The goal of the patch is to allow usage of header files from
`include/uapi` alongside with `vmlinux.h`. E.g. as follows:
#include <uapi/linux/tcp.h>
#include "vmlinux.h"
This goal is achieved by adding #ifndef / #endif guards in vmlinux.h
around definitions that originate from the `include/uapi` headers. The
guards emitted match the guards used in the original headers.
E.g. as follows:
include/uapi/linux/tcp.h:
#ifndef _UAPI_LINUX_TCP_H
#define _UAPI_LINUX_TCP_H
...
union tcp_word_hdr {
struct tcphdr hdr;
__be32 words[5];
};
...
#endif /* _UAPI_LINUX_TCP_H */
vmlinux.h:
...
#ifndef _UAPI_LINUX_TCP_H
union tcp_word_hdr {
struct tcphdr hdr;
__be32 words[5];
};
#endif /* _UAPI_LINUX_TCP_H */
...
The problem of identifying data structures from uapi and selecting
proper guard names is delegated to pahole. When configured pahole
generates fake `BTF_DECL_TAG` records with header guards information.
The fake tag is distinguished from a real tag by a prefix
"header_guard:" in its value. These tags could be present for unions,
structures, enums and typedefs, e.g.:
[24139] STRUCT 'tcphdr' size=20 vlen=17
...
[24296] DECL_TAG 'header_guard:_UAPI_LINUX_TCP_H' type_id=24139 ...
This patch adds An option `emit_header_guards` to `struct btf_dump_opts`.
When this option is present the function `btf_dump__dump_type` emits
header guards for top-level declarations. The header guards are
identified by inspecting fake `BTF_DECL_TAG` records described above.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/lib/bpf/btf.h | 7 +++-
tools/lib/bpf/btf_dump.c | 89 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 94 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8e6880d91c84..dcfb3f168750 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -235,8 +235,13 @@ struct btf_dump;
struct btf_dump_opts {
size_t sz;
+ /*
+ * if set to true #ifndef X ... #endif brackets would be printed
+ * for types marked by BTF_DECL_TAG with "header_guard:" prefix
+ */
+ bool emit_header_guards;
};
-#define btf_dump_opts__last_field sz
+#define btf_dump_opts__last_field emit_header_guards
typedef void (*btf_dump_printf_fn_t)(void *ctx, const char *fmt, va_list args);
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 9bfe2a4ae277..30b995d209c0 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -113,6 +113,8 @@ struct btf_dump {
int decl_stack_cap;
int decl_stack_cnt;
+ bool emit_header_guards;
+
/* maps struct/union/enum name to a number of name occurrences */
struct hashmap *type_names;
/*
@@ -202,6 +204,8 @@ struct btf_dump *btf_dump__new(const struct btf *btf,
d->cb_ctx = ctx;
d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *);
+ d->emit_header_guards = OPTS_GET(opts, emit_header_guards, false);
+
d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
if (IS_ERR(d->type_names)) {
err = PTR_ERR(d->type_names);
@@ -347,6 +351,8 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id)
return 0;
}
+static const char *btf_dump_is_header_guard_tag(struct btf_dump *d, const struct btf_type *t);
+
/*
* Mark all types that are referenced from any other type. This is used to
* determine top-level anonymous enums that need to be emitted as an
@@ -384,11 +390,15 @@ static int btf_dump_mark_referenced(struct btf_dump *d)
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
- case BTF_KIND_DECL_TAG:
case BTF_KIND_TYPE_TAG:
d->type_states[t->type].referenced = 1;
break;
+ case BTF_KIND_DECL_TAG:
+ if (!btf_dump_is_header_guard_tag(d, t))
+ d->type_states[t->type].referenced = 1;
+ break;
+
case BTF_KIND_ARRAY: {
const struct btf_array *a = btf_array(t);
@@ -449,6 +459,40 @@ static struct decl_tag_array *realloc_decl_tags(struct decl_tag_array *tags, __u
return new_tags;
}
+#define HEADER_GUARD_TAG "header_guard:"
+
+static const char *btf_dump_is_header_guard_tag(struct btf_dump *d, const struct btf_type *t)
+{
+ const char *tag_value;
+ int tag_len = strlen(HEADER_GUARD_TAG);
+
+ tag_value = btf__str_by_offset(d->btf, t->name_off);
+ if (strncmp(tag_value, HEADER_GUARD_TAG, tag_len))
+ return NULL;
+
+ return &tag_value[tag_len];
+}
+
+static const char *btf_dump_find_header_guard(struct btf_dump *d, __u32 id)
+{
+ struct decl_tag_array *decl_tags = btf_dump_find_decl_tags(d, id);
+ const struct btf_type *t;
+ const char *guard;
+ int i;
+
+ if (!decl_tags)
+ return NULL;
+
+ for (i = 0; i < decl_tags->cnt; ++i) {
+ t = btf__type_by_id(d->btf, decl_tags->tag_ids[i]);
+ guard = btf_dump_is_header_guard_tag(d, t);
+ if (guard)
+ return guard;
+ }
+
+ return NULL;
+}
+
/*
* Scans all BTF objects looking for BTF_KIND_DECL_TAG entries.
