- 15 Nov, 2023 14 commits
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Alexei Starovoitov authored
Andrii Nakryiko says: ==================== BPF register bounds range vs range support This patch set is a continuation of work started in [0]. It adds a big set of manual, auto-generated, and now also random test cases validating BPF verifier's register bounds tracking and deduction logic. First few patches generalize verifier's logic to handle conditional jumps and corresponding range adjustments in case when two non-const registers are compared to each other. Patch #1 generalizes reg_set_min_max() portion, while patch #2 does the same for is_branch_taken() part of the overall solution. Patch #3 improves equality and inequality for cases when BPF program code mixes 64-bit and 32-bit uses of the same register. Depending on specific sequence, it's possible to get to the point where u64/s64 bounds will be very generic (e.g., after signed 32-bit comparison), while we still keep pretty tight u32/s32 bounds. If in such state we proceed with 32-bit equality or inequality comparison, reg_set_min_max() might have to deal with adjusting s32 bounds for two registers that don't overlap, which breaks reg_set_min_max(). This doesn't manifest in <range> vs <const> cases, because if that happens reg_set_min_max() in effect will force s32 bounds to be a new "impossible" constant (from original smin32/smax32 bounds point of view). Things get tricky when we have <range> vs <range> adjustments, so instead of trying to somehow make sense out of such situations, it's best to detect such impossible situations and prune the branch that can't be taken in is_branch_taken() logic. This equality/inequality was the only such category of situations with auto-generated tests added later in the patch set. But when we start mixing arithmetic operations in different numeric domains and conditionals, things get even hairier. So, patch #4 adds sanity checking logic after all ALU/ALU64, JMP/JMP32, and LDX operations. By default, instead of failing verification, we conservatively reset range bounds to unknown values, reporting violation in verifier log (if verbose logs are requested). But to aid development, detection, and debugging, we also introduce a new test flag, BPF_F_TEST_SANITY_STRICT, which triggers verification failure on range sanity violation. Patch #11 sets BPF_F_TEST_SANITY_STRICT by default for test_progs and test_verifier. Patch #12 adds support for controlling this in veristat for testing with production BPF object files. Getting back to BPF verifier, patches #5 and #6 complete verifier's range tracking logic clean up. See respective patches for details. With kernel-side taken care of, we move to testing. We start with building a tester that validates existing <range> vs <scalar> verifier logic for range bounds. Patch #7 implements an initial version of such a tester. We guard millions of generated tests behind SLOW_TESTS=1 envvar requirement, but also have a relatively small number of tricky cases that came up during development and debugging of this work. Those will be executed as part of a normal test_progs run. Patch #8 simulates more nuanced JEQ/JNE logic we added to verifier in patch #3. Patch #9 adds <range> vs <range> "slow tests". Patch #10 is a completely new one, it adds a bunch of randomly generated cases to be run normally, without SLOW_TESTS=1 guard. This should help to get a bunch of cover, and hopefully find some remaining latent problems if verifier proactively as part of normal BPF CI runs. Finally, a tiny test which was, amazingly, an initial motivation for this whole work, is added in lucky patch #13, demonstrating how verifier is now smart enough to track actual number of elements in the array and won't require additional checks on loop iteration variable inside the bpf_for() open-coded iterator loop. [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=798308&state=* v1->v2: - use x < y => y > x property to minimize reg_set_min_max (Eduard); - fix for JEQ/JNE logic in reg_bounds.c (Eduard); - split BPF_JSET and !BPF_JSET cases handling (Shung-Hsi); - adjustments to reg_bounds.c to make it easier to follow (Alexei); - added acks (Eduard, Shung-Hsi). ==================== Link: https://lore.kernel.org/r/20231112010609.848406-1-andrii@kernel.orgSigned-off-by:
Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Add a simple verifier test that requires deriving reg bounds for one register from another register that's not a constant. This is a realistic example of iterating elements of an array with fixed maximum number of elements, but smaller actual number of elements. This small example was an original motivation for doing this whole patch set in the first place, yes. Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231112010609.848406-14-andrii@kernel.orgSigned-off-by:
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Andrii Nakryiko authored
Add a new flag -r (--test-sanity), similar to -t (--test-states), to add extra BPF program flags when loading BPF programs. This allows to use veristat to easily catch sanity violations in production BPF programs. reg_bounds tests are also enforcing BPF_F_TEST_SANITY_STRICT flag now. Signed-off-by:
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Andrii Nakryiko authored
Make sure to set BPF_F_TEST_SANITY_STRICT program flag by default across most verifier tests (and a bunch of others that set custom prog flags). There are currently two tests that do fail validation, if enforced strictly: verifier_bounds/crossing_64_bit_signed_boundary_2 and verifier_bounds/crossing_32_bit_signed_boundary_2. To accommodate them, we teach test_loader a flag negation: __flag(!<flagname>) will *clear* specified flag, allowing easy opt-out. We apply __flag(!BPF_F_TEST_SANITY_STRICT) to these to tests. Also sprinkle BPF_F_TEST_SANITY_STRICT everywhere where we already set test-only BPF_F_TEST_RND_HI32 flag, for completeness. Acked-by:
Eduard Zingerman <eddyz87@gmail.com> Signed-off-by:
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Andrii Nakryiko authored
Add random cases generation to reg_bounds.c and run them without SLOW_TESTS=1 to increase a chance of BPF CI catching latent issues. Suggested-by:
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Andrii Nakryiko authored
Now that verifier supports range vs range bounds adjustments, validate that by checking each generated range against every other generated range, across all supported operators (everything by JSET). We also add few cases that were problematic during development either for verifier or for selftest's range tracking implementation. Note that we utilize the same trick with splitting everything into multiple independent parallelizable tests, but init_t and cond_t. This brings down verification time in parallel mode from more than 8 hours down to less that 1.5 hours. 106 million cases were successfully validate for range vs range logic, in addition to about 7 million range vs const cases, added in earlier patch. Signed-off-by:
