On 5/9/24 17:08, Alan Maguire wrote:
On 09/05/2024 16:17, Mykyta@xxxxxxxxxxxxxxxxxx wrote:
From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
Sort bpftool c dump output; aiming to simplify vmlinux.h diffing and
forcing more natural type definitions ordering.
Definitions are sorted first by their BTF kind ranks, then by their base
type name and by their own name.
Type ranks
Assign ranks to btf kinds (defined in function btf_type_rank) to set
next order:
1. Anonymous enums/enums64
2. Named enums/enums64
3. Trivial types typedefs (ints, then floats)
4. Structs/Unions
5. Function prototypes
6. Forward declarations
Type rank is set to maximum for unnamed reference types, structs and
unions to avoid emitting those types early. They will be emitted as
part of the type chain starting with named type.
Lexicographical ordering
Each type is assigned a sort_name and own_name.
sort_name is the resolved name of the final base type for reference
types (typedef, pointer, array etc). Sorting by sort_name allows to
group typedefs of the same base type. sort_name for non-reference type
is the same as own_name. own_name is a direct name of particular type,
is used as final sorting step.
Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
This looks great! Not sure if you experimented with sorting for the
split BTF case (dumping /sys/kernel/btf/tun say); are there any
additional issues in doing that? From what I can see below the sort
would just be applied across base and split BTF and should just work, is
that right? A few suggestions below, but
This functionality is oblivious to split BTF, dumping
/sys/kernel/btf/tun will
sort all types across both base and split BTF, not distinguishing where
those
types come from.
Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
tools/bpf/bpftool/btf.c | 125 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 122 insertions(+), 3 deletions(-)
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 91fcb75babe3..09ecd2abf066 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -43,6 +43,13 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_ENUM64] = "ENUM64",
};
+struct sort_datum {
+ int index;
+ int type_rank;
+ const char *sort_name;
+ const char *own_name;
+};
+
static const char *btf_int_enc_str(__u8 encoding)
{
switch (encoding) {
@@ -460,11 +467,114 @@ static void __printf(2, 0) btf_dump_printf(void *ctx,
vfprintf(stdout, fmt, args);
}
+static bool is_reference_type(const struct btf_type *t)
+{
+ int kind = btf_kind(t);
+
+ return kind == BTF_KIND_CONST || kind == BTF_KIND_PTR || kind == BTF_KIND_VOLATILE ||
+ kind == BTF_KIND_RESTRICT || kind == BTF_KIND_ARRAY || kind == BTF_KIND_TYPEDEF ||
+ kind == BTF_KIND_DECL_TAG;
+}
+
+static int btf_type_rank(const struct btf *btf, __u32 index, bool has_name)
+{
+ const struct btf_type *t = btf__type_by_id(btf, index);
+ const int max_rank = 10;
+ const int kind = btf_kind(t);
+
+ if (t->name_off)
+ has_name = true;
+
+ switch (kind) {
+ case BTF_KIND_ENUM:
+ case BTF_KIND_ENUM64:
+ return has_name ? 1 : 0;
+ case BTF_KIND_INT:
+ case BTF_KIND_FLOAT:
+ return 2;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ return has_name ? 3 : max_rank;
+ case BTF_KIND_FUNC_PROTO:
+ return has_name ? 4 : max_rank;
+
Don't think a FUNC_PROTO will ever have a name, so has_name check
probably not needed here.
The reason for that check is to penalize FUNC_PROTO type (assign
max_rank to it),
but assign rank 4 to typedef type pointing to that FUNC_PROTO. You can
see that
for reference types this function is called recursively until
non-reference type
is reached, we assign non-maximum rank only if there was a named type along
the chain of recursive calls. Assigning rank 4 to FUNC_PROTO will lead
to printing
those function prototypes unordered, as their names are assigned to
typedef type.
+ default: {
+ if (has_name && is_reference_type(t)) {
+ const int parent = kind == BTF_KIND_ARRAY ? btf_array(t)->type : t->type;
+
+ return btf_type_rank(btf, parent, has_name);
+ }
+ return max_rank;
+ }
+ }
+}
+
+static const char *btf_type_sort_name(const struct btf *btf, __u32 index)
+{
+ const struct btf_type *t = btf__type_by_id(btf, index);
+ int kind = btf_kind(t);
+
+ /* Use name of the first element for anonymous enums */
+ if (!t->name_off && (kind == BTF_KIND_ENUM || kind == BTF_KIND_ENUM64) &&
+ BTF_INFO_VLEN(t->info))
+ return btf__name_by_offset(btf, btf_enum(t)->name_off);
+
+ /* Return base type name for reference types */
+ while (is_reference_type(t)) {
The two times is_reference_type() is used, we use this conditional to
get the array type; worth rolling this into a get_reference_type(t)
function that returns t->type for reference types, btf_array(t)->type
for arrays and -1 otherwise perhaps?
