[v2,2/3] arm: Update _dl_tlsdesc_dynamic to preserve caller-saved registers (BZ 31372)

ARM _dl_tlsdesc_dynamic slow path has two issues:

  * The ip/r12 is defined by AAPCS as a scratch register, and gcc is
    used to save the stack pointer before on some function calls.  So it
    should also be saved/restored as well.  It fixes the tst-gnu2-tls2.

  * None of the possible VFP registers are saved/restored.  ARM has the
    additional complexity to have different VFP bank sizes (depending of
    VFP support by the chip).

The tst-gnu2-tls2 test is extended to check for VFP registers, although
only for hardfp builds.  Different than setcontext, _dl_tlsdesc_dynamic
does not have  HWCAP_ARM_IWMMXT (I don't have a way to properly test
it and it is almost a decade since newer hardware was released).

With this patch there is no need to mark tst-gnu2-tls2 as XFAIL.

Checked on arm-linux-gnueabihf.
---
 config.h.in                 |   3 +
 elf/Makefile                |   4 --
 elf/tst-gnu2-tls2.h         |   4 ++
 elf/tst-gnu2-tls2mod0.c     |   3 +-
 elf/tst-gnu2-tls2mod1.c     |   3 +-
 elf/tst-gnu2-tls2mod2.c     |   3 +-
 sysdeps/arm/configure       |  32 +++++++++
 sysdeps/arm/configure.ac    |  15 +++++
 sysdeps/arm/dl-tlsdesc.S    |  70 +++++++++++++++++---
 sysdeps/arm/tst-gnu2-tls2.h | 128 ++++++++++++++++++++++++++++++++++++
 10 files changed, 250 insertions(+), 15 deletions(-)
 create mode 100644 sysdeps/arm/tst-gnu2-tls2.h

On Tue, Mar 12, 2024 at 9:21 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> ARM _dl_tlsdesc_dynamic slow path has two issues:
>
>   * The ip/r12 is defined by AAPCS as a scratch register, and gcc is
>     used to save the stack pointer before on some function calls.  So it
>     should also be saved/restored as well.  It fixes the tst-gnu2-tls2.
>
>   * None of the possible VFP registers are saved/restored.  ARM has the
>     additional complexity to have different VFP bank sizes (depending of
>     VFP support by the chip).
>
> The tst-gnu2-tls2 test is extended to check for VFP registers, although
> only for hardfp builds.  Different than setcontext, _dl_tlsdesc_dynamic
> does not have  HWCAP_ARM_IWMMXT (I don't have a way to properly test
> it and it is almost a decade since newer hardware was released).
>
> With this patch there is no need to mark tst-gnu2-tls2 as XFAIL.
>
> Checked on arm-linux-gnueabihf.
> ---
>  config.h.in                 |   3 +
>  elf/Makefile                |   4 --
>  elf/tst-gnu2-tls2.h         |   4 ++
>  elf/tst-gnu2-tls2mod0.c     |   3 +-
>  elf/tst-gnu2-tls2mod1.c     |   3 +-
>  elf/tst-gnu2-tls2mod2.c     |   3 +-
>  sysdeps/arm/configure       |  32 +++++++++
>  sysdeps/arm/configure.ac    |  15 +++++
>  sysdeps/arm/dl-tlsdesc.S    |  70 +++++++++++++++++---
>  sysdeps/arm/tst-gnu2-tls2.h | 128 ++++++++++++++++++++++++++++++++++++
>  10 files changed, 250 insertions(+), 15 deletions(-)
>  create mode 100644 sysdeps/arm/tst-gnu2-tls2.h
>
> diff --git a/config.h.in b/config.h.in
> index 2f0669e19b..cf4212f5eb 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -141,6 +141,9 @@
>  /* LOONGARCH floating-point ABI for ld.so.  */
>  #undef LOONGARCH_ABI_FRLEN
>
> +/* Define whether ARM used hard-float and support VFPvX-D32.  */
> +#undef HAVE_ARM_PCS_VFP_D32
> +
>  /* Linux specific: minimum supported kernel version.  */
>  #undef __LINUX_KERNEL_VERSION
>
> diff --git a/elf/Makefile b/elf/Makefile
> index 520a270f0f..393a27ef2a 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -3059,10 +3059,6 @@ $(objpfx)tst-gnu2-tls2.out: \
>    $(objpfx)tst-gnu2-tls2mod2.so
>