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Andrii Nakryiko authored
Similar to kernel-side BPF verifier logic enhancements, use 32-bit subrange knowledge for is_branch_taken() logic in reg_bounds selftests. Signed-off-by:
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Andrii Nakryiko authored
Add test to validate BPF verifier's register range bounds tracking logic. The main bulk is a lot of auto-generated tests based on a small set of seed values for lower and upper 32 bits of full 64-bit values. Currently we validate only range vs const comparisons, but the idea is to start validating range over range comparisons in subsequent patch set. When setting up initial register ranges we treat registers as one of u64/s64/u32/s32 numeric types, and then independently perform conditional comparisons based on a potentially different u64/s64/u32/s32 types. This tests lots of tricky cases of deriving bounds information across different numeric domains. Given there are lots of auto-generated cases, we guard them behind SLOW_TESTS=1 envvar requirement, and skip them altogether otherwise. With current full set of upper/lower seed value, all supported comparison operators and all the combinations of u64/s64/u32/s32 number domains, we get about 7.7 million tests, which run in about 35 minutes on my local qemu instance without parallelization. But we also split those tests by init/cond numeric types, which allows to rely on test_progs's parallelization of tests with `-j` option, getting run time down to about 5 minutes on 8 cores. It's still something that shouldn't be run during normal test_progs run. But we can run it a reasonable time, and so perhaps a nightly CI test run (once we have it) would be a good option for this. We also add a small set of tricky conditions that came up during development and triggered various bugs or corner cases in either selftest's reimplementation of range bounds logic or in verifier's logic itself. These are fast enough to be run as part of normal test_progs test run and are great for a quick sanity checking. Let's take a look at test output to understand what's going on: $ sudo ./test_progs -t reg_bounds_crafted #191/1 reg_bounds_crafted/(u64)[0; 0xffffffff] (u64)< 0:OK ... #191/115 reg_bounds_crafted/(u64)[0; 0x17fffffff] (s32)< 0:OK ... #191/137 reg_bounds_crafted/(u64)[0xffffffff; 0x100000000] (u64)== 0:OK Each test case is uniquely and fully described by this generated string. E.g.: "(u64)[0; 0x17fffffff] (s32)< 0". This means that we initialize a register (R6) in such a way that verifier knows that it can have a value in [(u64)0; (u64)0x17fffffff] range. Another register (R7) is also set up as u64, but this time a constant (zero in this case). They then are compared using 32-bit signed < operation. Resulting TRUE/FALSE branches are evaluated (including cases where it's known that one of the branches will never be taken, in which case we validate that verifier also determines this as a dead code). Test validates that verifier's final register state matches expected state based on selftest's own reg_state logic, implemented from scratch for cross-checking purposes. These test names can be conveniently used for further debugging, and if -vv verboseness is requested we can get a corresponding verifier log (with mark_precise logs filtered out as irrelevant and distracting). Example below is slightly redacted for brevity, omitting irrelevant register output in some places, marked with [...]. $ sudo ./test_progs -a 'reg_bounds_crafted/(u32)[0; U32_MAX] (s32)< -1' -vv ... VERIFIER LOG: ======================== func#0 @0 0: R1=ctx(off=0,imm=0) R10=fp0 0: (05) goto pc+2 3: (85) call bpf_get_current_pid_tgid#14 ; R0_w=scalar() 4: (bc) w6 = w0 ; R0_w=scalar() R6_w=scalar(smin=0,smax=umax=4294967295,var_off=(0x0; 0xffffffff)) 5: (85) call bpf_get_current_pid_tgid#14 ; R0_w=scalar() 6: (bc) w7 = w0 ; R0_w=scalar() R7_w=scalar(smin=0,smax=umax=4294967295,var_off=(0x0; 0xffffffff)) 7: (b4) w1 = 0 ; R1_w=0 8: (b4) w2 = -1 ; R2=4294967295 9: (ae) if w6 < w1 goto pc-9 9: R1=0 R6=scalar(smin=0,smax=umax=4294967295,var_off=(0x0; 0xffffffff)) 10: (2e) if w6 > w2 goto pc-10 10: R2=4294967295 R6=scalar(smin=0,smax=umax=4294967295,var_off=(0x0; 0xffffffff)) 11: (b4) w1 = -1 ; R1_w=4294967295 12: (b4) w2 = -1 ; R2_w=4294967295 13: (ae) if w7 < w1 goto pc-13 ; R1_w=4294967295 R7=4294967295 14: (2e) if w7 > w2 goto pc-14 14: R2_w=4294967295 R7=4294967295 15: (bc) w0 = w6 ; [...] R6=scalar(id=1,smin=0,smax=umax=4294967295,var_off=(0x0; 0xffffffff)) 16: (bc) w0 = w7 ; [...] R7=4294967295 17: (ce) if w6 s< w7 goto pc+3 ; R6=scalar(id=1,smin=0,smax=umax=4294967295,smin32=-1,var_off=(0x0; 0xffffffff)) R7=4294967295 18: (bc) w0 = w6 ; [...] R6=scalar(id=1,smin=0,smax=umax=4294967295,smin32=-1,var_off=(0x0; 0xffffffff)) 19: (bc) w0 = w7 ; [...] R7=4294967295 20: (95) exit from 17 to 21: [...] 21: (bc) w0 = w6 ; [...] R6=scalar(id=1,smin=umin=umin32=2147483648,smax=umax=umax32=4294967294,smax32=-2,var_off=(0x80000000; 0x7fffffff)) 22: (bc) w0 = w7 ; [...] R7=4294967295 23: (95) exit from 13 to 1: [...] 1: [...] 1: (b7) r0 = 0 ; R0_w=0 2: (95) exit processed 24 insns (limit 1000000) max_states_per_insn 0 total_states 2 peak_states 2 mark_read 1 ===================== Verifier log above is for `(u32)[0; U32_MAX] (s32)< -1` use cases, where u32 range is used for initialization, followed by signed < operator. Note how we use w6/w7 in this case for register initialization (it would be R6/R7 for 64-bit types) and then `if w6 s< w7` for comparison at instruction #17. It will be `if R6 < R7` for 64-bit unsigned comparison. Above example gives a good impression of the overall structure of a BPF programs generated for reg_bounds tests. In the future, this "framework" can be extended to test not just conditional jumps, but also arithmetic operations. Adding randomized testing is another possibility. Some implementation notes. We basically have our own generics-like operations on numbers, where all the numbers are stored in u64, but how they are interpreted is passed as runtime argument enum num_t. Further, `struct range` represents a bounds range, and those are collected together into a minimal `struct reg_state`, which collects range bounds across all four numberical domains: u64, s64, u32, s64. Based on these primitives and `enum op` representing possible conditional operation (<, <=, >, >=, ==, !=), there is a set of generic helpers to perform "range arithmetics", which is used to maintain struct reg_state. We simulate what verifier will do for reg bounds of R6 and R7 registers using these range and reg_state primitives. Simulated information is used to determine branch taken conclusion and expected exact register state across all four number domains. Implementation of "range arithmetics" is more generic than what verifier is currently performing: it allows range over range comparisons and adjustments. This is the intended end goal of this patch set overall and verifier logic is enhanced in subsequent patches in this series to handle range vs range operations, at which point selftests are extended to validate these conditions as well. For now it's range vs const cases only. Note that tests are split into multiple groups by their numeric types for initialization of ranges and for comparison operation. This allows to use test_progs's -j parallelization to speed up tests, as we now have 16 groups of parallel running tests. Overall reduction of running time that allows is pretty good, we go down from more than 30 minutes to slightly less than 5 minutes running time. Acked-by:
Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/r/20231112010609.848406-8-andrii@kernel.orgSigned-off-by:
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Andrii Nakryiko authored
This change doesn't seem to have any effect on selftests and production BPF object files, but we preemptively try to make it more robust. First, "learn sign from signed bounds" comment is misleading, as we are learning not just sign, but also values. Second, we simplify the check for determining whether entire range is positive or negative similarly to other checks added earlier, using appropriate u32/u64 cast and single comparisons. As explain in comments in __reg64_deduce_bounds(), the checks are equivalent. Last but not least, smin/smax and s32_min/s32_max reassignment based on min/max of both umin/umax and smin/smax (and 32-bit equivalents) is hard to explain and justify. We are updating unsigned bounds from signed bounds, why would we update signed bounds at the same time? This might be correct, but it's far from obvious why and the code or comments don't try to justify this. Given we've added a separate deduction of signed bounds from unsigned bounds earlier, this seems at least redundant, if not just wrong. In short, we remove doubtful pieces, and streamline the rest to follow the logic and approach of the rest of reg_bounds_sync() checks. Acked-by:
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Andrii Nakryiko authored
Equivalent checks were recently added in more succinct and, arguably, safer form in: - f188765f23a5 ("bpf: derive smin32/smax32 from umin32/umax32 bounds"); - 2e74aef782d3 ("bpf: derive smin/smax from umin/max bounds"). The checks we are removing in this patch set do similar checks to detect if entire u32/u64 range has signed bit set or not set, but does it with two separate checks. Further, we forcefully overwrite either smin or smax (and 32-bit equvalents) without applying normal min/max intersection logic. It's not clear why that would be correct in all cases and seems to work by accident. This logic is also "gated" by previous signed -> unsigned derivation, which returns early. All this is quite confusing and seems error-prone, while we already have at least equivalent checks happening earlier. So remove this duplicate and error-prone logic to simplify things a bit. Acked-by: -
Andrii Nakryiko authored
Add simple sanity checks that validate well-formed ranges (min <= max) across u64, s64, u32, and s32 ranges. Also for cases when the value is constant (either 64-bit or 32-bit), we validate that ranges and tnums are in agreement. These bounds checks are performed at the end of BPF_ALU/BPF_ALU64 operations, on conditional jumps, and for LDX instructions (where subreg zero/sign extension is probably the most important to check). This covers most of the interesting cases. Also, we validate the sanity of the return register when manually adjusting it for some special helpers. By default, sanity violation will trigger a warning in verifier log and resetting register bounds to "unbounded" ones. But to aid development and debugging, BPF_F_TEST_SANITY_STRICT flag is added, which will trigger hard failure of verification with -EFAULT on register bounds violations. This allows selftests to catch such issues. veristat will also gain a CLI option to enable this behavior. Acked-by:
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Andrii Nakryiko authored
Use 32-bit subranges to prune some 64-bit BPF_JEQ/BPF_JNE conditions that otherwise would be "inconclusive" (i.e., is_branch_taken() would return -1). This can happen, for example, when registers are initialized as 64-bit u64/s64, then compared for inequality as 32-bit subregisters, and then followed by 64-bit equality/inequality check. That 32-bit inequality can establish some pattern for lower 32 bits of a register (e.g., s< 0 condition determines whether the bit #31 is zero or not), while overall 64-bit value could be anything (according to a value range representation). This is not a fancy quirky special case, but actually a handling that's necessary to prevent correctness issue with BPF verifier's range tracking: set_range_min_max() assumes that register ranges are non-overlapping, and if that condition is not guaranteed by is_branch_taken() we can end up with invalid ranges, where min > max. [0] https://lore.kernel.org/bpf/CACkBjsY2q1_fUohD7hRmKGqv1MV=eP2f6XK8kjkYNw7BaiF8iQ@mail.gmail.com/Acked-by:
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Andrii Nakryiko authored
Generalize is_branch_taken logic for SCALAR_VALUE register to handle cases when both registers are not constants. Previously supported <range> vs <scalar> cases are a natural subset of more generic <range> vs <range> set of cases. Generalized logic relies on straightforward segment intersection checks. Acked-by:
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Andrii Nakryiko authored
Generalize bounds adjustment logic of reg_set_min_max() to handle not just register vs constant case, but in general any register vs any register cases. For most of the operations it's trivial extension based on range vs range comparison logic, we just need to properly pick min/max of a range to compare against min/max of the other range. For BPF_JSET we keep the original capabilities, just make sure JSET is integrated in the common framework. This is manifested in the internal-only BPF_JSET + BPF_X "opcode" to allow for simpler and more uniform rev_opcode() handling. See the code for details. This allows to reuse the same code exactly both for TRUE and FALSE branches without explicitly handling both conditions with custom code. Note also that now we don't need a special handling of BPF_JEQ/BPF_JNE case none of the registers are constants. This is now just a normal generic case handled by reg_set_min_max(). To make tnum handling cleaner, tnum_with_subreg() helper is added, as that's a common operator when dealing with 32-bit subregister bounds. This keeps the overall logic much less noisy when it comes to tnums. Acked-by:
