From 7a366da2d2ba86316d3ec408f70d19b63916f9ce Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:31 +0200 Subject: [PATCH 1/6] libbpf: Fix LIBBPF_1.0.0 declaration in libbpf.map Add the missing LIBBPF_0.8.0 at the end of the LIBBPF_1.0.0 declaration, similarly to other version declarations. Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-2-roberto.sassu@huaweicloud.com --- tools/lib/bpf/libbpf.map | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index c1d6aa7c82b6..04fab9f1fdd7 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -367,7 +367,7 @@ LIBBPF_1.0.0 { libbpf_bpf_map_type_str; libbpf_bpf_prog_type_str; perf_buffer__buffer; -}; +} LIBBPF_0.8.0; LIBBPF_1.1.0 { global: From 243e300563b1b39ac669c7698742931427699184 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:32 +0200 Subject: [PATCH 2/6] libbpf: Introduce bpf_get_fd_by_id_opts and bpf_map_get_fd_by_id_opts() Define a new data structure called bpf_get_fd_by_id_opts, with the member open_flags, to be used by callers of the _opts variants of bpf_*_get_fd_by_id() to specify the permissions needed for the file descriptor to be obtained. Also, introduce bpf_map_get_fd_by_id_opts(), to let the caller pass a bpf_get_fd_by_id_opts structure. Finally, keep the existing bpf_map_get_fd_by_id(), and call bpf_map_get_fd_by_id_opts() with NULL as opts argument, to request read-write permissions (current behavior). Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-3-roberto.sassu@huaweicloud.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 10 ++++++++++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 1d49a0352836..c08d7509553d 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -948,19 +948,29 @@ 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_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd; + if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.map_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0); fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); } +int bpf_map_get_fd_by_id(__u32 id) +{ + return bpf_map_get_fd_by_id_opts(id, NULL); +} + int bpf_btf_get_fd_by_id(__u32 id) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 9c50beabdd14..10ce38f0a9ef 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -365,8 +365,18 @@ LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id); 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); + +struct bpf_get_fd_by_id_opts { + size_t sz; /* size of this struct for forward/backward compatibility */ + __u32 open_flags; /* permissions requested for the operation on fd */ + size_t :0; +}; +#define bpf_get_fd_by_id_opts__last_field open_flags + LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 04fab9f1fdd7..2e665b21d84f 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -371,6 +371,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: + bpf_map_get_fd_by_id_opts; user_ring_buffer__discard; user_ring_buffer__free; user_ring_buffer__new; From 8f13f168ea14333ac971e5404800b7fb3658e782 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:33 +0200 Subject: [PATCH 3/6] libbpf: Introduce bpf_prog_get_fd_by_id_opts() Introduce bpf_prog_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_by_id_opts. Keep the existing bpf_prog_get_fd_by_id(), and call bpf_prog_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags. Currently, the kernel does not support non-zero open_flags for bpf_prog_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags. Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-4-roberto.sassu@huaweicloud.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index c08d7509553d..03be8c96bbac 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -935,19 +935,29 @@ int bpf_link_get_next_id(__u32 start_id, __u32 *next_id) return bpf_obj_get_next_id(start_id, next_id, BPF_LINK_GET_NEXT_ID); } -int bpf_prog_get_fd_by_id(__u32 id) +int bpf_prog_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd; + if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.prog_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0); fd = sys_bpf_fd(BPF_PROG_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); } +int bpf_prog_get_fd_by_id(__u32 id) +{ + return bpf_prog_get_fd_by_id_opts(id, NULL); +} + int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_by_id_opts *opts) { diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 10ce38f0a9ef..4558bafbce14 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -374,6 +374,8 @@ struct bpf_get_fd_by_id_opts { #define bpf_get_fd_by_id_opts__last_field open_flags LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_prog_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_by_id_opts *opts); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 2e665b21d84f..c3604eaa220d 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -372,6 +372,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: bpf_map_get_fd_by_id_opts; + bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard; user_ring_buffer__free; user_ring_buffer__new; From 2ce7cbf2ba71bb03542af739af80e86b6855ae48 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:34 +0200 Subject: [PATCH 4/6] libbpf: Introduce bpf_btf_get_fd_by_id_opts() Introduce bpf_btf_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_by_id_opts. Keep the existing bpf_btf_get_fd_by_id(), and call bpf_btf_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags. Currently, the kernel does not support non-zero open_flags for bpf_btf_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags. Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-5-roberto.sassu@huaweicloud.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 03be8c96bbac..b95fed0c1644 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -981,19 +981,29 @@ int bpf_map_get_fd_by_id(__u32 id) return bpf_map_get_fd_by_id_opts(id, NULL); } -int bpf_btf_get_fd_by_id(__u32 id) +int bpf_btf_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd; + if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.btf_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0); fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); } +int bpf_btf_get_fd_by_id(__u32 id) +{ + return bpf_btf_get_fd_by_id_opts(id, NULL); +} + int bpf_link_get_fd_by_id(__u32 id) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 4558bafbce14..4b487305eeb8 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -380,6 +380,8 @@ LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index c3604eaa220d..7011d5eec67b 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -371,6 +371,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: + bpf_btf_get_fd_by_id_opts; bpf_map_get_fd_by_id_opts; bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard; From 97c8f9dd5db839f2387785ee936d0a5b257b31d3 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:35 +0200 Subject: [PATCH 5/6] libbpf: Introduce bpf_link_get_fd_by_id_opts() Introduce bpf_link_get_fd_by_id_opts(), for symmetry with bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced data structure bpf_get_fd_by_id_opts. Keep the existing bpf_link_get_fd_by_id(), and call bpf_link_get_fd_by_id_opts() with NULL as opts argument, to prevent setting open_flags. Currently, the kernel does not support non-zero open_flags for bpf_link_get_fd_by_id_opts(), and a call with them will result in an error returned by the bpf() system call. The caller should always pass zero open_flags. Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-6-roberto.sassu@huaweicloud.com --- tools/lib/bpf/bpf.c | 12 +++++++++++- tools/lib/bpf/bpf.h | 2 ++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index b95fed0c1644..9aff98f42a3d 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -1004,19 +1004,29 @@ int bpf_btf_get_fd_by_id(__u32 id) return bpf_btf_get_fd_by_id_opts(id, NULL); } -int bpf_link_get_fd_by_id(__u32 id) +int bpf_link_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts) { const size_t attr_sz = offsetofend(union bpf_attr, open_flags); union bpf_attr attr; int fd; + if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.link_id = id; + attr.open_flags = OPTS_GET(opts, open_flags, 0); fd = sys_bpf_fd(BPF_LINK_GET_FD_BY_ID, &attr, attr_sz); return libbpf_err_errno(fd); } +int bpf_link_get_fd_by_id(__u32 id) +{ + return bpf_link_get_fd_by_id_opts(id, NULL); +} + int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len) { const size_t attr_sz = offsetofend(union bpf_attr, info); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 4b487305eeb8..a112e0ed1b19 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -383,6 +383,8 @@ LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id, const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); +LIBBPF_API int bpf_link_get_fd_by_id_opts(__u32 id, + const struct bpf_get_fd_by_id_opts *opts); LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len); struct bpf_prog_query_opts { diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 7011d5eec67b..71bf5691a689 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -372,6 +372,7 @@ LIBBPF_1.0.0 { LIBBPF_1.1.0 { global: bpf_btf_get_fd_by_id_opts; + bpf_link_get_fd_by_id_opts; bpf_map_get_fd_by_id_opts; bpf_prog_get_fd_by_id_opts; user_ring_buffer__discard; From a9c7c18b57594c72a63fad749021b743c65a098b Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Thu, 6 Oct 2022 13:07:36 +0200 Subject: [PATCH 6/6] selftests/bpf: Add tests for _opts variants of bpf_*_get_fd_by_id() Introduce the data_input map, write-protected with a small eBPF program implementing the lsm/bpf_map hook. Then, ensure that bpf_map_get_fd_by_id() and bpf_map_get_fd_by_id_opts() with NULL opts don't succeed due to requesting read-write access to the write-protected map. Also, ensure that