- 19 Nov, 2023 3 commits
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Oleg Nesterov authored
This looks more clear and simplifies the code. While at it, remove the unnecessary initialization of pos/task at the start of bpf_iter_task_new(). Note that we can even kill kit->task, we can just use pos->group_leader, but I don't understand the BUILD_BUG_ON() checks in bpf_iter_task_new(). Signed-off-by:
Oleg Nesterov <oleg@redhat.com> Acked-by:
Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20231114163239.GA903@redhat.comSigned-off-by:
Alexei Starovoitov <ast@kernel.org>
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Oleg Nesterov authored
Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c is the last user and the usage is wrong. bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never happen if kit->pos execs. Change this code to use __next_thread(). With or without this change the usage of kit->pos/task and next_task() doesn't look nice, see the next patch. Signed-off-by:
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Oleg Nesterov authored
Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c is the last user and the usage is wrong. task_group_seq_get_next() can return the group leader twice if it races with mt-thread exec which changes the group->leader's pid. Change the main loop to use __next_thread(), kill "next_tid == common->pid" check. __next_thread() can't loop forever, we can also change this code to retry if next_tid == 0. Signed-off-by:
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- 18 Nov, 2023 9 commits
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Alexei Starovoitov authored
Andrii Nakryiko says: ==================== BPF verifier log improvements This patch set moves a big chunk of verifier log related code from gigantic verifier.c file into more focused kernel/bpf/log.c. This is not essential to the rest of functionality in this patch set, so I can undo it, but it felt like it's good to start chipping away from 20K+ verifier.c whenever we can. The main purpose of the patch set, though, is in improving verifier log further. Patches #3-#4 start printing out register state even if that register is spilled into stack slot. Previously we'd get only spilled register type, but no additional information, like SCALAR_VALUE's ranges. Super limiting during debugging. For cases of register spills smaller than 8 bytes, we also print out STACK_MISC/STACK_ZERO/STACK_INVALID markers. This, among other things, will make it easier to write tests for these mixed spill/misc cases. Patch #5 prints map name for PTR_TO_MAP_VALUE/PTR_TO_MAP_KEY/CONST_PTR_TO_MAP registers. In big production BPF programs, it's important to map assembly to actual map, and it's often non-trivial. Having map name helps. Patch #6 just removes visual noise in form of ubiquitous imm=0 and off=0. They are default values, omit them. Patch #7 is probably the most controversial, but it reworks how verifier log prints numbers. For small valued integers we use decimals, but for large ones we switch to hexadecimal. From personal experience this is a much more useful convention. We can tune what consitutes "small value", for now it's 16-bit range. Patch #8 prints frame number for PTR_TO_CTX registers, if that frame is different from the "current" one. This removes ambiguity and confusion, especially in complicated cases with multiple subprogs passing around pointers. v2->v3: - adjust reg_bounds tester to parse hex form of reg state as well; - print reg->range as unsigned (Alexei); v1->v2: - use verbose_snum() for range and offset in register state (Eduard); - fixed typos and added acks from Eduard and Stanislav. ==================== Link: https://lore.kernel.org/r/20231118034623.3320920-1-andrii@kernel.orgSigned-off-by:
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Andrii Nakryiko authored
It's possible to pass a pointer to parent's stack to child subprogs. In such case verifier state output is ambiguous not showing whether register container a pointer to "current" stack, belonging to current subprog (frame), or it's actually a pointer to one of parent frames. So emit this information if frame number differs between the state which register is part of. E.g., if current state is in frame 2 and it has a register pointing to stack in grand parent state (frame #0), we'll see something like 'R1=fp[0]-16', while "local stack pointer" will be just 'R2=fp-16'. Acked-by:
Eduard Zingerman <eddyz87@gmail.com> Acked-by:
Stanislav Fomichev <sdf@google.com> Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231118034623.3320920-9-andrii@kernel.orgSigned-off-by:
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Andrii Nakryiko authored
Instead of always printing numbers as either decimals (and in some cases, like for "imm=%llx", in hexadecimals), decide the form based on actual values. For numbers in a reasonably small range (currently, [0, U16_MAX] for unsigned values, and [S16_MIN, S16_MAX] for signed ones), emit them as decimals. In all other cases, even for signed values, emit them in hexadecimals. For large values hex form is often times way more useful: it's easier to see an exact difference between 0xffffffff80000000 and 0xffffffff7fffffff, than between 18446744071562067966 and 18446744071562067967, as one particular example. Small values representing small pointer offsets or application constants, on the other hand, are way more useful to be represented in decimal notation. Adjust reg_bounds register state parsing logic to take into account this change. Acked-by:
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Andrii Nakryiko authored
Simplify BPF verifier log further by omitting default (and frequently irrelevant) off=0 and imm=0 parts for non-SCALAR_VALUE registers. As can be seen from fixed tests, this is often a visual noise for PTR_TO_CTX register and even for PTR_TO_PACKET registers. Omitting default values follows the rest of register state logic: we omit default values to keep verifier log succinct and to highlight interesting state that deviates from default one. E.g., we do the same for var_off, when it's unknown, which gives no additional information. Acked-by:
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Andrii Nakryiko authored
In complicated real-world applications, whenever debugging some verification error through verifier log, it often would be very useful to see map name for PTR_TO_MAP_VALUE register. Usually this needs to be inferred from key/value sizes and maybe trying to guess C code location, but it's not always clear. Given verifier has the name, and it's never too long, let's just emit it for ptr_to_map_key, ptr_to_map_value, and const_ptr_to_map registers. We reshuffle the order a bit, so that map name, key size, and value size appear before offset and immediate values, which seems like a more logical order. Current output: R1_w=map_ptr(map=array_map,ks=4,vs=8,off=0,imm=0) But we'll get rid of useless off=0 and imm=0 parts in the next patch. Acked-by:
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Andrii Nakryiko authored
Print the same register state representation when printing stack state, as we do for normal registers. Note that if stack slot contains subregister spill (1, 2, or 4 byte long), we'll still emit "m0?" mask for those bytes that are not part of spilled register. While means we can get something like fp-8=0000scalar() for a 4-byte spill with other 4 bytes still being STACK_ZERO. Some example before and after, taken from the log of pyperf_subprogs.bpf.o: 49: (7b) *(u64 *)(r10 -256) = r1 ; frame1: R1_w=ctx(off=0,imm=0) R10=fp0 fp-256_w=ctx 49: (7b) *(u64 *)(r10 -256) = r1 ; frame1: R1_w=ctx(off=0,imm=0) R10=fp0 fp-256_w=ctx(off=0,imm=0) 150: (7b) *(u64 *)(r10 -264) = r0 ; frame1: R0_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0) R10=fp0 fp-264_w=map_value_or_null 150: (7b) *(u64 *)(r10 -264) = r0 ; frame1: R0_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0) R10=fp0 fp-264_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0) 5192: (61) r1 = *(u32 *)(r10 -272) ; frame1: R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf)) R10=fp0 fp-272= 5192: (61) r1 = *(u32 *)(r10 -272) ; frame1: R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf)) R10=fp0 fp-272=????scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf)) While at it, do a few other simple clean ups: - skip slot if it's not scratched before detecting whether it's valid; - move taking spilled_reg pointer outside of switch (only DYNPTR has to adjust that to get to the "main" slot); - don't recalculate types_buf second time for MISC/ZERO/default case. Acked-by: -
Andrii Nakryiko authored
Extract printing register state representation logic into a separate helper, as we are going to reuse it for spilled register state printing in the next patch. This also nicely reduces code nestedness. No functional changes. Acked-by:
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Andrii Nakryiko authored
Move a good chunk of code from verifier.c to log.c: verifier state verbose printing logic. This is an important and very much logging/debugging oriented code. It fits the overlall log.c's focus on verifier logging, and moving it allows to keep growing it without unnecessarily adding to verifier.c code that otherwise contains a core verification logic. There are not many shared dependencies between this code and the rest of verifier.c code, except a few single-line helpers for various register type checks and a bit of state "scratching" helpers. We move all such trivial helpers into include/bpf/bpf_verifier.h as static inlines. No functional changes in this patch. Acked-by:
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Andrii Nakryiko authored
verifier.c is huge. Let's try to move out parts that are logging-related into log.c, as we previously did with bpf_log() and other related stuff. This patch moves line info verbose output routines: it's pretty self-contained and isolated code, so there is no problem with this. Acked-by:
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- 17 Nov, 2023 1 commit
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Andrii Nakryiko authored
Rename verifier internal flag BPF_F_TEST_SANITY_STRICT to more neutral BPF_F_TEST_REG_INVARIANTS. This is a follow up to [0]. A few selftests and veristat need to be adjusted in the same patch as well. [0] https://patchwork.kernel.org/project/netdevbpf/patch/20231112010609.848406-5-andrii@kernel.org/Signed-off-by:
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- 15 Nov, 2023 15 commits
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Puranjay Mohan authored
MOVSX32 only supports sign extending 8-bit and 16-bit operands into 32 bit operands. The "ALU_MOVSX | BPF_W" test tries to sign extend a 32 bit operand into a 32 bit operand which is equivalent to a normal BPF_MOV. Remove this test as it tries to run an invalid instruction. Fixes: daabb2b0 ("bpf/tests: add tests for cpuv4 instructions") Signed-off-by:
Puranjay Mohan <puranjay12@gmail.com> Reported-by:
kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202310111838.46ff5b6a-oliver.sang@intel.comAcked-by:
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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:
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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:
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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:
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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:
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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: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 3 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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