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- 14 Nov, 2023 8 commits
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Alexei Starovoitov authored
Yafang Shao says: ==================== bpf: Add support for cgroup1, BPF part This is the BPF part of the series "bpf, cgroup: Add BPF support for cgroup1 hierarchy" with adjustment in the last two patches compared to the previous one. v3->v4: - use subsys_name instead of cgrp_name in get_cgroup_hierarchy_id() (Tejun) - use local bpf_link instead of modifying the skeleton in the selftests v3: https://lwn.net/Articles/949264/ ==================== Link: https://lore.kernel.org/r/20231111090034.4248-1-laoar.shao@gmail.comSigned-off-by: -
Yafang Shao authored
Add selftests for cgroup1 hierarchy. The result as follows, $ tools/testing/selftests/bpf/test_progs --name=cgroup1_hierarchy #36/1 cgroup1_hierarchy/test_cgroup1_hierarchy:OK #36/2 cgroup1_hierarchy/test_root_cgid:OK #36/3 cgroup1_hierarchy/test_invalid_level:OK #36/4 cgroup1_hierarchy/test_invalid_cgid:OK #36/5 cgroup1_hierarchy/test_invalid_hid:OK #36/6 cgroup1_hierarchy/test_invalid_cgrp_name:OK #36/7 cgroup1_hierarchy/test_invalid_cgrp_name2:OK #36/8 cgroup1_hierarchy/test_sleepable_prog:OK #36 cgroup1_hierarchy:OK Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED Besides, I also did some stress test similar to the patch #2 in this series, as follows (with CONFIG_PROVE_RCU_LIST enabled): - Continuously mounting and unmounting named cgroups in some tasks, for example: cgrp_name=$1 while true do mount -t cgroup -o none,name=$cgrp_name none /$cgrp_name umount /$cgrp_name done - Continuously run this selftest concurrently, while true; do ./test_progs --name=cgroup1_hierarchy; done They can ran successfully without any RCU warnings in dmesg. Signed-off-by:Yafang Shao <laoar.shao@gmail.com> Link: https://lore.kernel.org/r/20231111090034.4248-7-laoar.shao@gmail.comSigned-off-by:
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Yafang Shao authored
A new cgroup helper function, get_cgroup1_hierarchy_id(), has been introduced to obtain the ID of a cgroup1 hierarchy based on the provided cgroup name. This cgroup name can be obtained from the /proc/self/cgroup file. Signed-off-by:
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Yafang Shao authored
Introduce a new helper function to retrieve the cgroup ID from a net_cls cgroup directory. Signed-off-by:
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Yafang Shao authored
Include the current pid in the classid cgroup path. This way, different testers relying on classid-based configurations will have distinct classid cgroup directories, enabling them to run concurrently. Additionally, we leverage the current pid as the classid, ensuring unique identification. Signed-off-by:
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Yafang Shao authored
If the net_cls subsystem is already mounted, attempting to mount it again in setup_classid_environment() will result in a failure with the error code EBUSY. Despite this, tmpfs will have been successfully mounted at /sys/fs/cgroup/net_cls. Consequently, the /sys/fs/cgroup/net_cls directory will be empty, causing subsequent setup operations to fail. Here's an error log excerpt illustrating the issue when net_cls has already been mounted at /sys/fs/cgroup/net_cls prior to running setup_classid_environment(): - Before that change $ tools/testing/selftests/bpf/test_progs --name=cgroup_v1v2 test_cgroup_v1v2:PASS:server_fd 0 nsec test_cgroup_v1v2:PASS:client_fd 0 nsec test_cgroup_v1v2:PASS:cgroup_fd 0 nsec test_cgroup_v1v2:PASS:server_fd 0 nsec run_test:PASS:skel_open 0 nsec run_test:PASS:prog_attach 0 nsec test_cgroup_v1v2:PASS:cgroup-v2-only 0 nsec (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup.procs (cgroup_helpers.c:540: errno: No such file or directory) Opening cgroup classid: /sys/fs/cgroup/net_cls/cgroup-test-work-dir/net_cls.classid run_test:PASS:skel_open 0 nsec run_test:PASS:prog_attach 0 nsec (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup-test-work-dir/cgroup.procs run_test:FAIL:join_classid unexpected error: 1 (errno 2) test_cgroup_v1v2:FAIL:cgroup-v1v2 unexpected error: -1 (errno 2) (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup.procs #44 cgroup_v1v2:FAIL Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED - After that change $ tools/testing/selftests/bpf/test_progs --name=cgroup_v1v2 #44 cgroup_v1v2:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by:
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Yafang Shao authored
A new kfunc is added to acquire cgroup1 of a task: - bpf_task_get_cgroup1 Acquires the associated cgroup of a task whithin a specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID. This new kfunc enables the tracing of tasks within a designated container or cgroup directory in BPF programs. Suggested-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
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Jordan Rome authored
This is a follow up to: commit b8e3a87a ("bpf: Add crosstask check to __bpf_get_stack"). This test ensures that the task iterator only gets a single user stack (for the current task). Signed-off-by:
Jordan Rome <linux@jordanrome.com> Signed-off-by:
Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20231112023010.144675-1-linux@jordanrome.com
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- 11 Nov, 2023 1 commit
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Yonghong Song authored
With latest clang18 (main branch of llvm-project repo), when building bpf selftests, [~/work/bpf-next (master)]$ make -C tools/testing/selftests/bpf LLVM=1 -j The following compilation error happens: fatal error: error in backend: Branch target out of insn range ... Stack dump: 0. Program arguments: clang -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -I/home/yhs/work/bpf-next/tools/include/uapi -I/home/yhs/work/bpf-next/tools/testing/selftests/usr/include -idirafter /home/yhs/work/llvm-project/llvm/build.18/install/lib/clang/18/include -idirafter /usr/local/include -idirafter /usr/include -Wno-compare-distinct-pointer-types -DENABLE_ATOMICS_TESTS -O2 --target=bpf -c progs/pyperf180.c -mcpu=v3 -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/pyperf180.bpf.o 1. <eof> parser at end of file 2. Code generation ... The compilation failure only happens to cpu=v2 and cpu=v3. cpu=v4 is okay since cpu=v4 supports 32-bit branch target offset. The above failure is due to upstream llvm patch [1] where some inlining behavior are changed in clang18. To workaround the issue, previously all 180 loop iterations are fully unrolled. The bpf macro __BPF_CPU_VERSION__ (implemented in clang18 recently) is used to avoid unrolling changes if cpu=v4. If __BPF_CPU_VERSION__ is not available and the compiler is clang18, the unrollng amount is unconditionally reduced. [1] https://github.com/llvm/llvm-project/commit/1a2e77cf9e11dbf56b5720c607313a566eebb16eSigned-off-by:Yonghong Song <yonghong.song@linux.dev> Signed-off-by:
Alan Maguire <alan.maguire@oracle.com> Link: https://lore.kernel.org/bpf/20231110193644.3130906-1-yonghong.song@linux.dev
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- 10 Nov, 2023 17 commits
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Jordan Rome authored
Currently get_perf_callchain only supports user stack walking for the current task. Passing the correct *crosstask* param will return 0 frames if the task passed to __bpf_get_stack isn't the current one instead of a single incorrect frame/address. This change passes the correct *crosstask* param but also does a preemptive check in __bpf_get_stack if the task is current and returns -EOPNOTSUPP if it is not. This issue was found using bpf_get_task_stack inside a BPF iterator ("iter/task"), which iterates over all tasks. bpf_get_task_stack works fine for fetching kernel stacks but because get_perf_callchain relies on the caller to know if the requested *task* is the current one (via *crosstask*) it was failing in a confusing way. It might be possible to get user stacks for all tasks utilizing something like access_process_vm but that requires the bpf program calling bpf_get_task_stack to be sleepable and would therefore be a breaking change. Fixes: fa28dcb8 ("bpf: Introduce helper bpf_get_task_stack()") Signed-off-by:Jordan Rome <jordalgo@meta.com> Signed-off-by:
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Alexei Starovoitov authored
Merge branch 'for-6.8-bpf' of https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup into bpf-next Merge cgroup prerequisite patches. Link: https://lore.kernel.org/bpf/20231029061438.4215-1-laoar.shao@gmail.com/Signed-off-by:
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Yafang Shao authored
The kernel supports a minimum GCC version of 5.1.0 for building. However, the "__diag_ignore_all" directive only suppresses the "-Wmissing-prototypes" warning for GCC versions >= 8.0.0. As a result, when building the kernel with older GCC versions, warnings may be triggered. The example below illustrates the warnings reported by the kernel test robot using GCC 7.5.0: compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0 All warnings (new ones prefixed by >>): kernel/bpf/helpers.c:1893:19: warning: no previous prototype for 'bpf_obj_new_impl' [-Wmissing-prototypes] __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign) ^~~~~~~~~~~~~~~~ kernel/bpf/helpers.c:1907:19: warning: no previous prototype for 'bpf_percpu_obj_new_impl' [-Wmissing-prototypes] __bpf_kfunc void *bpf_percpu_obj_new_impl(u64 local_type_id__k, void *meta__ign) [...] To address this, we should also suppress the "-Wmissing-prototypes" warning for older GCC versions. "#pragma GCC diagnostic push" is supported as of GCC 4.6, and both "-Wmissing-prototypes" and "-Wmissing-declarations" are supported for all the GCC versions that we currently support. Therefore, it is reasonable to suppress these warnings for all supported GCC versions. With this adjustment, it's important to note that after implementing "__diag_ignore_all", it will effectively suppress warnings for all the supported GCC versions. In the future, if you wish to suppress warnings that are only supported on higher GCC versions, it is advisable to explicitly use "__diag_ignore" to specify the GCC version you are targeting. Reported-by:kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202311031651.A7crZEur-lkp@intel.com/Suggested-by:
Arnd Bergmann <arnd@arndb.de> Signed-off-by:
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Yonghong Song authored
Martin and Vadim reported a verifier failure with bpf_dynptr usage. The issue is mentioned but Vadim workarounded the issue with source change ([1]). The below describes what is the issue and why there is a verification failure. int BPF_PROG(skb_crypto_setup) { struct bpf_dynptr algo, key; ... bpf_dynptr_from_mem(..., ..., 0, &algo); ... } The bpf program is using vmlinux.h, so we have the following definition in vmlinux.h: struct bpf_dynptr { long: 64; long: 64; }; Note that in uapi header bpf.h, we have struct bpf_dynptr { long: 64; long: 64; } __attribute__((aligned(8))); So we lost alignment information for struct bpf_dynptr by using vmlinux.h. Let us take a look at a simple program below: $ cat align.c typedef unsigned long long __u64; struct bpf_dynptr_no_align { __u64 :64; __u64 :64; }; struct bpf_dynptr_yes_align { __u64 :64; __u64 :64; } __attribute__((aligned(8))); void bar(void *, void *); int foo() { struct bpf_dynptr_no_align a; struct bpf_dynptr_yes_align b; bar(&a, &b); return 0; } $ clang --target=bpf -O2 -S -emit-llvm align.c Look at the generated IR file align.ll: ... %a = alloca %struct.bpf_dynptr_no_align, align 1 %b = alloca %struct.bpf_dynptr_yes_align, align 8 ... The compiler dictates the alignment for struct bpf_dynptr_no_align is 1 and the alignment for struct bpf_dynptr_yes_align is 8. So theoretically compiler could allocate variable %a with alignment 1 although in reallity the compiler may choose a different alignment by considering other local variables. In [1], the verification failure happens because variable 'algo' is allocated on the stack with alignment 4 (fp-28). But the verifer wants its alignment to be 8. To fix the issue, the RFC patch ([1]) tried to add '__attribute__((aligned(8)))' to struct bpf_dynptr plus other similar structs. Andrii suggested that we could directly modify uapi struct with named fields like struct 'bpf_iter_num': struct bpf_iter_num { /* opaque iterator state; having __u64 here allows to preserve correct * alignment requirements in vmlinux.h, generated from BTF */ __u64 __opaque[1]; } __attribute__((aligned(8))); Indeed, adding named fields for those affected structs in this patch can preserve alignment when bpf program references them in vmlinux.h. With this patch, the verification failure in [1] can also be resolved. [1] https://lore.kernel.org/bpf/1b100f73-7625-4c1f-3ae5-50ecf84d3ff0@linux.dev/ [2] https://lore.kernel.org/bpf/20231103055218.2395034-1-yonghong.song@linux.dev/ Cc: Vadim Fedorenko <vadfed@meta.com> Cc: Martin KaFai Lau <martin.lau@linux.dev> Suggested-by: -
Alexei Starovoitov authored