bpf_map_get_fd_by_id_opts() with open_flags in opts set to BPF_F_RDONLY instead succeeds. After obtaining a read-only fd, ensure that only map lookup succeeds and not update. Ensure that update works only with the read-write fd obtained at program loading time, when the write protection was not yet enabled. Finally, ensure that the other _opts variants of bpf_*_get_fd_by_id() don't work if the BPF_F_RDONLY flag is set in opts (due to the kernel not handling the open_flags member of bpf_attr). Signed-off-by: Roberto Sassu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221006110736.84253-7-roberto.sassu@huaweicloud.com --- tools/testing/selftests/bpf/DENYLIST.s390x | 1 + .../bpf/prog_tests/libbpf_get_fd_by_id_opts.c | 87 +++++++++++++++++++ .../bpf/progs/test_libbpf_get_fd_by_id_opts.c | 36 ++++++++ 3 files changed, 124 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c create mode 100644 tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x index 0fb03b8047d5..beef1232a47a 100644 --- a/tools/testing/selftests/bpf/DENYLIST.s390x +++ b/tools/testing/selftests/bpf/DENYLIST.s390x @@ -76,3 +76,4 @@ lookup_key # JIT does not support calling kernel f verify_pkcs7_sig # JIT does not support calling kernel function (kfunc) kfunc_dynptr_param # JIT does not support calling kernel function (kfunc) deny_namespace # failed to attach: ERROR: strerror_r(-524)=22 (trampoline) +libbpf_get_fd_by_id_opts # failed to attach: ERROR: strerror_r(-524)=22 (trampoline) diff --git a/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c new file mode 100644 index 000000000000..25e5dfa9c315 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu + */ + +#include + +#include "test_libbpf_get_fd_by_id_opts.skel.h" + +void test_libbpf_get_fd_by_id_opts(void) +{ + struct test_libbpf_get_fd_by_id_opts *skel; + struct bpf_map_info info_m = {}; + __u32 len = sizeof(info_m), value; + int ret, zero = 0, fd = -1; + LIBBPF_OPTS(bpf_get_fd_by_id_opts, fd_opts_rdonly, + .open_flags = BPF_F_RDONLY, + ); + + skel = test_libbpf_get_fd_by_id_opts__open_and_load(); + if (!ASSERT_OK_PTR(skel, + "test_libbpf_get_fd_by_id_opts__open_and_load")) + return; + + ret = test_libbpf_get_fd_by_id_opts__attach(skel); + if (!ASSERT_OK(ret, "test_libbpf_get_fd_by_id_opts__attach")) + goto close_prog; + + ret = bpf_obj_get_info_by_fd(bpf_map__fd(skel->maps.data_input), + &info_m, &len); + if (!ASSERT_OK(ret, "bpf_obj_get_info_by_fd")) + goto close_prog; + + fd = bpf_map_get_fd_by_id(info_m.id); + if (!ASSERT_LT(fd, 0, "bpf_map_get_fd_by_id")) + goto close_prog; + + fd = bpf_map_get_fd_by_id_opts(info_m.id, NULL); + if (!ASSERT_LT(fd, 0, "bpf_map_get_fd_by_id_opts")) + goto close_prog; + + fd = bpf_map_get_fd_by_id_opts(info_m.id, &fd_opts_rdonly); + if (!ASSERT_GE(fd, 0, "bpf_map_get_fd_by_id_opts")) + goto close_prog; + + /* Map lookup should work with read-only fd. */ + ret = bpf_map_lookup_elem(fd, &zero, &value); + if (!ASSERT_OK(ret, "bpf_map_lookup_elem")) + goto close_prog; + + if (!ASSERT_EQ(value, 0, "map value mismatch")) + goto close_prog; + + /* Map update should not work with read-only fd. */ + ret = bpf_map_update_elem(fd, &zero, &len, BPF_ANY); + if (!ASSERT_LT(ret, 0, "bpf_map_update_elem")) + goto close_prog; + + /* Map update should work with read-write fd. */ + ret = bpf_map_update_elem(bpf_map__fd(skel->maps.data_input), &zero, + &len, BPF_ANY); + if (!ASSERT_OK(ret, "bpf_map_update_elem")) + goto close_prog; + + /* Prog get fd with opts set should not work (no kernel support). */ + ret = bpf_prog_get_fd_by_id_opts(0, &fd_opts_rdonly); + if (!ASSERT_EQ(ret, -EINVAL, "bpf_prog_get_fd_by_id_opts")) + goto close_prog; + + /* Link get fd with opts set should not work (no kernel support). */ + ret = bpf_link_get_fd_by_id_opts(0, &fd_opts_rdonly); + if (!ASSERT_EQ(ret, -EINVAL, "bpf_link_get_fd_by_id_opts")) + goto close_prog; + + /* BTF get fd with opts set should not work (no kernel support). */ + ret = bpf_btf_get_fd_by_id_opts(0, &fd_opts_rdonly); + ASSERT_EQ(ret, -EINVAL, "bpf_btf_get_fd_by_id_opts"); + +close_prog: + if (fd >= 0) + close(fd); + + test_libbpf_get_fd_by_id_opts__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c new file mode 100644 index 000000000000..f5ac5f3e8919 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_libbpf_get_fd_by_id_opts.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu + */ + +#include "vmlinux.h" +#include +#include +#include + +/* From include/linux/mm.h. */ +#define FMODE_WRITE 0x2 + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, __u32); + __type(value, __u32); +} data_input SEC(".maps"); + +char _license[] SEC("license") = "GPL"; + +SEC("lsm/bpf_map") +int BPF_PROG(check_access, struct bpf_map *map, fmode_t fmode) +{ + if (map != (struct bpf_map *)&data_input) + return 0; + + if (fmode & FMODE_WRITE) + return -EACCES; + + return 0; +}