8000 Fix recursive anon structures in btf. by haesbaert · Pull Request #187 · elastic/quark · GitHub
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Fix recursive anon structures in btf. #187

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Merged
merged 3 commits into from
Jun 9, 2025
Merged

Fix recursive anon structures in btf. #187

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3c86070
Fix recursive anon structures in btf
haesbaert Jun 7, 2025
5218815
Adapt libbpf error handling to post 1.0
haesbaert Jun 8, 2025
dd1da10
Zap (anon) from btfhub
haesbaert Jun 7, 2025
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163 changes: 111 additions & 52 deletions btf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,6 @@
#include "quark.h"

#include <bpf/btf.h>
#include "libbpf/include/linux/err.h" /* IS_ERR :( */

struct quark_btf_target base_targets[] = {
{ "cred.cap_ambient", -1 },
Expand All @@ -31,7 +30,7 @@ struct quark_btf_target base_targets[] = {
{ "fs_struct.pwd.mnt", -1 },
{ "fs_struct.root.dentry", -1 },
{ "ipc_namespace.proc_inum", -1 }, /* or ipc_namespace.ns.inum */
{ "mm_struct.(anon).start_stack",-1 }, /* or mm_struct.start_stack */
{ "mm_struct.start_stack", -1 },
{ "mount.mnt", -1 },
{ "mount.mnt_mountpoint", -1 },
{ "mnt_namespace.proc_inum", -1 }, /* or mnt_namespace.ns.inum */
Expand Down Expand Up @@ -73,7 +72,6 @@ struct btf_alternative {
const char *old;
} btf_alternatives[] = {
{ "task_struct.start_boottime", "task_struct.real_start_time" },
{ "mm_struct.(anon).start_stack", "mm_struct.start_stack" },
{ "uts_namespace.proc_inum", "uts_namespace.ns.inum" },
{ "ipc_namespace.proc_inum", "ipc_namespace.ns.inum" },
{ "mnt_namespace.proc_inum", "mnt_namespace.ns.inum" },
Expand All @@ -92,86 +90,147 @@ btf_type_by_name_kind(struct btf *btf, s32 *off, const char *name, int kind)
if (off1 < 0)
return (NULL);
t = btf__type_by_id(btf, off1);
/* libbpf doesn't respect its own convention :( */
if (IS_ERR_OR_NULL(t))
if (t == NULL)
return (NULL);
if (off)
*off = off1;

return (t);
}

static const struct btf_member *
btf_offsetof(struct btf *btf, struct btf_type const *t, const char *mname)
/*
* Given the structure or union type in t, find the offset of member_name.
* In foo.bar, t would be the type of foo.
*/
static s32
btf_offsetof_rec(struct btf *btf, struct btf_type const *t, const char *member_name,
struct btf_member **ret_member, s32 cur_off)
{
int i, vlen;
const struct btf_member *m;
const char *mname1;

if (btf_kind(t) != BTF_KIND_STRUCT)
return (errno = EINVAL, NULL);
vlen = btf_vlen(t);
m = (const struct btf_member *)(t + 1);
if (!strcmp(mname, "(anon)"))
mname = "";

for (i = 0; i < vlen; i++, m++) {
mname1 = btf__name_by_offset(btf, m->name_off);
if (IS_ERR_OR_NULL(mname1)) {
qwarnx("btf__name_by_offset(%d)", m->name_off);
int i;
s32 off;
struct btf_member *m;
const char *name;

if (!btf_is_struct(t) && !btf_is_union(t)) {
errno = EINVAL;
goto fail;
}
m = btf_members(t);

for (i = 0; i < btf_vlen(t); i++, m++) {
name = btf__name_by_offset(btf, m->name_off);
if (name == NULL)
continue;

