From: Kui-Feng Lee <sinquersw@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Kui-Feng Lee <kuifeng@meta.com>
Cc: bpf@vger.kernel.org, ast@kernel.org, martin.lau@linux.dev,
song@kernel.org, kernel-team@meta.com, andrii@kernel.org,
sdf@google.com
Subject: Re: [PATCH bpf-next v4 8/9] libbpf: Use .struct_ops.link section to indicate a struct_ops with a link.
Date: Tue, 7 Mar 2023 20:23:05 -0800 [thread overview]
Message-ID: <7425b219-4b47-c3f1-844d-61e27d03af03@gmail.com> (raw)
In-Reply-To: <CAEf4BzaopfY5azUh4yi=Bx3h7x9W9r=XCA1OeVrTFSK_X3s7UQ@mail.gmail.com>
On 3/7/23 17:07, Andrii Nakryiko wrote:
> On Tue, Mar 7, 2023 at 3:33 PM Kui-Feng Lee <kuifeng@meta.com> wrote:
>>
>> Flags a struct_ops is to back a bpf_link by putting it to the
>> ".struct_ops.link" section. Once it is flagged, the created
>> struct_ops can be used to create a bpf_link or update a bpf_link that
>> has been backed by another struct_ops.
>>
>> Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
>> ---
>> tools/lib/bpf/libbpf.c | 64 +++++++++++++++++++++++++++++++++---------
>> 1 file changed, 50 insertions(+), 14 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 247de39d136f..d66acd2fdbaa 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -467,6 +467,7 @@ struct bpf_struct_ops {
>> #define KCONFIG_SEC ".kconfig"
>> #define KSYMS_SEC ".ksyms"
>> #define STRUCT_OPS_SEC ".struct_ops"
>> +#define STRUCT_OPS_LINK_SEC ".struct_ops.link"
>>
>> enum libbpf_map_type {
>> LIBBPF_MAP_UNSPEC,
>> @@ -596,6 +597,7 @@ struct elf_state {
>> Elf64_Ehdr *ehdr;
>> Elf_Data *symbols;
>> Elf_Data *st_ops_data;
>> + Elf_Data *st_ops_link_data;
>> size_t shstrndx; /* section index for section name strings */
>> size_t strtabidx;
>> struct elf_sec_desc *secs;
>> @@ -605,6 +607,7 @@ struct elf_state {
>> int text_shndx;
>> int symbols_shndx;
>> int st_ops_shndx;
>> + int st_ops_link_shndx;
>> };
>>
>> struct usdt_manager;
>> @@ -1119,7 +1122,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
>> return 0;
>> }
>>
>> -static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> +static int bpf_object__init_struct_ops_maps_link(struct bpf_object *obj, bool link)
>
> let's shorten it and not use double underscores, as this is not a
> public bpf_object API, just "init_struct_ops_maps" probably is fine
>
>> {
>> const struct btf_type *type, *datasec;
>> const struct btf_var_secinfo *vsi;
>> @@ -1127,18 +1130,33 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> const char *tname, *var_name;
>> __s32 type_id, datasec_id;
>> const struct btf *btf;
>> + const char *sec_name;
>> struct bpf_map *map;
>> - __u32 i;
>> + __u32 i, map_flags;
>> + Elf_Data *data;
>> + int shndx;
>>
>> - if (obj->efile.st_ops_shndx == -1)
>> + if (link) {
>> + sec_name = STRUCT_OPS_LINK_SEC;
>> + shndx = obj->efile.st_ops_link_shndx;
>> + data = obj->efile.st_ops_link_data;
>> + map_flags = BPF_F_LINK;
>> + } else {
>> + sec_name = STRUCT_OPS_SEC;
>> + shndx = obj->efile.st_ops_shndx;
>> + data = obj->efile.st_ops_data;
>> + map_flags = 0;
>> + }
>
> let's pass these as function arguments instead
>
>> +
>> + if (shndx == -1)
>> return 0;
>>
>> btf = obj->btf;
>> - datasec_id = btf__find_by_name_kind(btf, STRUCT_OPS_SEC,
>> + datasec_id = btf__find_by_name_kind(btf, sec_name,
>> BTF_KIND_DATASEC);
>> if (datasec_id < 0) {
>> pr_warn("struct_ops init: DATASEC %s not found\n",
>> - STRUCT_OPS_SEC);
>> + sec_name);
>> return -EINVAL;
>> }
>>
