From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>,
Hao Luo <haoluo@google.com>, Yonghong Song <yhs@fb.com>
Subject: [PATCH v3 bpf-next 6/7] libbpf: support kernel module ksym externs
Date: Mon, 11 Jan 2021 23:55:19 -0800 [thread overview]
Message-ID: <20210112075520.4103414-7-andrii@kernel.org> (raw)
In-Reply-To: <20210112075520.4103414-1-andrii@kernel.org>
Add support for searching for ksym externs not just in vmlinux BTF, but across
all module BTFs, similarly to how it's done for CO-RE relocations. Kernels
that expose module BTFs through sysfs are assumed to support new ldimm64
instruction extension with BTF FD provided in insn[1].imm field, so no extra
feature detection is performed.
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
tools/lib/bpf/libbpf.c | 50 +++++++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 18 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6ae748f6ea11..2abbc3800568 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -395,7 +395,8 @@ struct extern_desc {
unsigned long long addr;
/* target btf_id of the corresponding kernel var. */
- int vmlinux_btf_id;
+ int kernel_btf_obj_fd;
+ int kernel_btf_id;
/* local btf_id of the ksym extern's type. */
__u32 type_id;
@@ -6162,7 +6163,8 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
} else /* EXT_KSYM */ {
if (ext->ksym.type_id) { /* typed ksyms */
insn[0].src_reg = BPF_PSEUDO_BTF_ID;
- insn[0].imm = ext->ksym.vmlinux_btf_id;
+ insn[0].imm = ext->ksym.kernel_btf_id;
+ insn[1].imm = ext->ksym.kernel_btf_obj_fd;
} else { /* typeless ksyms */
insn[0].imm = (__u32)ext->ksym.addr;
insn[1].imm = ext->ksym.addr >> 32;
@@ -7319,7 +7321,8 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj)
static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
{
struct extern_desc *ext;
- int i, id;
+ struct btf *btf;
+ int i, j, id, btf_fd, err;
for (i = 0; i < obj->nr_extern; i++) {
const struct btf_type *targ_var, *targ_type;
@@ -7331,10 +7334,25 @@ static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
if (ext->type != EXT_KSYM || !ext->ksym.type_id)
continue;
- id = btf__find_by_name_kind(obj->btf_vmlinux, ext->name,
- BTF_KIND_VAR);
+ btf = obj->btf_vmlinux;
+ btf_fd = 0;
+ id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);
+ if (id == -ENOENT) {
+ err = load_module_btfs(obj);
+ if (err)
+ return err;
+
+ for (j = 0; j < obj->btf_module_cnt; j++) {
+ btf = obj->btf_modules[j].btf;
+ /* we assume module BTF FD is always >0 */
+ btf_fd = obj->btf_modules[j].fd;
+ id = btf__find_by_name_kind(btf, ext->name, BTF_KIND_VAR);
+ if (id != -ENOENT)
+ break;
+ }
+ }
if (id <= 0) {
- pr_warn("extern (ksym) '%s': failed to find BTF ID in vmlinux BTF.\n",
+ pr_warn("extern (ksym) '%s': failed to find BTF ID in kernel BTF(s).\n",
ext->name);
return -ESRCH;
}
@@ -7343,24 +7361,19 @@ static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
local_type_id = ext->ksym.type_id;
/* find target type_id */
- targ_var = btf__type_by_id(obj->btf_vmlinux, id);
- targ_var_name = btf__name_by_offset(obj->btf_vmlinux,
- targ_var->name_off);
- targ_type = skip_mods_and_typedefs(obj->btf_vmlinux,
- targ_var->type,
- &targ_type_id);
+ targ_var = btf__type_by_id(btf, id);
+ targ_var_name = btf__name_by_offset(btf, targ_var->name_off);
+ targ_type = skip_mods_and_typedefs(btf, targ_var->type, &targ_type_id);
ret = bpf_core_types_are_compat(obj->btf, local_type_id,
- obj->btf_vmlinux, targ_type_id);
+ btf, targ_type_id);
if (ret <= 0) {
const struct btf_type *local_type;
const char *targ_name, *local_name;
local_type = btf__type_by_id(obj->btf, local_type_id);
- local_name = btf__name_by_offset(obj->btf,
- local_type->name_off);
- targ_name = btf__name_by_offset(obj->btf_vmlinux,
- targ_type->name_off);
+ local_name = btf__name_by_offset(obj->btf, local_type->name_off);
+ targ_name = btf__name_by_offset(btf, targ_type->name_off);
pr_warn("extern (ksym) '%s': incompatible types, expected [%d] %s %s, but kernel has [%d] %s %s\n",
ext->name, local_type_id,
@@ -7370,7 +7383,8 @@ static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj)
}
ext->is_set = true;
- ext->ksym.vmlinux_btf_id = id;
+ ext->ksym.kernel_btf_obj_fd = btf_fd;
+ ext->ksym.kernel_btf_id = id;
pr_debug("extern (ksym) '%s': resolved to [%d] %s %s\n",
ext->name, id, btf_kind_str(targ_var), targ_var_name);
}
--
2.24.1
next prev parent reply other threads:[~2021-01-12 7:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 7:55 [PATCH v3 bpf-next 0/7] Support kernel module ksym variables Andrii Nakryiko
2021-01-12 7:55 ` [PATCH v3 bpf-next 1/7] bpf: add bpf_patch_call_args prototype to include/linux/bpf.h Andrii Nakryiko
2021-01-12 7:55 ` [PATCH v3 bpf-next 2/7] bpf: avoid warning when re-casting __bpf_call_base into __bpf_call_base_args Andrii Nakryiko
2021-01-12 7:55 ` [PATCH v3 bpf-next 3/7] bpf: declare __bpf_free_used_maps() unconditionally Andrii Nakryiko
2021-01-12 7:55 ` [PATCH v3 bpf-next 4/7] selftests/bpf: sync RCU before unloading bpf_testmod Andrii Nakryiko
2021-01-12 7:55 ` [PATCH v3 bpf-next 5/7] bpf: support BPF ksym variables in kernel modules Andrii Nakryiko
2021-01-12 16:27 ` Daniel Borkmann
2021-01-12 20:38 ` Andrii Nakryiko
2021-01-12 23:18 ` Alexei Starovoitov
2021-01-13 22:55 ` Daniel Borkmann
2021-01-12 7:55 ` Andrii Nakryiko [this message]
2021-01-12 7:55 ` [PATCH v3 bpf-next 7/7] selftests/bpf: test kernel module ksym externs Andrii Nakryiko
2021-01-13 1:29 ` Alexei Starovoitov
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