Re: [PATCH v7 2/2] x86: Update _dl_tlsdesc_dynamic to preserve caller-saved registers

["H.J. Lu" <hjl.tools@gmail.com>]

On Fri, Feb 16, 2024 at 12:05 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Fri, Feb 16, 2024 at 12:21 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > Compiler generates the following instruction sequence for GNU2 dynamic
> > TLS access:
> >
> >         leaq    tls_var@TLSDESC(%rip), %rax
> >         call    *tls_var@TLSCALL(%rax)
> >
> > or
> >
> >         leal    tls_var@TLSDESC(%ebx), %eax
> >         call    *tls_var@TLSCALL(%eax)
> >
> > CALL instruction is transparent to compiler which assumes all registers,
> > except for EFLAGS and RAX/EAX, are unchanged after CALL.  When
> > _dl_tlsdesc_dynamic is called, it calls __tls_get_addr on the slow
> > path.  __tls_get_addr is a normal function which doesn't preserve any
> > caller-saved registers.  _dl_tlsdesc_dynamic saved and restored integer
> > caller-saved registers, but didn't preserve any other caller-saved
> > registers.  Add _dl_tlsdesc_dynamic IFUNC functions for FNSAVE, FXSAVE,
> > XSAVE and XSAVEC to save and restore all caller-saved registers.  This
> > fixes BZ #31372.
> >
> > Add GLRO(dl_x86_64_runtime_resolve) with GLRO(dl_x86_tlsdesc_dynamic)
> > to optimize elf_machine_runtime_setup.
> > ---
> >  elf/Makefile                                 |  36 +++-
> >  elf/malloc-for-test.c                        |  32 ++++
> >  elf/malloc-for-test.map.in                   |   8 +
> >  elf/tst-gnu2-tls2.c                          |  97 ++++++++++
> >  elf/tst-gnu2-tls2.h                          |  26 +++
> >  elf/tst-gnu2-tls2mod0.c                      |  28 +++
> >  elf/tst-gnu2-tls2mod1.c                      |  28 +++
> >  elf/tst-gnu2-tls2mod2.c                      |  28 +++
> >  sysdeps/i386/dl-machine.h                    |   2 +-
> >  sysdeps/i386/dl-tlsdesc-dynamic.h            | 190 +++++++++++++++++++
> >  sysdeps/i386/dl-tlsdesc.S                    | 115 +++++------
> >  sysdeps/i386/tst-gnu2-tls2.c                 |   5 +
> >  sysdeps/x86/Makefile                         |   7 +-
> >  sysdeps/x86/cpu-features.c                   |  56 +++++-
> >  sysdeps/x86/dl-procinfo.c                    |  16 ++
> >  sysdeps/{x86_64 => x86}/features-offsets.sym |   2 +
> >  sysdeps/x86/malloc-for-test.c                |  33 ++++
> >  sysdeps/x86/sysdep.h                         |   6 +
> >  sysdeps/x86_64/Makefile                      |   2 +-
> >  sysdeps/x86_64/dl-machine.h                  |  19 +-
> >  sysdeps/x86_64/dl-procinfo.c                 |  16 ++
> >  sysdeps/x86_64/dl-tlsdesc-dynamic.h          | 166 ++++++++++++++++
> >  sysdeps/x86_64/dl-tlsdesc.S                  | 108 ++++-------
> >  sysdeps/x86_64/dl-trampoline-save.h          |  34 ++++
> >  sysdeps/x86_64/dl-trampoline-state.h         |  51 +++++
> >  sysdeps/x86_64/dl-trampoline.S               |  20 +-
> >  sysdeps/x86_64/dl-trampoline.h               |  34 +---
> >  27 files changed, 950 insertions(+), 215 deletions(-)
> >  create mode 100644 elf/malloc-for-test.c
> >  create mode 100644 elf/malloc-for-test.map.in
> >  create mode 100644 elf/tst-gnu2-tls2.c
> >  create mode 100644 elf/tst-gnu2-tls2.h
> >  create mode 100644 elf/tst-gnu2-tls2mod0.c
> >  create mode 100644 elf/tst-gnu2-tls2mod1.c
> >  create mode 100644 elf/tst-gnu2-tls2mod2.c
> >  create mode 100644 sysdeps/i386/dl-tlsdesc-dynamic.h
> >  create mode 100644 sysdeps/i386/tst-gnu2-tls2.c
> >  rename sysdeps/{x86_64 => x86}/features-offsets.sym (89%)
> >  create mode 100644 sysdeps/x86/malloc-for-test.c
> >  create mode 100644 sysdeps/x86_64/dl-tlsdesc-dynamic.h
> >  create mode 100644 sysdeps/x86_64/dl-trampoline-save.h
> >  create mode 100644 sysdeps/x86_64/dl-trampoline-state.h
> >
...
> > diff --git a/sysdeps/i386/dl-tlsdesc-dynamic.h b/sysdeps/i386/dl-tlsdesc-dynamic.h
> > new file mode 100644
> > index 0000000000..c857c68c55
> > --- /dev/null
> > +++ b/sysdeps/i386/dl-tlsdesc-dynamic.h
> > @@ -0,0 +1,190 @@
> > +/* Thread-local storage handling in the ELF dynamic linker.  i386 version.
> > +   Copyright (C) 2004-2024 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/>.  */
> > +
> > +#undef REGISTER_SAVE_AREA
> > +
> > +#if !defined USE_FNSAVE && (STATE_SAVE_ALIGNMENT % 16) != 0
> > +# error STATE_SAVE_ALIGNMENT must be multiple of 16
> > +#endif
> > +
> > +#if DL_RUNTIME_RESOLVE_REALIGN_STACK
> > +# ifdef USE_FNSAVE
> > +#  error USE_FNSAVE shouldn't be defined
> > +# endif
> > +# ifdef USE_FXSAVE
> > +/* Use fxsave to save all registers.  */
> > +#  define REGISTER_SAVE_AREA   512
> > +# endif
> > +#else
> > +# ifdef USE_FNSAVE
> > +/* Use fnsave to save x87 FPU stack registers.  */
> > +#  define REGISTER_SAVE_AREA   108
> > +# else
> > +#  ifndef USE_FXSAVE
> > +#   error USE_FXSAVE must be defined
> > +#  endif
> > +/* Use fxsave to save all registers.  Add 12 bytes to align the stack
> > +   to 16 bytes.  */
> > +#  define REGISTER_SAVE_AREA   (512 + 12)
> > +# endif
> > +#endif
> > +
> > +       .hidden _dl_tlsdesc_dynamic
> > +       .global _dl_tlsdesc_dynamic
> > +       .type   _dl_tlsdesc_dynamic,@function
> > +
> > +     /* This function is used for symbols that need dynamic TLS.
> > +
> nit: comment start at line start.

