Commit 15728ad3 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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libbpf: Fix BTF-defined map-in-map initialization on 32-bit host arches 



Libbpf built in 32-bit mode should be careful about not conflating 64-bit BPF
pointers in BPF ELF file and host architecture pointers. This patch fixes
issue of incorrect initializating of map-in-map inner map slots due to such
difference.

Fixes: 646f02ff ("libbpf: Add BTF-defined map-in-map support")
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200813204945.1020225-4-andriin@fb.com
parent 9028bbcc

tools/lib/bpf/libbpf.c

+10 −6
Original line number Diff line number Diff line
@@ -5195,7 +5195,8 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj, 
static int bpf_object__collect_map_relos(struct bpf_object *obj,

					 GElf_Shdr *shdr, Elf_Data *data)

{

	int i, j, nrels, new_sz, ptr_sz = sizeof(void *);

	const int bpf_ptr_sz = 8, host_ptr_sz = sizeof(void *);

	int i, j, nrels, new_sz;

	const struct btf_var_secinfo *vi = NULL;

	const struct btf_type *sec, *var, *def;

	const struct btf_member *member;
@@ -5244,7 +5245,7 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 


			vi = btf_var_secinfos(sec) + map->btf_var_idx;

			if (vi->offset <= rel.r_offset &&

			    rel.r_offset + sizeof(void *) <= vi->offset + vi->size)

			    rel.r_offset + bpf_ptr_sz <= vi->offset + vi->size)

				break;

		}

		if (j == obj->nr_maps) {
@@ -5280,17 +5281,20 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 
			return -EINVAL;



		moff = rel.r_offset - vi->offset - moff;

		if (moff % ptr_sz)

		/* here we use BPF pointer size, which is always 64 bit, as we

		 * are parsing ELF that was built for BPF target

		 */

		if (moff % bpf_ptr_sz)

			return -EINVAL;

		moff /= ptr_sz;

		moff /= bpf_ptr_sz;

		if (moff >= map->init_slots_sz) {

			new_sz = moff + 1;

			tmp = realloc(map->init_slots, new_sz * ptr_sz);

			tmp = realloc(map->init_slots, new_sz * host_ptr_sz);

			if (!tmp)

				return -ENOMEM;

			map->init_slots = tmp;

			memset(map->init_slots + map->init_slots_sz, 0,

			       (new_sz - map->init_slots_sz) * ptr_sz);

			       (new_sz - map->init_slots_sz) * host_ptr_sz);

			map->init_slots_sz = new_sz;

		}

		map->init_slots[moff] = targ_map;