On 1/2/24 11:05 PM, Ilya Leoshkevich wrote:
On Tue, 2024-01-02 at 16:41 -0800, Yonghong Song wrote:
On 1/2/24 11:30 AM, Ilya Leoshkevich wrote:
Testing long jumps requires having >32k instructions. That many
instructions require the verifier log buffer of 2 megabytes.
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
---
tools/testing/selftests/bpf/test_loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/test_loader.c
b/tools/testing/selftests/bpf/test_loader.c
index 37ffa57f28a1..b0bfcc8d4638 100644
--- a/tools/testing/selftests/bpf/test_loader.c
+++ b/tools/testing/selftests/bpf/test_loader.c
@@ -12,7 +12,7 @@
#define str_has_pfx(str, pfx) \
(strncmp(str, pfx, __builtin_constant_p(pfx) ? sizeof(pfx)
- 1 : strlen(pfx)) == 0)
-#define TEST_LOADER_LOG_BUF_SZ 1048576
+#define TEST_LOADER_LOG_BUF_SZ 2097152
I think this patch is not necessary.
If the log buffer size is not enough, the kernel
verifier will wrap around and overwrite some initial states,
but all later states are still preserved. In my opinion,
there is really no need to increase the buffer size in this case,
esp. it is a verification success case.
What I observed in this case was that bpf_check() still returned
-ENOSPC and failed the prog load. IIUC you are referring to the
functionality introduced by the following commit:
commit 1216640938035e63bdbd32438e91c9bcc1fd8ee1
Author: Andrii Nakryiko <andrii@xxxxxxxxxx>
Date: Thu Apr 6 16:41:49 2023 -0700
bpf: Switch BPF verifier log to be a rotating log by default
The commit message says, among other things:
The only user-visible change is which portion of verifier log user
ends up seeing *if buffer is too small*.
So if we don't increase the log size, we would still have to deal with
-ENOSPC. An alternative would be to reallocate the log buffer and try
again. But I thought that for the test code we better keep it as simple
as possible.
Okay, thanks for the explanation. I applied the patch set to
my local env and indeed, with this patch, I can see libbpf returns
an error. So as you suggested, let us increase the buffer size to
avoid extra handling in test_progs. So
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
#define TEST_TAG_EXPECT_FAILURE "comment:test_expect_failure"
#define TEST_TAG_EXPECT_SUCCESS "comment:test_expect_success"