This is copied from the original dl-tlsdesc.S.  I prefer to leave it
alone.

> > +       %eax points to the TLS descriptor, such that 0(%eax) points to
> > +       _dl_tlsdesc_dynamic itself, and 4(%eax) points to a struct
> > +       tlsdesc_dynamic_arg object.  It must return in %eax the offset
> > +       between the thread pointer and the object denoted by the
> > +       argument, without clobbering any registers.
> > +
> > +       The assembly code that follows is a rendition of the following
> > +       C code, hand-optimized a little bit.
> > +
> > +ptrdiff_t
> > +__attribute__ ((__regparm__ (1)))
> > +_dl_tlsdesc_dynamic (struct tlsdesc *tdp)
> > +{
> > +  struct tlsdesc_dynamic_arg *td = tdp->arg;
> > +  dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + DTV_OFFSET);
> > +  if (__builtin_expect (td->gen_count <= dtv[0].counter
> > +                       && (dtv[td->tlsinfo.ti_module].pointer.val
> > +                           != TLS_DTV_UNALLOCATED),
> > +                       1))
> > +    return dtv[td->tlsinfo.ti_module].pointer.val + td->tlsinfo.ti_offset
> > +      - __thread_pointer;
> > +
> > +  return ___tls_get_addr (&td->tlsinfo) - __thread_pointer;
> > +}
> > +*/
> > +       cfi_startproc
> > +       .align 16
> > +_dl_tlsdesc_dynamic:
> > +       /* Like all TLS resolvers, preserve call-clobbered registers.
> > +          We need two scratch regs anyway.  */
> > +       subl    $32, %esp
> > +       cfi_adjust_cfa_offset (32)
> > +       movl    %ecx, 20(%esp)
> > +       movl    %edx, 24(%esp)
> > +       movl    TLSDESC_ARG(%eax), %eax
> > +       movl    %gs:DTV_OFFSET, %edx
> > +       movl    TLSDESC_GEN_COUNT(%eax), %ecx
> > +       cmpl    (%edx), %ecx
> > +       ja      2f
> > +       movl    TLSDESC_MODID(%eax), %ecx
> > +       movl    (%edx,%ecx,8), %edx
> maybe 8 -> TLSDESC_DTV_SIZE?

This is copied from the original dl-tlsdesc.S.  I prefer to leave it
alone.

> > +       cmpl    $-1, %edx
> -1 -> TLS_DTV_UNALLOCATED

This is copied from the original dl-tlsdesc.S.  I prefer to leave it
alone.

