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[v4] x86-64: Allocate state buffer space for RDI, RSI and RBX

Message ID 20240317125541.799962-1-hjl.tools@gmail.com
State New
Headers show
Series [v4] x86-64: Allocate state buffer space for RDI, RSI and RBX | expand

Commit Message

H.J. Lu March 17, 2024, 12:55 p.m. UTC 
_dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
STATE_SAVE_OFFSET(%rsp).

   +==================+<- stack frame start aligned at 8 or 16 bytes
   |                  |<- RDI
   |                  |<- RSI
   |                  |<- RBX
   |                  |<- paddings from stack realignment of 64 bytes
   |------------------|<- xsave buffer end aligned at 64 bytes
   |                  |<-
   |                  |<-
   |                  |<-
   |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
   |                  |<- 8-byte padding
   |                  |<- 8-byte padding
   |                  |<- R11
   |                  |<- R10
   |                  |<- R9
   |                  |<- R8
   |                  |<- RDX
   |                  |<- RCX
   +==================+<- State buffer start aligned at 64 bytes

This fixes BZ #31501.
---
 sysdeps/x86/cpu-features.c         | 11 ++--
 sysdeps/x86/sysdep.h               | 29 ++++++++++
 sysdeps/x86_64/tst-gnu2-tls2mod1.S | 87 ++++++++++++++++++++++++++++++
 3 files changed, 123 insertions(+), 4 deletions(-)
 create mode 100644 sysdeps/x86_64/tst-gnu2-tls2mod1.S

