| Message ID | 20230428222754.183432-2-inwardvessel@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | libbpf: capability for resizing datasec maps | expand |
On 04/28, JP Kobryn wrote: > This patch updates bpf_map__set_value_size() so that if the given map is a > datasec, it will attempt to resize it. If the following criteria is met, > the resizing can be performed: > - BTF info is present > - the map is a datasec > - the datasec contains a single variable > - the single variable is an array > > The new map_datasec_resize() function is used to perform the resizing > of the associated memory mapped region and adjust BTF so that the original > array variable points to a new BTF array that is sized to cover the > requested size. The new array size will be rounded up to a multiple of > the element size. > > Signed-off-by: JP Kobryn <inwardvessel@gmail.com> > --- > tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 138 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 1cbacf9e71f3..991649cacc10 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -9412,12 +9412,150 @@ __u32 bpf_map__value_size(const struct bpf_map *map) > return map->def.value_size; > } > > +static bool map_is_datasec(struct bpf_map *map) > +{ > + struct btf *btf; > + struct btf_type *map_type; > + > + btf = bpf_object__btf(map->obj); > + if (!btf) > + return false; > + > + map_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > + > + return btf_is_datasec(map_type); > +} > + > +static int map_datasec_resize(struct bpf_map *map, __u32 size) > +{ > + int err; > + struct btf *btf; > + struct btf_type *datasec_type, *var_type, *resolved_type, *array_element_type; > + struct btf_var_secinfo *var; > + struct btf_array *array; > + __u32 resolved_id, new_array_id; > + __u32 rounded_sz; > + __u32 nr_elements; > + __u32 old_value_sz = map->def.value_size; > + size_t old_mmap_sz, new_mmap_sz; > + > + /* btf is required and datasec map must be memory mapped */ > + btf = bpf_object__btf(map->obj); > + if (!btf) { > + pr_warn("cannot resize datasec map '%s' while btf info is not present\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > + if (!btf_is_datasec(datasec_type)) { > + pr_warn("attempted to resize datasec map '%s' but map is not a datasec\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + if (!map->mmaped) { > + pr_warn("cannot resize datasec map '%s' while map is unexpectedly not memory mapped\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* datasec must only have a single variable */ > + if (btf_vlen(datasec_type) != 1) { > + pr_warn("cannot resize datasec map '%s' that does not consist of a single var\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* the single variable has to be an array */ > + var = btf_var_secinfos(datasec_type); > + resolved_id = btf__resolve_type(btf, var->type); > + resolved_type = btf_type_by_id(btf, resolved_id); > + if (!btf_is_array(resolved_type)) { > + pr_warn("cannot resize datasec map '%s' whose single var is not an array\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* create a new array based on the existing array but with new length, > + * rounding up the requested size for alignment > + */ > + array = btf_array(resolved_type); > + array_element_type = btf_type_by_id(btf, array->type); > + rounded_sz = roundup(size, array_element_type->size); > + nr_elements = rounded_sz / array_element_type->size; > + new_array_id = btf__add_array(btf, array->index_type, array->type, > + nr_elements); > + if (new_array_id < 0) { > + pr_warn("failed to resize datasec map '%s' due to failure in creating new array\n", > + bpf_map__name(map)); > + err = new_array_id; > + > + goto fail_array; > + } > + > + /* adding a new btf type invalidates existing pointers to btf objects. > + * refresh pointers before proceeding > + */ > + datasec_type = btf_type_by_id(btf, map->btf_value_type_id); > + var = btf_var_secinfos(datasec_type); > + var_type = btf_type_by_id(btf, var->type); > + > + /* remap the associated memory */ > + old_value_sz = map->def.value_size; > + old_mmap_sz = bpf_map_mmap_sz(map); > + map->def.value_size = rounded_sz; > + new_mmap_sz = bpf_map_mmap_sz(map); > + > + if (munmap(map->mmaped, old_mmap_sz)) { > + err = -errno; > + pr_warn("failed to resize datasec map '%s' due to failure in munmap(), err:%d\n", > + bpf_map__name(map), err); > + > + goto fail_mmap; > + } > + > + map->mmaped = mmap(NULL, new_mmap_sz, PROT_READ | PROT_WRITE, > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); I'm probably missing something, but how does it work? This just mmaps new memory which the user-space side will see. What about the BPF side? I'm also assuming (maybe incorrectly?) that if the map is mmaped, it's already created in the kernel, so what's the point of the resizing?