> > +       je      2f
> > +       movl    TLSDESC_MODOFF(%eax), %eax
> > +       addl    %edx, %eax
> > +1:
> > +       movl    20(%esp), %ecx
> > +       subl    %gs:0, %eax
> > +       movl    24(%esp), %edx
> > +       addl    $32, %esp
> > +       cfi_adjust_cfa_offset (-32)
> > +       ret
> > +       .p2align 4,,7
> > +2:
> > +       cfi_adjust_cfa_offset (32)
> I still don't understand what this cfi is for?
> You already have `cfi_adjust_cfa_offset (32)` above right after
> the `subl $32, %esp`

There are

        subl    $32, %esp
        cfi_adjust_cfa_offset (32)
...
        addl    $32, %esp
        cfi_adjust_cfa_offset (-32)
        ret
        .p2align 4,,7
2:

What is the CFA at the label 2 for GDB?  GDB only consumes CFI
directives.

> > +#if DL_RUNTIME_RESOLVE_REALIGN_STACK
> > +       movl    %ebx, -28(%esp)
> > +       movl    %esp, %ebx
> > +       cfi_def_cfa_register(%ebx)
> > +       and     $-STATE_SAVE_ALIGNMENT, %esp
> > +#endif
> > +#ifdef REGISTER_SAVE_AREA
> > +       subl    $REGISTER_SAVE_AREA, %esp
> > +# if !DL_RUNTIME_RESOLVE_REALIGN_STACK
> > +       cfi_adjust_cfa_offset(REGISTER_SAVE_AREA)
> > +# endif
> > +#else
> > +# if !DL_RUNTIME_RESOLVE_REALIGN_STACK
> > +#  error DL_RUNTIME_RESOLVE_REALIGN_STACK must be true
> > +# endif
> > +       # Allocate stack space of the required size to save the state.
> nit: comment with /* or //
> likewise below.

Will fix them.