Comments

H.J. Lu March 17, 2024, 1:02 p.m. UTC | #1 
On Sun, Mar 17, 2024 at 5:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
> After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
> TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
> to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
> STATE_SAVE_OFFSET(%rsp).
>
>    +==================+<- stack frame start aligned at 8 or 16 bytes
>    |                  |<- RDI
>    |                  |<- RSI
>    |                  |<- RBX
>    |                  |<- paddings from stack realignment of 64 bytes
>    |------------------|<- xsave buffer end aligned at 64 bytes
>    |                  |<-
>    |                  |<-
>    |                  |<-
>    |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
>    |                  |<- 8-byte padding
>    |                  |<- 8-byte padding
>    |                  |<- R11
>    |                  |<- R10
>    |                  |<- R9
>    |                  |<- R8
>    |                  |<- RDX
>    |                  |<- RCX
>    +==================+<- State buffer start aligned at 64 bytes
>
> This fixes BZ #31501.
> ---
>  sysdeps/x86/cpu-features.c         | 11 ++--
>  sysdeps/x86/sysdep.h               | 29 ++++++++++
>  sysdeps/x86_64/tst-gnu2-tls2mod1.S | 87 ++++++++++++++++++++++++++++++
>  3 files changed, 123 insertions(+), 4 deletions(-)
>  create mode 100644 sysdeps/x86_64/tst-gnu2-tls2mod1.S
>
> diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> index 4ea373dffa..3d7c2819d7 100644
> --- a/sysdeps/x86/cpu-features.c
> +++ b/sysdeps/x86/cpu-features.c
> @@ -311,7 +311,7 @@ update_active (struct cpu_features *cpu_features)
>               /* NB: On AMX capable processors, ebx always includes AMX
>                  states.  */
>               unsigned int xsave_state_full_size
> -               = ALIGN_UP (ebx + STATE_SAVE_OFFSET, 64);
> +               = ALIGN_UP (ebx + TLSDESC_CALL_REGISTER_SAVE_AREA, 64);
>
>               cpu_features->xsave_state_size
>                 = xsave_state_full_size;
> @@ -401,8 +401,10 @@ update_active (struct cpu_features *cpu_features)
>                       unsigned int amx_size
>                         = (xstate_amx_comp_offsets[31]
>                            + xstate_amx_comp_sizes[31]);
> -                     amx_size = ALIGN_UP (amx_size + STATE_SAVE_OFFSET,
> -                                          64);
> +                     amx_size
> +                       = ALIGN_UP ((amx_size
> +                                    + TLSDESC_CALL_REGISTER_SAVE_AREA),
> +                                   64);
>                       /* Set xsave_state_full_size to the compact AMX
>                          state size for XSAVEC.  NB: xsave_state_full_size
>                          is only used in _dl_tlsdesc_dynamic_xsave and
> @@ -410,7 +412,8 @@ update_active (struct cpu_features *cpu_features)
>                       cpu_features->xsave_state_full_size = amx_size;
>  #endif
>                       cpu_features->xsave_state_size
> -                       = ALIGN_UP (size + STATE_SAVE_OFFSET, 64);
> +                       = ALIGN_UP (size + TLSDESC_CALL_REGISTER_SAVE_AREA,
> +                                   64);
>                       CPU_FEATURE_SET (cpu_features, XSAVEC);
>                     }
>                 }
> diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
> index db8e576e91..46fcd27345 100644
> --- a/sysdeps/x86/sysdep.h
> +++ b/sysdeps/x86/sysdep.h
> @@ -46,6 +46,34 @@
>     red-zone into account.  */
>  # define STATE_SAVE_OFFSET (8 * 7 + 8)
>
> +/* _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning
> +   stack.  After realigning stack, it saves RCX, RDX, R8, R9, R10 and
> +   R11.  Allocate space for RDI, RSI and RBX to avoid clobbering saved
> +   RDI, RSI and RBX values on stack by xsave.
> +
> +   +==================+<- stack frame start aligned at 8 or 16 bytes
