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libbpf: Add BTF_KIND_FLOAT support

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The logic follows that of BTF_KIND_INT most of the time. Sanitization
replaces BTF_KIND_FLOATs with equally-sized empty BTF_KIND_STRUCTs on
older kernels, for example, the following:

    [4] FLOAT 'float' size=4

becomes the following:

    [4] STRUCT '(anon)' size=4 vlen=0

With dwarves patch [1] and this patch, the older kernels, which were
failing with the floating-point-related errors, will now start working
correctly.

[1] https://github.com/iii-i/dwarves/commit/btf-kind-float-v2

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226202256.116518-4-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich
2021-02-26 21:22:49 +01:00
committed by Andrii Nakryiko
parent 617f781804
commit 471e7c241d
6 changed files with 94 additions and 1 deletions
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49
src/btf.c
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@@ -291,6 +291,7 @@ static int btf_type_size(const struct btf_type *t)
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_FLOAT:
return base_size;
case BTF_KIND_INT:
return base_size + sizeof(__u32);
@@ -338,6 +339,7 @@ static int btf_bswap_type_rest(struct btf_type *t)
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_FLOAT:
return 0;
case BTF_KIND_INT:
*(__u32 *)(t + 1) = bswap_32(*(__u32 *)(t + 1));
@@ -578,6 +580,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
case BTF_KIND_UNION:
case BTF_KIND_ENUM:
case BTF_KIND_DATASEC:
case BTF_KIND_FLOAT:
size = t->size;
goto done;
case BTF_KIND_PTR:
@@ -621,6 +624,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
switch (kind) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
case BTF_KIND_FLOAT:
return min(btf_ptr_sz(btf), (size_t)t->size);
case BTF_KIND_PTR:
return btf_ptr_sz(btf);
@@ -1756,6 +1760,47 @@ int btf__add_int(struct btf *btf, const char *name, size_t byte_sz, int encoding
return btf_commit_type(btf, sz);
}
/*
* Append new BTF_KIND_FLOAT type with:
* - *name* - non-empty, non-NULL type name;
* - *sz* - size of the type, in bytes;
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_float(struct btf *btf, const char *name, size_t byte_sz)
{
struct btf_type *t;
int sz, name_off;
/* non-empty name */
if (!name || !name[0])
return -EINVAL;
/* byte_sz must be one of the explicitly allowed values */
if (byte_sz != 2 && byte_sz != 4 && byte_sz != 8 && byte_sz != 12 &&
byte_sz != 16)
return -EINVAL;
if (btf_ensure_modifiable(btf))
return -ENOMEM;
sz = sizeof(struct btf_type);
t = btf_add_type_mem(btf, sz);
if (!t)
return -ENOMEM;
name_off = btf__add_str(btf, name);
if (name_off < 0)
return name_off;
t->name_off = name_off;
t->info = btf_type_info(BTF_KIND_FLOAT, 0, 0);
t->size = byte_sz;
return btf_commit_type(btf, sz);
}
/* it's completely legal to append BTF types with type IDs pointing forward to
* types that haven't been appended yet, so we only make sure that id looks
* sane, we can't guarantee that ID will always be valid
@@ -3626,6 +3671,7 @@ static int btf_dedup_prep(struct btf_dedup *d)
case BTF_KIND_FWD:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_FLOAT:
h = btf_hash_common(t);
break;
case BTF_KIND_INT:
@@ -3722,6 +3768,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
break;
case BTF_KIND_FWD:
case BTF_KIND_FLOAT:
h = btf_hash_common(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
@@ -3983,6 +4030,7 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
return btf_compat_enum(cand_type, canon_type);
case BTF_KIND_FWD:
case BTF_KIND_FLOAT:
return btf_equal_common(cand_type, canon_type);
case BTF_KIND_CONST:
@@ -4479,6 +4527,7 @@ static int btf_dedup_remap_type(struct btf_dedup *d, __u32 type_id)
switch (btf_kind(t)) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
case BTF_KIND_FLOAT:
break;
case BTF_KIND_FWD: