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authorAndrii Nakryiko <andriin@fb.com>2019-11-27 21:06:50 +0100
committerAlexei Starovoitov <ast@kernel.org>2019-11-28 01:34:21 +0100
commit53f8dd434b6fe666b1c4e0be80a8727e8fa9839f (patch)
treebe37020c2c607328241889de5890eb1ed460a2d7 /tools/lib
parentlibbpf: Fix Makefile' libbpf symbol mismatch diagnostic (diff)
downloadlinux-53f8dd434b6fe666b1c4e0be80a8727e8fa9839f.tar.xz
linux-53f8dd434b6fe666b1c4e0be80a8727e8fa9839f.zip
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 <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20191127200651.1381348-1-andriin@fb.com
Diffstat (limited to 'tools/lib')
-rw-r--r--tools/lib/bpf/libbpf.c43
1 files changed, 19 insertions, 24 deletions
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;
}