This patch series builds upon the discussion in "[PATCH bpf-next v4 0/4] bpf: Improve error reporting for freplace attachment failure" [1].
This patch series introduces support for *common attributes* in the BPF syscall, providing a unified mechanism for passing shared metadata across all BPF commands, initially used by BPF_PROG_LOAD, BPF_BTF_LOAD, and BPF_MAP_CREATE. The initial set of common attributes includes: 1. 'log_buf': User-provided buffer for storing log output. 2. 'log_size': Size of the provided log buffer. 3. 'log_level': Verbosity level for logging. 4. 'log_true_size': Actual log size reported by kernel. With this extension, the BPF syscall will be able to return meaningful error messages (e.g., map creation failures), improving debuggability and user experience. Links: [1] https://lore.kernel.org/bpf/[email protected]/ Changes: v10 -> v11: * Collect Acked-by from Andrii, thanks. * Validate whether log_buf, log_size, and log_level are valid by reusing bpf_verifier_log_attr_valid() in patch #4 (per Andrii). * v10: https://lore.kernel.org/bpf/[email protected]/ v9 -> v10: * Collect Acked-by from Andrii, thanks. * Address comments from Andrii: * Drop log NULL check in bpf_log_attr_finalize(). * Return -EFAULT early in bpf_log_attr_finalize(). * Validate whether log_buf, log_size, and log_level are set. * Keep log_buf, log_size, log_level, and user-pointer log_true_size in struct bpf_log_attr. * Make prog_load and btf_load work with the new struct bpf_log_attr. * Add comment to log_true_size of struct bpf_log_opts in libbpf. * Address comment from Alexei: * Avoid using BPF_LOG_FIXED as log_level in tests. * v9: https://lore.kernel.org/bpf/[email protected]/ v8 -> v9: * Rework reporting 'log_true_size' for prog_load, btf_load, and map_create to simplify struct bpf_log_attr (per Alexei). * v8: https://lore.kernel.org/bpf/[email protected]/ v7 -> v8: * Return 0 when fd < 0 and errno != EFAULT in probe_sys_bpf_ext(), then simplify probe_bpf_syscall_common_attrs() (per Alexei and Andrii). * v7: https://lore.kernel.org/bpf/[email protected]/ v6 -> v7: * Return -errno when fd < 0 and errno != EFAULT in probe_sys_bpf_ext(). * Convert return value of probe_sys_bpf_ext() to bool in probe_bpf_syscall_common_attrs(). * Address comments from Andrii: * Drop the comment, and handle fd >= 0 case explicitly in probe_sys_bpf_ext(). * Return an error when fd >= 0 in probe_sys_bpf_ext(). * v6: https://lore.kernel.org/bpf/[email protected]/ v5 -> v6: * Address comments from Andrii: * Update some variables' name. * Drop unnecessary 'close(fd)' in libbpf. * Rename FEAT_EXTENDED_SYSCALL to FEAT_BPF_SYSCALL_COMMON_ATTRS with updated description in libbpf. * Use EINVAL instead of EUSERS, as EUSERS is not used in bpf yet. * Rename struct bpf_syscall_common_attr_opts to bpf_log_opts in libbpf. * Add 'OPTS_SET(log_opts, log_true_size, 0);' in libbpf's 'bpf_map_create()'. * v5: https://lore.kernel.org/bpf/[email protected]/ v4 -> v5: * Rework reporting 'log_true_size' for prog_load, btf_load, and map_create (per Alexei). * v4: https://lore.kernel.org/bpf/[email protected]/ RFC v3 -> v4: * Drop RFC. * Address comments from Andrii: * Add parentheses in 'sys_bpf_ext()'. * Avoid creating new fd in 'probe_sys_bpf_ext()'. * Add a new struct to wrap log fields in libbpf. * Address comments from Alexei: * Do not skip writing to user space when log_true_size is zero. * Do not use 'bool' arguments. * Drop the adding WARN_ON_ONCE()'s. * v3: https://lore.kernel.org/bpf/[email protected]/ RFC v2 -> RFC v3: * Rename probe_sys_bpf_extended to probe_sys_bpf_ext. * Refactor reporting 'log_true_size' for prog_load. * Refactor reporting 'btf_log_true_size' for btf_load. * Add warnings for internal bugs in map_create. * Check log_true_size in test cases. * Address comment from Alexei: * Change kvzalloc/kvfree to kzalloc/kfree. * Address comments from Andrii: * Move BPF_COMMON_ATTRS to 'enum bpf_cmd' alongside brief comment. * Add bpf_check_uarg_tail_zero() for extra checks. * Rename sys_bpf_extended to sys_bpf_ext. * Rename sys_bpf_fd_extended to sys_bpf_ext_fd. * Probe the new feature using NULL and -EFAULT. * Move probe_sys_bpf_ext to libbpf_internal.h and drop LIBBPF_API. * Return -EUSERS when log attrs are conflict between bpf_attr and bpf_common_attr. * Avoid touching bpf_vlog_init(). * Update the reason messages in map_create. * Finalize the log using __cleanup(). * Report log size to users. * Change type of log_buf from '__u64' to 'const char *' and cast type using ptr_to_u64() in bpf_map_create(). * Do not return -EOPNOTSUPP when kernel doesn't support this feature in bpf_map_create(). * Add log_level support for map creation for consistency. * Address comment from Eduard: * Use common_attrs->log_level instead of BPF_LOG_FIXED. * v2: https://lore.kernel.org/bpf/[email protected]/ RFC v1 -> RFC v2: * Fix build error reported by test bot. * Address comments from Alexei: * Drop new uapi for freplace. * Add common attributes support for prog_load and btf_load. * Add common attributes support for map_create. * v1: https://lore.kernel.org/bpf/[email protected]/ Leon Hwang (8): bpf: Extend BPF syscall with common attributes support libbpf: Add support for extended BPF syscall bpf: Refactor reporting log_true_size for prog_load bpf: Add syscall common attributes support for prog_load bpf: Add syscall common attributes support for btf_load bpf: Add syscall common attributes support for map_create libbpf: Add syscall common attributes support for map_create selftests/bpf: Add tests to verify map create failure log include/linux/bpf.h | 4 +- include/linux/bpf_verifier.h | 15 ++ include/linux/btf.h | 3 +- include/linux/syscalls.h | 3 +- include/uapi/linux/bpf.h | 8 + kernel/bpf/btf.c | 30 +--- kernel/bpf/log.c | 89 +++++++++- kernel/bpf/syscall.c | 114 +++++++++--- kernel/bpf/verifier.c | 17 +- tools/include/uapi/linux/bpf.h | 8 + tools/lib/bpf/bpf.c | 52 +++++- tools/lib/bpf/bpf.h | 17 +- tools/lib/bpf/features.c | 8 + tools/lib/bpf/libbpf_internal.h | 3 + .../selftests/bpf/prog_tests/map_init.c | 166 ++++++++++++++++++ 15 files changed, 470 insertions(+), 67 deletions(-) -- 2.52.0
