Failed to build bpftool from source

[chenhengqi]

clang \
        -I. \
        -I/home/ubuntu/bpf/bpftool/include/uapi/ \
        -I/home/ubuntu/bpf/bpftool/src/bootstrap/libbpf/include \
        -g -O2 -Wall -target bpf -c skeleton/pid_iter.bpf.c -o pid_iter.bpf.o
skeleton/pid_iter.bpf.c:47:14: error: incomplete definition of type 'struct bpf_perf_link'
        perf_link = container_of(link, struct bpf_perf_link, link);
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[qmonnet]

Hi, thanks for the report!
What's your kernel version, please? I guess it is lower than 5.15? It seems that commit cbdaf71f7e65 introduced requirements for recent structures to be present in kernel's BTF when compiling :/.

[chenhengqi]

Yes, I tried it on 5.4 and 5.11.

[withlin]

+1 5.11.0-49-generic

[qmonnet]

Thanks for the reports!

Since d97300d, kernel 5.15 is a requirement for building bpftool with all its features. The definition may also be missing if the kernel of the host has not been compiled with CONFIG_PERF_EVENTS.

Workarounds:

• Work with an older version (the latest release should not include this commit and should compile fine).
• Disable the “skeletons” feature (feature-clang-bpf-co-re), but there's currently no clean way to do this (I'm planning to add Makefile options for that when I have some cycles) so you'll have to edit the Makefile manually.

I'll try to submit a fix upstream.

[chenhengqi]

diff --git a/src/Makefile b/src/Makefile
index bffd4e7..5fc927e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -125,7 +125,7 @@ all: $(OUTPUT)bpftool
 
 BFD_SRCS = jit_disasm.c
 
-SRCS = $(filter-out $(BFD_SRCS),$(wildcard *.c))
+SRCS = $(filter-out $(BFD_SRCS) pids.c,$(wildcard *.c))
 
 ifeq ($(feature-libbfd),1)
   LIBS += -lbfd -ldl -lopcodes

[qmonnet]

I haven't managed to find a fix myself (I was missing the ...___local change), but I believe that the patch currently discussed on the mailing list should address the issue.

https://lore.kernel.org/bpf/[email protected]/T/#u

[liusy58]

diff --git a/src/Makefile b/src/Makefile
index bffd4e7..5fc927e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -125,7 +125,7 @@ all: $(OUTPUT)bpftool
 
 BFD_SRCS = jit_disasm.c
 
-SRCS = $(filter-out $(BFD_SRCS),$(wildcard *.c))
+SRCS = $(filter-out $(BFD_SRCS) pids.c,$(wildcard *.c))
 
 ifeq ($(feature-libbfd),1)
   LIBS += -lbfd -ldl -lopcodes

This can compile successfully but everytime I execute sudo bpftool prog show, segmentation fault pops up.

[adamzhoul]

same issue. +1

[qmonnet]

I re-submitted the patches today (at https://lore.kernel.org/bpf/[email protected]/t/#u).

[EDIT: v2 at https://lore.kernel.org/bpf/[email protected]/t/#u]

[qmonnet]

Apologies, this had taken more time than I expected - or than it should have. At last, we have the fix merged in bpf-next. I'll pull it in this repo at the next sync.