selftests/bpf: add test for LDX/STX/ST relocations over array field

Add a simple repro for the issue of miscalculating LDX/STX/ST CO-RE
relocation size adjustment when the CO-RE relocation target type is an
ARRAY.

We need to make sure that compiler generates LDX/STX/ST instruction with
CO-RE relocation against entire ARRAY type, not ARRAY's element. With
the code pattern in selftest, we get this:

      59:       61 71 00 00 00 00 00 00 w1 = *(u32 *)(r7 + 0x0)
                00000000000001d8:  CO-RE <byte_off> [5] struct core_reloc_arrays::a (0:0)

Where offset of `int a[5]` is embedded (through CO-RE relocation) into memory
load instruction itself.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250207014809.1573841-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index e10ea92c3fe224fc4c7b60c7108e890a524b469a..08963c82f30ba70270e8253353bd058f0ed1ab26 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -85,11 +85,11 @@ static int duration = 0;
 #define NESTING_ERR_CASE(name) {                                       \
        NESTING_CASE_COMMON(name),                                      \
        .fails = true,                                                  \
-       .run_btfgen_fails = true,                                                       \
+       .run_btfgen_fails = true,                                       \
 }
 
 #define ARRAYS_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) {     \
-       .a = { [2] = 1 },                                               \
+       .a = { [2] = 1, [3] = 11 },                                     \
        .b = { [1] = { [2] = { [3] = 2 } } },                           \
        .c = { [1] = { .c =  3 } },                                     \
        .d = { [0] = { [0] = { .d = 4 } } },                            \
@@ -108,6 +108,7 @@ static int duration = 0;
        .input_len = sizeof(struct core_reloc_##name),                  \
        .output = STRUCT_TO_CHAR_PTR(core_reloc_arrays_output) {        \
                .a2   = 1,                                              \
+               .a3   = 12,                                             \
                .b123 = 2,                                              \
                .c1c  = 3,                                              \
                .d00d = 4,                                              \
@@ -602,6 +603,7 @@ static const struct core_reloc_test_case test_cases[] = {
        ARRAYS_ERR_CASE(arrays___err_non_array),
        ARRAYS_ERR_CASE(arrays___err_wrong_val_type),
        ARRAYS_ERR_CASE(arrays___err_bad_zero_sz_arr),
+       ARRAYS_ERR_CASE(arrays___err_bad_signed_arr_elem_sz),
 
        /* enum/ptr/int handling scenarios */
        PRIMITIVES_CASE(primitives),

diff --git a/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_signed_arr_elem_sz.c b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_signed_arr_elem_sz.c
new file mode 100644 (file)
index 0000000..21a5604
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_signed_arr_elem_sz.c
@@ -0,0 +1,3 @@
+#include "core_reloc_types.h"
+
+void f(struct core_reloc_arrays___err_bad_signed_arr_elem_sz x) {}

diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index fd8e1b4c67620fd84e3d67494b3850577d283d32..5760ae015e096d639fd33cfc3d9f4982847858a0 100644 (file)
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -347,6 +347,7 @@ struct core_reloc_nesting___err_too_deep {
  */
 struct core_reloc_arrays_output {
        int a2;
+       int a3;
        char b123;
        int c1c;
        int d00d;
@@ -455,6 +456,15 @@ struct core_reloc_arrays___err_bad_zero_sz_arr {
        struct core_reloc_arrays_substruct d[1][2];
 };
 
+struct core_reloc_arrays___err_bad_signed_arr_elem_sz {
+       /* int -> short (signed!): not supported case */
+       short a[5];
+       char b[2][3][4];
+       struct core_reloc_arrays_substruct c[3];
+       struct core_reloc_arrays_substruct d[1][2];
+       struct core_reloc_arrays_substruct f[][2];
+};
+
 /*
  * PRIMITIVES
  */

diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c b/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
index 51b3f79df5235708220e66b9b926be8c714e3c32..448403634eeabc22fa6846dd1d16b47b37b8d4cf 100644 (file)
--- a/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
@@ -15,6 +15,7 @@ struct {
 
 struct core_reloc_arrays_output {
        int a2;
+       int a3;
        char b123;
        int c1c;
        int d00d;
@@ -41,6 +42,7 @@ int test_core_arrays(void *ctx)
 {
        struct core_reloc_arrays *in = (void *)&data.in;
        struct core_reloc_arrays_output *out = (void *)&data.out;
+       int *a;
 
        if (CORE_READ(&out->a2, &in->a[2]))
                return 1;
@@ -53,6 +55,9 @@ int test_core_arrays(void *ctx)
        if (CORE_READ(&out->f01c, &in->f[0][1].c))
                return 1;
 
+       a = __builtin_preserve_access_index(({ in->a; }));
+       out->a3 = a[0] + a[1] + a[2] + a[3];
+
        return 0;
 }