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bpf: btf: Add pretty print capability for data with BTF type info
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This patch adds pretty print capability for data with BTF type info.
The current usage is to allow pretty print for a BPF map.

The next few patches will allow a read() on a pinned map with BTF
type info for its key and value.

This patch uses the seq_printf() infra.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Martin KaFai Lau authored and Daniel Borkmann committed Apr 19, 2018
1 parent 179cde8 commit b00b8da
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2 changes: 2 additions & 0 deletions include/linux/btf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,5 +33,7 @@ struct btf_type;
const struct btf_type *btf_type_id_size(const struct btf *btf,
u32 *type_id,
u32 *ret_size);
void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m);

#endif
198 changes: 198 additions & 0 deletions kernel/bpf/btf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

#include <uapi/linux/btf.h>
#include <uapi/linux/types.h>
#include <linux/seq_file.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/slab.h>
Expand Down Expand Up @@ -256,6 +257,9 @@ struct btf_kind_operations {
const struct btf_type *member_type);
void (*log_details)(struct btf_verifier_env *env,
const struct btf_type *t);
void (*seq_show)(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offsets,
struct seq_file *m);
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
Expand Down Expand Up @@ -781,6 +785,13 @@ static int btf_df_resolve(struct btf_verifier_env *env,
return -EINVAL;
}

static void btf_df_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offsets,
struct seq_file *m)
{
seq_printf(m, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
}

static int btf_int_check_member(struct btf_verifier_env *env,
const struct btf_type *struct_type,
const struct btf_member *member,
Expand Down Expand Up @@ -879,11 +890,96 @@ static void btf_int_log(struct btf_verifier_env *env,
btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}

static void btf_int_bits_seq_show(const struct btf *btf,
const struct btf_type *t,
void *data, u8 bits_offset,
struct seq_file *m)
{
u32 int_data = btf_type_int(t);
u16 nr_bits = BTF_INT_BITS(int_data);
u16 total_bits_offset;
u16 nr_copy_bytes;
u16 nr_copy_bits;
u8 nr_upper_bits;
union {
u64 u64_num;
u8 u8_nums[8];
} print_num;

total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
nr_copy_bits = nr_bits + bits_offset;
nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);

print_num.u64_num = 0;
memcpy(&print_num.u64_num, data, nr_copy_bytes);

/* Ditch the higher order bits */
nr_upper_bits = BITS_PER_BYTE_MASKED(nr_copy_bits);
if (nr_upper_bits) {
/* We need to mask out some bits of the upper byte. */
u8 mask = (1 << nr_upper_bits) - 1;

print_num.u8_nums[nr_copy_bytes - 1] &= mask;
}

print_num.u64_num >>= bits_offset;

seq_printf(m, "0x%llx", print_num.u64_num);
}

static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
u32 int_data = btf_type_int(t);
u8 encoding = BTF_INT_ENCODING(int_data);
bool sign = encoding & BTF_INT_SIGNED;
u32 nr_bits = BTF_INT_BITS(int_data);

if (bits_offset || BTF_INT_OFFSET(int_data) ||
BITS_PER_BYTE_MASKED(nr_bits)) {
btf_int_bits_seq_show(btf, t, data, bits_offset, m);
return;
}

switch (nr_bits) {
case 64:
if (sign)
seq_printf(m, "%lld", *(s64 *)data);
else
seq_printf(m, "%llu", *(u64 *)data);
break;
case 32:
if (sign)
seq_printf(m, "%d", *(s32 *)data);
else
seq_printf(m, "%u", *(u32 *)data);
break;
case 16:
if (sign)
seq_printf(m, "%d", *(s16 *)data);
else
seq_printf(m, "%u", *(u16 *)data);
break;
case 8:
if (sign)
seq_printf(m, "%d", *(s8 *)data);
else
seq_printf(m, "%u", *(u8 *)data);
break;
default:
btf_int_bits_seq_show(btf, t, data, bits_offset, m);
}
}

static const struct btf_kind_operations int_ops = {
.check_meta = btf_int_check_meta,
.resolve = btf_df_resolve,
.check_member = btf_int_check_member,
.log_details = btf_int_log,
.seq_show = btf_int_seq_show,
};

static int btf_modifier_check_member(struct btf_verifier_env *env,
Expand Down Expand Up @@ -1054,6 +1150,24 @@ static int btf_ptr_resolve(struct btf_verifier_env *env,
return 0;
}