> > +       LOAD_PIC_REG (cx)
> > +       subl    RTLD_GLOBAL_RO_DL_X86_CPU_FEATURES_OFFSET+XSAVE_STATE_SIZE_OFFSET+_rtld_local_ro@GOTOFF(%ecx), %esp
> > +#endif
> > +#ifdef USE_FNSAVE
> > +       fnsave  (%esp)
> > +#elif defined USE_FXSAVE
> > +       fxsave  (%esp)
> > +#else
> > +       # Save the argument for ___tls_get_addr in EAX.
> > +       movl    %eax, %ecx
> > +       movl    $TLSDESC_CALL_STATE_SAVE_MASK, %eax
> > +       xorl    %edx, %edx
> > +       # Clear the XSAVE Header.
> > +# ifdef USE_XSAVE
> > +       movl    %edx, (512)(%esp)
> > +       movl    %edx, (512 + 4 * 1)(%esp)
> > +       movl    %edx, (512 + 4 * 2)(%esp)
> > +       movl    %edx, (512 + 4 * 3)(%esp)
> > +# endif
> > +       movl    %edx, (512 + 4 * 4)(%esp)
> > +       movl    %edx, (512 + 4 * 5)(%esp)
> > +       movl    %edx, (512 + 4 * 6)(%esp)
> > +       movl    %edx, (512 + 4 * 7)(%esp)
> > +       movl    %edx, (512 + 4 * 8)(%esp)
> > +       movl    %edx, (512 + 4 * 9)(%esp)
> > +       movl    %edx, (512 + 4 * 10)(%esp)
> > +       movl    %edx, (512 + 4 * 11)(%esp)
> > +       movl    %edx, (512 + 4 * 12)(%esp)
> > +       movl    %edx, (512 + 4 * 13)(%esp)
> > +       movl    %edx, (512 + 4 * 14)(%esp)
> > +       movl    %edx, (512 + 4 * 15)(%esp)
> > +# ifdef USE_XSAVE
> > +       xsave   (%esp)
> > +# else
> > +       xsavec  (%esp)
> > +# endif
> > +       # Restore the argument for ___tls_get_addr in EAX.
> > +       movl    %ecx, %eax
> > +#endif
> > +       call    HIDDEN_JUMPTARGET (___tls_get_addr)
> > +       # Get register content back.
> > +#ifdef USE_FNSAVE
> > +       frstor  (%esp)
> > +#elif defined USE_FXSAVE
> > +       fxrstor (%esp)
> > +#else
> > +       /* Save and retore ___tls_get_addr return value stored in EAX.  */
> > +       movl    %eax, %ecx
> > +       movl    $TLSDESC_CALL_STATE_SAVE_MASK, %eax
> > +       xorl    %edx, %edx
> > +       xrstor  (%esp)
> > +       movl    %ecx, %eax
> > +#endif
> > +#if DL_RUNTIME_RESOLVE_REALIGN_STACK
> > +       mov     %ebx, %esp
> > +       cfi_def_cfa_register(%esp)
> > +       movl    -28(%esp), %ebx
> > +       cfi_restore(%ebx)
> > +#else
> > +       addl    $REGISTER_SAVE_AREA, %esp
> > +       cfi_adjust_cfa_offset(-REGISTER_SAVE_AREA)
> > +#endif
> > +       jmp     1b
> > +       cfi_endproc
> > +       .size   _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
> > +
> > +#undef STATE_SAVE_ALIGNMENT
> > diff --git a/sysdeps/i386/dl-tlsdesc.S b/sysdeps/i386/dl-tlsdesc.S
> > index 90d93caa0c..f002feee56 100644
> > --- a/sysdeps/i386/dl-tlsdesc.S
> > +++ b/sysdeps/i386/dl-tlsdesc.S
> > @@ -18,8 +18,27 @@
> >
> >  #include <sysdep.h>
> >  #include <tls.h>
> > +#include <cpu-features-offsets.h>
> > +#include <features-offsets.h>
> >  #include "tlsdesc.h"
> >
> > +#ifndef DL_STACK_ALIGNMENT
> > +/* Due to GCC bug:
> > +
> > +   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
> > +
> > +   __tls_get_addr may be called with 4-byte stack alignment.  Although
> > +   this bug has been fixed in GCC 4.9.4, 5.3 and 6, we can't assume
> > +   that stack will be always aligned at 16 bytes.  */
> > +# define DL_STACK_ALIGNMENT 4
> > +#endif
> > +
> > +/* True if _dl_tlsdesc_dynamic should align stack for STATE_SAVE or align
> > +   stack to MINIMUM_ALIGNMENT bytes before calling ___tls_get_addr.  */
> > +#define DL_RUNTIME_RESOLVE_REALIGN_STACK \
> > +  (STATE_SAVE_ALIGNMENT > DL_STACK_ALIGNMENT \
> > +   || MINIMUM_ALIGNMENT > DL_STACK_ALIGNMENT)
> > +
> >         .text
> >
> >       /* This function is used to compute the TP offset for symbols in
> > @@ -65,69 +84,35 @@ _dl_tlsdesc_undefweak:
> >         .size   _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak
> >
> >  #ifdef SHARED
> > -       .hidden _dl_tlsdesc_dynamic
> > -       .global _dl_tlsdesc_dynamic
> > -       .type   _dl_tlsdesc_dynamic,@function
> > -
> > -     /* This function is used for symbols that need dynamic TLS.
> > -
> > -       %eax points to the TLS descriptor, such that 0(%eax) points to
> > -       _dl_tlsdesc_dynamic itself, and 4(%eax) points to a struct
