Re: [PATCH RFC 5/5] selftests/bpf: Add iter_task_vma_buildid test

Jiri Olsa
2023-02-09T14:04:22Z

On Wed, Feb 08, 2023 at 04:01:42PM -0800, Andrii Nakryiko wrote:

SNIP

> > +static void test_task_vma_buildid(void)
> > +{
> > + int err, iter_fd = -1, proc_maps_fd = -1;
> > + struct bpf_iter_task_vma_buildid *skel;
> > + char key[D_PATH_BUF_SIZE], *prev_key;
> > + char bpf_build_id[BUILDID_STR_SIZE];
> > + int len, files_fd, i, cnt = 0;
> > + struct build_id val;
> > + char *build_id;
> > + char c;
> > +
> > + skel = bpf_iter_task_vma_buildid__open();
> > + if (!ASSERT_OK_PTR(skel, "bpf_iter_task_vma_buildid__open"))
> > + return;
> > +
> > + err = bpf_iter_task_vma_buildid__load(skel);
> > + if (!ASSERT_OK(err, "bpf_iter_task_vma_buildid__load"))
> > + goto out;
>
> minor: you can do __open_and_load() in one step

right, I copied that from another test, but removed all the
setup in between, so we can actually call just __open_and_load

SNIP

> > + memset(bpf_build_id, 0x0, sizeof(bpf_build_id));
> > + for (i = 0; i < val.sz; i++) {
> > + sprintf(bpf_build_id + i*2, "%02x",
> > + (unsigned char) val.data[i]);
> > + }
> > +
> > + if (!ASSERT_OK(read_buildid(key, &build_id), "read_buildid"))
> > + break;
> > +
> > + printf("BUILDID %s %s %s\n", bpf_build_id, build_id, key);
>
> debugging leftover or intentional?
>
> > + ASSERT_OK(strncmp(bpf_build_id, build_id, strlen(bpf_build_id)), "buildid_cmp");
> > +
> > + free(build_id);
> > + prev_key = key;
> > + cnt++;
> > + }
> > +
> > + printf("checked %d files\n", cnt);
>
> ditto

both intentional, first one can go out I guess, but the
number of checked files seemed interesting to me ;-)

SNIP

> > diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
> > new file mode 100644
> > index 000000000000..25e2179ae5f4
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
> > @@ -0,0 +1,49 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include "bpf_iter.h"
> > +#include <bpf/bpf_helpers.h>
> > +#include <string.h>
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +#define VM_EXEC 0x00000004
> > +#define D_PATH_BUF_SIZE 1024
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_HASH);
> > + __uint(max_entries, 10000);
> > + __type(key, char[D_PATH_BUF_SIZE]);
> > + __type(value, struct build_id);
> > +} files SEC(".maps");
> > +
> > +static char tmp_key[D_PATH_BUF_SIZE];
> > +static struct build_id tmp_data;
> > +
> > +SEC("iter/task_vma") int proc_maps(struct bpf_iter__task_vma *ctx)
>
> nit: let's keep SEC() on separate line from function itself

ok

>
> > +{
> > + struct vm_area_struct *vma = ctx->vma;
> > + struct seq_file *seq = ctx->meta->seq;
> > + struct task_struct *task = ctx->task;
> > + unsigned long file_key;
> > + struct file *file;
> > +
> > + if (task == (void *)0 || vma == (void *)0)
> > + return 0;
> > +
> > + if (!(vma->vm_flags & VM_EXEC))
> > + return 0;
> > +
> > + file = vma->vm_file;
> > + if (!file)
> > + return 0;
> > +
> > + memset(tmp_key, 0x0, D_PATH_BUF_SIZE);
>
> __builtin_memset() to not rely on compiler optimization?
>
> > + bpf_d_path(&file->f_path, (char *) &tmp_key, D_PATH_BUF_SIZE);
> > +
> > + if (bpf_map_lookup_elem(&files, &tmp_key))
> > + return 0;
> > +
> > + memcpy(&tmp_data, file->f_bid, sizeof(*file->f_bid));
>
> same about __builtin_memcpy()

ah ok, did not know that, will check.. curious what could
go wrong by using not '__builtin_...' version?

thanks,
jirka