[lttng-dev] [RFC PATCH lttng-ust 2/2] dl instrumentation: add dlmopen event, trace dlopen flags

[Mathieu Desnoyers]

----- On Feb 21, 2017, at 9:19 AM, Thomas Petazzoni thomas.petazzoni at free-electrons.com wrote:

> Hello,
> 
> On Tue, 21 Feb 2017 14:08:08 +0000 (UTC), Mathieu Desnoyers wrote:
> 
>> My expectation is that the dlmopen override symbol gets generated,
>> but it is never invoked in builds where the libc does not implement
>> it, so we never have to look it up dynamically through dlsym().
> 
> The main issue is that the Lmid_t type doesn't exist I believe.

Ah yes, good point. This typedef is only there with glibc header
files.

So we'd have to add a configure.ac test that would detect if dlmopen()
is there, and expose a define to lttng-ust to skip the dlmopen() bits
accordingly.

Jonathan, can you have a look and prepare a patch please ?

Thanks,

Mathieu

> 
>> How does the build fail with musl ? Can you provide the build
>> output ?
> 
> Sure:
> 
>  http://autobuild.buildroot.net/results/113/113fa95a054df183014b43ec36b329f9c59bd356/build-end.log
> 
> If you want to reproduce:
> 
> $ git clone git://git.busybox.net/buildroot
> $ cd buildroot/
> $ git checkout 2017.02-rc2
> $ cat > .config
> BR2_arm=y
> BR2_cortex_a9=y
> BR2_ARM_ENABLE_VFP=y
> BR2_TOOLCHAIN_EXTERNAL=y
> BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
> BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
> BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-cortex-a9-musl-2017.02-rc1-2-g133c5ac.tar.bz2"
> BR2_TOOLCHAIN_EXTERNAL_GCC_5=y
> BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_9=y
> BR2_TOOLCHAIN_EXTERNAL_CUSTOM_MUSL=y
> BR2_TOOLCHAIN_EXTERNAL_CXX=y
> BR2_INIT_NONE=y
> BR2_SYSTEM_BIN_SH_NONE=y
> # BR2_PACKAGE_BUSYBOX is not set
> BR2_PACKAGE_LTTNG_LIBUST=y
> # BR2_TARGET_ROOTFS_TAR is not set
> $ make olddefconfig
> $ make
> 
> Takes ~5 minutes maybe for the all build to proceed until it breaks on
> lttng-ust.
> 
> Thanks!
> 
> Thomas
> --
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com