> > -       tlsdesc_dynamic_arg object.  It must return in %eax the offset
> > -       between the thread pointer and the object denoted by the
> > -       argument, without clobbering any registers.
> > -
> > -       The assembly code that follows is a rendition of the following
> > -       C code, hand-optimized a little bit.
> > -
> > -ptrdiff_t
> > -__attribute__ ((__regparm__ (1)))
> > -_dl_tlsdesc_dynamic (struct tlsdesc *tdp)
> > -{
> > -  struct tlsdesc_dynamic_arg *td = tdp->arg;
> > -  dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + DTV_OFFSET);
> > -  if (__builtin_expect (td->gen_count <= dtv[0].counter
> > -                       && (dtv[td->tlsinfo.ti_module].pointer.val
> > -                           != TLS_DTV_UNALLOCATED),
> > -                       1))
> > -    return dtv[td->tlsinfo.ti_module].pointer.val + td->tlsinfo.ti_offset
> > -      - __thread_pointer;
> > -
> > -  return ___tls_get_addr (&td->tlsinfo) - __thread_pointer;
> > -}
> > -*/
> > -       cfi_startproc
> > -       .align 16
> > -_dl_tlsdesc_dynamic:
> > -       /* Like all TLS resolvers, preserve call-clobbered registers.
> > -          We need two scratch regs anyway.  */
> > -       subl    $28, %esp
> > -       cfi_adjust_cfa_offset (28)
> > -       movl    %ecx, 20(%esp)
> > -       movl    %edx, 24(%esp)
> > -       movl    TLSDESC_ARG(%eax), %eax
> > -       movl    %gs:DTV_OFFSET, %edx
> > -       movl    TLSDESC_GEN_COUNT(%eax), %ecx
> > -       cmpl    (%edx), %ecx
> > -       ja      .Lslow
> > -       movl    TLSDESC_MODID(%eax), %ecx
> > -       movl    (%edx,%ecx,8), %edx
> > -       cmpl    $-1, %edx
> > -       je      .Lslow
> > -       movl    TLSDESC_MODOFF(%eax), %eax
> > -       addl    %edx, %eax
> > -.Lret:
> > -       movl    20(%esp), %ecx
> > -       subl    %gs:0, %eax
> > -       movl    24(%esp), %edx
> > -       addl    $28, %esp
> > -       cfi_adjust_cfa_offset (-28)
> > -       ret
> > -       .p2align 4,,7
> > -.Lslow:
> > -       cfi_adjust_cfa_offset (28)
> > -       call    HIDDEN_JUMPTARGET (___tls_get_addr)
> > -       jmp     .Lret
> > -       cfi_endproc
> > -       .size   _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
> > +# define USE_FNSAVE
> > +# define MINIMUM_ALIGNMENT     4
> > +# define STATE_SAVE_ALIGNMENT  4
> > +# define _dl_tlsdesc_dynamic   _dl_tlsdesc_dynamic_fnsave
> > +# include "dl-tlsdesc-dynamic.h"
> > +# undef _dl_tlsdesc_dynamic
> > +# undef MINIMUM_ALIGNMENT
> > +# undef USE_FNSAVE
> > +
> > +# define MINIMUM_ALIGNMENT     16
> > +
> > +# define USE_FXSAVE
> > +# define STATE_SAVE_ALIGNMENT  16
> > +# define _dl_tlsdesc_dynamic   _dl_tlsdesc_dynamic_fxsave
> > +# include "dl-tlsdesc-dynamic.h"
> > +# undef _dl_tlsdesc_dynamic
> > +# undef USE_FXSAVE
> > +
> > +# define USE_XSAVE
> > +# define STATE_SAVE_ALIGNMENT  64
> > +# define _dl_tlsdesc_dynamic   _dl_tlsdesc_dynamic_xsave
> > +# include "dl-tlsdesc-dynamic.h"
> > +# undef _dl_tlsdesc_dynamic
> > +# undef USE_XSAVE
> > +
> > +# define USE_XSAVEC
> > +# define STATE_SAVE_ALIGNMENT  64
> > +# define _dl_tlsdesc_dynamic   _dl_tlsdesc_dynamic_xsavec
> > +# include "dl-tlsdesc-dynamic.h"
> > +# undef _dl_tlsdesc_dynamic
> > +# undef USE_XSAVEC
> >  #endif /* SHARED */
> > diff --git a/sysdeps/i386/tst-gnu2-tls2.c b/sysdeps/i386/tst-gnu2-tls2.c
> > new file mode 100644
> > index 0000000000..92e7fbff89
> > --- /dev/null
> > +++ b/sysdeps/i386/tst-gnu2-tls2.c
> > @@ -0,0 +1,5 @@
> > +#include <sys/platform/x86.h>
> > +
> > +#define IS_SUPPORTED() CPU_FEATURE_ACTIVE (SSE2)
> > +
> > +#include <elf/tst-gnu2-tls2.c>
> > diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
> > index 73b29cc78c..581086305d 100644
> > --- a/sysdeps/x86/Makefile
> > +++ b/sysdeps/x86/Makefile
> > @@ -1,5 +1,5 @@
> >  ifeq ($(subdir),csu)
> > -gen-as-const-headers += cpu-features-offsets.sym
> > +gen-as-const-headers += cpu-features-offsets.sym features-offsets.sym
> >  endif
> >
> >  ifeq ($(subdir),elf)
> > @@ -86,6 +86,11 @@ endif