Dave Marchevsky says: ==================== Allow bpf_refcount_acquire of mapval obtained via direct LD Consider this BPF program: struct cgv_node { int d; struct bpf_refcount r; struct bpf_rb_node rb; }; struct val_stash { struct cgv_node __kptr *v; }; struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(key, int); __type(value, struct val_stash); __uint(max_entries, 10); } array_map SEC(".maps"); long bpf_program(void *ctx) { struct val_stash *mapval; struct cgv_node *p; int idx = 0; mapval = bpf_map_lookup_elem(&array_map, &idx); if (!mapval || !mapval->v) { /* omitted */ } p = bpf_refcount_acquire(mapval->v); /* Verification FAILs here */ /* Add p to some tree */ return 0; } Verification fails on the refcount_acquire: 160: (79) r1 = *(u64 *)(r8 +8) ; R1_w=untrusted_ptr_or_null_cgv_node(id=11,off=0,imm=0) R8_w=map_value(id=10,off=0,ks=8,vs=16,imm=0) refs=6 161: (b7) r2 = 0 ; R2_w=0 refs=6 162: (85) call bpf_refcount_acquire_impl#117824 arg#0 is neither owning or non-owning ref The above verifier dump is actually from sched_ext's scx_flatcg [0], which is the motivating usecase for this series' changes. Specifically, scx_flatcg stashes a rb_node type w/ cgroup-specific info (struct cgv_node) in a map when the cgroup is created, then later puts that cgroup's node in a rbtree in .enqueue . Making struct cgv_node refcounted would simplify the code a bit by virtue of allowing us to remove the kptr_xchg's, but "later puts that cgroups node in a rbtree" is not possible without a refcount_acquire, which suffers from the above verification failure. If we get rid of PTR_UNTRUSTED flag, and add MEM_ALLOC | NON_OWN_REF, mapval->v would be a non-owning ref and verification would succeed. Due to the most recent set of refcount changes [1], which modified bpf_obj_drop behavior to not reuse refcounted graph node's underlying memory until after RCU grace period, this is safe to do. Once mapval->v has the correct flags it _is_ a non-owning reference and verification of the motivating example will succeed. [0]: https://github.com/sched-ext/sched_ext/blob/52911e1040a0f94b9c426dddcc00be5364a7ae9f/tools/sched_ext/scx_flatcg.bpf.c#L275 [1]: https://lore.kernel.org/bpf/20230821193311.3290257-1-davemarchevsky@fb.com/ Summary of patches: * Patch 1 fixes an issue with bpf_refcount_acquire verification letting MAYBE_NULL ptrs through * Patch 2 tests Patch 1's fix * Patch 3 broadens the use of "free only after RCU GP" to all user-allocated types * Patch 4 is a small nonfunctional refactoring * Patch 5 changes verifier to mark direct LD of stashed graph node kptr as non-owning ref * Patch 6 tests Patch 5's verifier changes Changelog: v1 -> v2: https://lore.kernel.org/bpf/20231025214007.2920506-1-davemarchevsky@fb.com/ Series title changed to "Allow bpf_refcount_acquire of mapval obtained via direct LD". V1's title was mistakenly truncated. * Patch 5 ("bpf: Mark direct ld of stashed bpf_{rb,list}_node as non-owning ref") * Direct LD of percpu kptr should not have MEM_ALLOC flag (Yonghong) * Patch 6 ("selftests/bpf: Test bpf_refcount_acquire of node obtained via direct ld") * Test read from stashed value as well ==================== Link: https://lore.kernel.org/r/20231107085639.3016113-1-davemarchevsky@fb.comSigned-off-by: -
Shung-Hsi Yu authored
The addition of is_reg_const() in commit 171de12646d2 ("bpf: generalize is_branch_taken to handle all conditional jumps in one place") has made the register_is_const() redundant. Give the former has more feature, plus the fact the latter is only used in one place, replace register_is_const() with is_reg_const(), and remove the definition of register_is_const. This requires moving the definition of is_reg_const() further up. And since the comment of reg_const_value() reference is_reg_const(), move it up as well. Signed-off-by: -
Dave Marchevsky authored
This patch demonstrates that verifier changes earlier in this series result in bpf_refcount_acquire(mapval->stashed_kptr) passing verification. The added test additionally validates that stashing a kptr in mapval and - in a separate BPF program - refcount_acquiring the kptr without unstashing works as expected at runtime. Signed-off-by:
Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/r/20231107085639.3016113-7-davemarchevsky@fb.comSigned-off-by:
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Andrii Nakryiko authored
Add ability to filter top B results, both in replay/verifier mode and comparison mode. Just adding `-n10` will emit only first 10 rows, or less, if there is not enough rows. This is not just a shortcut instead of passing veristat output through `head`, though. Filtering out all the other rows influences final table formatting, as table column widths are calculated based on actual emitted test. To demonstrate the difference, compare two "equivalent" forms below, one using head and another using -n argument. TOP N FEATURE ============= [vmuser@archvm bpf]$ sudo ./veristat -C ~/baseline-results-selftests.csv ~/sanity2-results-selftests.csv -e file,prog,insns,states -s '|insns_diff|' -n10 File Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ---------------------------------------- --------------------- --------- --------- ------------ ---------- ---------- ------------- test_seg6_loop.bpf.linked3.o __add_egr_x 12440 12360 -80 (-0.64%) 364 357 -7 (-1.92%) async_stack_depth.bpf.linked3.o async_call_root_check 145 145 +0 (+0.00%) 3 3 +0 (+0.00%) async_stack_depth.bpf.linked3.o pseudo_call_check 139 139 +0 (+0.00%) 3 3 +0 (+0.00%) atomic_bounds.bpf.linked3.o sub 7 7 +0 (+0.00%) 0 0 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o kmalloc 5 5 +0 (+0.00%) 0 0 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o sched_process_fork 22 22 +0 (+0.00%) 2 2 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o socket_post_create 23 23 +0 (+0.00%) 2 2 +0 (+0.00%) bind4_prog.bpf.linked3.o bind_v4_prog 358 358 +0 (+0.00%) 33 33 +0 (+0.00%) bind6_prog.bpf.linked3.o bind_v6_prog 429 429 +0 (+0.00%) 37 37 +0 (+0.00%) bind_perm.bpf.linked3.o bind_v4_prog 15 15 +0 (+0.00%) 1 1 +0 (+0.00%) PIPING TO HEAD ============== [vmuser@archvm bpf]$ sudo ./veristat -C ~/baseline-results-selftests.csv ~/sanity2-results-selftests.csv -e file,prog,insns,states -s '|insns_diff|' | head -n12 File Program Insns (A) Insns (B) Insns (DIFF) States (A) States (B) States (DIFF) ----------------------------------------------------- ---------------------------------------------------- --------- --------- ------------ ---------- ---------- ------------- test_seg6_loop.bpf.linked3.o __add_egr_x 12440 12360 -80 (-0.64%) 364 357 -7 (-1.92%) async_stack_depth.bpf.linked3.o async_call_root_check 145 145 +0 (+0.00%) 3 3 +0 (+0.00%) async_stack_depth.bpf.linked3.o pseudo_call_check 139 139 +0 (+0.00%) 3 3 +0 (+0.00%) atomic_bounds.bpf.linked3.o sub 7 7 +0 (+0.00%) 0 0 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o kmalloc 5 5 +0 (+0.00%) 0 0 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o sched_process_fork 22 22 +0 (+0.00%) 2 2 +0 (+0.00%) bench_local_storage_create.bpf.linked3.o socket_post_create 23 23 +0 (+0.00%) 2 2 +0 (+0.00%) bind4_prog.bpf.linked3.o bind_v4_prog 358 358 +0 (+0.00%) 33 33 +0 (+0.00%) bind6_prog.bpf.linked3.o bind_v6_prog 429 429 +0 (+0.00%) 37 37 +0 (+0.00%) bind_perm.bpf.linked3.o bind_v4_prog 15 15 +0 (+0.00%) 1 1 +0 (+0.00%) Note all the wasted whitespace in the "PIPING TO HEAD" variant. Signed-off-by:
