Re: [PATCH 1/1] Perf: Compile failed when compile with libelf.

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Thu, Oct 18, 2018 at 04:36:46PM +0800, Nickhu escreveu:
> The error message:
> =====================================================================
> util/symbol-elf.c:46:12: error: static declaration of 'elf_getphdrnum'
> follows non-static declaration
> static int elf_getphdrnum(Elf *elf, size_t *dst)
>             ^~~~~~~~~~~~~~
> In file included from util/symbol.h:20,
>                  from util/symbol-elf.c:9:
> /local/nickhu/build-system-3/toolchain/nds32le-linux-glibc-v3-upstream/
> nds32le-linux/sysroot/usr/include/libelf.h:266:12: note: previous declaration
> of 'elf_getphdrnum' was here
> extern int elf_getphdrnum (Elf *__elf, size_t *__dst);
>             ^~~~~~~~~~~~~~
> util/symbol-elf.c:62:12: error: static declaration of 'elf_getshdrstrndx'
> follows non-static declaration
> static int elf_getshdrstrndx(Elf *elf __maybe_unused, size_t *dst __maybe
> _unused)
>             ^~~~~~~~~~~~~~~~~
> In file included from util/symbol.h:20,
>                  from util/symbol-elf.c:9:
> /local/nickhu/build-system-3/toolchain/nds32le-linux-glibc-v3-upstream/
> nds32le-linux/sysroot/usr/include/libelf.h:316:12: note: previous declaration
> of 'elf_getshdrstrndx' was here
> extern int elf_getshdrstrndx (Elf *__elf, size_t *__dst);
> =====================================================================
> 
> Fix it.

Humm, I think the fix lies elsewhere.

If you find that function in a header, then its probably because you
_have_ it in your system, right? In that case
HAVE_ELF_GETPHDRNUM_SUPPORT should be defined and that elf_getphdrnum()
fallback implementation should not be compiled.

So looking at where HAVE_ELF_GETPHDRNUM_SUPPORT is defined, in
tools/build/feature, more specifically here:

[acme@jouet perf]$ cat tools/build/feature/test-libelf-getphdrnum.c 
// SPDX-License-Identifier: GPL-2.0
#include <libelf.h>

int main(void)
{
	size_t dst;

	return elf_getphdrnum(0, &dst);
}
[acme@jouet perf]$ 

[acme@jouet perf]$ find tools/ -type f | xargs grep HAVE_ELF_GETPHDRNUM_SUPPORT
tools/perf/Makefile.config:    CFLAGS += -DHAVE_ELF_GETPHDRNUM_SUPPORT
tools/perf/util/symbol-elf.c:#ifndef HAVE_ELF_GETPHDRNUM_SUPPORT
[acme@jouet perf]$ 

Can you take a look at:

[acme@jouet perf]$ ls -la /tmp/build/perf/feature/test-libelf-getphdrnum.*
-rwxrwxr-x. 1 acme acme 8240 Oct 17 09:20 /tmp/build/perf/feature/test-libelf-getphdrnum.bin
-rw-rw-r--. 1 acme acme 1373 Oct 17 09:20 /tmp/build/perf/feature/test-libelf-getphdrnum.d
-rw-rw-r--. 1 acme acme    0 Oct 17 09:20 /tmp/build/perf/feature/test-libelf-getphdrnum.make.output
[acme@jouet perf]$ 

So in my case, using this libelf:

[acme@jouet perf]$ rpm -qf /usr/include/libelf.h 
elfutils-libelf-devel-0.173-1.fc28.x86_64
[acme@jouet perf]$

the .make.output file is empty, the build was successful, without
warnings, that binary was generated:

[acme@jouet perf]$ ls -la /tmp/build/perf/feature/test-libelf-getphdrnum.bin
-rwxrwxr-x. 1 acme acme 8240 Oct 17 09:20 /tmp/build/perf/feature/test-libelf-getphdrnum.bin
[acme@jouet perf]$ ldd /tmp/build/perf/feature/test-libelf-getphdrnum.bin
	linux-vdso.so.1 (0x00007ffdf93ea000)
	libelf.so.1 => /lib64/libelf.so.1 (0x00007efc3f2d7000)
	libc.so.6 => /lib64/libc.so.6 (0x00007efc3ef21000)
	libz.so.1 => /lib64/libz.so.1 (0x00007efc3ed0a000)
	/lib64/ld-linux-x86-64.so.2 (0x00007efc3f4ef000)
[acme@jouet perf]$ nm /tmp/build/perf/feature/test-libelf-getphdrnum.bin | grep getphdrnum
                 U elf_getphdrnum@@ELFUTILS_1.6
[acme@jouet perf]$

And here are the headers used:

