On 11 May 2020, at 22:43, Yonghong Song wrote:
On 5/11/20 5:40 AM, Eelco Chaudron wrote:
When the probe code was failing for any reason ENOTSUP was returned,
even
if this was due to no having enough lock space. This patch fixes this
by
returning EPERM to the user application, so it can respond and
increase
the RLIMIT_MEMLOCK size.
Signed-off-by: Eelco Chaudron <echaudro@xxxxxxxxxx>
---
v3: Updated error message to be more specific as suggested by Andrii
v2: Split bpf_object__probe_name() in two functions as suggested by
Andrii
tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8f480e29a6b0..ad3043c5db13 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3149,7 +3149,7 @@ int bpf_map__resize(struct bpf_map *map, __u32
max_entries)
}
static int
-bpf_object__probe_name(struct bpf_object *obj)
+bpf_object__probe_loading(struct bpf_object *obj)
{
struct bpf_load_program_attr attr;
char *cp, errmsg[STRERR_BUFSIZE];
@@ -3170,14 +3170,34 @@ bpf_object__probe_name(struct bpf_object
*obj)
ret = bpf_load_program_xattr(&attr, NULL, 0);
if (ret < 0) {
cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
- pr_warn("Error in %s():%s(%d). Couldn't load basic 'r0 = 0' BPF
program.\n",
- __func__, cp, errno);
+ pr_warn("Error in %s():%s(%d). Couldn't load trivial BPF "
+ "program. Make sure your kernel supports BPF "
+ "(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is "
+ "set to big enough value.\n", __func__, cp, errno);
return -errno;
Just curious. Did "errno" always survive pr_warn() here? pr_warn() may
call user supplied print function which it outside libbpf control.
Maybe should cache errno before calling pr_warn()?
I guess this issue has always been there, however, I sent out a v4
fixing this case.
}
close(ret);
- /* now try the same program, but with the name */
+ return 0;
+}
+
+static int
+bpf_object__probe_name(struct bpf_object *obj)
+{
+ struct bpf_load_program_attr attr;
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int ret;
+
+ /* make sure loading with name works */
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+ attr.insns = insns;
+ attr.insns_cnt = ARRAY_SIZE(insns);
+ attr.license = "GPL";
attr.name = "test";
ret = bpf_load_program_xattr(&attr, NULL, 0);
if (ret >= 0) {
@@ -5386,7 +5406,8 @@ int bpf_object__load_xattr(struct
bpf_object_load_attr *attr)
obj->loaded = true;
- err = bpf_object__probe_caps(obj);
+ err = bpf_object__probe_loading(obj);
+ err = err ? : bpf_object__probe_caps(obj);
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__sanitize_maps(obj);
