Re: [PATCH bpf-next v9 4/9] bpf: Add syscall common attributes support for prog_load
From: Andrii Nakryiko <hidden>
Date: 2026-02-04 19:49:03
Also in:
bpf, linux-kselftest, lkml
On Mon, Feb 2, 2026 at 6:42 AM Leon Hwang [off-list ref] wrote:
quoted hunk ↗ jump to hunk
BPF_PROG_LOAD can now provide log parameters through both union bpf_attr and struct bpf_common_attr. Define clear conflict and precedence rules: - if both are provided and log_buf/log_size/log_level match, use them; - if only one side provides a log buffer, use that one; - if both provide log buffers but differ, return -EINVAL. Signed-off-by: Leon Hwang <redacted> --- include/linux/bpf_verifier.h | 3 ++- kernel/bpf/log.c | 24 ++++++++++++++++++++++-- kernel/bpf/syscall.c | 3 ++- 3 files changed, 26 insertions(+), 4 deletions(-)diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index c805b85b6f7a..0d106fddbbc5 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h@@ -638,7 +638,8 @@ struct bpf_log_attr { }; int bpf_prog_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *attr, - bpfptr_t uattr, u32 size); + bpfptr_t uattr, u32 size, struct bpf_common_attr *attr_common, + bpfptr_t uattr_common, u32 size_common); int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log); #define BPF_MAX_SUBPROGS 256diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c index ff579fcba36f..345005ba98dd 100644 --- a/kernel/bpf/log.c +++ b/kernel/bpf/log.c@@ -873,10 +873,30 @@ static void bpf_log_attr_init(struct bpf_log_attr *attr_log, int offsetof_true_s attr_log->uattr = uattr; } +static bool bpf_log_attrs_diff(struct bpf_common_attr *common, u64 log_buf, u32 log_size, + u32 log_level) +{ + return log_buf && common->log_buf && (log_buf != common->log_buf || + log_size != common->log_size || + log_level != common->log_level);
let's validate (unless we do this somewhere else) that if log_buf is set, then log_size and log_level (? not sure, maybe zero is fine) are set, or all three are not set. Same for common->log* fields...
+}
+
int bpf_prog_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *attr,
- bpfptr_t uattr, u32 size)
+ bpfptr_t uattr, u32 size, struct bpf_common_attr *attr_common,
+ bpfptr_t uattr_common, u32 size_common)
{
- bpf_log_attr_init(attr_log, offsetof(union bpf_attr, log_true_size), uattr, size);
+ if (bpf_log_attrs_diff(attr_common, attr->log_buf, attr->log_size, attr->log_level))
+ return -EINVAL;
+
+ if (!attr->log_buf && attr_common->log_buf) {
+ attr->log_buf = attr_common->log_buf;
+ attr->log_size = attr_common->log_size;
+ attr->log_level = attr_common->log_level;
why are we setting this? Do we still have code that can access
attr->log_buf even though we pass attr_log everywhere? If yes, should
we still have that "split brain" code?
If we don't have this assignment, then I think we don't need to have
bpf_prog_load-specific and btf_load-specific log_attr_init() helpers.
They can be unified into generic log_attr_init, where for
bpf_prog_load you'll pass offsetof(log_true_size) +
attr->log_{buf,size,level}, and for btf_load you'll pass different
offset of and btf-specific attr->btf_log*
This helper will just be making decision whether to use common_attr's
log fields or passed directly command-specific ones.
Or what am I missing?
quoted hunk ↗ jump to hunk
+ bpf_log_attr_init(attr_log, offsetof(struct bpf_common_attr, log_true_size), + uattr_common, size_common); + } else { + bpf_log_attr_init(attr_log, offsetof(union bpf_attr, log_true_size), uattr, size); + } return 0; }diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index e81199361241..7125ea445c6c 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c@@ -6232,7 +6232,8 @@ 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_log_attr_init(&attr_log, &attr, uattr, size); + err = bpf_prog_load_log_attr_init(&attr_log, &attr, uattr, size, &attr_common, + uattr_common, size_common); err = err ?: bpf_prog_load(&attr, uattr, &attr_log); break; case BPF_OBJ_PIN: --2.52.0