[acme@jouet perf]$ cat /tmp/build/perf/feature/test-libelf-getphdrnum.d 
/tmp/build/perf/feature/test-libelf-getphdrnum.bin: \
 test-libelf-getphdrnum.c /usr/include/stdc-predef.h \
 /usr/include/libelf.h \
 /usr/lib/gcc/x86_64-redhat-linux/7/include/stdint.h \
 /usr/include/stdint.h /usr/include/bits/libc-header-start.h \
 /usr/include/features.h /usr/include/sys/cdefs.h \
 /usr/include/bits/wordsize.h /usr/include/bits/long-double.h \
 /usr/include/gnu/stubs.h /usr/include/gnu/stubs-64.h \
 /usr/include/bits/types.h /usr/include/bits/typesizes.h \
 /usr/include/bits/wchar.h /usr/include/bits/stdint-intn.h \
 /usr/include/bits/stdint-uintn.h /usr/include/sys/types.h \
 /usr/include/bits/types/clock_t.h /usr/include/bits/types/clockid_t.h \
 /usr/include/bits/types/time_t.h /usr/include/bits/types/timer_t.h \
 /usr/lib/gcc/x86_64-redhat-linux/7/include/stddef.h \
 /usr/include/endian.h /usr/include/bits/endian.h \
 /usr/include/bits/byteswap.h /usr/include/bits/byteswap-16.h \
 /usr/include/bits/uintn-identity.h /usr/include/sys/select.h \
 /usr/include/bits/select.h /usr/include/bits/types/sigset_t.h \
 /usr/include/bits/types/__sigset_t.h \
 /usr/include/bits/types/struct_timeval.h \
 /usr/include/bits/types/struct_timespec.h /usr/include/sys/sysmacros.h \
 /usr/include/bits/sysmacros.h /usr/include/bits/pthreadtypes.h \
 /usr/include/bits/thread-shared-types.h \
 /usr/include/bits/pthreadtypes-arch.h /usr/include/elf.h
[acme@jouet perf]$

So, taking this into account, I think the feature test is using a
different include path than the tool, which may be a real bug in the
feature detection, how is the command line that led to this?

One other way to see that the feature test is not detecting that
library, use VF=1 after a clean and check if this line is present:

...             libelf-getphdrnum: [ OFF ]

[acme@jouet perf]$ rm -rf /tmp/build/perf/ ; mkdir -p /tmp/build/perf 
[acme@jouet perf]$ time make VF=1 -C tools/perf O=/tmp/build/perf
make: Entering directory '/home/acme/git/perf/tools/perf'
  BUILD:   Doing 'make -j4' parallel build
  HOSTCC   /tmp/build/perf/fixdep.o
  HOSTLD   /tmp/build/perf/fixdep-in.o
  LINK     /tmp/build/perf/fixdep
Warning: Kernel ABI header at 'tools/include/uapi/linux/mman.h' differs from latest version at 'include/uapi/linux/mman.h'
diff -u tools/include/uapi/linux/mman.h include/uapi/linux/mman.h

Auto-detecting system features:
...                         dwarf: [ on  ]
...            dwarf_getlocations: [ on  ]
...                         glibc: [ on  ]
...                          gtk2: [ on  ]
...                      libaudit: [ on  ]
...                        libbfd: [ on  ]
...                        libelf: [ on  ]
...                       libnuma: [ on  ]
...        numa_num_possible_cpus: [ on  ]
...                       libperl: [ on  ]
...                     libpython: [ on  ]
...                      libslang: [ on  ]
...                     libcrypto: [ on  ]
...                     libunwind: [ on  ]
...            libdw-dwarf-unwind: [ on  ]
...                          zlib: [ on  ]
...                          lzma: [ on  ]
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]
...                     backtrace: [ on  ]
...                fortify-source: [ on  ]
...         sync-compare-and-swap: [ on  ]
...                  gtk2-infobar: [ on  ]
...             libelf-getphdrnum: [ on  ]
...           libelf-gelf_getnote: [ on  ]
...          libelf-getshdrstrndx: [ on  ]
...                   libelf-mmap: [ on  ]
...             libpython-version: [ on  ]
...                 libunwind-x86: [ OFF ]
...              libunwind-x86_64: [ on  ]
...                 libunwind-arm: [ OFF ]
...             libunwind-aarch64: [ OFF ]
...   pthread-attr-setaffinity-np: [ on  ]
...               pthread-barrier: [ on  ]
...                  reallocarray: [ on  ]
...            stackprotector-all: [ on  ]
...                       timerfd: [ on  ]
...                  sched_getcpu: [ on  ]
...                           sdt: [ on  ]
...                         setns: [ on  ]
...                    libopencsd: [ OFF ]

 
> Signed-off-by: Nickhu <nickhu@andestech.com>
> ---
>  tools/perf/util/symbol-elf.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 29770ea61768..3ccdfe603d67 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -43,7 +43,7 @@ static inline char *bfd_demangle(void __maybe_unused *v,
>  #endif
>  
>  #ifndef HAVE_ELF_GETPHDRNUM_SUPPORT
> -static int elf_getphdrnum(Elf *elf, size_t *dst)
> +int elf_getphdrnum(Elf *elf, size_t *dst)
>  {
>  	GElf_Ehdr gehdr;
>  	GElf_Ehdr *ehdr;
> @@ -59,7 +59,7 @@ static int elf_getphdrnum(Elf *elf, size_t *dst)
>  #endif
>  
>  #ifndef HAVE_ELF_GETSHDRSTRNDX_SUPPORT
> -static int elf_getshdrstrndx(Elf *elf __maybe_unused, size_t *dst __maybe_unused)
> +int elf_getshdrstrndx(Elf *elf __maybe_unused, size_t *dst __maybe_unused)
>  {
>  	pr_err("%s: update your libelf to > 0.140, this one lacks elf_getshdrstrndx().\n", __func__);
>  	return -1;
> -- 
> 2.17.0