> +   |                  |<- RDI
> +   |                  |<- RSI
> +   |                  |<- RBX
> +   |                  |<- paddings from stack realignment of 64 bytes
> +   |------------------|<- xsave buffer end aligned at 64 bytes
> +   |                  |<-
> +   |                  |<-
> +   |                  |<-
> +   |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
> +   |                  |<- 8-byte padding
> +   |                  |<- 8-byte padding
> +   |                  |<- R11
> +   |                  |<- R10
> +   |                  |<- R9
> +   |                  |<- R8
> +   |                  |<- RDX
> +   |                  |<- RCX
> +   +==================+<- State buffer start aligned at 64 bytes
> +
> +*/
> +# define TLSDESC_CALL_REGISTER_SAVE_AREA (STATE_SAVE_OFFSET + 24)
> +
>  /* Save SSE, AVX, AVX512, mask, bound and APX registers.  Bound and APX
>     registers are mutually exclusive.  */
>  # define STATE_SAVE_MASK               \
> @@ -68,6 +96,7 @@
>  /* Offset for fxsave/xsave area used by _dl_tlsdesc_dynamic.  Since i386
>     doesn't have red-zone, use 0 here.  */
>  # define STATE_SAVE_OFFSET 0
> +# define TLSDESC_CALL_REGISTER_SAVE_AREA 0
>
>  /* Save SSE, AVX, AXV512, mask and bound registers.   */
>  # define STATE_SAVE_MASK               \
> diff --git a/sysdeps/x86_64/tst-gnu2-tls2mod1.S b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
> new file mode 100644
> index 0000000000..449ddd5c9d
> --- /dev/null
> +++ b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
> @@ -0,0 +1,87 @@
> +/* Check if TLSDESC relocation preserves %rdi, %rsi and %rbx.
> +   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/>.  */
> +
> +#include <sysdep.h>
> +
> +/* On AVX512 machines, OFFSET == 104 caused _dl_tlsdesc_dynamic_xsavec
> +   to clobber %rdi, %rsi and %rbx.  On Intel AVX CPUs, the state size
> +   is 960 bytes and this test didn't fail.  It may be due to the unused
> +   last 128 bytes.  On AMD AVX CPUs, the state size is 832 bytes and
> +   this test might fail without the fix.  */
> +#ifndef OFFSET
> +# define OFFSET 104
> +#endif
> +
> +       .text
> +       .p2align 4
> +       .globl  apply_tls
> +       .type   apply_tls, @function
> +apply_tls:
> +       cfi_startproc
> +       _CET_ENDBR
> +       pushq   %rbp
> +       cfi_def_cfa_offset (16)
> +       cfi_offset (6, -16)
> +       movdqu  (%RDI_LP), %xmm0
> +       lea     tls_var1@TLSDESC(%rip), %RAX_LP
> +       mov     %RSP_LP, %RBP_LP
> +       cfi_def_cfa_register (6)
> +       /* Align stack to 64 bytes.  */
> +       and     $-64, %RSP_LP
> +       sub     $OFFSET, %RSP_LP
> +       pushq   %rbx
> +       /* Set %ebx to 0xbadbeef.  */
> +       movl    $0xbadbeef, %ebx
> +       movl    $0xbadbeef, %esi
> +       movq    %rdi, saved_rdi(%rip)
> +       movq    %rsi, saved_rsi(%rip)
> +       call    *tls_var1@TLSCALL(%RAX_LP)
> +       /* Check if _dl_tlsdesc_dynamic preserves %rdi, %rsi and %rbx.  */
> +       cmpq    saved_rdi(%rip), %rdi
> +       jne     L(hlt)
> +       cmpq    saved_rsi(%rip), %rsi
> +       jne     L(hlt)
> +       cmpl    $0xbadbeef, %ebx
> +       jne     L(hlt)
> +       add     %fs:0, %RAX_LP
> +       movups  %xmm0, 32(%RAX_LP)
> +       movdqu  16(%RDI_LP), %xmm1
> +       mov     %RAX_LP, %RBX_LP
> +       movups  %xmm1, 48(%RAX_LP)
> +       lea     32(%RBX_LP), %RAX_LP
> +       pop     %rbx
> +       leave
> +       cfi_def_cfa (7, 8)
> +       ret
> +L(hlt):
> +       hlt
> +       cfi_endproc
> +       .size   apply_tls, .-apply_tls
> +       .hidden tls_var1
> +       .globl  tls_var1
> +       .section        .tbss,"awT",@nobits
> +       .align 16
> +       .type   tls_var1, @object
> +       .size   tls_var1, 3200
> +tls_var1:
> +       .zero   3200
> +       .local  saved_rdi
> +       .comm   saved_rdi,8,8
> +       .local  saved_rsi
> +       .comm   saved_rsi,8,8
> +       .section        .note.GNU-stack,"",@progbits
> --
> 2.44.0
>

