- 23 Mar, 2023 4 commits
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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:
Kui-Feng Lee <kuifeng@meta.com> Link: https://lore.kernel.org/r/20230323032405.3735486-4-kuifeng@meta.comSigned-off-by:
Martin KaFai Lau <martin.lau@kernel.org>
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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:
Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230322232502.836171-1-andrii@kernel.orgSigned-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:Alexei Starovoitov <ast@kernel.org>
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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:
Eduard Zingerman <eddyz87@gmail.com> Signed-off-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:
David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230321203854.3035-3-alexei.starovoitov@gmail.com
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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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- 17 Mar, 2023 11 commits
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Manu Bretelle authored
Currently, test_progs outputs all stdout/stderr as it runs, and when it is done, prints a summary. It is non-trivial for tooling to parse that output and extract meaningful information from it. This change adds a new option, `--json-summary`/`-J` that let the caller specify a file where `test_progs{,-no_alu32}` can write a summary of the run in a json format that can later be parsed by tooling. Currently, it creates a summary section with successes/skipped/failures followed by a list of failed tests and subtests. A test contains the following fields: - name: the name of the test - number: the number of the test - message: the log message that was printed by the test. - failed: A boolean indicating whether the test failed or not. Currently we only output failed tests, but in the future, successful tests could be added. - subtests: A list of subtests associated with this test. A subtest contains the following fields: - name: same as above - number: sanme as above - message: the log message that was printed by the subtest. - failed: same as above but for the subtest An example run and json content below: ``` $ sudo ./test_progs -a $(grep -v '^#' ./DENYLIST.aarch64 | awk '{print $1","}' | tr -d '\n') -j -J /tmp/test_progs.json $ jq < /tmp/test_progs.json | head -n 30 { "success": 29, "success_subtest": 23, "skipped": 3, "failed": 28, "results": [ { "name": "bpf_cookie", "number": 10, "message": "test_bpf_cookie:PASS:skel_open 0 nsec\n", "failed": true, "subtests": [ { "name": "multi_kprobe_link_api", "number": 2, "message": "kprobe_multi_link_api_subtest:PASS:load_kallsyms 0 nsec\nlibbpf: extern 'bpf_testmod_fentry_test1' (strong): not resolved\nlibbpf: failed to load object 'kprobe_multi'\nlibbpf: failed to load BPF skeleton 'kprobe_multi': -3\nkprobe_multi_link_api_subtest:FAIL:fentry_raw_skel_load unexpected error: -3\n", "failed": true }, { "name": "multi_kprobe_attach_api", "number": 3, "message": "libbpf: extern 'bpf_testmod_fentry_test1' (strong): not resolved\nlibbpf: failed to load object 'kprobe_multi'\nlibbpf: failed to load BPF skeleton 'kprobe_multi': -3\nkprobe_multi_attach_api_subtest:FAIL:fentry_raw_skel_load unexpected error: -3\n", "failed": true }, { "name": "lsm", "number": 8, "message": "lsm_subtest:PASS:lsm.link_create 0 nsec\nlsm_subtest:FAIL:stack_mprotect unexpected stack_mprotect: actual 0 != expected -1\n", "failed": true } ``` The file can then be used to print a summary of the test run and list of failing tests/subtests: ``` $ jq -r < /tmp/test_progs.json '"Success: \(.success)/\(.success_subtest), Skipped: \(.skipped), Failed: \(.failed)"' Success: 29/23, Skipped: 3, Failed: 28 $ jq -r < /tmp/test_progs.json '.results | map([ if .failed then "#\(.number) \(.name)" else empty end, ( . as {name: $tname, number: $tnum} | .subtests | map( if .failed then "#\($tnum)/\(.number) \($tname)/\(.name)" else empty end ) ) ]) | flatten | .