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Dave Marchevsky authored
This patch enables the following pattern: /* mapval contains a __kptr pointing to refcounted local kptr */ mapval = bpf_map_lookup_elem(&map, &idx); if (!mapval || !mapval->some_kptr) { /* omitted */ } p = bpf_refcount_acquire(&mapval->some_kptr); Currently this doesn't work because bpf_refcount_acquire expects an owning or non-owning ref. The verifier defines non-owning ref as a type: PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF while mapval->some_kptr is PTR_TO_BTF_ID | PTR_UNTRUSTED. It's possible to do the refcount_acquire by first bpf_kptr_xchg'ing mapval->some_kptr into a temp kptr, refcount_acquiring that, and xchg'ing back into mapval, but this is unwieldy and shouldn't be necessary. This patch modifies btf_ld_kptr_type such that user-allocated types are marked MEM_ALLOC and if those types have a bpf_{rb,list}_node they're marked NON_OWN_REF as well. Additionally, due to changes to bpf_obj_drop_impl earlier in this series, rcu_protected_object now returns true for all user-allocated types, resulting in mapval->some_kptr being marked MEM_RCU. After this patch's changes, mapval->some_kptr is now: PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU which results in it passing the non-owning ref test, and the motivating example passing verification. Future work will likely get rid of special non-owning ref lifetime logic in the verifier, at which point we'll be able to delete the NON_OWN_REF flag entirely. Signed-off-by: -
Andrii Nakryiko authored
Add ability to sort results by absolute values of specified stats. This is especially useful to find biggest deviations in comparison mode. When comparing verifier change effect against a large base of BPF object files, it's necessary to see big changes both in positive and negative directions, as both might be a signal for regressions or bugs. The syntax is natural, e.g., adding `-s '|insns_diff|'^` will instruct veristat to sort by absolute value of instructions difference in ascending order. Signed-off-by:
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Dave Marchevsky authored
This refactoring patch removes the unused BPF_GRAPH_NODE_OR_ROOT btf_field_type and moves BPF_GRAPH_{NODE,ROOT} macros into the btf_field_type enum. Further patches in the series will use BPF_GRAPH_NODE, so let's move this useful definition out of btf.c. Signed-off-by: -
Yonghong Song authored
Martin reported that there is a libbpf complaining of non-zero-value tail padding with LIBBPF_OPTS_RESET macro if struct bpf_netkit_opts is modified to have a 4-byte tail padding. This only happens to clang compiler. The commend line is: ./test_progs -t tc_netkit_multi_links Martin and I did some investigation and found this indeed the case and the following are the investigation details. Clang: clang version 18.0.0 <I tried clang15/16/17 and they all have similar results> tools/lib/bpf/libbpf_common.h: #define LIBBPF_OPTS_RESET(NAME, ...) \ do { \ memset(&NAME, 0, sizeof(NAME)); \ NAME = (typeof(NAME)) { \ .sz = sizeof(NAME), \ __VA_ARGS__ \ }; \ } while (0) #endif tools/lib/bpf/libbpf.h: struct bpf_netkit_opts { /* size of this struct, for forward/backward compatibility */ size_t sz; __u32 flags; __u32 relative_fd; __u32 relative_id; __u64 expected_revision; size_t :0; }; #define bpf_netkit_opts__last_field expected_revision In the above struct bpf_netkit_opts, there is no tail padding. prog_tests/tc_netkit.c: static void serial_test_tc_netkit_multi_links_target(int mode, int target) { ... LIBBPF_OPTS(bpf_netkit_opts, optl); ... LIBBPF_OPTS_RESET(optl, .flags = BPF_F_BEFORE, .relative_fd = bpf_program__fd(skel->progs.tc1), ); ... } Let us make the following source change, note that we have a 4-byte tailing padding now. diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 6cd9c501624f..0dd83910ae9a 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -803,13 +803,13 @@ bpf_program__attach_tcx(const struct bpf_program *prog, int ifindex, struct bpf_netkit_opts { /* size of this struct, for forward/backward compatibility */ size_t sz; - __u32 flags; __u32 relative_fd; __u32 relative_id; __u64 expected_revision; + __u32 flags; size_t :0; }; -#define bpf_netkit_opts__last_field expected_revision +#define bpf_netkit_opts__last_field flags The clang 18 generated asm code looks like below: ; LIBBPF_OPTS_RESET(optl, 55e3: 48 8d 7d 98 leaq -0x68(%rbp), %rdi 55e7: 31 f6 xorl %esi, %esi 55e9: ba 20 00 00 00 movl $0x20, %edx 55ee: e8 00 00 00 00 callq 0x55f3 <serial_test_tc_netkit_multi_links_target+0x18d3> 55f3: 48 c7 85 10 fd ff ff 20 00 00 00 movq $0x20, -0x2f0(%rbp) 55fe: 48 8b 85 68 ff ff ff movq -0x98(%rbp), %rax 5605: 48 8b 78 18 movq 0x18(%rax), %rdi 5609: e8 00 00 00 00 callq 0x560e <serial_test_tc_netkit_multi_links_target+0x18ee> 560e: 89 85 18 fd ff ff movl %eax, -0x2e8(%rbp) 5614: c7 85 1c fd ff ff 00 00 00 00 movl $0x0, -0x2e4(%rbp) 561e: 48 c7 85 20 fd ff ff 00 00 00 00 movq $0x0, -0x2e0(%rbp) 5629: c7 85 28 fd ff ff 08 00 00 00 movl $0x8, -0x2d8(%rbp) 5633: 48 8b 85 10 fd ff ff movq -0x2f0(%rbp), %rax 563a: 48 89 45 98 movq %rax, -0x68(%rbp) 563e: 48 8b 85 18 fd ff ff movq -0x2e8(%rbp), %rax 5645: 48 89 45 a0 movq %rax, -0x60(%rbp) 5649: 48 8b 85 20 fd ff ff movq -0x2e0(%rbp), %rax 5650: 48 89 45 a8 movq %rax, -0x58(%rbp) 5654: 48 8b 85 28 fd ff ff movq -0x2d8(%rbp), %rax 565b: 48 89 45 b0 movq %rax, -0x50(%rbp) ; link = bpf_program__attach_netkit(skel->progs.tc2, ifindex, &optl); At -O0 level, the clang compiler creates an intermediate copy. We have below to store 'flags' with 4-byte store and leave another 4 byte in the same 8-byte-aligned storage undefined, 5629: c7 85 28 fd ff ff 08 00 00 00 movl $0x8, -0x2d8(%rbp) and later we store 8-byte to the original zero'ed buffer 5654: 48 8b 85 28 fd ff ff movq -0x2d8(%rbp), %rax 565b: 48 89 45 b0 movq %rax, -0x50(%rbp) This caused a problem as the 4-byte value at [%rbp-0x2dc, %rbp-0x2e0) may be garbage. gcc (gcc 11.4) does not have this issue as it does zeroing struct first before doing assignments: ; LIBBPF_OPTS_RESET(optl, 50fd: 48 8d 85 40 fc ff ff leaq -0x3c0(%rbp), %rax 5104: ba 20 00 00 00 movl $0x20, %edx 5109: be 00 00 00 00 movl $0x0, %esi 510e: 48 89 c7 movq %rax, %rdi 5111: e8 00 00 00 00 callq 0x5116 <serial_test_tc_netkit_multi_links_target+0x1522> 5116: 48 8b 45 f0 movq -0x10(%rbp), %rax 511a: 48 8b 40 18 movq 0x18(%rax), %rax 511e: 48 89 c7 movq %rax, %rdi 