* The id's of the entries are stored in the `btf_dump.decl_tags` table,
@@ -770,6 +814,8 @@ static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
const char *orig_name);
+static void btf_dump_emit_guard_start(struct btf_dump *d, __u32 id);
+static void btf_dump_emit_guard_end(struct btf_dump *d, __u32 id);
static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
{
@@ -835,8 +881,10 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
id);
return;
}
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_struct_fwd(d, id, t);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
tstate->fwd_emitted = 1;
break;
case BTF_KIND_TYPEDEF:
@@ -846,8 +894,10 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
* references through pointer only, not for embedding
*/
if (!btf_dump_is_blacklisted(d, id)) {
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_typedef_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
}
tstate->fwd_emitted = 1;
break;
@@ -868,8 +918,10 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
case BTF_KIND_ENUM:
case BTF_KIND_ENUM64:
if (top_level_def) {
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_enum_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
}
tstate->emit_state = EMITTED;
break;
@@ -884,8 +936,10 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
btf_dump_emit_type(d, btf_array(t)->type, cont_id);
break;
case BTF_KIND_FWD:
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_fwd_def(d, id, t);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
tstate->emit_state = EMITTED;
break;
case BTF_KIND_TYPEDEF:
@@ -899,8 +953,10 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
* emit typedef as a forward declaration
*/
if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_typedef_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
}
tstate->emit_state = EMITTED;
break;
@@ -923,14 +979,18 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
for (i = 0; i < vlen; i++, m++)
btf_dump_emit_type(d, m->type, new_cont_id);
} else if (!tstate->fwd_emitted && id != cont_id) {
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_struct_fwd(d, id, t);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
tstate->fwd_emitted = 1;
}
if (top_level_def) {
+ btf_dump_emit_guard_start(d, id);
btf_dump_emit_struct_def(d, id, t, 0);
btf_dump_printf(d, ";\n\n");
+ btf_dump_emit_guard_end(d, id);
tstate->emit_state = EMITTED;
} else {
tstate->emit_state = NOT_EMITTED;
@@ -1034,6 +1094,8 @@ static void btf_dump_emit_decl_tags(struct btf_dump *d, __u32 id)
for (i = 0; i < decl_tags->cnt; ++i) {
decl_tag_t = btf_type_by_id(d->btf, decl_tags->tag_ids[i]);
+ if (btf_dump_is_header_guard_tag(d, decl_tag_t))
+ continue;
decl_tag_text = btf__name_by_offset(d->btf, decl_tag_t->name_off);
btf_dump_printf(d, " __attribute__((btf_decl_tag(\"%s\")))", decl_tag_text);
}
@@ -1672,6 +1734,31 @@ static void btf_dump_emit_type_cast(struct btf_dump *d, __u32 id,
btf_dump_printf(d, ")");
}
+static void btf_dump_emit_guard_start(struct btf_dump *d, __u32 id)
+{
+ const char *header_guard;
+
+ if (!d->emit_header_guards)
+ return;
+
+ header_guard = btf_dump_find_header_guard(d, id);
+ if (!header_guard)
+ return;
+
+ btf_dump_printf(d, "#ifndef %s\n\n", header_guard);
+}
+
+static void btf_dump_emit_guard_end(struct btf_dump *d, __u32 id)
+{
+ if (!d->emit_header_guards)
+ return;
+
+ if (!btf_dump_find_header_guard(d, id))
+ return;
+
+ btf_dump_printf(d, "#endif\n\n");
+}
+
/* return number of duplicates (occurrences) of a given name */
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
const char *orig_name)
--
2.34.1
