On 01/15, Song, Yoong Siang wrote:
> On Wednesday, January 15, 2025 10:57 PM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> >On 1/14/25 4:27 PM, Song Yoong Siang wrote:
> >[...]
> >> + /* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
> >> + char map[256] = {0};
> >> + char queues[256] = {0};
> >> +
> >> + for (i = 0; i < rxq; i++) {
> >> + char buf[8];
> >> +
> >> + snprintf(buf, sizeof(buf), "%d ", i);
> >> + strcat(map, buf);
> >> +
> >> + snprintf(buf, sizeof(buf), "1@%d ", i);
> >> + strcat(queues, buf);
> >> + }
> >> + run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio
> >num_tc %d map %s queues %s hw 0",
> >> + ifname, rxq, map, queues);
> >
> >Fyi, above triggers selftest build errors:
> >
> > xdp_hw_metadata.c: In function ‘main’:
> > xdp_hw_metadata.c:763:45: error: ‘%d’ directive output may be truncated
> >writing between 1 and 10 bytes into a region of size 8 [-Werror=format-
> >truncation=]
> > 763 | snprintf(buf, sizeof(buf), "%d ", i);
> > | ^~
> > TEST-OBJ [test_progs] arg_parsing.test.o
> > xdp_hw_metadata.c:763:44: note: directive argument in the range [0,
> >2147483646]
> > 763 | snprintf(buf, sizeof(buf), "%d ", i);
> > | ^~~~~
> > xdp_hw_metadata.c:763:17: note: ‘snprintf’ output between 3 and 12 bytes into
> >a destination of size 8
> > 763 | snprintf(buf, sizeof(buf), "%d ", i);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > xdp_hw_metadata.c:766:47: error: ‘%d’ directive output may be truncated
> >writing between 1 and 10 bytes into a region of size 6 [-Werror=format-
> >truncation=]
> > 766 | snprintf(buf, sizeof(buf), "1@%d ", i);
> > | ^~
> > xdp_hw_metadata.c:766:44: note: directive argument in the range [0,
> >2147483646]
> > 766 | snprintf(buf, sizeof(buf), "1@%d ", i);
> > | ^~~~~~~
> > xdp_hw_metadata.c:766:17: note: ‘snprintf’ output between 5 and 14 bytes into
> >a destination of size 8
> > 766 | snprintf(buf, sizeof(buf), "1@%d ", i);
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Thanks for pointing this out.
> Btw, do you know which build command will trigger these errors?
> I am using "make -C tools/testing/selftests/bpf" but cannot
> reproduce the build error.
>
> Thanks & Regards
> Siang
Last time I used the following to reproduce similar issues on my side:
make -C tools/testing/selftests TARGETS="bpf" LLVM=1 USERCFLAGS="-Wformat-truncation"
You can also try to use something like asprintf instead of managing the buffer
sizes manually.