I need to adjust assembly codes.
H.J. Lu March 17, 2024, 1:04 p.m. UTC | #2 
On Sun, Mar 17, 2024 at 6:02 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Sun, Mar 17, 2024 at 5:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
> > After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
> > TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
> > to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
> > STATE_SAVE_OFFSET(%rsp).
> >
> >    +==================+<- stack frame start aligned at 8 or 16 bytes
> >    |                  |<- RDI
> >    |                  |<- RSI
> >    |                  |<- RBX
> >    |                  |<- paddings from stack realignment of 64 bytes
> >    |------------------|<- xsave buffer end aligned at 64 bytes
> >    |                  |<-
> >    |                  |<-
> >    |                  |<-
> >    |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
> >    |                  |<- 8-byte padding
> >    |                  |<- 8-byte padding
> >    |                  |<- R11
> >    |                  |<- R10
> >    |                  |<- R9
> >    |                  |<- R8
> >    |                  |<- RDX
> >    |                  |<- RCX
> >    +==================+<- State buffer start aligned at 64 bytes
> >
> > This fixes BZ #31501.
> > ---
> >  sysdeps/x86/cpu-features.c         | 11 ++--
> >  sysdeps/x86/sysdep.h               | 29 ++++++++++
> >  sysdeps/x86_64/tst-gnu2-tls2mod1.S | 87 ++++++++++++++++++++++++++++++
> >  3 files changed, 123 insertions(+), 4 deletions(-)
> >  create mode 100644 sysdeps/x86_64/tst-gnu2-tls2mod1.S
> >
> > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> > index 4ea373dffa..3d7c2819d7 100644
> > --- a/sysdeps/x86/cpu-features.c
> > +++ b/sysdeps/x86/cpu-features.c
> > @@ -311,7 +311,7 @@ update_active (struct cpu_features *cpu_features)
> >               /* NB: On AMX capable processors, ebx always includes AMX
> >                  states.  */
> >               unsigned int xsave_state_full_size
> > -               = ALIGN_UP (ebx + STATE_SAVE_OFFSET, 64);
> > +               = ALIGN_UP (ebx + TLSDESC_CALL_REGISTER_SAVE_AREA, 64);
> >
> >               cpu_features->xsave_state_size
> >                 = xsave_state_full_size;
> > @@ -401,8 +401,10 @@ update_active (struct cpu_features *cpu_features)
> >                       unsigned int amx_size
> >                         = (xstate_amx_comp_offsets[31]
> >                            + xstate_amx_comp_sizes[31]);
> > -                     amx_size = ALIGN_UP (amx_size + STATE_SAVE_OFFSET,
> > -                                          64);
> > +                     amx_size
> > +                       = ALIGN_UP ((amx_size
> > +                                    + TLSDESC_CALL_REGISTER_SAVE_AREA),
> > +                                   64);
> >                       /* Set xsave_state_full_size to the compact AMX
> >                          state size for XSAVEC.  NB: xsave_state_full_size
> >                          is only used in _dl_tlsdesc_dynamic_xsave and
> > @@ -410,7 +412,8 @@ update_active (struct cpu_features *cpu_features)
> >                       cpu_features->xsave_state_full_size = amx_size;
> >  #endif
> >                       cpu_features->xsave_state_size
> > -                       = ALIGN_UP (size + STATE_SAVE_OFFSET, 64);
> > +                       = ALIGN_UP (size + TLSDESC_CALL_REGISTER_SAVE_AREA,
> > +                                   64);
> >                       CPU_FEATURE_SET (cpu_features, XSAVEC);
> >                     }
> >                 }
> > diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
> > index db8e576e91..46fcd27345 100644
> > --- a/sysdeps/x86/sysdep.h
> > +++ b/sysdeps/x86/sysdep.h
> > @@ -46,6 +46,34 @@
> >     red-zone into account.  */
> >  # define STATE_SAVE_OFFSET (8 * 7 + 8)
> >
> > +/* _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning
> > +   stack.  After realigning stack, it saves RCX, RDX, R8, R9, R10 and
> > +   R11.  Allocate space for RDI, RSI and RBX to avoid clobbering saved
> > +   RDI, RSI and RBX values on stack by xsave.
> > +
> > +   +==================+<- stack frame start aligned at 8 or 16 bytes
