Re: [Buildroot] [RFC v2 2/2] package/libv4l: enable v4l2-tracer

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Peter, All,

On 2023-03-30 14:35 +0200, Peter Seiderer spake thusly:
> Signed-off-by: Peter Seiderer <ps.report@gmx.net>
> ---
> Changes v1 -> v2:
>   - fix --disable-v4l-tracer vs. --disable-v4l2-tracer typo
>   - enhance compile failure log/research
> 
> Fails with rpi4_64 config:

Obviously, we can't apply this for now, so I've marked is as "not
applicable" in patchwork.

>   .../host/bin/aarch64-buildroot-linux-gnu-g++ -DHAVE_CONFIG_H -I. -I../.. -I../../utils/common -I.../aarch64-buildroot-linux-gnu/sysroot/usr/in
> clude/json-c -I../../lib/include -Wall -Wpointer-arith -D_GNU_SOURCE -I../../include -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=6
> 4 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -D_FORTIFY_SOURCE=1 -std=gnu++11 -c libv4l2tracer.cpp  -fPIC -DPIC -o .libs/libv4l2tracer_la-libv4l2tracer.o
>   /tmp/ccXMMihl.s: Assembler messages:
>   /tmp/ccXMMihl.s:208: Error: symbol `open64' is already defined
>   /tmp/ccXMMihl.s:762: Error: symbol `mmap64' is already defined
>   make[5]: *** [Makefile:751: libv4l2tracer_la-libv4l2tracer.lo] Error 1

This is going to be tricky to investigate: indeed, AIUI, libv4l2tracer
is going to be a shared lib thatr can be LD_PRELOADed explicitly to
trace a few system calls, like open, open64, mmap, mmap64, and a few
others...

So, the solution is not to rename those functions in libv4l2tracer.

All those 64-bit flags are starting to be messing with my brain... :-(

Regards,
Yann E. MORIN.

> The preprocessor output shows:
> 
>   [...]
>   extern "C" {
>   # 61 ".../host/aarch64-buildroot-linux-gnu/sysroot/usr/include/sys/mman.h" 3 4
>   extern void * mmap (void *__addr, size_t __len, int __prot, int __flags, int __fd, __off64_t __offset) noexcept (true) __asm__ ("" "mmap64");
>   [...]
>   extern void *mmap64 (void *__addr, size_t __len, int __prot,
>          int __flags, int __fd, __off64_t __offset) noexcept (true);
> 
> And host/aarch64-buildroot-linux-gnu/sysroot/usr/include/sys/mman.h:
> 
>   56 #ifndef __USE_FILE_OFFSET64
>   57 extern void *mmap (void *__addr, size_t __len, int __prot,
>   58                    int __flags, int __fd, __off_t __offset) __THROW;
>   59 #else
>   60 # ifdef __REDIRECT_NTH
>   61 extern void * __REDIRECT_NTH (mmap,
>   62                               (void *__addr, size_t __len, int __prot,
>   63                                int __flags, int __fd, __off64_t __offset),
>   64                               mmap64);
>   65 # else
>   66 #  define mmap mmap64
>   67 # endif
>   68 #endif
>   69 #ifdef __USE_LARGEFILE64
>   70 extern void *mmap64 (void *__addr, size_t __len, int __prot,
>   71                      int __flags, int __fd, __off64_t __offset) __THROW;
>   72 #endif
> ---
>  package/libv4l/Config.in | 1 +
>  package/libv4l/libv4l.mk | 9 ++++++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/package/libv4l/Config.in b/package/libv4l/Config.in
> index c88f280c3b..7a86c7de15 100644
> --- a/package/libv4l/Config.in
> +++ b/package/libv4l/Config.in
> @@ -33,6 +33,7 @@ config BR2_PACKAGE_LIBV4L_UTILS
>  	  - v4l2-compliance
>  	  - v4l2-ctl, cx18-ctl, ivtv-ctl
>  	  - v4l2-sysfs-path
> +	  - v4l2-tracer (if json-c is enabled)
>  	  - rds-ctl
>  	  - qv4l2 (if Qt is enabled)
>  
> diff --git a/package/libv4l/libv4l.mk b/package/libv4l/libv4l.mk
> index 1142a7442f..ccb4da4fb7 100644
> --- a/package/libv4l/libv4l.mk
> +++ b/package/libv4l/libv4l.mk
> @@ -9,7 +9,7 @@ LIBV4L_SOURCE = v4l-utils-$(LIBV4L_VERSION).tar.bz2
>  LIBV4L_SITE = https://linuxtv.org/downloads/v4l-utils
>  LIBV4L_INSTALL_STAGING = YES
>  LIBV4L_DEPENDENCIES = host-pkgconf
> -LIBV4L_CONF_OPTS = --disable-doxygen-doc --disable-qvidcap --disable-v4l2-tracer
> +LIBV4L_CONF_OPTS = --disable-doxygen-doc --disable-qvidcap
>  # needed to get utils/qv4l link flags right
>  LIBV4L_AUTORECONF = YES
>  # add host-gettext for AM_ICONV macro
> @@ -66,6 +66,13 @@ LIBV4L_CONF_ENV += CXXFLAGS="$(TARGET_CXXFLAGS) -std=gnu++11"
>  # libelf and clang support
>  LIBV4L_CONF_OPTS += --disable-bpf
>  
> +ifeq ($(BR2_PACKAGE_JSON_C),y)
> +LIBV4L_CONF_OPTS += --enable-v4l2-tracer
> +LIBV4L_DEPENDENCIES += json-c
> +else
> +LIBV4L_CONF_OPTS += --disable-v4l2-tracer
> +endif
> +
>  ifeq ($(BR2_PACKAGE_QT5BASE)$(BR2_PACKAGE_QT5BASE_GUI)$(BR2_PACKAGE_QT5BASE_WIDGETS),yyy)
>  LIBV4L_CONF_OPTS += --enable-qv4l2
>  LIBV4L_DEPENDENCIES += qt5base
> -- 
> 2.40.0
> 
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