[]' | head -n 20 #10 bpf_cookie #10/2 bpf_cookie/multi_kprobe_link_api #10/3 bpf_cookie/multi_kprobe_attach_api #10/8 bpf_cookie/lsm #15 bpf_mod_race #15/1 bpf_mod_race/ksym (used_btfs UAF) #15/2 bpf_mod_race/kfunc (kfunc_btf_tab UAF) #36 cgroup_hierarchical_stats #61 deny_namespace #61/1 deny_namespace/unpriv_userns_create_no_bpf #73 fexit_stress #83 get_func_ip_test #99 kfunc_dynptr_param #99/1 kfunc_dynptr_param/dynptr_data_null #99/4 kfunc_dynptr_param/dynptr_data_null #100 kprobe_multi_bench_attach #100/1 kprobe_multi_bench_attach/kernel #100/2 kprobe_multi_bench_attach/modules #101 kprobe_multi_test #101/1 kprobe_multi_test/skel_api ``` Signed-off-by:Manu Bretelle <chantr4@gmail.com> Signed-off-by:
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Andrii Nakryiko authored
Alexei Starovoitov says: ==================== From: Alexei Starovoitov <ast@kernel.org> Allow BPF programs detect at load time whether particular kfunc exists. Patch 1: Allow ld_imm64 to point to kfunc in the kernel. Patch 2: Fix relocation of kfunc in ld_imm64 insn when kfunc is in kernel module. Patch 3: Introduce bpf_ksym_exists() macro. Patch 4: selftest. NOTE: detection of kfuncs from light skeleton is not supported yet. ==================== Signed-off-by: -
Alexei Starovoitov authored
Add load and run time test for bpf_ksym_exists() and check that the verifier performs dead code elimination for non-existing kfunc. Signed-off-by:
Toke Høiland-Jørgensen <toke@redhat.com> Acked-by:
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Alexei Starovoitov authored
Introduce bpf_ksym_exists() macro that can be used by BPF programs to detect at load time whether particular ksym (either variable or kfunc) is present in the kernel. Signed-off-by:
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Alexei Starovoitov authored
void *p = kfunc; -> generates ld_imm64 insn. kfunc() -> generates bpf_call insn. libbpf patches bpf_call insn correctly while only btf_id part of ld_imm64 is set in the former case. Which means that pointers to kfuncs in modules are not patched correctly and the verifier rejects load of such programs due to btf_id being out of range. Fix libbpf to patch ld_imm64 for kfunc. Signed-off-by:
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Alexei Starovoitov authored
Allow ld_imm64 insn with BPF_PSEUDO_BTF_ID to hold the address of kfunc. The ld_imm64 pointing to a valid kfunc will be seen as non-null PTR_TO_MEM by is_branch_taken() logic of the verifier, while libbpf will resolve address to unknown kfunc as ld_imm64 reg, 0 which will also be recognized by is_branch_taken() and the verifier will proceed dead code elimination. BPF programs can use this logic to detect at load time whether kfunc is present in the kernel with bpf_ksym_exists() macro that is introduced in the next patches. Signed-off-by:
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Bagas Sanjaya authored
Commit d56b0c46 ("bpf, docs: Fix link to netdev-FAQ target") attempts to fix linking problem to undefined "netdev-FAQ" label introduced in 287f4fa9 ("docs: Update references to netdev-FAQ") by changing internal cross reference to netdev subsystem documentation (Documentation/process/maintainer-netdev.rst) to external one at docs.kernel.org. However, the linking problem is still not resolved, as the generated link points to non-existent netdev-FAQ section of the external doc, which when clicked, will instead going to the top of the doc. Revert back to internal linking by simply mention the doc path while massaging the leading text to the link, since the netdev subsystem doc contains no FAQs but rather general information about the subsystem. Fixes: d56b0c46 ("bpf, docs: Fix link to netdev-FAQ target") Fixes: 287f4fa9 ("docs: Update references to netdev-FAQ") Signed-off-by:
Bagas Sanjaya <bagasdotme@gmail.com> Signed-off-by:
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Viktor Malik authored
Moving find_kallsyms_symbol_value from kernel/module/internal.h to include/linux/module.h. The reason is that internal.h is not prepared to be included when CONFIG_MODULES=n. find_kallsyms_symbol_value is used by kernel/bpf/verifier.c and including internal.h from it (without modules) leads into a compilation error: In file included from ../include/linux/container_of.h:5, from ../include/linux/list.h:5, from ../include/linux/timer.h:5, from ../include/linux/workqueue.h:9, from ../include/linux/bpf.h:10, from ../include/linux/bpf-cgroup.h:5, from ../kernel/bpf/verifier.c:7: ../kernel/bpf/../module/internal.h: In function 'mod_find': ../include/linux/container_of.h:20:54: error: invalid use of undefined type 'struct module' 20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \ | ^~ [...] This patch fixes the above error. Fixes: 31bf1dbc ("bpf: Fix attaching fentry/fexit/fmod_ret/lsm to modules") Reported-by:kernel test robot <lkp@intel.com> Signed-off-by:
Viktor Malik <vmalik@redhat.com> Signed-off-by:
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Alexei Starovoitov authored
Alexander Lobakin says: ==================== Enabling skb PP recycling revealed a couple issues in the bpf_test_run code. Recycling broke the assumption that the headroom won't ever be touched during the test_run execution: xdp_scrub_frame() invalidates the XDP frame at the headroom start, while neigh xmit code overwrites 2 bytes to the left of the Ethernet header. The first makes the kernel panic in certain cases, while the second breaks xdp_do_redirect selftest on BE. test_run is a limited-scope entity, so let's hope no more corner cases will happen here or at least they will be as easy and pleasant to fix as those two. ==================== Signed-off-by: -
Alexander Lobakin authored
Alexei noticed xdp_do_redirect test on BPF CI started failing on BE systems after skb PP recycling was enabled: test_xdp_do_redirect:PASS:prog_run 0 nsec test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec test_xdp_do_redirect:PASS:pkt_count_zero 0 nsec test_xdp_do_redirect:FAIL:pkt_count_tc unexpected pkt_count_tc: actual 220 != expected 9998 test_max_pkt_size:PASS:prog_run_max_size 0 nsec test_max_pkt_size:PASS:prog_run_too_big 0 nsec close_netns:PASS:setns 0 nsec #289 xdp_do_redirect:FAIL Summary: 270/1674 PASSED, 30 SKIPPED, 1 FAILED and it doesn't happen on LE systems. Ilya then hunted it down to: #0 0x0000000000aaeee6 in neigh_hh_output (hh=0x83258df0, skb=0x88142200) at linux/include/net/neighbour.h:503 #1 0x0000000000ab2cda in neigh_output (skip_cache=false, skb=0x88142200, n=<optimized out>) at linux/include/net/neighbour.h:544 #2 ip6_finish_output2 (net=net@entry=0x88edba00, sk=sk@entry=0x0, skb=skb@entry=0x88142200) at linux/net/ipv6/ip6_output.c:134 #3 0x0000000000ab4cbc in __ip6_finish_output (skb=0x88142200, sk=0x0, net=0x88edba00) at linux/net/ipv6/ip6_output.c:195 #4 ip6_finish_output (net=0x88edba00, sk=0x0, skb=0x88142200) at linux/net/ipv6/ip6_output.c:206 xdp_do_redirect test places a u32 marker (0x42) right before the Ethernet header to check it then in the XDP program and return %XDP_ABORTED if it's not there. Neigh xmit code likes to round up hard header length to speed up copying the header, so it overwrites two bytes in front of the Eth header. On LE systems, 0x42 is one byte at `data - 4`, while on BE it's `data - 1`, what explains why it happens only there. It didn't happen previously due to that %XDP_PASS meant the page will be discarded and replaced by a new one, but now it can be recycled as well, while bpf_test_run code doesn't reinitialize the content of recycled pages. This mark is limited to this particular test and its setup though, so there's no need to predict 1000 different possible cases. Just move it 4 bytes to the left, still keeping it 32 bit to match on more bytes. Fixes: 9c94bbf9 ("xdp: recycle Page Pool backed skbs built from XDP frames") Reported-by:
Alexander Lobakin <aleksander.lobakin@intel.com> Acked-by:
Ilya Leoshkevich <iii@linux.ibm.com> Link: https://lore.kernel.org/r/20230316175051.922550-3-aleksander.lobakin@intel.comSigned-off-by:
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Alexander Lobakin authored
syzbot and Ilya faced the splats when %XDP_PASS happens for bpf_test_run after skb PP recycling was enabled for {__,}xdp_build_skb_from_frame(): BUG: kernel NULL pointer dereference, address: 0000000000000d28 RIP: 0010:memset_erms+0xd/0x20 arch/x86/lib/memset_64.S:66 [...] Call Trace: <TASK> __finalize_skb_around net/core/skbuff.c:321 [inline] __build_skb_around+0x232/0x3a0 net/core/skbuff.c:379 build_skb_around+0x32/0x290 net/core/skbuff.c:444 __xdp_build_skb_from_frame+0x121/0x760 net/core/xdp.c:622 xdp_recv_frames net/bpf/test_run.c:248 [inline] xdp_test_run_batch net/bpf/test_run.c:334 [inline] bpf_test_run_xdp_live+0x1289/0x1930 net/bpf/test_run.c:362 bpf_prog_test_run_xdp+0xa05/0x14e0 net/bpf/test_run.c:1418 [...] This happens due to that it calls xdp_scrub_frame(), which nullifies xdpf->data. bpf_test_run code doesn't reinit the frame when the XDP program doesn't adjust head or tail. Previously, %XDP_PASS meant the page will be released from the pool and returned to the MM layer, but now it does return to the Pool with the nullified xdpf->data, which doesn't get reinitialized then. So, in addition to checking whether the head and/or tail have been adjusted, check also for a potential XDP frame corruption. xdpf->data is 100% affected and also xdpf->flags is the field closest to the metadata / frame start. Checking for these two should be enough for non-extreme cases. Fixes: 9c94bbf9 ("xdp: recycle Page Pool backed skbs built from XDP frames") Reported-by: syzbot+e1d1b65f7c32f2a86a9f@syzkaller.appspotmail.com Link: https://lore.kernel.org/bpf/000000000000f1985705f6ef2243@google.comReported-by:
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- 16 Mar, 2023 6 commits
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Luis Gerhorst authored
For every BPF_ADD/SUB involving a pointer, adjust_ptr_min_max_vals() ensures that the resulting pointer has a constant offset if bypass_spec_v1 is false. This is ensured by calling sanitize_check_bounds() which in turn calls check_stack_access_for_ptr_arithmetic(). There, -EACCESS is returned if the register's offset is not constant, thereby rejecting the program. In summary, an unprivileged user must never be able to create stack pointers with a variable offset. That is also the case, because a respective check in check_stack_write() is missing. If they were able to create a variable-offset pointer, users could still use it in a stack-write operation to trigger unsafe speculative behavior [1]. Because unprivileged users must already be prevented from creating variable-offset stack pointers, viable options are to either remove this check (replacing it with a clarifying comment), or to turn it into a "verifier BUG"-message, also adding a similar check in check_stack_write() (for consistency, as a second-level defense). This patch implements the first option to reduce verifier bloat. This check was introduced by commit 01f810ac ("bpf: Allow variable-offset stack access") which correctly notes that "variable-offset reads and writes are disallowed (they were already disallowed for the indirect access case) because the speculative execution checking code doesn't support them". However, it does not further discuss why the check in check_stack_read() is necessary. The code which made this check obsolete was also introduced in this commit. I have compiled ~650 programs from the Linux selftests, Linux samples, Cilium, and libbpf/examples projects and confirmed that none of these trigger the check in check_stack_read() [2]. Instead, all of these programs are, as expected, already rejected when constructing the variable-offset pointers. Note that the check in check_stack_access_for_ptr_arithmetic() also prints "off=%d" while the code removed by this patch does not (the error removed does not appear in the "verification_error" values). For reproducibility, the repository linked includes the raw data and scripts used to create the plot. [1] https://arxiv.org/pdf/1807.03757.pdf [2] https://gitlab.cs.fau.de/un65esoq/bpf-spectre/-/raw/53dc19fcf459c186613b1156a81504b39c8d49db/data/plots/23-02-26_23-56_bpftool/bpftool/0004-errors.pdf?inline=false Fixes: 01f810ac ("bpf: Allow variable-offset stack access") Signed-off-by:
Luis Gerhorst <gerhorst@cs.fau.de> Signed-off-by:
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Alexei Starovoitov authored
David Vernet says: ==================== The struct bpf_cpumask type is currently not RCU safe. It uses the bpf_mem_cache_{alloc,free}() APIs to allocate and release cpumasks, and those allocations may be reused before an RCU grace period has elapsed. We want to be able to enable using this pattern in BPF programs: private(MASK) static struct bpf_cpumask __kptr *global; int BPF_PROG(prog, ...) { struct bpf_cpumask *cpumask; bpf_rcu_read_lock(); cpumask = global; if (!cpumask) { bpf_rcu_read_unlock(); return -1; } bpf_cpumask_setall(cpumask); ... bpf_rcu_read_unlock(); } In other words, to be able to pass a kptr to KF_RCU bpf_cpumask kfuncs without requiring the acquisition and release of refcounts using bpf_cpumask_kptr_get(). This patchset enables this by making the struct bpf_cpumask type RCU safe, and removing the bpf_cpumask_kptr_get() function. --- v1: https://lore.kernel.org/all/20230316014122.678082-2-void@manifault.com/ Changelog: ---------- v1 -> v2: - Add doxygen comment for new @rcu field in struct bpf_cpumask. ==================== Signed-off-by: -
David Vernet authored
Now that the kfunc no longer exists, we can remove it and instead describe how RCU can be used to get a struct bpf_cpumask from a map value. This patch updates the BPF documentation accordingly. Signed-off-by:
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David Vernet authored
Now that struct bpf_cpumask is RCU safe, there's no need for this kfunc. Rather than doing the following: private(MASK) static struct bpf_cpumask __kptr *global; int BPF_PROG(prog, s32 cpu, ...) { struct bpf_cpumask *cpumask; bpf_rcu_read_lock(); cpumask = bpf_cpumask_kptr_get(&global); if (!cpumask) { bpf_rcu_read_unlock(); return -1; } bpf_cpumask_setall(cpumask); ... bpf_cpumask_release(cpumask); bpf_rcu_read_unlock(); } Programs can instead simply do (assume same global cpumask): int BPF_PROG(prog, ...) { struct bpf_cpumask *cpumask; bpf_rcu_read_lock(); cpumask = global; if (!cpumask) { bpf_rcu_read_unlock(); return -1; } bpf_cpumask_setall(cpumask); ... bpf_rcu_read_unlock(); } In other words, no extra atomic acquire / release, and less boilerplate code. This patch removes both the kfunc, as well as its selftests and documentation. Signed-off-by: -
David Vernet authored
Now that struct bpf_cpumask * is considered an RCU-safe type according to the verifier, we should add tests that validate its common usages. This patch adds those tests to the cpumask test suite. A subsequent changes will remove bpf_cpumask_kptr_get(), and will adjust the selftest and BPF documentation accordingly. Signed-off-by:
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David Vernet authored
struct bpf_cpumask is a BPF-wrapper around the struct cpumask type which can be instantiated by a BPF program, and then queried as a cpumask in similar fashion to normal kernel code. The previous patch in this series makes the type fully RCU safe, so the type can be included in the rcu_protected_type BTF ID list. A subsequent patch will remove bpf_cpumask_kptr_get(), as it's no longer useful now that we can just treat the type as RCU safe by default and do our own if check. Signed-off-by:
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