> >  tst-ifunc-isa-2-ENV = GLIBC_TUNABLES=glibc.cpu.hwcaps=-SSE4_2,-AVX,-AVX2,-AVX512F
> >  tst-ifunc-isa-2-static-ENV = $(tst-ifunc-isa-2-ENV)
> >  tst-hwcap-tunables-ARGS = -- $(host-test-program-cmd)
> > +
> > +CFLAGS-malloc-for-test.c += -msse2
> > +CFLAGS-tst-gnu2-tls2mod0.c += -msse2 -mtune=haswell
> > +CFLAGS-tst-gnu2-tls2mod1.c += -msse2 -mtune=haswell
> > +CFLAGS-tst-gnu2-tls2mod2.c += -msse2 -mtune=haswell
> >  endif
> >
> >  ifeq ($(subdir),math)
> > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> > index 25e6622a79..835113b42f 100644
> > --- a/sysdeps/x86/cpu-features.c
> > +++ b/sysdeps/x86/cpu-features.c
> > @@ -27,8 +27,13 @@
> >  extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
> >    attribute_hidden;
> >
> > -#if defined SHARED && defined __x86_64__
> > -# include <dl-plt-rewrite.h>
> > +#if defined SHARED
> > +extern void _dl_tlsdesc_dynamic_fxsave (void) attribute_hidden;
> > +extern void _dl_tlsdesc_dynamic_xsave (void) attribute_hidden;
> > +extern void _dl_tlsdesc_dynamic_xsavec (void) attribute_hidden;
> > +
> > +# ifdef __x86_64__
> > +#  include <dl-plt-rewrite.h>
> >
> >  static void
> >  TUNABLE_CALLBACK (set_plt_rewrite) (tunable_val_t *valp)
> > @@ -47,6 +52,15 @@ TUNABLE_CALLBACK (set_plt_rewrite) (tunable_val_t *valp)
> >                  : plt_rewrite_jmp);
> >      }
> >  }
> > +# else
> > +extern void _dl_tlsdesc_dynamic_fnsave (void) attribute_hidden;
> > +# endif
> > +#endif
> > +
> > +#ifdef __x86_64__
> > +extern void _dl_runtime_resolve_fxsave (void) attribute_hidden;
> > +extern void _dl_runtime_resolve_xsave (void) attribute_hidden;
> > +extern void _dl_runtime_resolve_xsavec (void) attribute_hidden;
> >  #endif
> >
> >  #ifdef __LP64__
> > @@ -1130,6 +1144,44 @@ no_cpuid:
> >                TUNABLE_CALLBACK (set_x86_shstk));
> >  #endif
> >
> > +  if (GLRO(dl_x86_cpu_features).xsave_state_size != 0)
> > +    {
> > +      if (CPU_FEATURE_USABLE_P (cpu_features, XSAVEC))
> > +       {
> > +#ifdef __x86_64__
> > +         GLRO(dl_x86_64_runtime_resolve) = _dl_runtime_resolve_xsavec;
> > +#endif
> > +#ifdef SHARED
> > +         GLRO(dl_x86_tlsdesc_dynamic) = _dl_tlsdesc_dynamic_xsavec;
> > +#endif
> > +       }
> > +      else
> > +       {
> > +#ifdef __x86_64__
> > +         GLRO(dl_x86_64_runtime_resolve) = _dl_runtime_resolve_xsave;
> > +#endif
> > +#ifdef SHARED
> > +         GLRO(dl_x86_tlsdesc_dynamic) = _dl_tlsdesc_dynamic_xsave;
> > +#endif
> > +       }
> > +    }
> > +  else
> > +    {
> > +#ifdef __x86_64__
> > +      GLRO(dl_x86_64_runtime_resolve) = _dl_runtime_resolve_fxsave;
> > +# ifdef SHARED
> > +      GLRO(dl_x86_tlsdesc_dynamic) = _dl_tlsdesc_dynamic_fxsave;
> > +# endif
> > +#else
> > +# ifdef SHARED
> > +      if (CPU_FEATURE_USABLE_P (cpu_features, FXSR))
> > +       GLRO(dl_x86_tlsdesc_dynamic) = _dl_tlsdesc_dynamic_fxsave;
> > +      else
> > +       GLRO(dl_x86_tlsdesc_dynamic) = _dl_tlsdesc_dynamic_fnsave;
> > +# endif
> > +#endif
> > +    }
> > +
> >  #ifdef SHARED
> >  # ifdef __x86_64__
> >    TUNABLE_GET (plt_rewrite, tunable_val_t *,
> > diff --git a/sysdeps/x86/dl-procinfo.c b/sysdeps/x86/dl-procinfo.c
> > index ee957b4d70..5920d4b320 100644
> > --- a/sysdeps/x86/dl-procinfo.c
> > +++ b/sysdeps/x86/dl-procinfo.c
> > @@ -86,3 +86,19 @@ PROCINFO_CLASS const char _dl_x86_platforms[4][9]
> >  #else
> >  ,
> >  #endif
> > +
> > +#if defined SHARED && !IS_IN (ldconfig)
> > +# if !defined PROCINFO_DECL
> > +  ._dl_x86_tlsdesc_dynamic
> > +# else
> > +PROCINFO_CLASS void * _dl_x86_tlsdesc_dynamic
> > +# endif
> > +# ifndef PROCINFO_DECL
> > += NULL
> > +# endif
> > +# ifdef PROCINFO_DECL
> > +;
> > +# else
> > +,
> > +# endif
> > +#endif
> > diff --git a/sysdeps/x86_64/features-offsets.sym b/sysdeps/x86/features-offsets.sym
> > similarity index 89%
> > rename from sysdeps/x86_64/features-offsets.sym
> > rename to sysdeps/x86/features-offsets.sym
> > index 9e4be3393a..77e990c705 100644
> > --- a/sysdeps/x86_64/features-offsets.sym
> > +++ b/sysdeps/x86/features-offsets.sym
> > @@ -3,4 +3,6 @@
> >  #include <ldsodefs.h>
> >
