linux-kernel - Re: [PATCH] selftests: bpf: fix urandom

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Date:   Thu, 7 Jun 2018 14:17:16 -0700
From:   Y Song <ys114321@...il.com>
To:     Anders Roxell <anders.roxell@...aro.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Shuah Khan <shuah@...nel.org>, netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] selftests: bpf: fix urandom_read build issue

On Thu, Jun 7, 2018 at 12:07 PM, Anders Roxell <anders.roxell@...aro.org> wrote:
> On 7 June 2018 at 19:52, Y Song <ys114321@...il.com> wrote:
>> On Thu, Jun 7, 2018 at 3:57 AM, Anders Roxell <anders.roxell@...aro.org> wrote:
>>> gcc complains that urandom_read gets built twice.
>>>
>>> gcc -o tools/testing/selftests/bpf/urandom_read
>>> -static urandom_read.c -Wl,--build-id
>>> gcc -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf
>>> -I../../../../include/generated  -I../../../include    urandom_read.c
>>> urandom_read -lcap -lelf -lrt -lpthread -o
>>> tools/testing/selftests/bpf/urandom_read
>>> gcc: fatal error: input file
>>> ‘tools/testing/selftests/bpf/urandom_read’ is the
>>> same as output file
>>> compilation terminated.
>>> ../lib.mk:110: recipe for target
>>> 'tools/testing/selftests/bpf/urandom_read' failed
>>
>> What is the build/make command to reproduce the above failure?
>
> make -C tools/testing/selftests

Thanks. The patch will break
   make -C tools/testing/selftests/bpf

[yhs@...alhost bpf-next]$ make -C tools/testing/selftests/bpf
make: Entering directory '/home/yhs/work/bpf-next/tools/testing/selftests/bpf'
gcc -o /urandom_read -static urandom_read.c -Wl,--build-id
/usr/bin/ld: cannot open output file /urandom_read: Permission denied
collect2: error: ld returned 1 exit status
make: *** [Makefile:20: /urandom_read] Error 1
make: Leaving directory '/home/yhs/work/bpf-next/tools/testing/selftests/bpf'
[yhs@...alhost bpf-next]$

Could you still make the above command work?

>
> Cheers,
> Anders
>
>>
>>> To fix this issue remove the urandom_read target and so target
>>> TEST_CUSTOM_PROGS gets used.
>>>
>>> Fixes: 81f77fd0deeb ("bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID")
>>> Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
>>> ---
>>>  tools/testing/selftests/bpf/Makefile | 6 ++----
>>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
>>> index 607ed8729c06..67285591ffd7 100644
>>> --- a/tools/testing/selftests/bpf/Makefile
>>> +++ b/tools/testing/selftests/bpf/Makefile
>>> @@ -16,10 +16,8 @@ LDLIBS += -lcap -lelf -lrt -lpthread
>>>  TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
>>>  all: $(TEST_CUSTOM_PROGS)
>>>
>>> -$(TEST_CUSTOM_PROGS): urandom_read
>>> -
>>> -urandom_read: urandom_read.c
>>> -       $(CC) -o $(TEST_CUSTOM_PROGS) -static $< -Wl,--build-id
>>> +$(TEST_CUSTOM_PROGS): $(OUTPUT)/%: %.c
>>> +       $(CC) -o $@ -static $< -Wl,--build-id
>>>
>>>  # Order correspond to 'make run_tests' order
>>>  TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
>>> --
>>> 2.17.1
>>>