>  ifeq (yes,$(have-mtls-dialect-gnu2))
> -# This test fails if dl_tlsdesc_dynamic doesn't preserve all caller-saved
> -# registers.  See https://sourceware.org/bugzilla/show_bug.cgi?id=31372
> -test-xfail-tst-gnu2-tls2 = yes
> -
>  CFLAGS-tst-tlsgap-mod0.c += -mtls-dialect=gnu2
>  CFLAGS-tst-tlsgap-mod1.c += -mtls-dialect=gnu2
>  CFLAGS-tst-tlsgap-mod2.c += -mtls-dialect=gnu2
> diff --git a/elf/tst-gnu2-tls2.h b/elf/tst-gnu2-tls2.h
> index 77964a57a3..1ade8151e2 100644
> --- a/elf/tst-gnu2-tls2.h
> +++ b/elf/tst-gnu2-tls2.h
> @@ -27,6 +27,10 @@ extern struct tls *apply_tls (struct tls *);
>
>  /* An architecture can define them to verify that clobber caller-saved
>     registers aren't changed by the implicit TLSDESC call.  */
> +#ifndef INIT_TLSDESC_CALL
> +# define INIT_TLSDESC_CALL()
> +#endif
> +
>  #ifndef BEFORE_TLSDESC_CALL
>  # define BEFORE_TLSDESC_CALL()
>  #endif
> diff --git a/elf/tst-gnu2-tls2mod0.c b/elf/tst-gnu2-tls2mod0.c
> index 45556a0e17..3fe3c14277 100644
> --- a/elf/tst-gnu2-tls2mod0.c
> +++ b/elf/tst-gnu2-tls2mod0.c
> @@ -16,13 +16,14 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include "tst-gnu2-tls2.h"
> +#include <tst-gnu2-tls2.h>
>
>  __thread struct tls tls_var0 __attribute__ ((visibility ("hidden")));
>
>  struct tls *
>  apply_tls (struct tls *p)
>  {
> +  INIT_TLSDESC_CALL ();
>    BEFORE_TLSDESC_CALL ();
>    tls_var0 = *p;
>    struct tls *ret = &tls_var0;
> diff --git a/elf/tst-gnu2-tls2mod1.c b/elf/tst-gnu2-tls2mod1.c
> index e10b9dbc0a..e210538468 100644
> --- a/elf/tst-gnu2-tls2mod1.c
> +++ b/elf/tst-gnu2-tls2mod1.c
> @@ -16,13 +16,14 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include "tst-gnu2-tls2.h"
> +#include <tst-gnu2-tls2.h>
>
>  __thread struct tls tls_var1[100] __attribute__ ((visibility ("hidden")));
>
>  struct tls *
>  apply_tls (struct tls *p)
>  {
> +  INIT_TLSDESC_CALL ();
>    BEFORE_TLSDESC_CALL ();
>    tls_var1[1] = *p;
>    struct tls *ret = &tls_var1[1];
> diff --git a/elf/tst-gnu2-tls2mod2.c b/elf/tst-gnu2-tls2mod2.c
> index 141af51e55..6d3031dc5f 100644
> --- a/elf/tst-gnu2-tls2mod2.c
> +++ b/elf/tst-gnu2-tls2mod2.c
> @@ -16,13 +16,14 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include "tst-gnu2-tls2.h"
> +#include <tst-gnu2-tls2.h>
>
>  __thread struct tls tls_var2 __attribute__ ((visibility ("hidden")));
>
>  struct tls *
>  apply_tls (struct tls *p)
>  {
> +  INIT_TLSDESC_CALL ();
>    BEFORE_TLSDESC_CALL ();
>    tls_var2 = *p;
>    struct tls *ret = &tls_var2;
> diff --git a/sysdeps/arm/configure b/sysdeps/arm/configure
> index 35e2918922..4ef4d46cbd 100644
> --- a/sysdeps/arm/configure
> +++ b/sysdeps/arm/configure
> @@ -187,6 +187,38 @@ else
>  default-abi = soft"
>  fi
>
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether VFP supports 32 registers" >&5
> +printf %s "checking whether VFP supports 32 registers... " >&6; }
> +if test ${libc_cv_arm_pcs_vfp_d32+y}
> +then :
> +  printf %s "(cached) " >&6
> +else $as_nop
> +
> +cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +
> +void foo (void)
> +{
> +  asm volatile ("vldr d16,=17" : : : "d16");
> +}
> +
> +_ACEOF
> +if ac_fn_c_try_compile "$LINENO"
> +then :
> +  libc_cv_arm_pcs_vfp_d32=yes
> +else $as_nop
> +  libc_cv_arm_pcs_vfp_d32=no
> +fi
> +rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
> +fi
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_arm_pcs_vfp_d32" >&5
> +printf "%s\n" "$libc_cv_arm_pcs_vfp_d32" >&6; }
> +if test "$libc_cv_arm_pcs_vfp_d32" = yes ;
> +then
> +  printf "%s\n" "#define HAVE_ARM_PCS_VFP_D32 1" >>confdefs.h
> +
> +fi
> +