> >  RTLD_GLOBAL_RO_DL_X86_CPU_FEATURES_OFFSET offsetof (struct rtld_global_ro, _dl_x86_cpu_features)
> > +#ifdef __x86_64__
> >  RTLD_GLOBAL_DL_X86_FEATURE_1_OFFSET offsetof (struct rtld_global, _dl_x86_feature_1)
> > +#endif
> > diff --git a/sysdeps/x86/malloc-for-test.c b/sysdeps/x86/malloc-for-test.c
> > new file mode 100644
> > index 0000000000..02f4dead5d
> > --- /dev/null
> > +++ b/sysdeps/x86/malloc-for-test.c
> > @@ -0,0 +1,33 @@
> > +/*  A malloc for intercept test.  x86 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
> > +   <http://www.gnu.org/licenses/>.  */
> > +
> > +
> > +/* Clear XMM0...XMM7  */
> > +#define PREPARE_MALLOC()                               \
> > +{                                                      \
> > +  asm volatile ("xorps %%xmm0, %%xmm0" : : : "xmm0" ); \
> > +  asm volatile ("xorps %%xmm1, %%xmm1" : : : "xmm1" ); \
> > +  asm volatile ("xorps %%xmm2, %%xmm2" : : : "xmm2" ); \
> > +  asm volatile ("xorps %%xmm3, %%xmm3" : : : "xmm3" ); \
> > +  asm volatile ("xorps %%xmm4, %%xmm4" : : : "xmm4" ); \
> > +  asm volatile ("xorps %%xmm5, %%xmm5" : : : "xmm5" ); \
> > +  asm volatile ("xorps %%xmm6, %%xmm6" : : : "xmm6" ); \
> > +  asm volatile ("xorps %%xmm7, %%xmm7" : : : "xmm7" ); \
> > +}
> > +
> > +#include <elf/malloc-for-test.c>
> > diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
> > index 837fd28734..485cad9c02 100644
> > --- a/sysdeps/x86/sysdep.h
> > +++ b/sysdeps/x86/sysdep.h
> > @@ -70,6 +70,12 @@
> >     | (1 << X86_XSTATE_ZMM_H_ID))
> >  #endif
> >
> > +/* States which should be saved for TLSDESC_CALL and TLS_DESC_CALL.
> > +   Compiler assumes that all registers, including x87 FPU stack registers,
> > +   are unchanged after CALL, except for EFLAGS and RAX/EAX.  */
> > +#define TLSDESC_CALL_STATE_SAVE_MASK   \
> > +  (STATE_SAVE_MASK | (1 << X86_XSTATE_X87_ID))
> > +
> >  /* Constants for bits in __x86_string_control:  */
> >
> >  /* Avoid short distance REP MOVSB.  */
> > diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
> > index 145f25e7f6..9337e95093 100644
> > --- a/sysdeps/x86_64/Makefile
> > +++ b/sysdeps/x86_64/Makefile
> > @@ -10,7 +10,7 @@ LDFLAGS-rtld += -Wl,-z,nomark-plt
> >  endif
> >
> >  ifeq ($(subdir),csu)
> > -gen-as-const-headers += features-offsets.sym link-defines.sym
> > +gen-as-const-headers += link-defines.sym
> >  endif
> >
> >  ifeq ($(subdir),gmon)
> > diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
> > index 6d605d0d32..ff5d45f7cb 100644
> > --- a/sysdeps/x86_64/dl-machine.h
> > +++ b/sysdeps/x86_64/dl-machine.h
> > @@ -71,9 +71,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> >                            int lazy, int profile)
> >  {
> >    Elf64_Addr *got;
> > -  extern void _dl_runtime_resolve_fxsave (ElfW(Word)) attribute_hidden;
> > -  extern void _dl_runtime_resolve_xsave (ElfW(Word)) attribute_hidden;
> > -  extern void _dl_runtime_resolve_xsavec (ElfW(Word)) attribute_hidden;
> >    extern void _dl_runtime_profile_sse (ElfW(Word)) attribute_hidden;
> >    extern void _dl_runtime_profile_avx (ElfW(Word)) attribute_hidden;
> >    extern void _dl_runtime_profile_avx512 (ElfW(Word)) attribute_hidden;
> > @@ -96,8 +93,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> >        /* Identify this shared object.  */
> >        *(ElfW(Addr) *) (got + 1) = (ElfW(Addr)) l;
> >
> > -      const struct cpu_features* cpu_features = __get_cpu_features ();
> > -
> >  #ifdef SHARED
> >        /* The got[2] entry contains the address of a function which gets
> >          called to get the address of a so far unresolved function and
> > @@ -107,6 +102,7 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> >          end in this function.  */
> >        if (__glibc_unlikely (profile))
> >         {
> > +         const struct cpu_features* cpu_features = __get_cpu_features ();
> >           if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512F))
> >             *(ElfW(Addr) *) (got + 2) = (ElfW(Addr)) &_dl_runtime_profile_avx512;
> >           else if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX))
