Hello Christophe,

On Wed, 4 Jul 2018 17:55:19 +0200, Christophe Lyon wrote:
> Implement _start: compute parameters for __self_reloc, and give
> control to the user program.
> 
>       * ldso/ldso/arm/dl-startup.h: Implement _start for __FDPIC__.
> 
> Signed-off-by: Mickaël Guêné <mickael.gu...@st.com>
> Signed-off-by: Christophe Lyon <christophe.l...@st.com>

This is very likely me not doing things correctly, but this change
doesn't build, because it uses ARM instructions on Thumb2-only systems.
I'm trying to build a Cortex-M4 FDPIC toolchain with your patches. My
gcc has the following details (it is gcc 8.1.0 on top of which I have
backported your ARM FDPIC patches):

/home/test/outputs/arm-fdpic/host/bin/arm-buildroot-uclinuxfdpiceabi-gcc -v
Using built-in specs.
COLLECT_GCC=/home/test/outputs/arm-fdpic/host/bin/arm-buildroot-uclinuxfdpiceabi-gcc.br_real
COLLECT_LTO_WRAPPER=/home/test/outputs/arm-fdpic/host/libexec/gcc/arm-buildroot-uclinuxfdpiceabi/8.1.0/lto-wrapper
Target: arm-buildroot-uclinuxfdpiceabi
Configured with: ./configure --prefix=/home/test/outputs/arm-fdpic/host 
--sysconfdir=/home/test/outputs/arm-fdpic/host/etc 
--localstatedir=/home/test/outputs/arm-fdpic/host/var --enable-shared 
--disable-static --disable-gtk-doc --disable-gtk-doc-html --disable-doc 
--disable-docs --disable-documentation --disable-debug --with-xmlto=no 
--with-fop=no --disable-dependency-tracking 
--target=arm-buildroot-uclinuxfdpiceabi 
--with-sysroot=/home/test/outputs/arm-fdpic/host/arm-buildroot-uclinuxfdpiceabi/sysroot
 --disable-__cxa_atexit --with-gnu-ld --disable-libssp --disable-multilib 
--with-gmp=/home/test/outputs/arm-fdpic/host 
--with-mpc=/home/test/outputs/arm-fdpic/host 
--with-mpfr=/home/test/outputs/arm-fdpic/host --with-pkgversion='Buildroot 
2018.08-git-00602-g3ecd583' --with-bugurl=http://bugs.buildroot.net/ 
--disable-libquadmath --disable-libsanitizer --disable-tls --disable-libmudflap 
--enable-threads --without-isl --without-cloog --with-float=soft 
--disable-decimal-float --with-abi=aapcs-linux --with-cpu=cortex-m4 
--with-float=soft --with-mode=thumb --enable-languages=c --disable-shared 
--without-headers --disable-threads --with-newlib --disable-largefile 
--disable-nls
Thread model: single
gcc version 8.1.0 (Buildroot 2018.08-git-00602-g3ecd583) 

I.e, it generates code for Cortex-M4, soft-float, Thumb by default.

The dl-startup code fails to build with:

/home/test/outputs/arm-fdpic/host/bin/arm-buildroot-uclinuxfdpiceabi-gcc -c 
ldso/ldso/ldso.c -o ldso/ldso/ldso.oS -Wall -Wstrict-prototypes 
-Wstrict-aliasing -Wno-nonnull-compare -funsigned-char -fno-builtin -fno-asm 
-fmerge-all-constants -msoft-float -st
d=gnu99 -mlittle-endian -fno-stack-protector -nostdinc -I./include -I./include 
-include libc-symbols.h -I./libc/sysdeps/linux/arm -I./libc/sysdeps/linux 
-I./ldso/ldso/arm -I./ldso/include -I. -Os -fstrict-aliasing 
-I./libpthread/linuxthreads/sysdeps/unix/
sysv/linux/arm -I./libpthread/linuxthreads/sysdeps/arm 
-I./libpthread/linuxthreads/sysdeps/unix/sysv/linux 
-I./libpthread/linuxthreads/sysdeps/pthread -I./libpthread/linuxthreads 
-I./libpthread -I./libc/sysdeps/linux/common -isystem /home/test/outputs/arm
-fdpic/host/lib/gcc/arm-buildroot-uclinuxfdpiceabi/8.1.0/include-fixed -isystem 
/home/test/outputs/arm-fdpic/host/lib/gcc/arm-buildroot-uclinuxfdpiceabi/8.1.0/include
 -I/home/test/outputs/arm-fdpic/build/linux-headers-4.17.4/usr/include/ 
-DNDEBUG -DNOT_IN
_libc -DIS_IN_rtld -fno-stack-protector -fno-omit-frame-pointer 
-fno-unwind-tables -fno-asynchronous-unwind-tables -I./ldso/ldso/arm 
-I./ldso/include -I./ldso/ldso -DUCLIBC_RUNTIME_PREFIX=\"/\" 
-DUCLIBC_LDSO=\"ld-uClibc.so.1\" -DIN_LIB=rtld -mfdpic -DSHAR
ED -DLDSO_ELFINTERP=\"arm/elfinterp.c\" -DLDSO_MULTILIB_DIR=\"lib/\" -MT 
ldso/ldso/ldso.oS -MD -MP -MF ldso/ldso/.ldso.oS.dep
In file included from ./include/bits/waitstatus.h:72,
                 from ./include/stdlib.h:44,
                 from ./ldso/include/ldso.h:33,
                 from ldso/ldso/ldso.c:32:
./ldso/include/dl-syscall.h: In function '_dl_pread':
./ldso/include/dl-syscall.h:169:69: warning: right shift count >= width of type 
[-Wshift-count-overflow]
  return __syscall_pread(fd, buf, count, 0, __LONG_LONG_PAIR((offset >> 32), 
(offset & 0xffffffff)));
                                                                     ^~
./include/endian.h:52:39: note: in definition of macro '__LONG_LONG_PAIR'
 # define __LONG_LONG_PAIR(HI, LO) LO, HI
                                       ^~
In file included from ./ldso/ldso/arm/dl-inlines.h:1,
                 from ./ldso/include/ldso.h:183,
                 from ldso/ldso/ldso.c:32:
./ldso/ldso/arm/../fdpic/dl-inlines.h: In function '_dl_funcdesc_for':
./ldso/ldso/arm/../fdpic/dl-inlines.h:180:8: warning: assignment to 'struct 
funcdesc_value **' from incompatible pointer type 'void **' 
[-Wincompatible-pointer-types]
  entry = htab_find_slot(ht, entry_point, 1, hash_pointer, eq_pointer);
        ^
In file included from ldso/ldso/ldso.c:45:
ldso/ldso/arm/elfinterp.c: In function '_dl_linux_resolver':
ldso/ldso/arm/elfinterp.c:95:9: warning: returning 'volatile struct 
funcdesc_value *' from a function with return type 'long unsigned int' makes 
integer from pointer without a cast [-Wint-conversion]
  return got_entry;
         ^~~~~~~~~
ldso/ldso/arm/elfinterp.c: In function '_dl_do_reloc':
ldso/ldso/arm/elfinterp.c:364:65: warning: passing argument 1 of 
'_dl_funcdesc_for' makes pointer from integer without a cast [-Wint-conversion]
      reloc_value = (unsigned long) _dl_funcdesc_for(symbol_addr + reloc_value, 
sym_ref.tpnt->loadaddr.got_value);
                                                     ~~~~~~~~~~~~^~~~~~~~~~~~~
In file included from ./ldso/ldso/arm/dl-inlines.h:1,
                 from ./ldso/include/ldso.h:183,
                 from ldso/ldso/ldso.c:32:
./ldso/ldso/arm/../fdpic/dl-inlines.h:165:25: note: expected 'void *' but 
argument is of type 'long unsigned int'
 _dl_funcdesc_for (void *entry_point, void *got_value)
                   ~~~~~~^~~~~~~~~~~
In file included from ldso/ldso/ldso.c:45:
ldso/ldso/arm/elfinterp.c: In function '_dl_do_lazy_reloc':
ldso/ldso/arm/elfinterp.c:429:23: warning: assignment to 'void *' from 
'unsigned int' makes pointer from integer without a cast [-Wint-conversion]
      dst->entry_point = DL_RELOC_ADDR(tpnt->loadaddr, dst->entry_point);
                       ^
In file included from ldso/ldso/ldso.c:86:
ldso/ldso/dl-startup.c: In function '_dl_start':
ldso/ldso/dl-startup.c:313:13: warning: variable 'strtab' set but not used 
[-Wunused-but-set-variable]
       char *strtab;
             ^~~~~~
ldso/ldso/dl-startup.c:125:13: warning: variable 'got' set but not used 
[-Wunused-but-set-variable]
  ElfW(Addr) got;
             ^~~
In file included from ./ldso/ldso/arm/dl-sysdep.h:135,
                 from ./ldso/include/dl-defs.h:77,
                 from ./ldso/include/dl-string.h:15,
                 from ./ldso/include/ldso.h:53,
