On 4/2/23 6:39 PM, Alexei Starovoitov wrote:
On Wed, Mar 29, 2023 at 10:56:36PM -0700, Yonghong Song wrote:With LLVM commit [1], loop6.c will fail verification without Commit 3c2611bac08a ("selftests/bpf: Fix trace_virtqueue_add_sgs test issue with LLVM 17."). Also, there is an effort to fix LLVM since LLVM17 may be used by old kernels for bpf development. A new test is added by manually doing similar transformation in [1] so it can be used to test related verifier changes. [1] https://reviews.llvm.org/D143726 Signed-off-by: Yonghong Song <yhs@xxxxxx> --- .../bpf/prog_tests/bpf_verif_scale.c | 5 + tools/testing/selftests/bpf/progs/loop7.c | 102 ++++++++++++++++++ 2 files changed, 107 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/loop7.c diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c index 731c343897d8..cb708235e654 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c @@ -180,6 +180,11 @@ void test_verif_scale_loop6() scale_test("loop6.bpf.o", BPF_PROG_TYPE_KPROBE, false); }+void test_verif_scale_loop7()+{ + scale_test("loop7.bpf.o", BPF_PROG_TYPE_KPROBE, false); +} + void test_verif_scale_strobemeta() { /* partial unroll. 19k insn in a loop. diff --git a/tools/testing/selftests/bpf/progs/loop7.c b/tools/testing/selftests/bpf/progs/loop7.c new file mode 100644 index 000000000000..b234ed6f0038 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/loop7.c @@ -0,0 +1,102 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/ptrace.h> +#include <stddef.h> +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +/* typically virtio scsi has max SGs of 6 */ +#define VIRTIO_MAX_SGS 6 + +/* Verifier will fail with SG_MAX = 128. The failure can be + * workarounded with a smaller SG_MAX, e.g. 10. + */ +#define WORKAROUND +#ifdef WORKAROUND +#define SG_MAX 10 +#else +/* typically virtio blk has max SEG of 128 */ +#define SG_MAX 128 +#endif + +#define SG_CHAIN 0x01UL +#define SG_END 0x02UL + +struct scatterlist { + unsigned long page_link; + unsigned int offset; + unsigned int length; +}; + +#define sg_is_chain(sg) ((sg)->page_link & SG_CHAIN) +#define sg_is_last(sg) ((sg)->page_link & SG_END) +#define sg_chain_ptr(sg) \ + ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END))) + +static inline struct scatterlist *__sg_next(struct scatterlist *sgp) +{ + struct scatterlist sg; + + bpf_probe_read_kernel(&sg, sizeof(sg), sgp); + if (sg_is_last(&sg)) + return NULL; + + sgp++; + + bpf_probe_read_kernel(&sg, sizeof(sg), sgp); + if (sg_is_chain(&sg)) + sgp = sg_chain_ptr(&sg); + + return sgp; +} + +static inline struct scatterlist *get_sgp(struct scatterlist **sgs, int i) +{ + struct scatterlist *sgp; + + bpf_probe_read_kernel(&sgp, sizeof(sgp), sgs + i); + return sgp; +} + +int config = 0; +int result = 0; + +SEC("kprobe/virtqueue_add_sgs") +int BPF_KPROBE(trace_virtqueue_add_sgs, void *unused, struct scatterlist **sgs, + unsigned int out_sgs, unsigned int in_sgs) +{ + struct scatterlist *sgp = NULL; + __u64 length1 = 0, length2 = 0; + unsigned int i, n, len, upper; + + if (config != 0) + return 0; + + upper = out_sgs < VIRTIO_MAX_SGS ? out_sgs : VIRTIO_MAX_SGS; + for (i = 0; i < upper; i++) {since this test is doing manual hoistMinMax, let's keep __sink() in test 6, so we guaranteed to have both flavors regardless of compiler choices?
Sounds good to me. Will drop patch 6.