> > +   |                  |<- RDI
> > +   |                  |<- RSI
> > +   |                  |<- RBX
> > +   |                  |<- paddings from stack realignment of 64 bytes
> > +   |------------------|<- xsave buffer end aligned at 64 bytes
> > +   |                  |<-
> > +   |                  |<-
> > +   |                  |<-
> > +   |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
> > +   |                  |<- 8-byte padding
> > +   |                  |<- 8-byte padding
> > +   |                  |<- R11
> > +   |                  |<- R10
> > +   |                  |<- R9
> > +   |                  |<- R8
> > +   |                  |<- RDX
> > +   |                  |<- RCX
> > +   +==================+<- State buffer start aligned at 64 bytes
> > +
> > +*/
> > +# define TLSDESC_CALL_REGISTER_SAVE_AREA (STATE_SAVE_OFFSET + 24)
> > +
> >  /* Save SSE, AVX, AVX512, mask, bound and APX registers.  Bound and APX
> >     registers are mutually exclusive.  */
> >  # define STATE_SAVE_MASK               \
> > @@ -68,6 +96,7 @@
> >  /* Offset for fxsave/xsave area used by _dl_tlsdesc_dynamic.  Since i386
> >     doesn't have red-zone, use 0 here.  */
> >  # define STATE_SAVE_OFFSET 0
> > +# define TLSDESC_CALL_REGISTER_SAVE_AREA 0
> >
> >  /* Save SSE, AVX, AXV512, mask and bound registers.   */
> >  # define STATE_SAVE_MASK               \
> > diff --git a/sysdeps/x86_64/tst-gnu2-tls2mod1.S b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
> > new file mode 100644
> > index 0000000000..449ddd5c9d
> > --- /dev/null
> > +++ b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
> > @@ -0,0 +1,87 @@
> > +/* Check if TLSDESC relocation preserves %rdi, %rsi and %rbx.
> > +   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/>.  */
> > +
> > +#include <sysdep.h>
> > +
> > +/* On AVX512 machines, OFFSET == 104 caused _dl_tlsdesc_dynamic_xsavec
> > +   to clobber %rdi, %rsi and %rbx.  On Intel AVX CPUs, the state size
> > +   is 960 bytes and this test didn't fail.  It may be due to the unused
> > +   last 128 bytes.  On AMD AVX CPUs, the state size is 832 bytes and
> > +   this test might fail without the fix.  */
> > +#ifndef OFFSET
> > +# define OFFSET 104
> > +#endif
> > +
> > +       .text
> > +       .p2align 4
> > +       .globl  apply_tls
> > +       .type   apply_tls, @function
> > +apply_tls:
> > +       cfi_startproc
> > +       _CET_ENDBR
> > +       pushq   %rbp
> > +       cfi_def_cfa_offset (16)
> > +       cfi_offset (6, -16)
> > +       movdqu  (%RDI_LP), %xmm0
> > +       lea     tls_var1@TLSDESC(%rip), %RAX_LP
> > +       mov     %RSP_LP, %RBP_LP
> > +       cfi_def_cfa_register (6)
> > +       /* Align stack to 64 bytes.  */
> > +       and     $-64, %RSP_LP
> > +       sub     $OFFSET, %RSP_LP
> > +       pushq   %rbx
> > +       /* Set %ebx to 0xbadbeef.  */
> > +       movl    $0xbadbeef, %ebx
> > +       movl    $0xbadbeef, %esi
> > +       movq    %rdi, saved_rdi(%rip)
> > +       movq    %rsi, saved_rsi(%rip)
> > +       call    *tls_var1@TLSCALL(%RAX_LP)
> > +       /* Check if _dl_tlsdesc_dynamic preserves %rdi, %rsi and %rbx.  */
> > +       cmpq    saved_rdi(%rip), %rdi
> > +       jne     L(hlt)
> > +       cmpq    saved_rsi(%rip), %rsi
> > +       jne     L(hlt)
> > +       cmpl    $0xbadbeef, %ebx
> > +       jne     L(hlt)
> > +       add     %fs:0, %RAX_LP
> > +       movups  %xmm0, 32(%RAX_LP)
> > +       movdqu  16(%RDI_LP), %xmm1
> > +       mov     %RAX_LP, %RBX_LP
> > +       movups  %xmm1, 48(%RAX_LP)
> > +       lea     32(%RBX_LP), %RAX_LP
> > +       pop     %rbx
> > +       leave
> > +       cfi_def_cfa (7, 8)
> > +       ret
> > +L(hlt):
> > +       hlt
> > +       cfi_endproc
> > +       .size   apply_tls, .-apply_tls
> > +       .hidden tls_var1
> > +       .globl  tls_var1
> > +       .section        .tbss,"awT",@nobits
> > +       .align 16
> > +       .type   tls_var1, @object
> > +       .size   tls_var1, 3200
> > +tls_var1:
> > +       .zero   3200
> > +       .local  saved_rdi
> > +       .comm   saved_rdi,8,8
> > +       .local  saved_rsi
> > +       .comm   saved_rsi,8,8
> > +       .section        .note.GNU-stack,"",@progbits
> > --
> > 2.44.0
> >
>
> I need to adjust assembly codes.
>

