[PATCH bpf 1/2] samples: bpf: fix xdp_sample_user.o linking with Clang

[Alexander Lobakin]

Clang (13) doesn't get the jokes about specifying libraries to link in
cclags of individual .o objects:

clang-13: warning: -lm: 'linker' input unused [-Wunused-command-line-argument]
[ ... ]
  LD  samples/bpf/xdp_redirect_cpu
  LD  samples/bpf/xdp_redirect_map_multi
  LD  samples/bpf/xdp_redirect_map
  LD  samples/bpf/xdp_redirect
  LD  samples/bpf/xdp_monitor
/usr/bin/ld: samples/bpf/xdp_sample_user.o: in function `sample_summary_print':
xdp_sample_user.c:(.text+0x84c): undefined reference to `floor'
/usr/bin/ld: xdp_sample_user.c:(.text+0x870): undefined reference to `ceil'
/usr/bin/ld: xdp_sample_user.c:(.text+0x8cf): undefined reference to `floor'
/usr/bin/ld: xdp_sample_user.c:(.text+0x8f3): undefined reference to `ceil'
[ more ]

Specify '-lm' as ldflags for all xdp_sample_user.o users in the main
Makefile and remove it from ccflags of ^ in Makefile.target -- just
like it's done for all other samples. This works with all compilers.

Fixes: 6e1051a54e31 ("samples: bpf: Convert xdp_monitor to XDP samples helper")
Fixes: b926c55d856c ("samples: bpf: Convert xdp_redirect to XDP samples helper")
Fixes: e531a220cc59 ("samples: bpf: Convert xdp_redirect_cpu to XDP samples helper")
Fixes: bbe65865aa05 ("samples: bpf: Convert xdp_redirect_map to XDP samples helper")
Fixes: 594a116b2aa1 ("samples: bpf: Convert xdp_redirect_map_multi to XDP samples helper")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx>
---
 samples/bpf/Makefile        | 5 +++++
 samples/bpf/Makefile.target | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index a886dff1ba89..e5b049ad5447 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -215,6 +215,11 @@ TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
 endif
 
 TPROGS_LDLIBS			+= $(LIBBPF) -lelf -lz
+TPROGLDLIBS_xdp_monitor		+= -lm
+TPROGLDLIBS_xdp_redirect	+= -lm
+TPROGLDLIBS_xdp_redirect_cpu	+= -lm
+TPROGLDLIBS_xdp_redirect_map	+= -lm
+TPROGLDLIBS_xdp_redirect_map_multi += -lm
 TPROGLDLIBS_tracex4		+= -lrt
 TPROGLDLIBS_trace_output	+= -lrt
 TPROGLDLIBS_map_perf_test	+= -lrt
diff --git a/samples/bpf/Makefile.target b/samples/bpf/Makefile.target
index 5a368affa038..379560f11db4 100644
--- a/samples/bpf/Makefile.target
+++ b/samples/bpf/Makefile.target
@@ -76,7 +76,7 @@ $(tprog-cobjs): $(obj)/%.o: $(src)/%.c FORCE
 
 # Override includes for xdp_sample_user.o because $(srctree)/usr/include in
 # TPROGS_CFLAGS causes conflicts
-XDP_SAMPLE_CFLAGS += -Wall -O2 -lm \
+XDP_SAMPLE_CFLAGS += -Wall -O2 \
 		     -I./tools/include \
 		     -I./tools/include/uapi \
 		     -I./tools/lib \
-- 
2.33.1