[PATCH bpf-next v12 3/8] bpf: Refactor reporting log_true_size for prog_load
From: Leon Hwang
Date: Mon Apr 20 2026 - 11:31:55 EST
The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.
To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:
* bpf_log_attr_init(): initialize log fields, which will support
extended common attributes in the next commit.
* bpf_log_attr_finalize(): handle log finalization and write back
'log_true_size' to userspace.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
---
include/linux/bpf.h | 4 +++-
include/linux/bpf_verifier.h | 12 ++++++++++++
kernel/bpf/log.c | 29 +++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 12 +++++++++---
kernel/bpf/verifier.c | 17 ++++-------------
5 files changed, 57 insertions(+), 17 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 30d35d5fe40b..76b28153224a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2912,7 +2912,9 @@ int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
size_t actual_size);
/* verify correctness of eBPF program */
-int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size);
+struct bpf_log_attr;
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr,
+ struct bpf_log_attr *attr_log);
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 36bfd96d4563..1162b5492841 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -647,6 +647,18 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
return log && log->level;
}
+struct bpf_log_attr {
+ char __user *ubuf;
+ u32 size;
+ u32 level;
+ u32 offsetof_true_size;
+ bpfptr_t uattr;
+};
+
+int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32 log_size, u32 log_level,
+ u32 offsetof_log_true_size, bpfptr_t uattr);
+int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log);
+
#define BPF_MAX_SUBPROGS 256
struct bpf_subprog_arg_info {
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 37d72b052192..9c5c755d5972 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -865,3 +865,32 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
}
print_verifier_state(env, vstate, frameno, false);
}
+
+int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32 log_size, u32 log_level,
+ u32 offsetof_log_true_size, bpfptr_t uattr)
+{
+ char __user *ubuf = u64_to_user_ptr(log_buf);
+
+ memset(log, 0, sizeof(*log));
+ log->ubuf = ubuf;
+ log->size = log_size;
+ log->level = log_level;
+ log->offsetof_true_size = offsetof_log_true_size;
+ log->uattr = uattr;
+ return 0;
+}
+
+int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log)
+{
+ u32 log_true_size;
+ int err;
+
+ err = bpf_vlog_finalize(log, &log_true_size);
+
+ if (attr->offsetof_true_size &&
+ copy_to_bpfptr_offset(attr->uattr, attr->offsetof_true_size, &log_true_size,
+ sizeof(log_true_size)))
+ return -EFAULT;
+
+ return err;
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5bf84ea21bf5..b560dab9bfa8 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2861,7 +2861,7 @@ static int bpf_prog_mark_insn_arrays_ready(struct bpf_prog *prog)
/* last field in 'union bpf_attr' used by this command */
#define BPF_PROG_LOAD_LAST_FIELD keyring_id
-static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)
{
enum bpf_prog_type type = attr->prog_type;
struct bpf_prog *prog, *dst_prog = NULL;
@@ -3079,7 +3079,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
goto free_prog_sec;
/* run eBPF verifier */
- err = bpf_check(&prog, attr, uattr, uattr_size);
+ err = bpf_check(&prog, attr, uattr, attr_log);
if (err < 0)
goto free_used_maps;
@@ -6214,6 +6214,8 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
bpfptr_t uattr_common, unsigned int size_common)
{
struct bpf_common_attr attr_common;
+ u32 offsetof_log_true_size = 0;
+ struct bpf_log_attr attr_log;
union bpf_attr attr;
int err;
@@ -6265,7 +6267,11 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
err = map_freeze(&attr);
break;
case BPF_PROG_LOAD:
- err = bpf_prog_load(&attr, uattr, size);
+ if (size >= offsetofend(union bpf_attr, log_true_size))
+ offsetof_log_true_size = offsetof(union bpf_attr, log_true_size);
+ err = bpf_log_attr_init(&attr_log, attr.log_buf, attr.log_size, attr.log_level,
+ offsetof_log_true_size, uattr);
+ err = err ?: bpf_prog_load(&attr, uattr, &attr_log);
break;
case BPF_OBJ_PIN:
err = bpf_obj_pin(&attr);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 594260c1f382..668a3628013e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -26526,12 +26526,12 @@ static int compute_scc(struct bpf_verifier_env *env)
return err;
}
-int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
+int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
+ struct bpf_log_attr *attr_log)
{
u64 start_time = ktime_get_ns();
struct bpf_verifier_env *env;
int i, len, ret = -EINVAL, err;
- u32 log_true_size;
bool is_priv;
BTF_TYPE_EMIT(enum bpf_features);
@@ -26578,9 +26578,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
/* user could have requested verbose verifier output
* and supplied buffer to store the verification trace
*/
- ret = bpf_vlog_init(&env->log, attr->log_level,
- (char __user *) (unsigned long) attr->log_buf,
- attr->log_size);
+ ret = bpf_vlog_init(&env->log, attr_log->level, attr_log->ubuf, attr_log->size);
if (ret)
goto err_unlock;
@@ -26742,17 +26740,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
env->prog->aux->verified_insns = env->insn_processed;
/* preserve original error even if log finalization is successful */
- err = bpf_vlog_finalize(&env->log, &log_true_size);
+ err = bpf_log_attr_finalize(attr_log, &env->log);
if (err)
ret = err;
- if (uattr_size >= offsetofend(union bpf_attr, log_true_size) &&
- copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
- &log_true_size, sizeof(log_true_size))) {
- ret = -EFAULT;
- goto err_release_maps;
- }
-
if (ret)
goto err_release_maps;
--
2.53.0