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?