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

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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>
This commit is contained in:
Andrii Nakryiko 2025-02-06 17:48:09 -08:00 committed by Alexei Starovoitov
parent 06096d19ee
commit 4eb93fea59
4 changed files with 22 additions and 2 deletions
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6
tools/testing/selftests/bpf/prog_tests/core_reloc.c
View File

@ -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),

3
tools/testing/selftests/bpf/progs/btf__core_reloc_arrays___err_bad_signed_arr_elem_sz.c Normal file
View File

@ -0,0 +1,3 @@
#include "core_reloc_types.h"
void f(struct core_reloc_arrays___err_bad_signed_arr_elem_sz x) {}

10
tools/testing/selftests/bpf/progs/core_reloc_types.h
View File

@ -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
*/

5
tools/testing/selftests/bpf/progs/test_core_reloc_arrays.c
View File

@ -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;
}