> > @@ -126,15 +122,8 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> >           /* This function will get called to fix up the GOT entry
> >              indicated by the offset on the stack, and then jump to
> >              the resolved address.  */
> > -         if (MINIMUM_X86_ISA_LEVEL >= AVX_X86_ISA_LEVEL
> > -             || GLRO(dl_x86_cpu_features).xsave_state_size != 0)
> > -           *(ElfW(Addr) *) (got + 2)
> > -             = (CPU_FEATURE_USABLE_P (cpu_features, XSAVEC)
> > -                ? (ElfW(Addr)) &_dl_runtime_resolve_xsavec
> > -                : (ElfW(Addr)) &_dl_runtime_resolve_xsave);
> > -         else
> > -           *(ElfW(Addr) *) (got + 2)
> > -             = (ElfW(Addr)) &_dl_runtime_resolve_fxsave;
> > +         *(ElfW(Addr) *) (got + 2)
> > +           = (ElfW(Addr)) GLRO(dl_x86_64_runtime_resolve);
> >         }
> >      }
> >
> > @@ -383,7 +372,7 @@ and creates an unsatisfiable circular dependency.\n",
> >                   {
> >                     td->arg = _dl_make_tlsdesc_dynamic
> >                       (sym_map, sym->st_value + reloc->r_addend);
> > -                   td->entry = _dl_tlsdesc_dynamic;
> > +                   td->entry = GLRO(dl_x86_tlsdesc_dynamic);
> >                   }
> >                 else
> >  #  endif
> > diff --git a/sysdeps/x86_64/dl-procinfo.c b/sysdeps/x86_64/dl-procinfo.c
> > index 4d1d790fbb..06637a8154 100644
> > --- a/sysdeps/x86_64/dl-procinfo.c
> > +++ b/sysdeps/x86_64/dl-procinfo.c
> > @@ -41,5 +41,21 @@
> >
> >  #include <sysdeps/x86/dl-procinfo.c>
> >
> > +#if !IS_IN (ldconfig)
> > +# if !defined PROCINFO_DECL && defined SHARED
> > +  ._dl_x86_64_runtime_resolve
> > +# else
> > +PROCINFO_CLASS void * _dl_x86_64_runtime_resolve
> > +# endif
> > +# ifndef PROCINFO_DECL
> > += NULL
> > +# endif
> > +# if !defined SHARED || defined PROCINFO_DECL
> > +;
> > +# else
> > +,
> > +# endif
> > +#endif
> > +
> >  #undef PROCINFO_DECL
> >  #undef PROCINFO_CLASS
> > diff --git a/sysdeps/x86_64/dl-tlsdesc-dynamic.h b/sysdeps/x86_64/dl-tlsdesc-dynamic.h
> > new file mode 100644
> > index 0000000000..ce0bc094ec
> > --- /dev/null
> > +++ b/sysdeps/x86_64/dl-tlsdesc-dynamic.h
> > @@ -0,0 +1,166 @@
> > +/* Thread-local storage handling in the ELF dynamic linker.  x86_64 version.
> > +   Copyright (C) 2004-2024 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/>.  */
> > +
> > +#ifndef SECTION
> > +# define SECTION(p)    p
> > +#endif
> > +
> > +#undef REGISTER_SAVE_AREA
> > +#undef LOCAL_STORAGE_AREA
> > +#undef BASE
> > +
> > +#include "dl-trampoline-state.h"
> > +
> > +       .section SECTION(.text),"ax",@progbits
> > +
> > +       .hidden _dl_tlsdesc_dynamic
> > +       .global _dl_tlsdesc_dynamic
> > +       .type   _dl_tlsdesc_dynamic,@function
> > +
> > +     /* %rax points to the TLS descriptor, such that 0(%rax) points to
> > +       _dl_tlsdesc_dynamic itself, and 8(%rax) points to a struct
> > +       tlsdesc_dynamic_arg object.  It must return in %rax the offset
> > +       between the thread pointer and the object denoted by the
> > +       argument, without clobbering any registers.
> > +
> > +       The assembly code that follows is a rendition of the following
> > +       C code, hand-optimized a little bit.
> > +
> > +ptrdiff_t
> > +_dl_tlsdesc_dynamic (register struct tlsdesc *tdp asm ("%rax"))
> > +{
> > +  struct tlsdesc_dynamic_arg *td = tdp->arg;
> > +  dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + DTV_OFFSET);
> > +  if (__builtin_expect (td->gen_count <= dtv[0].counter
> > +                       && (dtv[td->tlsinfo.ti_module].pointer.val
> > +                           != TLS_DTV_UNALLOCATED),
> > +                       1))
> > +    return dtv[td->tlsinfo.ti_module].pointer.val + td->tlsinfo.ti_offset
> > +      - __thread_pointer;
> > +
> > +  return __tls_get_addr_internal (&td->tlsinfo) - __thread_pointer;
> > +}
> > +*/
> basically same comments for x86 version as for i386.

I will leave the original code alone and only change comments
to /* ... */.



-- 
H.J.