>  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether PC-relative relocs in movw/movt work properly" >&5
>  printf %s "checking whether PC-relative relocs in movw/movt work properly... " >&6; }
>  if test ${libc_cv_arm_pcrel_movw+y}
> diff --git a/sysdeps/arm/configure.ac b/sysdeps/arm/configure.ac
> index 5172e30bbe..cd00ddc9d9 100644
> --- a/sysdeps/arm/configure.ac
> +++ b/sysdeps/arm/configure.ac
> @@ -21,6 +21,21 @@ else
>    LIBC_CONFIG_VAR([default-abi], [soft])
>  fi
>
> +AC_CACHE_CHECK([whether VFP supports 32 registers],
> +               libc_cv_arm_pcs_vfp_d32, [
> +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
> +void foo (void)
> +{
> +  asm volatile ("vldr d16,=17" : : : "d16");
> +}
> +]])],
> +                [libc_cv_arm_pcs_vfp_d32=yes],
> +                [libc_cv_arm_pcs_vfp_d32=no])])
> +if test "$libc_cv_arm_pcs_vfp_d32" = yes ;
> +then
> +  AC_DEFINE(HAVE_ARM_PCS_VFP_D32)
> +fi
> +
>  AC_CACHE_CHECK([whether PC-relative relocs in movw/movt work properly],
>                libc_cv_arm_pcrel_movw, [
>  cat > conftest.s <<\EOF
> diff --git a/sysdeps/arm/dl-tlsdesc.S b/sysdeps/arm/dl-tlsdesc.S
> index 764c56e70f..ada106521d 100644
> --- a/sysdeps/arm/dl-tlsdesc.S
> +++ b/sysdeps/arm/dl-tlsdesc.S
> @@ -19,6 +19,7 @@
>  #include <sysdep.h>
>  #include <arm-features.h>
>  #include <tls.h>
> +#include <rtld-global-offsets.h>
>  #include "tlsdesc.h"
>
>         .text
> @@ -83,14 +84,20 @@ _dl_tlsdesc_dynamic(struct tlsdesc *tdp)
>         .align 2
>  _dl_tlsdesc_dynamic:
>         /* Our calling convention is to clobber r0, r1 and the processor
> -          flags.  All others that are modified must be saved */
> -       eabi_save ({r2,r3,r4,lr})
> -       push    {r2,r3,r4,lr}
> -       cfi_adjust_cfa_offset (16)
> +          flags.  All others that are modified must be saved.  r5 is
> +          used as the hwcap value to avoid reload after __tls_get_addr
> +          call.  If required we will save the vector register on the slow
> +          path.  */
> +       eabi_save ({r2,r3,r4,r5,ip,lr})
> +       push    {r2,r3,r4,r5,ip,lr}
> +       cfi_adjust_cfa_offset (24)
>         cfi_rel_offset (r2,0)
>         cfi_rel_offset (r3,4)
>         cfi_rel_offset (r4,8)
> -       cfi_rel_offset (lr,12)
> +       cfi_rel_offset (r5,12)
> +       cfi_rel_offset (ip,16)
> +       cfi_rel_offset (lr,20)
> +
>         ldr     r1, [r0] /* td */
>         GET_TLS (lr)
>         mov     r4, r0 /* r4 = tp */
> @@ -113,22 +120,69 @@ _dl_tlsdesc_dynamic:
>         rsbne   r0, r4, r3
>         bne     2f
>  1:     mov     r0, r1
> +
> +       /* Load the hwcap to check for vector support.  */
> +       ldr     r2, 3f
> +       ldr     r1, .Lrtld_global_ro
> +0:     add     r2, pc, r2
> +       ldr     r2, [r2, r1]
> +       ldr     r5, [r2, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
> +
> +#ifdef __SOFTFP__
> +       tst     r5, #HWCAP_ARM_VFP
> +       beq     .Lno_vfp
> +#endif
> +
> +       /* Store the VFP registers.  Don't use VFP instructions directly
> +          because this code is used in non-VFP multilibs.  */
> +#define VFP_STACK_REQ (32*8 + 8)
> +       sub     sp, sp, VFP_STACK_REQ
> +       cfi_adjust_cfa_offset (VFP_STACK_REQ)
> +       mov     r3, sp
> +       .inst   0xeca30b20      /* vstmia r3!, {d0-d15} */
> +       tst     r5, #HWCAP_ARM_VFPD32
> +       beq     4f
> +       .inst   0xece30b20      /* vstmia r3!, {d16-d31}  */
> +       /* Store the floating-point status register.  */
> +4:     .inst   0xeef12a10      /* vmrs r2, fpscr */
> +       str     r2, [r3]
> +.Lno_vfp:
>         bl      __tls_get_addr
>         rsb     r0, r4, r0
> +#ifdef __SOFTFP__