>> @@ -1151,7 +1169,7 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> type_id = btf__resolve_type(obj->btf, vsi->type);
>> if (type_id < 0) {
>> pr_warn("struct_ops init: Cannot resolve var type_id %u in DATASEC %s\n",
>> - vsi->type, STRUCT_OPS_SEC);
>> + vsi->type, sec_name);
>> return -EINVAL;
>> }
>>
>> @@ -1170,7 +1188,7 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> if (IS_ERR(map))
>> return PTR_ERR(map);
>>
>> - map->sec_idx = obj->efile.st_ops_shndx;
>> + map->sec_idx = shndx;
>> map->sec_offset = vsi->offset;
>> map->name = strdup(var_name);
>> if (!map->name)
>> @@ -1180,6 +1198,7 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> map->def.key_size = sizeof(int);
>> map->def.value_size = type->size;
>> map->def.max_entries = 1;
>> + map->def.map_flags = map_flags;
>>
>> map->st_ops = calloc(1, sizeof(*map->st_ops));
>> if (!map->st_ops)
>> @@ -1192,14 +1211,14 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> if (!st_ops->data || !st_ops->progs || !st_ops->kern_func_off)
>> return -ENOMEM;
>>
>> - if (vsi->offset + type->size > obj->efile.st_ops_data->d_size) {
>> + if (vsi->offset + type->size > data->d_size) {
>> pr_warn("struct_ops init: var %s is beyond the end of DATASEC %s\n",
>> - var_name, STRUCT_OPS_SEC);
>> + var_name, sec_name);
>> return -EINVAL;
>> }
>>
>> memcpy(st_ops->data,
>> - obj->efile.st_ops_data->d_buf + vsi->offset,
>> + data->d_buf + vsi->offset,
>> type->size);
>> st_ops->tname = tname;
>> st_ops->type = type;
>> @@ -1212,6 +1231,15 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>> return 0;
>> }
>>
>> +static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
>
> let's name this bpf_object_init_struct_ops, no double underscores
>
>> +{
>> + int err;
>> +
>> + err = bpf_object__init_struct_ops_maps_link(obj, false);
>> + err = err ?: bpf_object__init_struct_ops_maps_link(obj, true);
>> + return err;
>> +}
>> +
>> static struct bpf_object *bpf_object__new(const char *path,
>> const void *obj_buf,
>> size_t obj_buf_sz,
>> @@ -1248,6 +1276,7 @@ static struct bpf_object *bpf_object__new(const char *path,
>> obj->efile.obj_buf_sz = obj_buf_sz;
>> obj->efile.btf_maps_shndx = -1;
>> obj->efile.st_ops_shndx = -1;
>> + obj->efile.st_ops_link_shndx = -1;
>> obj->kconfig_map_idx = -1;
>>
>> obj->kern_version = get_kernel_version();
>> @@ -1265,6 +1294,7 @@ static void bpf_object__elf_finish(struct bpf_object *obj)
>> obj->efile.elf = NULL;
>> obj->efile.symbols = NULL;
>> obj->efile.st_ops_data = NULL;
>> + obj->efile.st_ops_link_data = NULL;
>>
>> zfree(&obj->efile.secs);
>> obj->efile.sec_cnt = 0;
>> @@ -2753,12 +2783,13 @@ static bool libbpf_needs_btf(const struct bpf_object *obj)
>> {
>> return obj->efile.btf_maps_shndx >= 0 ||
>> obj->efile.st_ops_shndx >= 0 ||
>> + obj->efile.st_ops_link_shndx >= 0 ||
>> obj->nr_extern > 0;
>> }
>>
>> static bool kernel_needs_btf(const struct bpf_object *obj)
>> {
>> - return obj->efile.st_ops_shndx >= 0;
>> + return obj->efile.st_ops_shndx >= 0 || obj->efile.st_ops_link_shndx >= 0;
>> }
>>
>> static int bpf_object__init_btf(struct bpf_object *obj,
>> @@ -3451,6 +3482,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
>> } else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
>> obj->efile.st_ops_data = data;
>> obj->efile.st_ops_shndx = idx;
>> + } else if (strcmp(name, STRUCT_OPS_LINK_SEC) == 0) {
>> + obj->efile.st_ops_link_data = data;
>> + obj->efile.st_ops_link_shndx = idx;
>> } else {
