r1 goto pc-2 regs=2 stack=0 before 11: (07) r0 += 1 regs=2 stack=0 before 9: (18) r0 = 0x8000000000000000 regs=2 stack=0 before 8: (0f) r1 += r0 regs=3 stack=0 before 6: (18) r0 = 0x7fffffffffffff10 regs=2 stack=0 before 5: (71) r1 = *(u8 *)(r2 +0) 13: safe from 4 to 13: safe verification time 322 usec stack depth 0 processed 56 insns (limit 1000000) max_states_per_insn 1 total_states 3 peak_states 3 mark_read 1 This also fixes up a test case along with this improvement where we match on the verifier log. The updated log now has a refined var_off, too. Fixes: 3f50f132 ("bpf: Verifier, do explicit ALU32 bounds tracking") Reported-by:
Xu Kuohai <xukuohai@huaweicloud.com> Signed-off-by:
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Alexei Starovoitov authored
JP Kobryn says: ==================== Within bpf programs, the bpf helper functions can make inline calls to kernel functions. In this scenario there can be a disconnect between the register the kernel function writes a return value to and the register the bpf program uses to evaluate that return value. As an example, this bpf code: long err = bpf_map_update_elem(...); if (err && err != -EEXIST) // got some error other than -EEXIST ...can result in the bpf assembly: ; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST); 37: movabs $0xffff976a10730400,%rdi 41: mov $0x1,%ecx 46: call 0xffffffffe103291c ; htab_map_update_elem ; if (err && err != -EEXIST) { 4b: cmp $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax 4f: je 0x000000000000008e 51: test %rax,%rax 54: je 0x000000000000008e The compare operation here evaluates %rax, while in the preceding call to htab_map_update_elem the corresponding assembly returns -EEXIST via %eax (the lower 32 bits of %rax): movl $0xffffffef, %r9d ... movl %r9d, %eax ...since it's returning int (32-bit). So the resulting comparison becomes: cmp $0xffffffffffffffef, $0x00000000ffffffef ...making it not possible to check for negative errors or specific errors, since the sign value is left at the 32nd bit. It means in the original example, the conditional branch will be entered even when the error is -EEXIST, which was not intended. The selftests added cover these cases for the different bpf_map_ops functions. When the second patch is applied, changing the return type of those functions to long, the comparison works as intended and the tests pass. ==================== Signed-off-by: -
JP Kobryn authored
This patch changes the return types of bpf_map_ops functions to long, where previously int was returned. Using long allows for bpf programs to maintain the sign bit in the absence of sign extension during situations where inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative error is returned. The definitions of the helper funcs are generated from comments in the bpf uapi header at `include/uapi/linux/bpf.h`. The return type of these helpers was previously changed from int to long in commit bdb7b79b. For any case where one of the map helpers call the bpf_map_ops funcs that are still returning 32-bit int, a compiler might not include sign extension instructions to properly convert the 32-bit negative value a 64-bit negative value. For example: bpf assembly excerpt of an inlined helper calling a kernel function and checking for a specific error: ; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST); ... 46: call 0xffffffffe103291c ; htab_map_update_elem ; if (err && err != -EEXIST) { 4b: cmp $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax kernel function assembly excerpt of return value from `htab_map_update_elem` returning 32-bit int: movl $0xffffffef, %r9d ... movl %r9d, %eax ...results in the comparison: cmp $0xffffffffffffffef, $0x00000000ffffffef Fixes: bdb7b79b ("bpf: Switch most helper return values from 32-bit int to 64-bit long") Tested-by:
JP Kobryn <inwardvessel@gmail.com> Link: https://lore.kernel.org/r/20230322194754.185781-3-inwardvessel@gmail.comSigned-off-by:
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JP Kobryn authored
These tests expose the issue of being unable to properly check for errors returned from inlined bpf map helpers that make calls to the bpf_map_ops functions. At best, a check for zero or non-zero can be done but these tests show it is not possible to check for a negative value or for a specific error value. Signed-off-by:
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Andrii Nakryiko authored
Alexei Starovoitov says: ==================== From: Alexei Starovoitov <ast@kernel.org> v1->v2: update denylist on s390 Patch 1: Cleanup internal libbpf names. Patch 2: Teach the verifier that rdonly_mem != NULL. Patch 3: Fix gen_loader to support ksym detection. Patch 4: Selftest and update denylist. ==================== Signed-off-by: -
Alexei Starovoitov authored
Add light skeleton test for kfunc detection and denylist it for s390. Signed-off-by:
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Alexei Starovoitov authored
Teach gen_loader to find {btf_id, btf_obj_fd} of kernel variables and kfuncs and populate corresponding ld_imm64 and bpf_call insns. Signed-off-by: -
Alexei Starovoitov authored
Teach the verifier to recognize PTR_TO_MEM | MEM_RDONLY as not NULL otherwise if (!bpf_ksym_exists(known_kfunc)) doesn't go through dead code elimination. Signed-off-by:
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Alexei Starovoitov authored
RELO_EXTERN_VAR/FUNC names are not correct anymore. RELO_EXTERN_VAR represent ksym symbol in ld_imm64 insn. It can point to kernel variable or kfunc. Rename RELO_EXTERN_VAR->RELO_EXTERN_LD64 and RELO_EXTERN_FUNC->RELO_EXTERN_CALL to match what they actually represent. Signed-off-by:
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Tushar Vyavahare authored
Add a new test in copy-mode for testing the copying of metadata from the buffer in kernel-space to user-space. This is accomplished by adding a new XDP program and using the bss map to store a counter that is written to the metadata field. This counter is incremented for every packet so that the number becomes unique and should be the same as the payload. It is store in the bss so the value can be reset between runs. The XDP program populates the metadata and the userspace program checks the value stored in the metadata field against the payload using the new is_metadata_correct() function. To turn this verification on or off, add a new parameter (use_metadata) to the ifobject structure. Signed-off-by:
Tushar Vyavahare <tushar.vyavahare@intel.com> Reviewed-by:
Maciej Fijalkowski <maciej.fijalkowski@intel.com> Link: https://lore.kernel.org/r/20230320102705.306187-1-tushar.vyavahare@intel.comSigned-off-by:
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- 21 Mar, 2023 4 commits
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Martin KaFai Lau authored
Jakub Kicinski says: ==================== I'm trying to make more of the sk_buff bits optional. Move the BPF-accessed bits a little - because they must be at coding-time-constant offsets they must precede any optional bit. While at it clean up the naming a bit. v1: https://lore.kernel.org/all/20230308003159.441580-1-kuba@kernel.org/ ==================== Signed-off-by:
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Jakub Kicinski authored
To avoid more possible BPF dependencies with moving bitfields around keep the fields BPF cares about right next to the offset marker. Signed-off-by:
Jakub Kicinski <kuba@kernel.org> Link: https://lore.kernel.org/r/20230321014115.997841-4-kuba@kernel.orgSigned-off-by:
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Jakub Kicinski authored
BPF needs to know the offsets of fields it tries to access. Zero-length fields are added to make offsetof() work. This unfortunately partitions the bitfield (fields across the zero-length members can't be coalesced). Reorder bytes 2 and 3, BPF needs to know the offset of fields previously in byte 3 and some fields in byte 2 should really be optional. The two bytes are always in the same cacheline so it should not matter. Signed-off-by:
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Jakub Kicinski authored
vlan_present is gone since commit 354259fa ("net: remove skb->vlan_present") rename the offset field to what BPF is currently looking for in this byte - mono_delivery_time and tc_at_ingress. Signed-off-by:
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- 20 Mar, 2023 3 commits
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Liu Pan authored
Write data to fd by calling "vdprintf", in most implementations of the standard library, the data is finally written by the writev syscall. But "uprobe_events/kprobe_events" does not allow segmented writes, so switch the "append_to_file" function to explicit write() call. Signed-off-by:
Liu Pan <patteliu@gmail.com> Signed-off-by:
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Alexei Starovoitov authored
Add a test case to exercise {btf_id, btf_obj_fd} copy logic between ld_imm64 insns. Signed-off-by: -
Alexei Starovoitov authored
Unlike normal libbpf the light skeleton 'loader' program is doing btf_find_by_name_kind() call at run-time to find ksym in the kernel and populate its {btf_id, btf_obj_fd} pair in ld_imm64 insn. To avoid doing the search multiple times for the same ksym it remembers the first patched ld_imm64 insn and copies {btf_id, btf_obj_fd} from it into subsequent ld_imm64 insn. Fix a bug in copying logic, since it may incorrectly clear BPF_PSEUDO_BTF_ID flag. Also replace always true if (btf_obj_fd >= 0) check with unconditional JMP_JA to clarify the code. Fixes: d995816b ("libbpf: Avoid reload of imm for weak, unresolved, repeating ksym") Signed-off-by:
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- 18 Mar, 2023 1 commit
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Sreevani Sreejith authored
This patch documents overview of libbpf, including its features for developing BPF programs. Signed-off-by:
Sreevani Sreejith <ssreevani@meta.com> Signed-off-by:
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