libbpf: Making bpf_prog_load() ignore name if kernel doesn't support

Similar with commit 10b62d6a38f7 ("libbpf: Add names for auxiliary maps"),
let's make bpf_prog_load() also ignore name if kernel doesn't support
program name.

To achieve this, we need to call sys_bpf_prog_load() directly in
probe_kern_prog_name() to avoid circular dependency. sys_bpf_prog_load()
also need to be exported in the libbpf_internal.h file.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220813000936.6464-1-liuhangbin@gmail.com

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 6a96e66..575867d 100644 (file)
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -84,9 +84,7 @@ static inline int sys_bpf_fd(enum bpf_cmd cmd, union bpf_attr *attr,
        return ensure_good_fd(fd);
 }
 
-#define PROG_LOAD_ATTEMPTS 5
-
-static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
+int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
 {
        int fd;
 
@@ -263,7 +261,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
        attr.prog_ifindex = OPTS_GET(opts, prog_ifindex, 0);
        attr.kern_version = OPTS_GET(opts, kern_version, 0);
 
-       if (prog_name)
+       if (prog_name && kernel_supports(NULL, FEAT_PROG_NAME))
                libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
        attr.license = ptr_to_u64(license);
 

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3f01f5c..aa05a99 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4415,14 +4415,23 @@ static int probe_fd(int fd)
 
 static int probe_kern_prog_name(void)
 {
+       const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
        struct bpf_insn insns[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
                BPF_EXIT_INSN(),
        };
-       int ret, insn_cnt = ARRAY_SIZE(insns);
+       union bpf_attr attr;
+       int ret;
+
+       memset(&attr, 0, attr_sz);
+       attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+       attr.license = ptr_to_u64("GPL");
+       attr.insns = ptr_to_u64(insns);
+       attr.insn_cnt = (__u32)ARRAY_SIZE(insns);
+       libbpf_strlcpy(attr.prog_name, "libbpf_nametest", sizeof(attr.prog_name));
 
        /* make sure loading with name works */
-       ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "test", "GPL", insns, insn_cnt, NULL);
+       ret = sys_bpf_prog_load(&attr, attr_sz, PROG_LOAD_ATTEMPTS);
        return probe_fd(ret);
 }
 

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 4135ae0..377642f 100644 (file)
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -573,4 +573,7 @@ static inline bool is_pow_of_2(size_t x)
        return x && (x & (x - 1)) == 0;
 }
 
+#define PROG_LOAD_ATTEMPTS 5
+int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts);
+
 #endif /* __LIBBPF_LIBBPF_INTERNAL_H */