[PATCH 5.10 154/236] selftests/bpf: Fix test_core_autosize on big-endian machines

Greg Kroah-Hartman
2021-09-13T13:44:56Z

From: Ilya Leoshkevich <iii@linux.ibm.com>

[ Upstream commit d164dd9a5c08c16a883b3de97d13948c7be7fa4d ]

The "probed" part of test_core_autosize copies an integer using
bpf_core_read() into an integer of a potentially different size.
On big-endian machines a destination offset is required for this to
produce a sensible result.

Fixes: 888d83b961f6 ("selftests/bpf: Validate libbpf's auto-sizing of LD/ST/STX instructions")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210812224814.187460-1-iii@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../selftests/bpf/progs/test_core_autosize.c | 20 ++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/test_core_autosize.c b/tools/testing/selftests/bpf/progs/test_core_autosize.c
index 44f5aa2e8956..9a7829c5e4a7 100644
--- a/tools/testing/selftests/bpf/progs/test_core_autosize.c
+++ b/tools/testing/selftests/bpf/progs/test_core_autosize.c
@@ -125,6 +125,16 @@ int handle_downsize(void *ctx)
return 0;
}

+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define bpf_core_read_int bpf_core_read
+#else
+#define bpf_core_read_int(dst, sz, src) ({ \
+ /* Prevent "subtraction from stack pointer prohibited" */ \
+ volatile long __off = sizeof(*dst) - (sz); \
+ bpf_core_read((char *)(dst) + __off, sz, src); \
+})
+#endif
+
SEC("raw_tp/sys_enter")
int handle_probed(void *ctx)
{
@@ -132,23 +142,23 @@ int handle_probed(void *ctx)
__u64 tmp;

tmp = 0;
- bpf_core_read(&tmp, bpf_core_field_size(in->ptr), &in->ptr);
+ bpf_core_read_int(&tmp, bpf_core_field_size(in->ptr), &in->ptr);
ptr_probed = tmp;

tmp = 0;
- bpf_core_read(&tmp, bpf_core_field_size(in->val1), &in->val1);
+ bpf_core_read_int(&tmp, bpf_core_field_size(in->val1), &in->val1);
val1_probed = tmp;

tmp = 0;
- bpf_core_read(&tmp, bpf_core_field_size(in->val2), &in->val2);
+ bpf_core_read_int(&tmp, bpf_core_field_size(in->val2), &in->val2);
val2_probed = tmp;

tmp = 0;
- bpf_core_read(&tmp, bpf_core_field_size(in->val3), &in->val3);
+ bpf_core_read_int(&tmp, bpf_core_field_size(in->val3), &in->val3);
val3_probed = tmp;

tmp = 0;
- bpf_core_read(&tmp, bpf_core_field_size(in->val4), &in->val4);
+ bpf_core_read_int(&tmp, bpf_core_field_size(in->val4), &in->val4);
val4_probed = tmp;

return 0;
--
2.30.2