[Buildroot] [PATCH v2] toolchain-external: adjust logic for musl dynamic linker symlink

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

Thomas, All,

On 2017-06-24 23:49 +0200, Arnout Vandecappelle spake thusly:
> On 24-06-17 23:14, Thomas Petazzoni wrote:
> > This commit changes the strategy to know what symlink should be
> > created for the musl dynamic linker. For now, we have in Buildroot the
> > logic to decide what the symlink name should be. However, despite
> > numerous fixes, there are still some cases that are missing, such as
> > mips64el-n32, where the symlink is ld-musl-mipsn32el.so.1.
> > 
> > So, instead of trying to make Buildroot aware of all the possible
> > names, simply get it from the external toolchain.
> > 
> > Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> 
> Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

Not from me, see below (the worst offender being the missing LC_ALL).

>  With some nits.
> 
> > ---
> > Changes since v1:
> >  - As suggested by Yann E. Morin, build a sample program, and get its
> >    program interpreter with readelf, in order to find the program
> >    interpreter.
> > 
> > Note: I have tried to refactor this with the check_musl function in
> > toolchain/helpers.mk, with the idea of introducing a function
> > get_program_interpreter that would, given CC/READELF would return the
> > program interpreter path. However, for the life of me, I couldn't get
> > a make function invoking multiple shell commands to return a string.
> 
>  Huh?
> 
> get_program_interpreter = $(shell \
>  	echo 'void main(void) {}' | $(TOOLCHAIN_EXTERNAL_CC) -x c -o
> $(BUILD_DIR)/.br-toolchain-test.tmp - >/dev/null 2>&1; \
>  	$(TOOLCHAIN_EXTERNAL_READELF) -l $(BUILD_DIR)/.br-toolchain-test.tmp 2>
> /dev/null | sed -r -e '/.*Requesting program interpreter: (.+)\]$$/!d; s//\1/')
> 
> $(warning $(get_program_interpreter))
> 
> toolchain/helpers.mk:496: /lib/ld-musl-i386.so.1

Yup, works for me too...

Although I prefer such long macros be defined rather than assigned.

> > ---
> >  toolchain/toolchain-external/pkg-toolchain-external.mk | 17 +++--------------
> >  1 file changed, 3 insertions(+), 14 deletions(-)
> > 
> > diff --git a/toolchain/toolchain-external/pkg-toolchain-external.mk b/toolchain/toolchain-external/pkg-toolchain-external.mk
> > index 8269345..938f73d 100644
> > --- a/toolchain/toolchain-external/pkg-toolchain-external.mk
> > +++ b/toolchain/toolchain-external/pkg-toolchain-external.mk
> > @@ -476,21 +476,10 @@ endef
> >  # of the dynamic library loader. We just need to create a symbolic
> >  # link to libc.so with the appropriate name.
> >  ifeq ($(BR2_TOOLCHAIN_EXTERNAL_MUSL),y)
> > -ifeq ($(BR2_i386),y)
> > -MUSL_ARCH = i386
> > -else ifeq ($(BR2_ARM_EABIHF),y)
> > -MUSL_ARCH = armhf
> > -else ifeq ($(BR2_mips):$(BR2_SOFT_FLOAT),y:y)
> > -MUSL_ARCH = mips-sf
> > -else ifeq ($(BR2_mipsel):$(BR2_SOFT_FLOAT),y:y)
> > -MUSL_ARCH = mipsel-sf
> > -else ifeq ($(BR2_sh),y)
> > -MUSL_ARCH = sh
> > -else
> > -MUSL_ARCH = $(ARCH)
> > -endif
> >  define TOOLCHAIN_EXTERNAL_MUSL_LD_LINK
> > -	ln -sf libc.so $(TARGET_DIR)/lib/ld-musl-$(MUSL_ARCH).so.1
> > +	$(Q)echo 'void main(void) {}' | $(TOOLCHAIN_EXTERNAL_CC) -x c -o $(BUILD_DIR)/.br-toolchain-test.tmp - >/dev/null 2>&1; \
> > +	PROGRAM_INTERPRETER=`$(TOOLCHAIN_EXTERNAL_READELF) -l $(BUILD_DIR)/.br-toolchain-test.tmp 2> /dev/null | sed -r -e '/.*Requesting program interpreter: (.+)\]$$/!d; s//\1/'` ; \
> 
>  Perhaps split this ridiculously long line after the | ? Perhaps also split the
> two sed expressions with two -e.
> 
>  I personally prefer sed -n -e '/.../s//\1/p' but I don't care much.

Also:
  - force LC_ALL=C when calling readelf, to avoid any translation,
  - remove the generated file.

Regards,
Yann E. MORIN.

>  Regards,
>  Arnout
> 
> > +	ln -sf libc.so $(TARGET_DIR)/$${PROGRAM_INTERPRETER}
> >  endef
> >  endif
> >  
> > 
> 
> -- 
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'