>> pr_info("elf: skipping unrecognized data section(%d) %s\n",
>> idx, name);
>> @@ -3465,6 +3499,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
>> /* Only do relo for section with exec instructions */
>> if (!section_have_execinstr(obj, targ_sec_idx) &&
>> strcmp(name, ".rel" STRUCT_OPS_SEC) &&
>> + strcmp(name, ".rel" STRUCT_OPS_LINK_SEC) &&
>> strcmp(name, ".rel" MAPS_ELF_SEC)) {
>> pr_info("elf: skipping relo section(%d) %s for section(%d) %s\n",
>> idx, name, targ_sec_idx,
>> @@ -6611,7 +6646,7 @@ static int bpf_object__collect_relos(struct bpf_object *obj)
>> return -LIBBPF_ERRNO__INTERNAL;
>> }
>>
>> - if (idx == obj->efile.st_ops_shndx)
>> + if (idx == obj->efile.st_ops_shndx || idx == obj->efile.st_ops_link_shndx)
>> err = bpf_object__collect_st_ops_relos(obj, shdr, data);
>
> this function calls find_struct_ops_map_by_offset() which assumes we
> only have one struct_ops section. This won't work now, please double
> check all this, there should be no assumption about specific section
> index
Yes, I will check the section index of maps.
>
>> else if (idx == obj->efile.btf_maps_shndx)
>> err = bpf_object__collect_map_relos(obj, shdr, data);
>> @@ -8954,8 +8989,9 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
>> }
>>
>> /* struct_ops BPF prog can be re-used between multiple
>> - * .struct_ops as long as it's the same struct_ops struct
>> - * definition and the same function pointer field
>> + * .struct_ops & .struct_ops.link as long as it's the
>> + * same struct_ops struct definition and the same
>> + * function pointer field
>> */
>> if (prog->attach_btf_id != st_ops->type_id ||
>> prog->expected_attach_type != member_idx) {
>> --
>> 2.34.1
>>
next prev parent reply other threads:[~2023-03-08 4:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-07 23:32 [PATCH bpf-next v4 0/9] Transit between BPF TCP congestion controls Kui-Feng Lee
2023-03-07 23:32 ` [PATCH bpf-next v4 1/9] bpf: Retire the struct_ops map kvalue->refcnt Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 2/9] bpf: Create links for BPF struct_ops maps Kui-Feng Lee
2023-03-08 0:37 ` Andrii Nakryiko
2023-03-08 1:11 ` Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 3/9] net: Update an existing TCP congestion control algorithm Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 4/9] bpf: Validate kdata of a struct_ops before transiting to READY Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 5/9] libbpf: Create a bpf_link in bpf_map__attach_struct_ops() Kui-Feng Lee
2023-03-08 0:46 ` Andrii Nakryiko
2023-03-08 3:33 ` Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 6/9] bpf: Update the struct_ops of a bpf_link Kui-Feng Lee
2023-03-08 0:49 ` Andrii Nakryiko
2023-03-08 16:27 ` Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 7/9] libbpf: Update a bpf_link with another struct_ops Kui-Feng Lee
2023-03-08 0:53 ` Andrii Nakryiko
2023-03-08 1:45 ` Kui-Feng Lee
2023-03-07 23:33 ` [PATCH bpf-next v4 8/9] libbpf: Use .struct_ops.link section to indicate a struct_ops with a link Kui-Feng Lee
2023-03-08 1:07 ` Andrii Nakryiko
2023-03-08 4:23 ` Kui-Feng Lee [this message]
2023-03-07 23:33 ` [PATCH bpf-next v4 9/9] selftests/bpf: Test switching TCP Congestion Control algorithms Kui-Feng Lee
2023-03-08 1:10 ` Andrii Nakryiko
2023-03-08 15:58 ` Kui-Feng Lee
2023-03-08 17:18 ` Andrii Nakryiko
2023-03-08 18:10 ` Kui-Feng Lee
2023-03-08 18:43 ` Andrii Nakryiko
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