From 53f8dd434b6fe666b1c4e0be80a8727e8fa9839f Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 27 Nov 2019 12:06:50 -0800 Subject: [PATCH] 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 ++++++++----------- .../testing/selftests/bpf/progs/fentry_test.c | 12 +++--- .../selftests/bpf/progs/fexit_bpf2bpf.c | 6 +-- .../testing/selftests/bpf/progs/fexit_test.c | 12 +++--- tools/testing/selftests/bpf/progs/test_mmap.c | 4 +- 5 files changed, 36 insertions(+), 41 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; } diff --git a/tools/testing/selftests/bpf/progs/fentry_test.c b/tools/testing/selftests/bpf/progs/fentry_test.c index d2af9f039df5..615f7c6bca77 100644 --- a/tools/testing/selftests/bpf/progs/fentry_test.c +++ b/tools/testing/selftests/bpf/progs/fentry_test.c @@ -6,28 +6,28 @@ char _license[] SEC("license") = "GPL"; -static volatile __u64 test1_result; +__u64 test1_result = 0; BPF_TRACE_1("fentry/bpf_fentry_test1", test1, int, a) { test1_result = a == 1; return 0; } -static volatile __u64 test2_result; +__u64 test2_result = 0; BPF_TRACE_2("fentry/bpf_fentry_test2", test2, int, a, __u64, b) { test2_result = a == 2 && b == 3; return 0; } -static volatile __u64 test3_result; +__u64 test3_result = 0; BPF_TRACE_3("fentry/bpf_fentry_test3", test3, char, a, int, b, __u64, c) { test3_result = a == 4 && b == 5 && c == 6; return 0; } -static volatile __u64 test4_result; +__u64 test4_result = 0; BPF_TRACE_4("fentry/bpf_fentry_test4", test4, void *, a, char, b, int, c, __u64, d) { @@ -35,7 +35,7 @@ BPF_TRACE_4("fentry/bpf_fentry_test4", test4, return 0; } -static volatile __u64 test5_result; +__u64 test5_result = 0; BPF_TRACE_5("fentry/bpf_fentry_test5", test5, __u64, a, void *, b, short, c, int, d, __u64, e) { @@ -44,7 +44,7 @@ BPF_TRACE_5("fentry/bpf_fentry_test5", test5, return 0; } -static volatile __u64 test6_result; +__u64 test6_result = 0; BPF_TRACE_6("fentry/bpf_fentry_test6", test6, __u64, a, void *, b, short, c, int, d, void *, e, __u64, f) { diff --git a/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c index 525d47d7b589..2d211ee98a1c 100644 --- a/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c +++ b/tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c @@ -8,7 +8,7 @@ struct sk_buff { unsigned int len; }; -static volatile __u64 test_result; +__u64 test_result = 0; BPF_TRACE_2("fexit/test_pkt_access", test_main, struct sk_buff *, skb, int, ret) { @@ -23,7 +23,7 @@ BPF_TRACE_2("fexit/test_pkt_access", test_main, return 0; } -static volatile __u64 test_result_subprog1; +__u64 test_result_subprog1 = 0; BPF_TRACE_2("fexit/test_pkt_access_subprog1", test_subprog1, struct sk_buff *, skb, int, ret) { @@ -56,7 +56,7 @@ struct args_subprog2 { __u64 args[5]; __u64 ret; }; -static volatile __u64 test_result_subprog2; +__u64 test_result_subprog2 = 0; SEC("fexit/test_pkt_access_subprog2") int test_subprog2(struct args_subprog2 *ctx) { diff --git a/tools/testing/selftests/bpf/progs/fexit_test.c b/tools/testing/selftests/bpf/progs/fexit_test.c index 2487e98edb34..86db0d60fb6e 100644 --- a/tools/testing/selftests/bpf/progs/fexit_test.c +++ b/tools/testing/selftests/bpf/progs/fexit_test.c @@ -6,28 +6,28 @@ char _license[] SEC("license") = "GPL"; -static volatile __u64 test1_result; +__u64 test1_result = 0; BPF_TRACE_2("fexit/bpf_fentry_test1", test1, int, a, int, ret) { test1_result = a == 1 && ret == 2; return 0; } -static volatile __u64 test2_result; +__u64 test2_result = 0; BPF_TRACE_3("fexit/bpf_fentry_test2", test2, int, a, __u64, b, int, ret) { test2_result = a == 2 && b == 3 && ret == 5; return 0; } -static volatile __u64 test3_result; +__u64 test3_result = 0; BPF_TRACE_4("fexit/bpf_fentry_test3", test3, char, a, int, b, __u64, c, int, ret) { test3_result = a == 4 && b == 5 && c == 6 && ret == 15; return 0; } -static volatile __u64 test4_result; +__u64 test4_result = 0; BPF_TRACE_5("fexit/bpf_fentry_test4", test4, void *, a, char, b, int, c, __u64, d, int, ret) { @@ -37,7 +37,7 @@ BPF_TRACE_5("fexit/bpf_fentry_test4", test4, return 0; } -static volatile __u64 test5_result; +__u64 test5_result = 0; BPF_TRACE_6("fexit/bpf_fentry_test5", test5, __u64, a, void *, b, short, c, int, d, __u64, e, int, ret) { @@ -46,7 +46,7 @@ BPF_TRACE_6("fexit/bpf_fentry_test5", test5, return 0; } -static volatile __u64 test6_result; +__u64 test6_result = 0; BPF_TRACE_7("fexit/bpf_fentry_test6", test6, __u64, a, void *, b, short, c, int, d, void *, e, __u64, f, int, ret) diff --git a/tools/testing/selftests/bpf/progs/test_mmap.c b/tools/testing/selftests/bpf/progs/test_mmap.c index 0d2ec9fbcf61..e808791b7047 100644 --- a/tools/testing/selftests/bpf/progs/test_mmap.c +++ b/tools/testing/selftests/bpf/progs/test_mmap.c @@ -15,8 +15,8 @@ struct { __type(value, __u64); } data_map SEC(".maps"); -static volatile __u64 in_val; -static volatile __u64 out_val; +__u64 in_val = 0; +__u64 out_val = 0; SEC("raw_tracepoint/sys_enter") int test_mmap(void *ctx) -- 2.30.2