On Fri, Apr 28, 2023 at 04:58:40PM -0700, Stanislav Fomichev wrote: > On 04/28, JP Kobryn wrote: > > This patch updates bpf_map__set_value_size() so that if the given map is a > > datasec, it will attempt to resize it. If the following criteria is met, > > the resizing can be performed: > > - BTF info is present > > - the map is a datasec > > - the datasec contains a single variable > > - the single variable is an array > > > > The new map_datasec_resize() function is used to perform the resizing > > of the associated memory mapped region and adjust BTF so that the original > > array variable points to a new BTF array that is sized to cover the > > requested size. The new array size will be rounded up to a multiple of > > the element size. > > > > Signed-off-by: JP Kobryn <inwardvessel@gmail.com> > > --- > > tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 138 insertions(+) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index 1cbacf9e71f3..991649cacc10 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -9412,12 +9412,150 @@ __u32 bpf_map__value_size(const struct bpf_map *map) > > return map->def.value_size; > > } > > > > +static bool map_is_datasec(struct bpf_map *map) > > +{ > > + struct btf *btf; > > + struct btf_type *map_type; > > + > > + btf = bpf_object__btf(map->obj); > > + if (!btf) > > + return false; > > + > > + map_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > > + > > + return btf_is_datasec(map_type); > > +} > > + > > +static int map_datasec_resize(struct bpf_map *map, __u32 size) > > +{ > > + int err; > > + struct btf *btf; > > + struct btf_type *datasec_type, *var_type, *resolved_type, *array_element_type; > > + struct btf_var_secinfo *var; > > + struct btf_array *array; > > + __u32 resolved_id, new_array_id; > > + __u32 rounded_sz; > > + __u32 nr_elements; > > + __u32 old_value_sz = map->def.value_size; > > + size_t old_mmap_sz, new_mmap_sz; > > + > > + /* btf is required and datasec map must be memory mapped */ > > + btf = bpf_object__btf(map->obj); > > + if (!btf) { > > + pr_warn("cannot resize datasec map '%s' while btf info is not present\n", > > + bpf_map__name(map)); > > + > > + return -EINVAL; > > + } > > + > > + datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > > + if (!btf_is_datasec(datasec_type)) { > > + pr_warn("attempted to resize datasec map '%s' but map is not a datasec\n", > > + bpf_map__name(map)); > > + > > + return -EINVAL; > > + } > > + > > + if (!map->mmaped) { > > + pr_warn("cannot resize datasec map '%s' while map is unexpectedly not memory mapped\n", > > + bpf_map__name(map)); > > + > > + return -EINVAL; > > + } > > + > > + /* datasec must only have a single variable */ > > + if (btf_vlen(datasec_type) != 1) { > > + pr_warn("cannot resize datasec map '%s' that does not consist of a single var\n", > > + bpf_map__name(map)); > > + > > + return -EINVAL; > > + } > > + > > + /* the single variable has to be an array */ > > + var = btf_var_secinfos(datasec_type); > > + resolved_id = btf__resolve_type(btf, var->type); > > + resolved_type = btf_type_by_id(btf, resolved_id); > > + if (!btf_is_array(resolved_type)) { > > + pr_warn("cannot resize datasec map '%s' whose single var is not an array\n", > > + bpf_map__name(map)); > > + > > + return -EINVAL; > > + } > > + > > + /* create a new array based on the existing array but with new length, > > + * rounding up the requested size for alignment > > + */ > > + array = btf_array(resolved_type); > > + array_element_type = btf_type_by_id(btf, array->type); > > + rounded_sz = roundup(size, array_element_type->size); > > + nr_elements = rounded_sz / array_element_type->size; > > + new_array_id = btf__add_array(btf, array->index_type, array->type, > > + nr_elements); > > + if (new_array_id < 0) { > > + pr_warn("failed to resize datasec map '%s' due to failure in creating new array\n", > > + bpf_map__name(map)); > > + err = new_array_id; > > + > > + goto fail_array; > > + } > > + > > + /* adding a new btf type invalidates existing pointers to btf objects. > > + * refresh pointers before proceeding > > + */ > > + datasec_type = btf_type_by_id(btf, map->btf_value_type_id); > > + var = btf_var_secinfos(datasec_type); > > + var_type = btf_type_by_id(btf, var->type); > > + > > + /* remap the associated memory */ > > + old_value_sz = map->def.value_size; > > + old_mmap_sz = bpf_map_mmap_sz(map); > > + map->def.value_size = rounded_sz; > > + new_mmap_sz = bpf_map_mmap_sz(map); > > + > > + if (munmap(map->mmaped, old_mmap_sz)) { > > + err = -errno; > > + pr_warn("failed to resize datasec map '%s' due to failure in munmap(), err:%d\n", > > + bpf_map__name(map), err); > > + > > + goto fail_mmap; > > + } > > + > > + map->mmaped = mmap(NULL, new_mmap_sz, PROT_READ | PROT_WRITE, > > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); > > I'm probably missing something, but how does it work? This just mmaps > new memory which the user-space side will see. What about the BPF side? > In general (not specific to this patch), all datasec maps are memory mapped with an initialization image. See bpf_object__load_skeleton() to see how this initial mapping is later associated with the actual bpf maps (file descriptors) kernel side. > I'm also assuming (maybe incorrectly?) that if the map is mmaped, it's > already created in the kernel, so what's the point of the resizing? This is still the initialization image being resized. This resizing happens before the map is associated kernel side. If the map has already been created on the bpf side, attempting to resize returns -EBUSY (not new in this patch). --
On 05/01, JP Kobryn wrote: > On Fri, Apr 28, 2023 at 04:58:40PM -0700, Stanislav Fomichev wrote: > > On 04/28, JP Kobryn wrote: > > > This patch updates bpf_map__set_value_size() so that if the given map is a > > > datasec, it will attempt to resize it. If the following criteria is met, > > > the resizing can be performed: > > > - BTF info is present > > > - the map is a datasec > > > - the datasec contains a single variable > > > - the single variable is an array > > > > > > The new map_datasec_resize() function is used to perform the resizing > > > of the associated memory mapped region and adjust BTF so that the original > > > array variable points to a new BTF array that is sized to cover the > > > requested size. The new array size will be rounded up to a multiple of > > > the element size. > > > > > > Signed-off-by: JP Kobryn <inwardvessel@gmail.com> > > > --- > > > tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 138 insertions(+) > > > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > > index 1cbacf9e71f3..991649cacc10 100644 > > > --- a/tools/lib/bpf/libbpf.c > > > +++ b/tools/lib/bpf/libbpf.c > > > @@ -9412,12 +9412,150 @@ __u32 bpf_map__value_size(const struct bpf_map *map) > > > return map->def.value_size; > > > } > > > > > > +static bool map_is_datasec(struct bpf_map *map) > > > +{ > > > + struct btf *btf; > > > + struct btf_type *map_type; > > > + > > > + btf = bpf_object__btf(map->obj); > > > + if (!btf) > > > + return false; > > > + > > > + map_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > > > + > > > + return btf_is_datasec(map_type); > > > +} > > > + > > > +static int map_datasec_resize(struct bpf_map *map, __u32 size) > > > +{ > > > + int err; > > > + struct btf *btf; > > > + struct btf_type *datasec_type, *var_type, *resolved_type, *array_element_type; > > > + struct btf_var_secinfo *var; > > > + struct btf_array *array; > > > + __u32 resolved_id, new_array_id; > > > + __u32 rounded_sz; > > > + __u32 nr_elements; > > > + __u32 old_value_sz = map->def.value_size; > > > + size_t old_mmap_sz, new_mmap_sz; > > > + > > > + /* btf is required and datasec map must be memory mapped */ > > > + btf = bpf_object__btf(map->obj); > > > + if (!btf) { > > > + pr_warn("cannot resize datasec map '%s' while btf info is not present\n", > > > + bpf_map__name(map)); > > > + > > > + return -EINVAL; > > > + } > > > + > > > + datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > > > + if (!btf_is_datasec(datasec_type)) { > > > + pr_warn("attempted to resize datasec map '%s' but map is not a datasec\n", > > > + bpf_map__name(map)); > > > + > > > + return -EINVAL; > > > + } > > > + > > > + if (!map->mmaped) { > > > + pr_warn("cannot resize datasec map '%s' while map is unexpectedly not memory mapped\n", > > > + bpf_map__name(map)); > > > + > > > + return -EINVAL; > > > + } > > > + > > > + /* datasec must only have a single variable */ > > > + if (btf_vlen(datasec_type) != 1) { > > > + pr_warn("cannot resize datasec map '%s' that does not consist of a single var\n", > > > + bpf_map__name(map)); > > > + > > > + return -EINVAL; > > > + } > > > + > > > + /* the single variable has to be an array */ > > > + var = btf_var_secinfos(datasec_type); > > > + resolved_id = btf__resolve_type(btf, var->type); > > > + resolved_type = btf_type_by_id(btf, resolved_id); > > > + if (!btf_is_array(resolved_type)) { > > > + pr_warn("cannot resize datasec map '%s' whose single var is not an array\n", > > > + bpf_map__name(map)); > > > + > > > + return -EINVAL; > > > + } > > > + > > > + /* create a new array based on the existing array but with new length, > > > + * rounding up the requested size for alignment > > > + */ > > > + array = btf_array(resolved_type); > > > + array_element_type = btf_type_by_id(btf, array->type); > > > + rounded_sz = roundup(size, array_element_type->size); > > > + nr_elements = rounded_sz / array_element_type->size; > > > + new_array_id = btf__add_array(btf, array->index_type, array->type, > > > + nr_elements); > > > + if (new_array_id < 0) { > > > + pr_warn("failed to resize datasec map '%s' due to failure in creating new array\n", > > > + bpf_map__name(map)); > > > + err = new_array_id; > > > + > > > + goto fail_array; > > > + } > > > + > > > + /* adding a new btf type invalidates existing pointers to btf objects. > > > + * refresh pointers before proceeding > > > + */ > > > + datasec_type = btf_type_by_id(btf, map->btf_value_type_id); > > > + var = btf_var_secinfos(datasec_type); > > > + var_type = btf_type_by_id(btf, var->type); > > > + > > > + /* remap the associated memory */ > > > + old_value_sz = map->def.value_size; > > > + old_mmap_sz = bpf_map_mmap_sz(map); > > > + map->def.value_size = rounded_sz; > > > + new_mmap_sz = bpf_map_mmap_sz(map); > > > + > > > + if (munmap(map->mmaped, old_mmap_sz)) { > > > + err = -errno; > > > + pr_warn("failed to resize datasec map '%s' due to failure in munmap(), err:%d\n", > > > + bpf_map__name(map), err); > > > + > > > + goto fail_mmap; > > > + } > > > + > > > + map->mmaped = mmap(NULL, new_mmap_sz, PROT_READ | PROT_WRITE, > > > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); > > > > I'm probably missing something, but how does it work? This just mmaps > > new memory which the user-space side will see. What about the BPF side? > > > In general (not specific to this patch), all datasec maps are > memory mapped with an initialization image. See > bpf_object__load_skeleton() to see how this initial mapping is later > associated with the actual bpf maps (file descriptors) kernel side. > > > I'm also assuming (maybe incorrectly?) that if the map is mmaped, it's > > already created in the kernel, so what's the point of the resizing? > > This is still the initialization image being resized. This resizing > happens before the map is associated kernel side. If the map has already > been created on the bpf side, attempting to resize returns -EBUSY (not > new in this patch). I see, makes sense now, thanks! Acked-by: Stanislav Fomichev <sdf@google.com>
On Fri, Apr 28, 2023 at 3:28 PM JP Kobryn <inwardvessel@gmail.com> wrote: > > This patch updates bpf_map__set_value_size() so that if the given map is a > datasec, it will attempt to resize it. If the following criteria is met, > the resizing can be performed: > - BTF info is present > - the map is a datasec > - the datasec contains a single variable > - the single variable is an array > I think it's too restrictive to require all these conditions just to be able to resize the map. I'd prefer if libbpf allowed user to resize a map in any case, but if there is BTF information, libbpf will helpfully adjust it as necessary. > The new map_datasec_resize() function is used to perform the resizing > of the associated memory mapped region and adjust BTF so that the original > array variable points to a new BTF array that is sized to cover the > requested size. The new array size will be rounded up to a multiple of > the element size. > > Signed-off-by: JP Kobryn <inwardvessel@gmail.com> > --- > tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 138 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 1cbacf9e71f3..991649cacc10 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -9412,12 +9412,150 @@ __u32 bpf_map__value_size(const struct bpf_map *map) > return map->def.value_size; > } > > +static bool map_is_datasec(struct bpf_map *map) > +{ > + struct btf *btf; > + struct btf_type *map_type; > + > + btf = bpf_object__btf(map->obj); > + if (!btf) > + return false; > + > + map_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > + > + return btf_is_datasec(map_type); > +} > + > +static int map_datasec_resize(struct bpf_map *map, __u32 size) > +{ > + int err; > + struct btf *btf; > + struct btf_type *datasec_type, *var_type, *resolved_type, *array_element_type; > + struct btf_var_secinfo *var; > + struct btf_array *array; > + __u32 resolved_id, new_array_id; > + __u32 rounded_sz; > + __u32 nr_elements; > + __u32 old_value_sz = map->def.value_size; > + size_t old_mmap_sz, new_mmap_sz; > + > + /* btf is required and datasec map must be memory mapped */ as I mentioned above, I'd structure logic to take advantage and adjust BTF, but not necessarily block the operation > + btf = bpf_object__btf(map->obj); > + if (!btf) { > + pr_warn("cannot resize datasec map '%s' while btf info is not present\n", > + bpf_map__name(map)); > + nit: let's not have unnecessary empty lines (here and below in many places) another nit: see other pr_warn()s when something happens with map, we have relatively consistent "map '%s': <message>" pattern, so let's follow it here for error messages > + return -EINVAL; > + } > + > + datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); > + if (!btf_is_datasec(datasec_type)) { > + pr_warn("attempted to resize datasec map '%s' but map is not a datasec\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + if (!map->mmaped) { > + pr_warn("cannot resize datasec map '%s' while map is unexpectedly not memory mapped\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* datasec must only have a single variable */ > + if (btf_vlen(datasec_type) != 1) { so I've been thinking about case like this: int my_var; int my_arr[1]; /* should scale to number of CPUs */ I don't see why we wouldn't allow to resize this to 4 + cpu_cnt * 4 size. I don't think it will complicate anything, we just take last member of DATASEC, it's offset + N * sizeof(array element) > + pr_warn("cannot resize datasec map '%s' that does not consist of a single var\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* the single variable has to be an array */ > + var = btf_var_secinfos(datasec_type); > + resolved_id = btf__resolve_type(btf, var->type); use skip_mods_and_typedefs to skip mods and typedefs? btf__resolve_type() does more than what you want here > + resolved_type = btf_type_by_id(btf, resolved_id); > + if (!btf_is_array(resolved_type)) { > + pr_warn("cannot resize datasec map '%s' whose single var is not an array\n", > + bpf_map__name(map)); > + > + return -EINVAL; > + } > + > + /* create a new array based on the existing array but with new length, > + * rounding up the requested size for alignment > + */ > + array = btf_array(resolved_type); > + array_element_type = btf_type_by_id(btf, array->type); > + rounded_sz = roundup(size, array_element_type->size); let's not do auto-rounding, user should know what they are doing, and if they get calculation wrong, better return explicit error than try to guess what user actually wanted > + nr_elements = rounded_sz / array_element_type->size; > + new_array_id = btf__add_array(btf, array->index_type, array->type, > + nr_elements); > + if (new_array_id < 0) { > + pr_warn("failed to resize datasec map '%s' due to failure in creating new array\n", > + bpf_map__name(map)); > + err = new_array_id; > + > + goto fail_array; > + } > + > + /* adding a new btf type invalidates existing pointers to btf objects. > + * refresh pointers before proceeding > + */ > + datasec_type = btf_type_by_id(btf, map->btf_value_type_id); > + var = btf_var_secinfos(datasec_type); > + var_type = btf_type_by_id(btf, var->type); > + > + /* remap the associated memory */ > + old_value_sz = map->def.value_size; > + old_mmap_sz = bpf_map_mmap_sz(map); > + map->def.value_size = rounded_sz; > + new_mmap_sz = bpf_map_mmap_sz(map); > + > + if (munmap(map->mmaped, old_mmap_sz)) { > + err = -errno; > + pr_warn("failed to resize datasec map '%s' due to failure in munmap(), err:%d\n", > + bpf_map__name(map), err); > + > + goto fail_mmap; > + } > + > + map->mmaped = mmap(NULL, new_mmap_sz, PROT_READ | PROT_WRITE, > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); > + if (map->mmaped == MAP_FAILED) { let's mmap new memory first, and only if that succeeds unmap old one? Plus, we need to preserve initial values that might have been set through BPF skeleton or bpf_map__set_initial_value() and please adjust selftest to validate that modified/non-zero initial values are preserved during resize; similar to how realloc() behaves > + err = -errno; > + map->mmaped = NULL; > + pr_warn("failed to resize datasec map '%s' due to failure in mmap(), err:%d\n", > + bpf_map__name(map), err); > + > + goto fail_mmap; > + } > + > + /* finally update btf info */ > + datasec_type->size = var->size = rounded_sz; > + var_type->type = new_array_id; > + > + return 0; > + > +fail_mmap: > + map->def.value_size = old_value_sz; > + > +fail_array: > + return err; > +} > + > int bpf_map__set_value_size(struct bpf_map *map, __u32 size) > { > if (map->fd >= 0) > return libbpf_err(-EBUSY); > + > + if (map_is_datasec(map)) so, this is not the best way to check this, see LIBBPF_MAP_BSS, LIBBPF_MAP_DATA, LIBBPF_MAP_RODATA and libbpf_type field in bpf_map but as I mentioned above, let's structure it such that map->def.value_size can always be updated, but libbpf tries to adjust BTF (we can emit warning if all the logical constraints are not satisfied; and then clearing btf_value_type_id and btf_value_key_id)? > + return map_datasec_resize(map, size); > + > map->def.value_size = size; > + > return 0; > + > } > > __u32 bpf_map__btf_key_type_id(const struct bpf_map *map) > -- > 2.40.0 >
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1cbacf9e71f3..991649cacc10 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9412,12 +9412,150 @@ __u32 bpf_map__value_size(const struct bpf_map *map) return map->def.value_size; } +static bool map_is_datasec(struct bpf_map *map) +{ + struct btf *btf; + struct btf_type *map_type; + + btf = bpf_object__btf(map->obj); + if (!btf) + return false; + + map_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); + + return btf_is_datasec(map_type); +} + +static int map_datasec_resize(struct bpf_map *map, __u32 size) +{ + int err; + struct btf *btf; + struct btf_type *datasec_type, *var_type, *resolved_type, *array_element_type; + struct btf_var_secinfo *var; + struct btf_array *array; + __u32 resolved_id, new_array_id; + __u32 rounded_sz; + __u32 nr_elements; + __u32 old_value_sz = map->def.value_size; + size_t old_mmap_sz, new_mmap_sz; + + /* btf is required and