From: Andrii Nakryiko andrii@kernel.org
mainline inclusion from mainline-5.12-rc1 commit a4b09a9ef9451b09d87550720f8db3ae280b3eea category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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BPF_CORE_READ(), in addition to handling CO-RE relocations, also allows much nicer way to read data structures with nested pointers. Instead of writing a sequence of bpf_probe_read() calls to follow links, one can just write BPF_CORE_READ(a, b, c, d) to effectively do a->b->c->d read. This is a welcome ability when porting BCC code, which (in most cases) allows exactly the intuitive a->b->c->d variant.
This patch adds non-CO-RE variants of BPF_CORE_READ() family of macros for cases where CO-RE is not supported (e.g., old kernels). In such cases, the property of shortening a sequence of bpf_probe_read()s to a simple BPF_PROBE_READ(a, b, c, d) invocation is still desirable, especially when porting BCC code to libbpf. Yet, no CO-RE relocation is going to be emitted.
Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20201218235614.2284956-3-andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org (cherry picked from commit a4b09a9ef9451b09d87550720f8db3ae280b3eea) Signed-off-by: Wang Yufen wangyufen@huawei.com --- tools/lib/bpf/bpf_core_read.h | 38 +++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index a2d75ad8c706..c032f435ce35 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -316,6 +316,18 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ })
+/* Non-CO-RE variant of BPF_CORE_READ_INTO() */ +#define BPF_PROBE_READ_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_probe_read, bpf_probe_read, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + +/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO() */ +#define BPF_PROBE_READ_USER_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_probe_read_user, bpf_probe_read_user, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + /* * BPF_CORE_READ_STR_INTO() does same "pointer chasing" as * BPF_CORE_READ() for intermediate pointers, but then executes (and returns @@ -332,6 +344,18 @@ enum bpf_enum_value_kind { dst, (src), a, ##__VA_ARGS__) \ })
+/* Non-CO-RE variant of BPF_CORE_READ_STR_INTO() */ +#define BPF_PROBE_READ_STR_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_probe_read_str, bpf_probe_read, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + +/* Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO() */ +#define BPF_PROBE_READ_USER_STR_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_probe_read_user_str, bpf_probe_read_user, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + /* * BPF_CORE_READ() is used to simplify BPF CO-RE relocatable read, especially * when there are few pointer chasing steps. @@ -369,5 +393,19 @@ enum bpf_enum_value_kind { __r; \ })
+/* Non-CO-RE variant of BPF_CORE_READ() */ +#define BPF_PROBE_READ(src, a, ...) ({ \ + ___type((src), a, ##__VA_ARGS__) __r; \ + BPF_PROBE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ + __r; \ +}) + +/* Non-CO-RE variant of BPF_CORE_READ_USER() */ +#define BPF_PROBE_READ_USER(src, a, ...) ({ \ + ___type((src), a, ##__VA_ARGS__) __r; \ + BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ + __r; \ +}) + #endif