Re: [PATCH] aarch64: Remove ld.so __tls_get_addr plt usage

[Szabolcs Nagy <nsz@port70.net>]

* Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> [2024-04-05 13:29:48 -0300]:

> 
> 
> On 05/04/24 11:58, Szabolcs Nagy wrote:
> > The 04/05/2024 09:35, Adhemerval Zanella wrote:
> >> Use the hidden alias instead.
> >>
> >> Checked on aarch64-linux-gnu.
> > 
> > does this change behaviour in case __tls_get_addr is interposed?
> > 
> > 
> 
> Do we support symbol interposition for symbols in implementation namespace?
> If so, we will need to revert x86 to use the same semantic and document it
> properly.

i suspect this will partially break the sanitizers
and possibly other similar tools that hook internals
so i hoped at least for better commit msg pointing
out that this is deliberate behaviour change.



> 
> >> ---
> >>  sysdeps/aarch64/dl-tlsdesc.S                  | 3 ++-
> >>  sysdeps/unix/sysv/linux/aarch64/localplt.data | 2 --
> >>  2 files changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S
> >> index 9b253b39dd..4febf2ad21 100644
> >> --- a/sysdeps/aarch64/dl-tlsdesc.S
> >> +++ b/sysdeps/aarch64/dl-tlsdesc.S
> >> @@ -220,7 +220,7 @@ _dl_tlsdesc_dynamic:
> >>  	SAVE_Q_REGISTERS
> >>  
> >>  	mov	x0, x1
> >> -	bl	__tls_get_addr
> >> +	bl	HIDDEN_JUMPTARGET(__tls_get_addr)
> >>  
> >>  	mrs	x1, tpidr_el0
> >>  	sub	PTR_REG (0), PTR_REG (0), PTR_REG (1)
> >> @@ -246,5 +246,6 @@ _dl_tlsdesc_dynamic:
> >>  	b	1b
> >>  	cfi_endproc
> >>  	.size	_dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
> >> +	.hidden HIDDEN_JUMPTARGET(__tls_get_addr)
> >>  # undef NSAVEXREGPAIRS
> >>  #endif
> >> diff --git a/sysdeps/unix/sysv/linux/aarch64/localplt.data b/sysdeps/unix/sysv/linux/aarch64/localplt.data
> >> index 5d217cc50d..5dd07472df 100644
> >> --- a/sysdeps/unix/sysv/linux/aarch64/localplt.data
> >> +++ b/sysdeps/unix/sysv/linux/aarch64/localplt.data
> >> @@ -9,5 +9,3 @@ libm.so: matherr
> >>  # If outline atomics are used, libgcc (built outside of glibc) may
> >>  # call __getauxval using the PLT.
> >>  libc.so: __getauxval ?
> >> -# The dynamic loader needs __tls_get_addr for TLS.
> >> -ld.so: __tls_get_addr
> >> -- 
> >> 2.34.1
> >>