> +       tst     r5, #HWCAP_ARM_VFP
> +       beq     2f
> +#endif
> +       mov     r3, sp
> +       .inst   0xecb30b20      /* vldmia r3!, {d0-d15}  */
> +       tst     r5, #HWCAP_ARM_VFPD32
> +       beq     5f
> +       .inst   0xecf30b20      /* vldmia r3!, {d16-d31}  */
> +       ldr     r4, [r3]
> +5:     .inst   0xeee14a10      /* vmsr fpscr, r4  */
> +       add     sp, sp, VFP_STACK_REQ
> +       cfi_adjust_cfa_offset (-VFP_STACK_REQ)
> +
>  2:
>  #if ((defined (__ARM_ARCH_4T__) && defined (__THUMB_INTERWORK__)) \
>       || defined (ARM_ALWAYS_BX))
> -       pop     {r2,r3,r4, lr}
> -       cfi_adjust_cfa_offset (-16)
> +       pop     {r2,r3,r4,r5,ip, lr}
> +       cfi_adjust_cfa_offset (-20)
>         cfi_restore (lr)
> +       cfi_restore (ip)
> +       cfi_restore (r5)
>         cfi_restore (r4)
>         cfi_restore (r3)
>         cfi_restore (r2)
>         bx      lr
>  #else
> -       pop     {r2,r3,r4, pc}
> +       pop     {r2,r3,r4,r5,ip, pc}
>  #endif
>         eabi_fnend
>         cfi_endproc
>         .size   _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
> +
> +3:      .long   _GLOBAL_OFFSET_TABLE_ - 0b - PC_OFS
> +.Lrtld_global_ro:
> +       .long   C_SYMBOL_NAME(_rtld_global_ro)(GOT)
>  #endif /* SHARED */
> diff --git a/sysdeps/arm/tst-gnu2-tls2.h b/sysdeps/arm/tst-gnu2-tls2.h
> new file mode 100644
> index 0000000000..e413ac21fb
> --- /dev/null
> +++ b/sysdeps/arm/tst-gnu2-tls2.h
> @@ -0,0 +1,128 @@
> +/* Test TLSDESC relocation.  ARM version.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <config.h>
> +#include <sys/auxv.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <endian.h>
> +
> +#ifndef __SOFTFP__
> +
> +# ifdef HAVE_ARM_PCS_VFP_D32
> +#  define SAVE_VFP_D32                                 \
> +      asm volatile ("vldr d16,=17" : : : "d16");       \
> +      asm volatile ("vldr d17,=18" : : : "d17");       \
> +      asm volatile ("vldr d18,=19" : : : "d18");       \
> +      asm volatile ("vldr d19,=20" : : : "d19");       \
> +      asm volatile ("vldr d20,=21" : : : "d20");       \
> +      asm volatile ("vldr d21,=22" : : : "d21");       \
> +      asm volatile ("vldr d22,=23" : : : "d22");       \
> +      asm volatile ("vldr d23,=24" : : : "d23");       \
> +      asm volatile ("vldr d24,=25" : : : "d24");       \
> +      asm volatile ("vldr d25,=26" : : : "d25");       \
> +      asm volatile ("vldr d26,=27" : : : "d26");       \
> +      asm volatile ("vldr d27,=28" : : : "d27");       \
> +      asm volatile ("vldr d28,=29" : : : "d28");       \
> +      asm volatile ("vldr d29,=30" : : : "d29");       \
> +      asm volatile ("vldr d30,=31" : : : "d30");       \
> +      asm volatile ("vldr d31,=32" : : : "d31");
> +# else
> +#  define SAVE_VFP_D32
> +# endif
> +
> +# define INIT_TLSDESC_CALL()                           \
> +  unsigned long hwcap = getauxval (AT_HWCAP)
> +
> +/* Set each vector register to a value from 1 to 32 before the TLS access,
> +   dump to memory after TLS access, and compare with the expected values.  */
> +
> +# define BEFORE_TLSDESC_CALL()                         \
> +  if (hwcap & HWCAP_ARM_VFP)                           \
> +    {                                                  \
> +      asm volatile ("vldr  d0,=1" : : : "d0");         \
> +      asm volatile ("vldr  d1,=2" : : : "d1");         \
> +      asm volatile ("vldr  d2,=3" : : : "d1");         \
> +      asm volatile ("vldr  d3,=4" : : : "d3");         \
> +      asm volatile ("vldr  d4,=5" : : : "d4");         \
> +      asm volatile ("vldr  d5,=6" : : : "d5");         \
