Yonghong Song wrote: > > 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> LGTM. Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
