2022-06-02 16:09:09

by Roberto Sassu

Subject: [PATCH v2 1/9] libbpf: Introduce bpf_map_get_fd_by_id_flags()

Introduce bpf_map_get_fd_by_id_flags(), to let a caller specify the open
flags needed for the operation. This could make an operation succeed, if
access to a map is restricted (i.e. it allows only certain operations).

Signed-off-by: Roberto Sassu <[email protected]>
---
tools/lib/bpf/bpf.c | 8 +++++++-
tools/lib/bpf/bpf.h | 1 +
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 240186aac8e6..33bac2006043 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -1047,18 +1047,24 @@ int bpf_prog_get_fd_by_id(__u32 id)
return libbpf_err_errno(fd);
}

-int bpf_map_get_fd_by_id(__u32 id)
+int bpf_map_get_fd_by_id_flags(__u32 id, __u32 flags)
{
union bpf_attr attr;
int fd;

memset(&attr, 0, sizeof(attr));
attr.map_id = id;
+ attr.open_flags = flags;

fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
return libbpf_err_errno(fd);
}

+int bpf_map_get_fd_by_id(__u32 id)
+{
+ return bpf_map_get_fd_by_id_flags(id, 0);
+}
+
int bpf_btf_get_fd_by_id(__u32 id)
{
union bpf_attr attr;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index cabc03703e29..20e4c852362d 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -438,6 +438,7 @@ LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id);
LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_map_get_fd_by_id_flags(__u32 id, __u32 flags);
LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 38e284ff057d..019278e66836 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -466,6 +466,7 @@ LIBBPF_1.0.0 {
libbpf_bpf_link_type_str;
libbpf_bpf_map_type_str;
libbpf_bpf_prog_type_str;
+ bpf_map_get_fd_by_id_flags;

local: *;
};
--
2.25.1

2022-06-06 05:51:54

by Andrii Nakryiko

Subject: Re: [PATCH v2 1/9] libbpf: Introduce bpf_map_get_fd_by_id_flags()

On Thu, Jun 2, 2022 at 7:38 AM Roberto Sassu <[email protected]> wrote:
>
> Introduce bpf_map_get_fd_by_id_flags(), to let a caller specify the open
> flags needed for the operation. This could make an operation succeed, if
> access to a map is restricted (i.e. it allows only certain operations).
>
> Signed-off-by: Roberto Sassu <[email protected]>
> ---
> tools/lib/bpf/bpf.c | 8 +++++++-
> tools/lib/bpf/bpf.h | 1 +
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 240186aac8e6..33bac2006043 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -1047,18 +1047,24 @@ int bpf_prog_get_fd_by_id(__u32 id)
> return libbpf_err_errno(fd);
> }
>
> -int bpf_map_get_fd_by_id(__u32 id)
> +int bpf_map_get_fd_by_id_flags(__u32 id, __u32 flags)

let's go the OPTS route instead so that we don't have to add any more
new variants? We can probably use common bpf_get_fd_by_id_opts for
map/prog/link/btf get_fd_by_id operations (and let's add all variants
for consistency)?


> {
> union bpf_attr attr;
> int fd;
>
> memset(&attr, 0, sizeof(attr));
> attr.map_id = id;
> + attr.open_flags = flags;
>
> fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
> return libbpf_err_errno(fd);
> }
>
> +int bpf_map_get_fd_by_id(__u32 id)
> +{
> + return bpf_map_get_fd_by_id_flags(id, 0);
> +}
> +
> int bpf_btf_get_fd_by_id(__u32 id)
> {
> union bpf_attr attr;
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index cabc03703e29..20e4c852362d 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -438,6 +438,7 @@ LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
> +LIBBPF_API int bpf_map_get_fd_by_id_flags(__u32 id, __u32 flags);
> LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
> LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
> LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 38e284ff057d..019278e66836 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -466,6 +466,7 @@ LIBBPF_1.0.0 {
> libbpf_bpf_link_type_str;
> libbpf_bpf_map_type_str;
> libbpf_bpf_prog_type_str;
> + bpf_map_get_fd_by_id_flags;
>
> local: *;
> };
> --
> 2.25.1
>