> +      asm volatile ("vldr  d6,=7" : : : "d6");         \
> +      asm volatile ("vldr  d7,=8" : : : "d7");         \
> +      asm volatile ("vldr  d8,=9" : : : "d8");         \
> +      asm volatile ("vldr  d9,=10" : : : "d9");                \
> +      asm volatile ("vldr d10,=11" : : : "d10");       \
> +      asm volatile ("vldr d11,=12" : : : "d11");       \
> +      asm volatile ("vldr d12,=13" : : : "d12");       \
> +      asm volatile ("vldr d13,=14" : : : "d13");       \
> +      asm volatile ("vldr d14,=15" : : : "d14");       \
> +      asm volatile ("vldr d15,=16" : : : "d15");       \
> +    }                                                  \
> +  if (hwcap & HWCAP_ARM_VFPD32)                                \
> +    {                                                  \
> +      SAVE_VFP_D32                                     \
> +    }
> +
> +# define VFP_STACK_REQ (16*8)
> +# if __BYTE_ORDER == __BIG_ENDIAN
> +#  define DISP 7
> +# else
> +#  define DISP 0
> +# endif
> +
> +# ifdef HAVE_ARM_PCS_VFP_D32
> +#  define CHECK_VFP_D32                                                        \
> +      char vfp[VFP_STACK_REQ];                                         \
> +      asm volatile ("vstmia %0, {d16-d31}\n"                           \
> +                   :                                                   \
> +                   : "r" (vfp)                                         \
> +                   : "memory");                                        \
> +                                                                       \
> +      char expected[VFP_STACK_REQ] = { 0 };                            \
> +      for (int i = 0; i < 16; ++i)                                     \
> +       expected[i * 8 + DISP] = i + 17;                                \
> +                                                                       \
> +      if (memcmp (vfp, expected, VFP_STACK_REQ) != 0)                  \
> +        abort ();
> +# else
> +#  define CHECK_VFP_D32
> +# endif
> +
> +# define AFTER_TLSDESC_CALL()                                          \
> +  if (hwcap & HWCAP_ARM_VFP)                                           \
> +    {                                                                  \
> +      char vfp[VFP_STACK_REQ];                                         \
> +      asm volatile ("vstmia %0, {d0-d15}\n"                            \
> +                   :                                                   \
> +                   : "r" (vfp)                                         \
> +                   : "memory");                                        \
> +                                                                       \
> +      char expected[VFP_STACK_REQ] = { 0 };                            \
> +      for (int i = 0; i < 16; ++i)                                     \
> +       expected[i * 8 + DISP] = i + 1;                                 \
> +                                                                       \
> +      if (memcmp (vfp, expected, VFP_STACK_REQ) != 0)                  \
> +        abort ();                                                      \
> +    }                                                                  \
> +  if (hwcap & HWCAP_ARM_VFPD32)                                                \
> +    {                                                                  \
> +      CHECK_VFP_D32                                                    \
> +    }
> +
> +#endif /* __SOFTFP__ */
> +
> +#include_next <tst-gnu2-tls2.h>
> --
> 2.34.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.