| Message ID | 20220505130507.130670-1-larysa.zaremba@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next,v2] bpftool: Use sysfs vmlinux when dumping BTF by ID | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/fixes_present | success | Fixes tag not required for -next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Single patches do not need cover letters |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/cc_maintainers | success | CCed 12 of 12 maintainers |
| netdev/build_clang | success | Errors and warnings before: 0 this patch: 0 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/verify_fixes | success | No Fixes tag |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 88 lines checked |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
| bpf/vmtest-bpf-next-PR | success | PR summary |
| bpf/vmtest-bpf-next-VM_Test-1 | success | Logs for Kernel LATEST on ubuntu-latest + selftests |
| bpf/vmtest-bpf-next-VM_Test-2 | success | Logs for Kernel LATEST on z15 + selftests |
On Thu, May 5, 2022 at 6:17 AM Larysa Zaremba <larysa.zaremba@intel.com> wrote: > > Currently, dumping almost all BTFs specified by id requires > using the -B option to pass the base BTF. For kernel module > BTFs the vmlinux BTF sysfs path should work. > > This patch simplifies dumping by ID usage by attempting to > use vmlinux BTF from sysfs, if the first try of loading BTF by ID > fails with certain conditions and the ID corresponds to a kernel > module BTF. It feels sloppy to first try without base BTF and then fallback to base BTF. When specified ID of BTF object, let's just get its struct bpf_btf_info with bpf_obj_get_info_by_fd() and then check that kernel_btf is set and name isn't "vmlinux". This will mean it's kernel module, so load base BTF from /sys/kernel/btf/vmlinux. If that fails, there is no way that kernel module BTF will be successfully loaded, so there is no point in trying. > > Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com> > Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com> > --- > tools/bpf/bpftool/btf.c | 67 +++++++++++++++++++++++++++++++++++------ > 1 file changed, 58 insertions(+), 9 deletions(-) > [...]
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index a2c665beda87..070e0c1595d7 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -459,6 +459,56 @@ static int dump_btf_c(const struct btf *btf, return err; } +static const char sysfs_vmlinux[] = "/sys/kernel/btf/vmlinux"; + +static struct btf *get_vmlinux_btf_from_sysfs(void) +{ + struct btf *base; + + base = btf__parse(sysfs_vmlinux, NULL); + if (libbpf_get_error(base)) { + p_err("failed to parse vmlinux BTF at '%s': %ld\n", + sysfs_vmlinux, libbpf_get_error(base)); + base = NULL; + } + + return base; +} + +static struct btf *btf_try_load_with_vmlinux(__u32 btf_id, struct btf **base) +{ + struct bpf_btf_info btf_info = {}; + unsigned int len; + int btf_fd; + int err; + + btf_fd = bpf_btf_get_fd_by_id(btf_id); + if (btf_fd < 0) { + p_err("can't get BTF object by id (%u): %s", + btf_id, strerror(errno)); + return ERR_PTR(btf_fd); + } + + len = sizeof(btf_info); + err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len); + close(btf_fd); + + if (err) { + p_err("can't get BTF (ID %u) object info: %s", + btf_id, strerror(errno)); + return ERR_PTR(err); + } + + if (!btf_info.kernel_btf) { + p_err("BTF with ID %u is not a kernel module BTF, cannot use vmlinux as base", + btf_id); + return ERR_PTR(-EINVAL); + } + + *base = get_vmlinux_btf_from_sysfs(); + return btf__load_from_kernel_by_id_split(btf_id, *base); +} + static int do_dump(int argc, char **argv) { struct btf *btf = NULL, *base = NULL; @@ -536,18 +586,11 @@ static int do_dump(int argc, char **argv) NEXT_ARG(); } else if (is_prefix(src, "file")) { const char sysfs_prefix[] = "/sys/kernel/btf/"; - const char sysfs_vmlinux[] = "/sys/kernel/btf/vmlinux"; if (!base_btf && strncmp(*argv, sysfs_prefix, sizeof(sysfs_prefix) - 1) == 0 && - strcmp(*argv, sysfs_vmlinux) != 0) { - base = btf__parse(sysfs_vmlinux, NULL); - if (libbpf_get_error(base)) { - p_err("failed to parse vmlinux BTF at '%s': %ld\n", - sysfs_vmlinux, libbpf_get_error(base)); - base = NULL; - } - } + strcmp(*argv, sysfs_vmlinux)) + base = get_vmlinux_btf_from_sysfs(); btf = btf__parse_split(*argv, base ?: base_btf); err = libbpf_get_error(btf); @@ -593,6 +636,12 @@ static int do_dump(int argc, char **argv) if (!btf) { btf = btf__load_from_kernel_by_id_split(btf_id, base_btf); err = libbpf_get_error(btf); + if (err == -EINVAL && !base_btf) { + p_info("Warning: valid base BTF was not specified with -B option, falling back on standard base BTF (sysfs vmlinux)"); + btf = btf_try_load_with_vmlinux(btf_id, &base); + err = libbpf_get_error(btf); + } + if (err) { p_err("get btf by id (%u): %s", btf_id, strerror(err)); goto done;