/*
* Found it, make sure this is a multiple of 8.
*/
if (!strcmp(member_name, name)) {
if (btf_kflag(t)) {
off = BTF_MEMBER_BIT_OFFSET(m->offset);
/* no bit_size things for now */
if (BTF_MEMBER_BITFIELD_SIZE(m->offset) != 0)
goto fail;
} else
off = m->offset;

off += cur_off;
if ((off % 8) != 0)
goto fail;
off /= 8;
if (ret_member != NULL)
*ret_member = m;

return (off);
}
if (strcmp(mname, mname1))
continue;

return (m);
/*
* If this is an anonymous structure or union, recurse into it
* and see if we match member name.
*/
if (!strlen(name)) {
struct btf_type const *t1;

t1 = btf__type_by_id(btf, m->type);
if (t1 == NULL)
continue;
off = btf_offsetof_rec(btf, t1, member_name, ret_member,
cur_off + m->offset);
if (off != -1)
return (off);
}
}

return (NULL);
fail:
if (ret_member != NULL)
*ret_member = NULL;

return (-1);
}

/*
* Given a struct or union parent_name, find member_name, return the offset
* within that structure and, if ret_member is not NULL, return the btf_member
* of member_name.
*/
static s32
btf_offsetof(struct btf *btf, const char *parent_name, const char *member_name,
struct btf_member **ret_member)
{
struct btf_type const *parent_t;

/*
* Parent must be a struct or a union
*/
parent_t = btf_type_by_name_kind(btf, NULL, parent_name, BTF_KIND_STRUCT);
if (parent_t == NULL)
parent_t = btf_type_by_name_kind(btf, NULL, parent_name,
BTF_KIND_UNION);
if (parent_t == NULL)
return (-1);

return (btf_offsetof_rec(btf, parent_t, member_name, ret_member, 0));

}

static s32
btf_root_offset2(struct btf *btf, const char *dotname)
{
const struct btf_type *parent;
const char *root_name, *child_name;
const struct btf_member *m;
const char *parent_name, *child_name;
struct btf_member *m;
const struct btf_type *t;
char *last, buf[1024];
s32 off;
s32 off, off1;

if (strlcpy(buf, dotname, sizeof(buf)) >= sizeof(buf))
return (-1);
root_name = strtok_r(buf, ".", &last);
if (root_name == NULL)
return (-1);
/* root must be a struct */
parent = btf_type_by_name_kind(btf, NULL, root_name, BTF_KIND_STRUCT);
if (parent == NULL)
parent_name = strtok_r(buf, ".", &last);
if (parent_name == NULL)
return (-1);

off = 0;
while ((child_name = strtok_r(NULL, ".", &last)) != NULL) {
m = btf_offsetof(btf, parent, child_name);
if (m == NULL)
m = NULL;
off1 = btf_offsetof(btf, parent_name, child_name, &m);
if (off1 == -1 || m == NULL)
return (-1);
off += off1;

t = btf__type_by_id(btf, m->type);
if (t == NULL)
return (-1);
if (btf_kflag(parent)) {
off += BTF_MEMBER_BIT_OFFSET(m->offset);
/* no bit_size things for now */
if (BTF_MEMBER_BITFIELD_SIZE(m->offset) != 0)
return (-1);
} else
off += m->offset;
parent = btf__type_by_id(btf, m->type);
if (IS_ERR_OR_NULL(parent))
parent_name = btf__name_by_offset(btf, t->name_off);
if (parent_name == NULL)
return (-1);
}

if ((off % 8) != 0)
return (-1);

return (off / 8);
return (off);
}

/*
* Given a dotname notation, find the offset within, dotname can be
* sock.foo.bar.x, it will try to find the offset of x relative to sock.
*/
s32
btf_root_offset(struct btf *btf, const char *dotname, int alternatives)
{
Expand Down Expand Up @@ -390,7 +449,7 @@ quark_btf_open2(const char *path, const char *kname)
btf = btf__load_vmlinux_btf();
else
btf = btf__parse(path, NULL);
if (IS_ERR_OR_NULL(btf)) {
if (btf == NULL) {
if (errno == 0)
errno = ENOTSUP;
return (NULL);
Expand Down
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