Never mind.  Not needed.
Florian Weimer March 18, 2024, 10:22 a.m. UTC | #3 
* H. J. Lu:

> _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
> After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
> TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
> to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
> STATE_SAVE_OFFSET(%rsp).
>
>    +==================+<- stack frame start aligned at 8 or 16 bytes

It's 8-byte aligned only?  If the caller uses the psABI convention, we
have %rsp ≡ 8 (mod 16).

>    |                  |<- RDI
>    |                  |<- RSI
>    |                  |<- RBX

I would add something like “originally in the red zone” here.

>    |                  |<- paddings from stack realignment of 64 bytes
>    |------------------|<- xsave buffer end aligned at 64 bytes


>    |                  |<-
>    |                  |<-
>    |                  |<-
>    |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
>    |                  |<- 8-byte padding

Maybe add “to achieve 64-bit alignment”.

>    |                  |<- 8-byte padding
>    |                  |<- R11
>    |                  |<- R10
>    |                  |<- R9
>    |                  |<- R8
>    |                  |<- RDX
>    |                  |<- RCX
>    +==================+<- State buffer start aligned at 64 bytes

Isn't this “%rsp  aligned at 64 bytes”?

Likewise for the comment in the sources below.

> diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
> index db8e576e91..46fcd27345 100644
> --- a/sysdeps/x86/sysdep.h
> +++ b/sysdeps/x86/sysdep.h
> @@ -46,6 +46,34 @@
>     red-zone into account.  */
>  # define STATE_SAVE_OFFSET (8 * 7 + 8)

The comment on STATE_SAVE_OFFSET needs updating, too.

I would like to see comments from Noah or Sunil.  You'll have to
maintain this, too. 8-)

I find the macro consts rather confusing, but maybe that's just me.

Thanks,
Florian
H.J. Lu March 18, 2024, 12:32 p.m. UTC | #4 
On Mon, Mar 18, 2024 at 3:22 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> > _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
> > After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
> > TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
> > to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
> > STATE_SAVE_OFFSET(%rsp).
> >
> >    +==================+<- stack frame start aligned at 8 or 16 bytes
>
> It's 8-byte aligned only?  If the caller uses the psABI convention, we
> have %rsp ≡ 8 (mod 16).

It is due to:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066

Do we need to support older compilers?

>
> >    |                  |<- RDI
> >    |                  |<- RSI
> >    |                  |<- RBX
>
> I would add something like “originally in the red zone” here.

Fixed.

> >    |                  |<- paddings from stack realignment of 64 bytes
> >    |------------------|<- xsave buffer end aligned at 64 bytes
>
>
> >    |                  |<-
> >    |                  |<-
> >    |                  |<-
> >    |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
> >    |                  |<- 8-byte padding
>
> Maybe add “to achieve 64-bit alignment”.

Fixed.

> >    |                  |<- 8-byte padding
> >    |                  |<- R11
> >    |                  |<- R10
> >    |                  |<- R9
> >    |                  |<- R8
> >    |                  |<- RDX
> >    |                  |<- RCX
> >    +==================+<- State buffer start aligned at 64 bytes
>
> Isn't this “%rsp  aligned at 64 bytes”?

Fixed.

> Likewise for the comment in the sources below.

Fixed.

> > diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
> > index db8e576e91..46fcd27345 100644
> > --- a/sysdeps/x86/sysdep.h
> > +++ b/sysdeps/x86/sysdep.h
> > @@ -46,6 +46,34 @@
> >     red-zone into account.  */
> >  # define STATE_SAVE_OFFSET (8 * 7 + 8)
>
> The comment on STATE_SAVE_OFFSET needs updating, too.

Fixed.

> I would like to see comments from Noah or Sunil.  You'll have to
> maintain this, too. 8-)

CCed Noah and Sunil.

> I find the macro consts rather confusing, but maybe that's just me.

Can you suggest a different name?

The v5 patch is at

https://patchwork.sourceware.org/project/glibc/list/?series=31992

Thanks.
diff mbox series

Patch

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 4ea373dffa..3d7c2819d7 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -311,7 +311,7 @@  update_active (struct cpu_features *cpu_features)
 	      /* NB: On AMX capable processors, ebx always includes AMX
 		 states.  */
 	      unsigned int xsave_state_full_size
-		= ALIGN_UP (ebx + STATE_SAVE_OFFSET, 64);
+		= ALIGN_UP (ebx + TLSDESC_CALL_REGISTER_SAVE_AREA, 64);
 
 	      cpu_features->xsave_state_size
 		= xsave_state_full_size;
@@ -401,8 +401,10 @@  update_active (struct cpu_features *cpu_features)
 		      unsigned int amx_size
 			= (xstate_amx_comp_offsets[31]
 			   + xstate_amx_comp_sizes[31]);
-		      amx_size = ALIGN_UP (amx_size + STATE_SAVE_OFFSET,
-					   64);
+		      amx_size
+			= ALIGN_UP ((amx_size
+				     + TLSDESC_CALL_REGISTER_SAVE_AREA),
+				    64);
 		      /* Set xsave_state_full_size to the compact AMX
 			 state size for XSAVEC.  NB: xsave_state_full_size
 			 is only used in _dl_tlsdesc_dynamic_xsave and
@@ -410,7 +412,8 @@  update_active (struct cpu_features *cpu_features)
 		      cpu_features->xsave_state_full_size = amx_size;
 #endif
 		      cpu_features->xsave_state_size
-			= ALIGN_UP (size + STATE_SAVE_OFFSET, 64);
+			= ALIGN_UP (size + TLSDESC_CALL_REGISTER_SAVE_AREA,
+				    64);
 		      CPU_FEATURE_SET (cpu_features, XSAVEC);
 		    }
 		}
diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
index db8e576e91..46fcd27345 100644
--- a/sysdeps/x86/sysdep.h
+++ b/sysdeps/x86/sysdep.h
@@ -46,6 +46,34 @@ 
    red-zone into account.  */
 # define STATE_SAVE_OFFSET (8 * 7 + 8)
 
+/* _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning
+   stack.  After realigning stack, it saves RCX, RDX, R8, R9, R10 and
+   R11.  Allocate space for RDI, RSI and RBX to avoid clobbering saved
+   RDI, RSI and RBX values on stack by xsave.
+
+   +==================+<- stack frame start aligned at 8 or 16 bytes
+   |                  |<- RDI
+   |                  |<- RSI
+   |                  |<- RBX
+   |                  |<- paddings from stack realignment of 64 bytes
+   |------------------|<- xsave buffer end aligned at 64 bytes
+   |                  |<-
+   |                  |<-
+   |                  |<-
+   |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
+   |                  |<- 8-byte padding
+   |                  |<- 8-byte padding
+   |                  |<- R11
+   |                  |<- R10
+   |                  |<- R9
+   |                  |<- R8
+   |                  |<- RDX
+   |                  |<- RCX
+   +==================+<- State buffer start aligned at 64 bytes
+
+*/
+# define TLSDESC_CALL_REGISTER_SAVE_AREA (STATE_SAVE_OFFSET + 24)
+
 /* Save SSE, AVX, AVX512, mask, bound and APX registers.  Bound and APX
    registers are mutually exclusive.  */
 # define STATE_SAVE_MASK		\
@@ -68,6 +96,7 @@ 
 /* Offset for fxsave/xsave area used by _dl_tlsdesc_dynamic.  Since i386
    doesn't have red-zone, use 0 here.  */
 # define STATE_SAVE_OFFSET 0
+# define TLSDESC_CALL_REGISTER_SAVE_AREA 0
 