static void btf_modifier_seq_show(const struct btf *btf,
const struct btf_type *t,
u32 type_id, void *data,
u8 bits_offset, struct seq_file *m)
{
t = btf_type_id_resolve(btf, &type_id);

btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}

static void btf_ptr_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
/* It is a hashed value */
seq_printf(m, "%p", *(void **)data);
}

static void btf_ref_type_log(struct btf_verifier_env *env,
const struct btf_type *t)
{
Expand All @@ -1065,20 +1179,23 @@ static struct btf_kind_operations modifier_ops = {
.resolve = btf_modifier_resolve,
.check_member = btf_modifier_check_member,
.log_details = btf_ref_type_log,
.seq_show = btf_modifier_seq_show,
};

static struct btf_kind_operations ptr_ops = {
.check_meta = btf_ref_type_check_meta,
.resolve = btf_ptr_resolve,
.check_member = btf_ptr_check_member,
.log_details = btf_ref_type_log,
.seq_show = btf_ptr_seq_show,
};

static struct btf_kind_operations fwd_ops = {
.check_meta = btf_ref_type_check_meta,
.resolve = btf_df_resolve,
.check_member = btf_df_check_member,
.log_details = btf_ref_type_log,
.seq_show = btf_df_seq_show,
};

static int btf_array_check_member(struct btf_verifier_env *env,
Expand Down Expand Up @@ -1209,11 +1326,36 @@ static void btf_array_log(struct btf_verifier_env *env,
array->type, array->index_type, array->nelems);
}

static void btf_array_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
const struct btf_array *array = btf_type_array(t);
const struct btf_kind_operations *elem_ops;
const struct btf_type *elem_type;
u32 i, elem_size, elem_type_id;

elem_type_id = array->type;
elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
elem_ops = btf_type_ops(elem_type);
seq_puts(m, "[");
for (i = 0; i < array->nelems; i++) {
if (i)
seq_puts(m, ",");

elem_ops->seq_show(btf, elem_type, elem_type_id, data,
bits_offset, m);
data += elem_size;
}
seq_puts(m, "]");
}

static struct btf_kind_operations array_ops = {
.check_meta = btf_array_check_meta,
.resolve = btf_array_resolve,
.check_member = btf_array_check_member,
.log_details = btf_array_log,
.seq_show = btf_array_seq_show,
};

static int btf_struct_check_member(struct btf_verifier_env *env,
Expand Down Expand Up @@ -1361,11 +1503,39 @@ static void btf_struct_log(struct btf_verifier_env *env,
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
const char *seq = BTF_INFO_KIND(t->info) == BTF_KIND_UNION ? "|" : ",";
const struct btf_member *member;
u32 i;

seq_puts(m, "{");
for_each_member(i, t, member) {
const struct btf_type *member_type = btf_type_by_id(btf,
member->type);
u32 member_offset = member->offset;
u32 bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
u8 bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
const struct btf_kind_operations *ops;

if (i)
seq_puts(m, seq);

ops = btf_type_ops(member_type);
ops->seq_show(btf, member_type, member->type,
data + bytes_offset, bits8_offset, m);
}
seq_puts(m, "}");
}

static struct btf_kind_operations struct_ops = {
.check_meta = btf_struct_check_meta,
.resolve = btf_struct_resolve,
.check_member = btf_struct_check_member,
.log_details = btf_struct_log,
.seq_show = btf_struct_seq_show,
};

static int btf_enum_check_member(struct btf_verifier_env *env,
Expand Down Expand Up @@ -1441,11 +1611,31 @@ static void btf_enum_log(struct btf_verifier_env *env,
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
const struct btf_enum *enums = btf_type_enum(t);
u32 i, nr_enums = btf_type_vlen(t);
int v = *(int *)data;

for (i = 0; i < nr_enums; i++) {
if (v == enums[i].val) {
seq_printf(m, "%s",
btf_name_by_offset(btf, enums[i].name));
return;
}
}

seq_printf(m, "%d", v);
}

static struct btf_kind_operations enum_ops = {
.check_meta = btf_enum_check_meta,
.resolve = btf_df_resolve,
.check_member = btf_enum_check_member,
.log_details = btf_enum_log,
.seq_show = btf_enum_seq_show,
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
Expand Down Expand Up @@ -1782,3 +1972,11 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
btf_free(btf);
return ERR_PTR(err);
}

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m)
{
const struct btf_type *t = btf_type_by_id(btf, type_id);

btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m);
}

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