On 1/8/21 2:09 PM, Andrii Nakryiko wrote:
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.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 47 +++++++++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 17 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6ae748f6ea11..57559a71e4de 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;
@@ -7331,8 +7334,22 @@ 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;
+ btf_fd = obj->btf_modules[j].fd;
Do we have possibility btf_fd == 0 here?
+ 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",
ext->name);
@@ -7343,24 +7360,19 @@ 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 +7382,8 @@ 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);
}
