From 53f8dd434b6fe666b1c4e0be80a8727e8fa9839f Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 27 Nov 2019 12:06:50 -0800 Subject: libbpf: Fix global variable relocation Similarly to a0d7da26ce86 ("libbpf: Fix call relocation offset calculation bug"), relocations against global variables need to take into account referenced symbol's st_value, which holds offset into a corresponding data section (and, subsequently, offset into internal backing map). For static variables this offset is always zero and data offset is completely described by respective instruction's imm field. Convert a bunch of selftests to global variables. Previously they were relying on `static volatile` trick to ensure Clang doesn't inline static variables, which with global variables is not necessary anymore. Fixes: 393cdfbee809 ("libbpf: Support initialized global variables") Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20191127200651.1381348-1-andriin@fb.com --- tools/lib/bpf/libbpf.c | 43 +++++++++++++++++++------------------------ 1 file changed, 19 insertions(+), 24 deletions(-) (limited to 'tools/lib/bpf/libbpf.c') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index b20f82e58989..bae692831e14 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -171,10 +171,8 @@ struct bpf_program { RELO_DATA, } type; int insn_idx; - union { - int map_idx; - int text_off; - }; + int map_idx; + int sym_off; } *reloc_desc; int nr_reloc; int log_level; @@ -1824,7 +1822,7 @@ static int bpf_program__record_reloc(struct bpf_program *prog, } reloc_desc->type = RELO_CALL; reloc_desc->insn_idx = insn_idx; - reloc_desc->text_off = sym->st_value / 8; + reloc_desc->sym_off = sym->st_value; obj->has_pseudo_calls = true; return 0; } @@ -1868,6 +1866,7 @@ static int bpf_program__record_reloc(struct bpf_program *prog, reloc_desc->type = RELO_LD64; reloc_desc->insn_idx = insn_idx; reloc_desc->map_idx = map_idx; + reloc_desc->sym_off = 0; /* sym->st_value determines map_idx */ return 0; } @@ -1899,6 +1898,7 @@ static int bpf_program__record_reloc(struct bpf_program *prog, reloc_desc->type = RELO_DATA; reloc_desc->insn_idx = insn_idx; reloc_desc->map_idx = map_idx; + reloc_desc->sym_off = sym->st_value; return 0; } @@ -3563,8 +3563,8 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, return -LIBBPF_ERRNO__RELOC; if (prog->idx == obj->efile.text_shndx) { - pr_warn("relo in .text insn %d into off %d\n", - relo->insn_idx, relo->text_off); + pr_warn("relo in .text insn %d into off %d (insn #%d)\n", + relo->insn_idx, relo->sym_off, relo->sym_off / 8); return -LIBBPF_ERRNO__RELOC; } @@ -3599,7 +3599,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, prog->section_name); } insn = &prog->insns[relo->insn_idx]; - insn->imm += relo->text_off + prog->main_prog_cnt - relo->insn_idx; + insn->imm += relo->sym_off / 8 + prog->main_prog_cnt - relo->insn_idx; return 0; } @@ -3622,31 +3622,26 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) return 0; for (i = 0; i < prog->nr_reloc; i++) { - if (prog->reloc_desc[i].type == RELO_LD64 || - prog->reloc_desc[i].type == RELO_DATA) { - bool relo_data = prog->reloc_desc[i].type == RELO_DATA; - struct bpf_insn *insns = prog->insns; - int insn_idx, map_idx; + struct reloc_desc *relo = &prog->reloc_desc[i]; - insn_idx = prog->reloc_desc[i].insn_idx; - map_idx = prog->reloc_desc[i].map_idx; + if (relo->type == RELO_LD64 || relo->type == RELO_DATA) { + struct bpf_insn *insn = &prog->insns[relo->insn_idx]; - if (insn_idx + 1 >= (int)prog->insns_cnt) { + if (relo->insn_idx + 1 >= (int)prog->insns_cnt) { pr_warn("relocation out of range: '%s'\n", prog->section_name); return -LIBBPF_ERRNO__RELOC; } - if (!relo_data) { - insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD; + if (relo->type != RELO_DATA) { + insn[0].src_reg = BPF_PSEUDO_MAP_FD; } else { - insns[insn_idx].src_reg = BPF_PSEUDO_MAP_VALUE; - insns[insn_idx + 1].imm = insns[insn_idx].imm; + insn[0].src_reg = BPF_PSEUDO_MAP_VALUE; + insn[1].imm = insn[0].imm + relo->sym_off; } - insns[insn_idx].imm = obj->maps[map_idx].fd; - } else if (prog->reloc_desc[i].type == RELO_CALL) { - err = bpf_program__reloc_text(prog, obj, - &prog->reloc_desc[i]); + insn[0].imm = obj->maps[relo->map_idx].fd; + } else if (relo->type == RELO_CALL) { + err = bpf_program__reloc_text(prog, obj, relo); if (err) return err; } -- cgit v1.2.3-59-g8ed1b