kernel/linux.git/lib/test_bpf.c, branch v4.16.11

test_bpf: Fix testing with CONFIG_BPF_JIT_ALWAYS_ON=y on other arches

2018-03-20T22:04:30+00:00

Function bpf_fill_maxinsns11 is designed to not be able to be JITed on x86_64. So, it fails when CONFIG_BPF_JIT_ALWAYS_ON=y, and commit 09584b406742 ("bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y") makes sure that failure is detected on that case. However, it does not fail on other architectures, which have a different JIT compiler design. So, test_bpf has started to fail to load on those. After this fix, test_bpf loads fine on both x86_64 and ppc64el. Fixes: 09584b406742 ("bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y") Signed-off-by: Thadeu Lima de Souza Cascardo Reviewed-by: Yonghong Song Signed-off-by: Daniel Borkmann

test_bpf: reduce MAX_TESTRUNS

2018-02-28T16:49:18+00:00

For tests that are using the maximal number of BPF instruction, each run takes 20 usec. Looping 10,000 times on them totals 200 ms, which is bad when the loop is not preemptible. test_bpf: #264 BPF_MAXINSNS: Call heavy transformations jited:1 19248 18548 PASS test_bpf: #269 BPF_MAXINSNS: ld_abs+get_processor_id jited:1 20896 PASS Lets divide by ten the number of iterations, so that max latency is 20ms. We could use need_resched() to break the loop earlier if we believe 20 ms is too much. Signed-off-by: Eric Dumazet Signed-off-by: Daniel Borkmann

test_bpf: add a schedule point

2018-02-26T20:06:56+00:00

test_bpf() is taking 1.6 seconds nowadays, it is time to add a schedule point in it. Signed-off-by: Eric Dumazet Signed-off-by: Daniel Borkmann

bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y

2018-02-04T23:31:57+00:00

With CONFIG_BPF_JIT_ALWAYS_ON is defined in the config file, tools/testing/selftests/bpf/test_kmod.sh failed like below: [root@localhost bpf]# ./test_kmod.sh sysctl: setting key "net.core.bpf_jit_enable": Invalid argument [ JIT enabled:0 hardened:0 ] [ 132.175681] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096 [ 132.458834] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed] [ JIT enabled:1 hardened:0 ] [ 133.456025] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096 [ 133.730935] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed] [ JIT enabled:1 hardened:1 ] [ 134.769730] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096 [ 135.050864] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed] [ JIT enabled:1 hardened:2 ] [ 136.442882] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096 [ 136.821810] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed] [root@localhost bpf]# The test_kmod.sh load/remove test_bpf.ko multiple times with different settings for sysctl net.core.bpf_jit_{enable,harden}. The failed test #297 of test_bpf.ko is designed such that JIT always fails. Commit 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config) introduced the following tightening logic: ... if (!bpf_prog_is_dev_bound(fp->aux)) { fp = bpf_int_jit_compile(fp); #ifdef CONFIG_BPF_JIT_ALWAYS_ON if (!fp->jited) { *err = -ENOTSUPP; return fp; } #endif ... With this logic, Test #297 always gets return value -ENOTSUPP when CONFIG_BPF_JIT_ALWAYS_ON is defined, causing the test failure. This patch fixed the failure by marking Test #297 as expected failure when CONFIG_BPF_JIT_ALWAYS_ON is defined. Fixes: 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config) Signed-off-by: Yonghong Song Signed-off-by: Daniel Borkmann

bpf: add further test cases around div/mod and others

2018-01-27T00:42:07+00:00

Update selftests to relfect recent changes and add various new test cases. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

bpf: add couple of test cases for signed extended imms

2018-01-20T02:36:59+00:00

Add a couple of test cases for interpreter and JIT that are related to an issue we faced some time ago in Cilium [1], which is fixed in LLVM with commit e53750e1e086 ("bpf: fix bug on silently truncating 64-bit immediate"). Test cases were run-time checking kernel to behave as intended which should also provide some guidance for current or new JITs in case they should trip over this. Added for cBPF and eBPF. [1] https://github.com/cilium/cilium/pull/2162 Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

bpf: introduce BPF_JIT_ALWAYS_ON config

2018-01-09T21:25:26+00:00

The BPF interpreter has been used as part of the spectre 2 attack CVE-2017-5715. A quote from goolge project zero blog: "At this point, it would normally be necessary to locate gadgets in the host kernel code that can be used to actually leak data by reading from an attacker-controlled location, shifting and masking the result appropriately and then using the result of that as offset to an attacker-controlled address for a load. But piecing gadgets together and figuring out which ones work in a speculation context seems annoying. So instead, we decided to use the eBPF interpreter, which is built into the host kernel - while there is no legitimate way to invoke it from inside a VM, the presence of the code in the host kernel's text section is sufficient to make it usable for the attack, just like with ordinary ROP gadgets." To make attacker job harder introduce BPF_JIT_ALWAYS_ON config option that removes interpreter from the kernel in favor of JIT-only mode. So far eBPF JIT is supported by: x64, arm64, arm32, sparc64, s390, powerpc64, mips64 The start of JITed program is randomized and code page is marked as read-only. In addition "constant blinding" can be turned on with net.core.bpf_jit_harden v2->v3: - move __bpf_prog_ret0 under ifdef (Daniel) v1->v2: - fix init order, test_bpf and cBPF (Daniel's feedback) - fix offloaded bpf (Jakub's feedback) - add 'return 0' dummy in case something can invoke prog->bpf_func - retarget bpf tree. For bpf-next the patch would need one extra hunk. It will be sent when the trees are merged back to net-next Considered doing: int bpf_jit_enable __read_mostly = BPF_EBPF_JIT_DEFAULT; but it seems better to land the patch as-is and in bpf-next remove bpf_jit_enable global variable from all JITs, consolidate in one place and remove this jit_init() function. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann

bpf: add test case for ld_abs and helper changing pkt data

2017-12-15T17:19:36+00:00

Add a test that i) uses LD_ABS, ii) zeroing R6 before call, iii) calls a helper that triggers reload of cached skb data, iv) uses LD_ABS again. It's added for test_bpf in order to do runtime testing after JITing as well as test_verifier to test that the sequence is allowed. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

bpf: add BPF_J{LT,LE,SLT,SLE} instructions

2017-08-09T23:53:56+00:00

Currently, eBPF only understands BPF_JGT (>), BPF_JGE (>=), BPF_JSGT (s>), BPF_JSGE (s>=) instructions, this means that particularly *JLT/*JLE counterparts involving immediates need to be rewritten from e.g. X < [IMM] by swapping arguments into [IMM] > X, meaning the immediate first is required to be loaded into a register Y := [IMM], such that then we can compare with Y > X. Note that the destination operand is always required to be a register. This has the downside of having unnecessarily increased register pressure, meaning complex program would need to spill other registers temporarily to stack in order to obtain an unused register for the [IMM]. Loading to registers will thus also affect state pruning since we need to account for that register use and potentially those registers that had to be spilled/filled again. As a consequence slightly more stack space might have been used due to spilling, and BPF programs are a bit longer due to extra code involving the register load and potentially required spill/fills. Thus, add BPF_JLT (<), BPF_JLE (<=), BPF_JSLT (s<), BPF_JSLE (s<=) counterparts to the eBPF instruction set. Modifying LLVM to remove the NegateCC() workaround in a PoC patch at [1] and allowing it to also emit the new instructions resulted in cilium's BPF programs that are injected into the fast-path to have a reduced program length in the range of 2-3% (e.g. accumulated main and tail call sections from one of the object file reduced from 4864 to 4729 insns), reduced complexity in the range of 10-30% (e.g. accumulated sections reduced in one of the cases from 116432 to 88428 insns), and reduced stack usage in the range of 1-5% (e.g. accumulated sections from one of the object files reduced from 824 to 784b). The modification for LLVM will be incorporated in a backwards compatible way. Plan is for LLVM to have i) a target specific option to offer a possibility to explicitly enable the extension by the user (as we have with -m target specific extensions today for various CPU insns), and ii) have the kernel checked for presence of the extensions and enable them transparently when the user is selecting more aggressive options such as -march=native in a bpf target context. (Other frontends generating BPF byte code, e.g. ply can probe the kernel directly for its code generation.) [1] https://github.com/borkmann/llvm/tree/bpf-insns Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

net: introduce __skb_put_[zero, data, u8]

2017-06-20T17:30:14+00:00

follow Johannes Berg, semantic patch file as below, @@ identifier p, p2; expression len; expression skb; type t, t2; @@ ( -p = __skb_put(skb, len); +p = __skb_put_zero(skb, len); | -p = (t)__skb_put(skb, len); +p = __skb_put_zero(skb, len); ) ... when != p ( p2 = (t2)p; -memset(p2, 0, len); | -memset(p, 0, len); ) @@ identifier p; expression len; expression skb; type t; @@ ( -t p = __skb_put(skb, len); +t p = __skb_put_zero(skb, len); ) ... when != p ( -memset(p, 0, len); ) @@ type t, t2; identifier p, p2; expression skb; @@ t *p; ... ( -p = __skb_put(skb, sizeof(t)); +p = __skb_put_zero(skb, sizeof(t)); | -p = (t *)__skb_put(skb, sizeof(t)); +p = __skb_put_zero(skb, sizeof(t)); ) ... when != p ( p2 = (t2)p; -memset(p2, 0, sizeof(*p)); | -memset(p, 0, sizeof(*p)); ) @@ expression skb, len; @@ -memset(__skb_put(skb, len), 0, len); +__skb_put_zero(skb, len); @@ expression skb, len, data; @@ -memcpy(__skb_put(skb, len), data, len); +__skb_put_data(skb, data, len); @@ expression SKB, C, S; typedef u8; identifier fn = {__skb_put}; fresh identifier fn2 = fn ## "_u8"; @@ - *(u8 *)fn(SKB, S) = C; + fn2(SKB, C); Signed-off-by: yuan linyu Signed-off-by: David S. Miller