Re: [PATCH bpf-next 4/4] selftests/bpf: add test for bpf_iter_task_vma

[Yonghong Song <yhs@fb.com>]

On 12/11/20 6:48 PM, Song Liu wrote:
> The test dumps information similar to /proc/pid/maps. The first line of
> the output is compared against the /proc file to make sure they match.
> 
> Signed-off-by: Song Liu <songliubraving@fb.com>
> ---
>   .../selftests/bpf/prog_tests/bpf_iter.c       | 106 ++++++++++++++++--
>   tools/testing/selftests/bpf/progs/bpf_iter.h  |   9 ++
>   .../selftests/bpf/progs/bpf_iter_task_vma.c   |  55 +++++++++
>   3 files changed, 160 insertions(+), 10 deletions(-)
>   create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> index 0e586368948dd..7afd3abae1899 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> @@ -7,6 +7,7 @@
>   #include "bpf_iter_task.skel.h"
>   #include "bpf_iter_task_stack.skel.h"
>   #include "bpf_iter_task_file.skel.h"
> +#include "bpf_iter_task_vma.skel.h"
>   #include "bpf_iter_task_btf.skel.h"
>   #include "bpf_iter_tcp4.skel.h"
>   #include "bpf_iter_tcp6.skel.h"
> @@ -64,6 +65,22 @@ static void do_dummy_read(struct bpf_program *prog)
>   	bpf_link__destroy(link);
>   }
>   
[...]
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> new file mode 100644
> index 0000000000000..d60b5b38cb396
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */
> +#include "bpf_iter.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +/* Copied from mm.h */
> +#define VM_READ		0x00000001
> +#define VM_WRITE	0x00000002
> +#define VM_EXEC		0x00000004
> +#define VM_MAYSHARE	0x00000080
> +
> +/* Copied from kdev_t.h */
> +#define MINORBITS	20
> +#define MINORMASK	((1U << MINORBITS) - 1)
> +#define MAJOR(dev)	((unsigned int) ((dev) >> MINORBITS))
> +#define MINOR(dev)	((unsigned int) ((dev) & MINORMASK))
> +
> +#define D_PATH_BUF_SIZE 1024
> +char d_path_buf[D_PATH_BUF_SIZE];
> +__u32 pid;
> +
> +SEC("iter.s/task_vma") int proc_maps(struct bpf_iter__task_vma *ctx)
> +{
> +	struct __vm_area_struct *vma = ctx->vma;
> +	struct seq_file *seq = ctx->meta->seq;
> +	struct task_struct *task = ctx->task;
> +	struct file *file = ctx->file;
> +	char perm_str[] = "----";
> +
> +	if (task == (void *)0 || vma == (void *)0 || task->pid != pid)
> +		return 0;
> +
> +	perm_str[0] = (vma->flags & VM_READ) ? 'r' : '-';
> +	perm_str[1] = (vma->flags & VM_WRITE) ? 'w' : '-';
> +	perm_str[1] = (vma->flags & VM_EXEC) ? 'x' : '-';

typo here? The above should be perm_str[2].

> +	perm_str[3] = (vma->flags & VM_MAYSHARE) ? 's' : 'p';
> +	BPF_SEQ_PRINTF(seq, "%08llx-%08llx %s ", vma->start, vma->end, perm_str);
> +
> +	if (file) {
> +		__u32 dev = file->f_inode->i_sb->s_dev;
> +
> +		bpf_d_path(&file->f_path, d_path_buf, D_PATH_BUF_SIZE);
> +
> +		BPF_SEQ_PRINTF(seq, "%08llx ", vma->pgoff << 12);
> +		BPF_SEQ_PRINTF(seq, "%02x:%02x %u", MAJOR(dev), MINOR(dev),
> +			       file->f_inode->i_ino);
> +		BPF_SEQ_PRINTF(seq, "\t%s\n", d_path_buf);
> +	} else {
> +		BPF_SEQ_PRINTF(seq, "%08llx 00:00 0\n", 0ULL);
> +	}
> +	return 0;
> +}
>