Adding bpf_vma_build_id_parse function to retrieve build id from
passed vma object and making it available as bpf kfunc.
We can't use build_id_parse directly as kfunc, because we would
not have control over the build id buffer size provided by user.
Instead we are adding new bpf_vma_build_id_parse function with
'build_id__sz' argument that instructs verifier to check for the
available space in build_id buffer.
This way we check that there's always available memory space
behind build_id pointer. We also check that the build_id__sz is
at least BUILD_ID_SIZE_MAX so we can place any buildid in.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
include/linux/bpf.h | 5 +++++
kernel/bpf/helpers.c | 16 ++++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 798aec816970..5e7c4c50da8e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2779,4 +2779,9 @@ struct bpf_key {
bool has_ref;
};
#endif /* CONFIG_KEYS */
+
+extern int bpf_vma_build_id_parse(struct vm_area_struct *vma,
+ unsigned char *build_id,
+ size_t build_id__sz);
+
#endif /* _LINUX_BPF_H */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 283f55bbeb70..af7a30dafff3 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -19,6 +19,7 @@
#include <linux/proc_ns.h>
#include <linux/security.h>
#include <linux/btf_ids.h>
+#include <linux/buildid.h>
#include "../../lib/kstrtox.h"
@@ -1706,10 +1707,25 @@ bpf_base_func_proto(enum bpf_func_id func_id)
}
}
+int bpf_vma_build_id_parse(struct vm_area_struct *vma,
+ unsigned char *build_id,
+ size_t build_id__sz)
+{
+ __u32 size;
+ int err;
+
+ if (build_id__sz < BUILD_ID_SIZE_MAX)
+ return -EINVAL;
+
+ err = build_id_parse(vma, build_id, &size);
+ return err ?: (int) size;
+}
+
BTF_SET8_START(tracing_btf_ids)
#ifdef CONFIG_KEXEC_CORE
BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
#endif
+BTF_ID_FLAGS(func, bpf_vma_build_id_parse)
BTF_SET8_END(tracing_btf_ids)
static const struct btf_kfunc_id_set tracing_kfunc_set = {
--
2.38.1