 /* Save SSE, AVX, AXV512, mask and bound registers.   */
 # define STATE_SAVE_MASK		\
diff --git a/sysdeps/x86_64/tst-gnu2-tls2mod1.S b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
new file mode 100644
index 0000000000..449ddd5c9d
--- /dev/null
+++ b/sysdeps/x86_64/tst-gnu2-tls2mod1.S
@@ -0,0 +1,87 @@ 
+/* Check if TLSDESC relocation preserves %rdi, %rsi and %rbx.
+   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/>.  */
+
+#include <sysdep.h>
+
+/* On AVX512 machines, OFFSET == 104 caused _dl_tlsdesc_dynamic_xsavec
+   to clobber %rdi, %rsi and %rbx.  On Intel AVX CPUs, the state size
+   is 960 bytes and this test didn't fail.  It may be due to the unused
+   last 128 bytes.  On AMD AVX CPUs, the state size is 832 bytes and
+   this test might fail without the fix.  */
+#ifndef OFFSET
+# define OFFSET 104
+#endif
+
+	.text
+	.p2align 4
+	.globl	apply_tls
+	.type	apply_tls, @function
+apply_tls:
+	cfi_startproc
+	_CET_ENDBR
+	pushq	%rbp
+	cfi_def_cfa_offset (16)
+	cfi_offset (6, -16)
+	movdqu	(%RDI_LP), %xmm0
+	lea	tls_var1@TLSDESC(%rip), %RAX_LP
+	mov	%RSP_LP, %RBP_LP
+	cfi_def_cfa_register (6)
+	/* Align stack to 64 bytes.  */
+	and	$-64, %RSP_LP
+	sub	$OFFSET, %RSP_LP
+	pushq	%rbx
+	/* Set %ebx to 0xbadbeef.  */
+	movl	$0xbadbeef, %ebx
+	movl	$0xbadbeef, %esi
+	movq	%rdi, saved_rdi(%rip)
+	movq	%rsi, saved_rsi(%rip)
+	call	*tls_var1@TLSCALL(%RAX_LP)
+	/* Check if _dl_tlsdesc_dynamic preserves %rdi, %rsi and %rbx.  */
+	cmpq	saved_rdi(%rip), %rdi
+	jne	L(hlt)
+	cmpq	saved_rsi(%rip), %rsi
+	jne	L(hlt)
+	cmpl	$0xbadbeef, %ebx
+	jne	L(hlt)
+	add	%fs:0, %RAX_LP
+	movups	%xmm0, 32(%RAX_LP)
+	movdqu	16(%RDI_LP), %xmm1
+	mov	%RAX_LP, %RBX_LP
+	movups	%xmm1, 48(%RAX_LP)
+	lea	32(%RBX_LP), %RAX_LP
+	pop	%rbx
+	leave
+	cfi_def_cfa (7, 8)
+	ret
+L(hlt):
+	hlt
+	cfi_endproc
+	.size	apply_tls, .-apply_tls
+	.hidden	tls_var1
+	.globl	tls_var1
+	.section	.tbss,"awT",@nobits
+	.align 16
+	.type	tls_var1, @object
+	.size	tls_var1, 3200
+tls_var1:
+	.zero	3200
+	.local	saved_rdi
+	.comm	saved_rdi,8,8
+	.local	saved_rsi
+	.comm	saved_rsi,8,8
+	.section	.note.GNU-stack,"",@progbits