[PATCH v5 7/7] Make libc symbols hidden in static PIE

[Tulio Magno Quites Machado Filho]

Szabolcs Nagy via Libc-alpha <libc-alpha@sourceware.org> writes:

> Hidden visibility can avoid indirections and RELATIVE relocs in
> static PIE libc.
>
> The check should use IS_IN_LIB instead of IS_IN(libc) since all
> symbols are defined locally in static PIE and the optimization is
> useful in all libraries not just libc. However the test system
> links objects from libcrypt.a into dynamic linked test binaries
> where hidden visibility does not work.  I think mixing static and
> shared libc components in the same binary should not be supported
> usage, but to be safe only use hidden in libc.a.
>
> On some targets (i386) this optimization cannot be applied because
> hidden visibility PIE ifunc functions don't work, so it is gated by
> NO_HIDDEN_EXTERN_FUNC_IN_PIE.
>
> From -static-pie linked 'int main(){}' this shaves off 71 relative
> relocs on aarch64 and reduces code size by about 2k.

After this patch got merged, I noticed that
malloc/tst-malloc-stats-cancellation never returns on ppc (32-bit only).

It seems stuck in a futex_wait:

#0  0x6fddab58 in futex_wait (private=0, expected=2, futex_word=0x6ff405ec <main_arena>) at ../sysdeps/nptl/futex-internal.h:146
#1  __lll_lock_wait_private (futex=0x6ff405ec <main_arena>) at ./lowlevellock.c:35
#2  0x6fde3614 in __GI___libc_malloc (bytes=bytes@entry=4096) at malloc.c:3235
#3  0x6fdbf7f0 in __GI__IO_file_doallocate (fp=0xf7dc01a0) at filedoalloc.c:101
#4  0x6fdd6c20 in __GI__IO_doallocbuf (fp=0xf7dc01a0) at libioP.h:948
#5  __GI__IO_doallocbuf (fp=fp@entry=0xf7dc01a0) at genops.c:342
#6  0x6fdd5768 in _IO_new_file_overflow (f=0xf7dc01a0, ch=-1) at fileops.c:745
#7  0x6fdd41c0 in _IO_new_file_xsputn (n=37, data=<optimized out>, f=<optimized out>) at libioP.h:948
#8  _IO_new_file_xsputn (f=0xf7dc01a0, data=<optimized out>, n=37) at fileops.c:1197
#9  0x6fdc19e8 in __GI__IO_fwrite (buf=0x6ffc1880, size=1, count=37, fp=0xf7dc01a0) at libioP.h:948
#10 0x6ffc0e80 in ?? ()
#11 0x6fd6641c in generic_start_main (main=0x6ffc0b10, argc=1, argv=0xf6c00760, auxvec=0x0, init=<optimized out>, rtld_fini=<optimized out>, stack_end=<optimized out>, fini=<optimized out>) at ../csu/libc-start.c:332
#12 0x6fd665c0 in __libc_start_main (argc=<optimized out>, argv=<optimized out>, ev=<optimized out>, auxvec=<optimized out>, rtld_fini=<optimized out>, stinfo=<optimized out>, stack_on_entry=<optimized out>) at ../sysdeps/unix/sysv/linux/powerpc/libc-start.c:98
#13 0x00000000 in ?? ()

-- 
Tulio Magno