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

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b20f82e..bae6928 100644 (file)
--- 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 d2af9f0..615f7c6 100644 (file)
--- 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 525d47d..2d211ee 100644 (file)
--- 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 2487e98..86db0d6 100644 (file)
--- 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 0d2ec9f..e808791 100644 (file)
--- 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)