datasec map must be memory mapped */ + btf = bpf_object__btf(map->obj); + if (!btf) { + pr_warn("cannot resize datasec map '%s' while btf info is not present\n", + bpf_map__name(map)); + + return -EINVAL; + } + + datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map)); + if (!btf_is_datasec(datasec_type)) { + pr_warn("attempted to resize datasec map '%s' but map is not a datasec\n", + bpf_map__name(map)); + + return -EINVAL; + } + + if (!map->mmaped) { + pr_warn("cannot resize datasec map '%s' while map is unexpectedly not memory mapped\n", + bpf_map__name(map)); + + return -EINVAL; + } + + /* datasec must only have a single variable */ + if (btf_vlen(datasec_type) != 1) { + pr_warn("cannot resize datasec map '%s' that does not consist of a single var\n", + bpf_map__name(map)); + + return -EINVAL; + } + + /* the single variable has to be an array */ + var = btf_var_secinfos(datasec_type); + resolved_id = btf__resolve_type(btf, var->type); + resolved_type = btf_type_by_id(btf, resolved_id); + if (!btf_is_array(resolved_type)) { + pr_warn("cannot resize datasec map '%s' whose single var is not an array\n", + bpf_map__name(map)); + + return -EINVAL; + } + + /* create a new array based on the existing array but with new length, + * rounding up the requested size for alignment + */ + array = btf_array(resolved_type); + array_element_type = btf_type_by_id(btf, array->type); + rounded_sz = roundup(size, array_element_type->size); + nr_elements = rounded_sz / array_element_type->size; + new_array_id = btf__add_array(btf, array->index_type, array->type, + nr_elements); + if (new_array_id < 0) { + pr_warn("failed to resize datasec map '%s' due to failure in creating new array\n", + bpf_map__name(map)); + err = new_array_id; + + goto fail_array; + } + + /* adding a new btf type invalidates existing pointers to btf objects. + * refresh pointers before proceeding + */ + datasec_type = btf_type_by_id(btf, map->btf_value_type_id); + var = btf_var_secinfos(datasec_type); + var_type = btf_type_by_id(btf, var->type); + + /* remap the associated memory */ + old_value_sz = map->def.value_size; + old_mmap_sz = bpf_map_mmap_sz(map); + map->def.value_size = rounded_sz; + new_mmap_sz = bpf_map_mmap_sz(map); + + if (munmap(map->mmaped, old_mmap_sz)) { + err = -errno; + pr_warn("failed to resize datasec map '%s' due to failure in munmap(), err:%d\n", + bpf_map__name(map), err); + + goto fail_mmap; + } + + map->mmaped = mmap(NULL, new_mmap_sz, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if (map->mmaped == MAP_FAILED) { + err = -errno; + map->mmaped = NULL; + pr_warn("failed to resize datasec map '%s' due to failure in mmap(), err:%d\n", + bpf_map__name(map), err); + + goto fail_mmap; + } + + /* finally update btf info */ + datasec_type->size = var->size = rounded_sz; + var_type->type = new_array_id; + + return 0; + +fail_mmap: + map->def.value_size = old_value_sz; + +fail_array: + return err; +} + int bpf_map__set_value_size(struct bpf_map *map, __u32 size) { if (map->fd >= 0) return libbpf_err(-EBUSY); + + if (map_is_datasec(map)) + return map_datasec_resize(map, size); + map->def.value_size = size; + return 0; + } __u32 bpf_map__btf_key_type_id(const struct bpf_map *map)
This patch updates bpf_map__set_value_size() so that if the given map is a datasec, it will attempt to resize it. If the following criteria is met, the resizing can be performed: - BTF info is present - the map is a datasec - the datasec contains a single variable - the single variable is an array The new map_datasec_resize() function is used to perform the resizing of the associated memory mapped region and adjust BTF so that the original array variable points to a new BTF array that is sized to cover the requested size. The new array size will be rounded up to a multiple of the element size. Signed-off-by: JP Kobryn <inwardvessel@gmail.com> --- tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 138 insertions(+)