5121: e8 00 00 00 00 callq 0x5126 <serial_test_tc_netkit_multi_links_target+0x1532> 5126: 48 c7 85 40 fc ff ff 00 00 00 00 movq $0x0, -0x3c0(%rbp) 5131: 48 c7 85 48 fc ff ff 00 00 00 00 movq $0x0, -0x3b8(%rbp) 513c: 48 c7 85 50 fc ff ff 00 00 00 00 movq $0x0, -0x3b0(%rbp) 5147: 48 c7 85 58 fc ff ff 00 00 00 00 movq $0x0, -0x3a8(%rbp) 5152: 48 c7 85 40 fc ff ff 20 00 00 00 movq $0x20, -0x3c0(%rbp) 515d: 89 85 48 fc ff ff movl %eax, -0x3b8(%rbp) 5163: c7 85 58 fc ff ff 08 00 00 00 movl $0x8, -0x3a8(%rbp) ; link = bpf_program__attach_netkit(skel->progs.tc2, ifindex, &optl); It is not clear how to resolve the compiler code generation as the compiler generates correct code w.r.t. how to handle unnamed padding in C standard. So this patch changed LIBBPF_OPTS_RESET macro to avoid uninitialized tail padding. We already knows LIBBPF_OPTS macro works on both gcc and clang, even with tail padding. So LIBBPF_OPTS_RESET is changed to be a LIBBPF_OPTS followed by a memcpy(), thus avoiding uninitialized tail padding. The below is asm code generated with this patch and with clang compiler: ; LIBBPF_OPTS_RESET(optl, 55e3: 48 8d bd 10 fd ff ff leaq -0x2f0(%rbp), %rdi 55ea: 31 f6 xorl %esi, %esi 55ec: ba 20 00 00 00 movl $0x20, %edx 55f1: e8 00 00 00 00 callq 0x55f6 <serial_test_tc_netkit_multi_links_target+0x18d6> 55f6: 48 c7 85 10 fd ff ff 20 00 00 00 movq $0x20, -0x2f0(%rbp) 5601: 48 8b 85 68 ff ff ff movq -0x98(%rbp), %rax 5608: 48 8b 78 18 movq 0x18(%rax), %rdi 560c: e8 00 00 00 00 callq 0x5611 <serial_test_tc_netkit_multi_links_target+0x18f1> 5611: 89 85 18 fd ff ff movl %eax, -0x2e8(%rbp) 5617: c7 85 1c fd ff ff 00 00 00 00 movl $0x0, -0x2e4(%rbp) 5621: 48 c7 85 20 fd ff ff 00 00 00 00 movq $0x0, -0x2e0(%rbp) 562c: c7 85 28 fd ff ff 08 00 00 00 movl $0x8, -0x2d8(%rbp) 5636: 48 8b 85 10 fd ff ff movq -0x2f0(%rbp), %rax 563d: 48 89 45 98 movq %rax, -0x68(%rbp) 5641: 48 8b 85 18 fd ff ff movq -0x2e8(%rbp), %rax 5648: 48 89 45 a0 movq %rax, -0x60(%rbp) 564c: 48 8b 85 20 fd ff ff movq -0x2e0(%rbp), %rax 5653: 48 89 45 a8 movq %rax, -0x58(%rbp) 5657: 48 8b 85 28 fd ff ff movq -0x2d8(%rbp), %rax 565e: 48 89 45 b0 movq %rax, -0x50(%rbp) ; link = bpf_program__attach_netkit(skel->progs.tc2, ifindex, &optl); In the above code, a temporary buffer is zeroed and then has proper value assigned. Finally, values in temporary buffer are copied to the original variable buffer, hence tail padding is guaranteed to be 0. Signed-off-by:Martin KaFai Lau <martin.lau@kernel.org> Link: https://lore.kernel.org/bpf/20231107201511.2548645-1-yonghong.song@linux.devSigned-off-by:
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Dave Marchevsky authored
The use of bpf_mem_free_rcu to free refcounted local kptrs was added in commit 7e26cd12 ("bpf: Use bpf_mem_free_rcu when bpf_obj_dropping refcounted nodes"). In the cover letter for the series containing that patch [0] I commented: Perhaps it makes sense to move to mem_free_rcu for _all_ non-owning refs in the future, not just refcounted. This might allow custom non-owning ref lifetime + invalidation logic to be entirely subsumed by MEM_RCU handling. IMO this needs a bit more thought and should be tackled outside of a fix series, so it's not attempted here. It's time to start moving in the "non-owning refs have MEM_RCU lifetime" direction. As mentioned in that comment, using bpf_mem_free_rcu for all local kptrs - not just refcounted - is necessarily the first step towards that goal. This patch does so. After this patch the memory pointed to by all local kptrs will not be reused until RCU grace period elapses. The verifier's understanding of non-owning ref validity and the clobbering logic it uses to enforce that understanding are not changed here, that'll happen gradually in future work, including further patches in the series. [0]: https://lore.kernel.org/all/20230821193311.3290257-1-davemarchevsky@fb.com/Signed-off-by:
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Dave Marchevsky authored
The test added in this patch exercises the logic fixed in the previous patch in this series. Before the previous patch's changes, bpf_refcount_acquire accepts MAYBE_NULL local kptrs; after the change the verifier correctly rejects the such a call. Signed-off-by:
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Dave Marchevsky authored
Refcounted local kptrs are kptrs to user-defined types with a bpf_refcount field. Recent commits ([0], [1]) modified the lifetime of refcounted local kptrs such that the underlying memory is not reused until RCU grace period has elapsed. Separately, verification of bpf_refcount_acquire calls currently succeeds for MAYBE_NULL non-owning reference input, which is a problem as bpf_refcount_acquire_impl has no handling for this case. This patch takes advantage of aforementioned lifetime changes to tag bpf_refcount_acquire_impl kfunc KF_RCU, thereby preventing MAYBE_NULL input to the kfunc. The KF_RCU flag applies to all kfunc params; it's fine for it to apply to the void *meta__ign param as that's populated by the verifier and is tagged __ign regardless. [0]: commit 7e26cd12 ("bpf: Use bpf_mem_free_rcu when bpf_obj_dropping refcounted nodes") is the actual change to allocation behaivor [1]: commit 0816b8c6 ("bpf: Consider non-owning refs to refcounted nodes RCU protected") modified verifier understanding of refcounted local kptrs to match [0]'s changes Signed-off-by:
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Andrii Nakryiko authored
Song Liu says: ==================== This set contains the first 3 patches of set [1]. Currently, [1] is waiting for [3] to be merged to bpf-next tree. So send these 3 patches first to unblock other works, such as [2]. This set is verified with new version of [1] in CI run [4]. Changes since v12 of [1]: 1. Reuse bpf_dynptr_slice() in __bpf_dynptr_data(). (Andrii) 2. Add Acked-by from Vadim Fedorenko. [1] https://lore.kernel.org/bpf/20231104001313.3538201-1-song@kernel.org/ [2] https://lore.kernel.org/bpf/20231031134900.1432945-1-vadfed@meta.com/ [3] https://lore.kernel.org/bpf/20231031215625.2343848-1-davemarchevsky@fb.com/ [4] https://github.com/kernel-patches/bpf/actions/runs/6779945063/job/18427926114 ==================== Signed-off-by:
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Florian Lehner authored
When looking up an element in LPM trie, the condition 'matchlen == trie->max_prefixlen' will never return true, if key->prefixlen is larger than trie->max_prefixlen. Consequently all elements in the LPM trie will be visited and no element is returned in the end. To resolve this, check key->prefixlen first before walking the LPM trie. Fixes: b95a5c4d ("bpf: add a longest prefix match trie map implementation") Signed-off-by:
Florian Lehner <dev@der-flo.net> Signed-off-by:
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