...skipping...
In file included from ./ldso/ldso/arm/dl-inlines.h:1,
                 from ./ldso/include/ldso.h:183,
                 from ldso/ldso/ldso.c:32:
./ldso/ldso/arm/../fdpic/dl-inlines.h:165:25: note: expected 'void *' but 
argument is of type 'long unsigned int'
 _dl_funcdesc_for (void *entry_point, void *got_value)
                   ~~~~~~^~~~~~~~~~~
In file included from ldso/ldso/ldso.c:45:
ldso/ldso/arm/elfinterp.c: In function '_dl_do_lazy_reloc':
ldso/ldso/arm/elfinterp.c:429:23: warning: assignment to 'void *' from 
'unsigned int' makes pointer from integer without a cast [-Wint-conversion]
      dst->entry_point = DL_RELOC_ADDR(tpnt->loadaddr, dst->entry_point);
                       ^
In file included from ldso/ldso/ldso.c:86:
ldso/ldso/dl-startup.c: In function '_dl_start':
ldso/ldso/dl-startup.c:313:13: warning: variable 'strtab' set but not used 
[-Wunused-but-set-variable]
       char *strtab;
             ^~~~~~
ldso/ldso/dl-startup.c:125:13: warning: variable 'got' set but not used 
[-Wunused-but-set-variable]
  ElfW(Addr) got;
             ^~~
In file included from ./ldso/ldso/arm/dl-sysdep.h:135,
                 from ./ldso/include/dl-defs.h:77,
                 from ./ldso/include/dl-string.h:15,
                 from ./ldso/include/ldso.h:53,
                 from ldso/ldso/ldso.c:32:
ldso/ldso/dl-hash.c: In function '_dl_find_hash':
./ldso/ldso/arm/../fdpic/dl-sysdep.h:111:4: warning: pointer/integer type 
mismatch in conditional expression
    : DL_RELOC_ADDR ((TPNT)->loadaddr, (SYM)->st_value))
    ^
ldso/ldso/dl-hash.c:384:20: note: in expansion of macro 'DL_FIND_HASH_VALUE'
     return (char *)DL_FIND_HASH_VALUE(tpnt, type_class, sym);
                    ^~~~~~~~~~~~~~~~~~
/tmp/cceTVltl.s: Assembler messages:
/tmp/cceTVltl.s:14: Error: selected processor does not support ARM opcodes
/tmp/cceTVltl.s:19: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `sub r4,pc,#8'
/tmp/cceTVltl.s:20: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `ldr r1,.L__ROFIXUP_LIST__'
/tmp/cceTVltl.s:21: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `add r1,r1,r4'
/tmp/cceTVltl.s:22: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `ldr r2,.L__ROFIXUP_END__'
/tmp/cceTVltl.s:23: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `add r2,r2,r4'
/tmp/cceTVltl.s:24: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `movs r0,r8'
/tmp/cceTVltl.s:25: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `moveq r0,r7'
/tmp/cceTVltl.s:26: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `push {r7,r8,r9,r10}'
/tmp/cceTVltl.s:27: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `bl __self_reloc'
/tmp/cceTVltl.s:28: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `pop {r7,r8,r9,r10}'
/tmp/cceTVltl.s:29: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r1,r7'
/tmp/cceTVltl.s:30: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r2,r8'
/tmp/cceTVltl.s:31: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r3,r9'
/tmp/cceTVltl.s:32: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r4,sp'
/tmp/cceTVltl.s:33: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `sub r5,sp,#8'
/tmp/cceTVltl.s:34: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `sub sp,sp,#16'
/tmp/cceTVltl.s:35: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `str r4,[sp,#4]'
/tmp/cceTVltl.s:36: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `str r5,[sp,#0]'
/tmp/cceTVltl.s:37: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r9,r0'
/tmp/cceTVltl.s:38: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `mov r4,r9'
/tmp/cceTVltl.s:39: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `bl _dl_start'
/tmp/cceTVltl.s:40: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `ldr r10,.L_dl_fini_gotofffuncdesc'
/tmp/cceTVltl.s:41: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `add r10,r10,r4'
/tmp/cceTVltl.s:42: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `ldr r5,[sp,#8]'
/tmp/cceTVltl.s:43: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `ldr r9,[sp,#12]'
/tmp/cceTVltl.s:44: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `add sp,sp,#16'
/tmp/cceTVltl.s:45: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `bx r5'
/tmp/cceTVltl.s:47: Error: attempt to use an ARM instruction on a Thumb-only 
processor -- `b .loopforever'
make[2]: *** [ldso/ldso/ldso.oS] Error 1
make[1]: *** [/home/test/outputs/arm-fdpic/build/uclibc-1.0.30/.stamp_built] 
Error 2
make: *** [_all] Error 2

Any idea ?

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
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