Agree.
+ index = btf_kind(t) == BTF_KIND_ARRAY ? btf_array(t)->type : t->type;
+ t = btf__type_by_id(btf, index);
+ }
+
+ return btf__name_by_offset(btf, t->name_off);
+}
+
+static int btf_type_compare(const void *left, const void *right)
+{
+ const struct sort_datum *datum1 = (const struct sort_datum *)left;
+ const struct sort_datum *datum2 = (const struct sort_datum *)right;
+ int sort_name_cmp;
+
+ if (datum1->type_rank != datum2->type_rank)
+ return datum1->type_rank < datum2->type_rank ? -1 : 1;
+
+ sort_name_cmp = strcmp(datum1->sort_name, datum2->sort_name);
+ if (sort_name_cmp)
+ return sort_name_cmp;
+
+ return strcmp(datum1->own_name, datum2->own_name);
+}
+
+static struct sort_datum *sort_btf_c(const struct btf *btf)
+{
+ int total_root_types;
+ struct sort_datum *datums;
+
+ total_root_types = btf__type_cnt(btf);
+ datums = malloc(sizeof(struct sort_datum) * total_root_types);
calloc(total_root_types, sizeof(*datums)) will get you a
zero-initialized array, which may be useful below...
+ if (!datums)
+ return NULL;
+
+ for (int i = 0; i < total_root_types; ++i) {
you're starting from zero here so you'll get &btf_void below; if you
zero-initialize above I think you can just start from 1.
+ struct sort_datum *current_datum = datums + i;
+ const struct btf_type *t = btf__type_by_id(btf, i);
+
+ current_datum->index = i;
+ current_datum->type_rank = btf_type_rank(btf, i, false);
+ current_datum->sort_name = btf_type_sort_name(btf, i);
+ current_datum->own_name = btf__name_by_offset(btf, t->name_off);
+ }
+
+ qsort(datums, total_root_types, sizeof(struct sort_datum), btf_type_compare);
+
+ return datums;
+}
+
static int dump_btf_c(const struct btf *btf,
- __u32 *root_type_ids, int root_type_cnt)
+ __u32 *root_type_ids, int root_type_cnt, bool sort_dump)
{
struct btf_dump *d;
int err = 0, i;
+ struct sort_datum *datums = NULL;
d = btf_dump__new(btf, btf_dump_printf, NULL, NULL);
if (!d)
@@ -486,8 +596,12 @@ static int dump_btf_c(const struct btf *btf,
} else {
int cnt = btf__type_cnt(btf);
+ if (sort_dump)
+ datums = sort_btf_c(btf);
for (i = 1; i < cnt; i++) {
- err = btf_dump__dump_type(d, i);
+ int idx = datums ? datums[i].index : i;
+
+ err = btf_dump__dump_type(d, idx);
if (err)
goto done;
}
@@ -501,6 +615,7 @@ static int dump_btf_c(const struct btf *btf,
done:
btf_dump__free(d);
+ free(datums);
return err;
}
@@ -553,6 +668,7 @@ static int do_dump(int argc, char **argv)
__u32 root_type_ids[2];
int root_type_cnt = 0;
bool dump_c = false;
+ bool sort_dump_c = true;
__u32 btf_id = -1;
const char *src;
int fd = -1;
@@ -663,6 +779,9 @@ static int do_dump(int argc, char **argv)
goto done;
}
NEXT_ARG();
+ } else if (is_prefix(*argv, "unordered")) {
you'll need to update the man page and add to the bash completion for
this new argument I think.
+ sort_dump_c = false;
+ NEXT_ARG();
} else {
p_err("unrecognized option: '%s'", *argv);
err = -EINVAL;
@@ -691,7 +810,7 @@ static int do_dump(int argc, char **argv)
err = -ENOTSUP;
goto done;
}
- err = dump_btf_c(btf, root_type_ids, root_type_cnt);
+ err = dump_btf_c(btf, root_type_ids, root_type_cnt, sort_dump_c);
} else {
err = dump_btf_raw(btf, root_type_ids, root_type_cnt);
}
