[4/5] i386: Honor I386_USE_SYSENTER for 6-argument Linux system calls

  Introduce an int-80h-based version of __libc_do_syscall and use
it if I386_USE_SYSENTER is defined as 0.
---
 sysdeps/unix/sysv/linux/i386/Makefile         |  2 +-
 .../sysv/linux/i386/libc-do-syscall-int80.S   | 25 +++++++++++++++++++
 sysdeps/unix/sysv/linux/i386/sysdep.h         | 13 ++++++++--
 3 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/i386/libc-do-syscall-int80.S
  

On Mon, May 2, 2022 at 12:18 PM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Introduce an int-80h-based version of __libc_do_syscall and use
> it if I386_USE_SYSENTER is defined as 0.
> ---
>  sysdeps/unix/sysv/linux/i386/Makefile         |  2 +-
>  .../sysv/linux/i386/libc-do-syscall-int80.S   | 25 +++++++++++++++++++
>  sysdeps/unix/sysv/linux/i386/sysdep.h         | 13 ++++++++--
>  3 files changed, 37 insertions(+), 3 deletions(-)
>  create mode 100644 sysdeps/unix/sysv/linux/i386/libc-do-syscall-int80.S
>
> diff --git a/sysdeps/unix/sysv/linux/i386/Makefile b/sysdeps/unix/sysv/linux/i386/Makefile
> index fcab129fc1..598e27dcda 100644
> --- a/sysdeps/unix/sysv/linux/i386/Makefile
> +++ b/sysdeps/unix/sysv/linux/i386/Makefile
> @@ -13,7 +13,7 @@ install-bin += lddlibc4
>  endif
>
>  ifeq ($(subdir),io)
> -sysdep_routines += libc-do-syscall
> +sysdep_routines += libc-do-syscall libc-do-syscall-int80
>  endif
>
>  ifeq ($(subdir),stdlib)
> diff --git a/sysdeps/unix/sysv/linux/i386/libc-do-syscall-int80.S b/sysdeps/unix/sysv/linux/i386/libc-do-syscall-int80.S
> new file mode 100644
> index 0000000000..2c472f2557
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/i386/libc-do-syscall-int80.S
> @@ -0,0 +1,25 @@
> +/* Out-of-line syscall stub for six-argument syscalls from C.  For static PIE.
> +   Copyright (C) 2022 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 SHARED
> +# define I386_USE_SYSENTER 0
> +# include <sysdep.h>
> +
> +# define __libc_do_syscall __libc_do_syscall_int80
> +# include "libc-do-syscall.S"
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
> index 4558ab66cb..7085f7e19a 100644
> --- a/sysdeps/unix/sysv/linux/i386/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
> @@ -42,6 +42,15 @@
>  # endif
>  #endif
>
> +#if !I386_USE_SYSENTER && IS_IN (libc) && !defined SHARED
> +/* Inside static libc, we have two versions.  For compilation units
> +   with !I386_USE_SYSENTER, the vDSO entry mechanism cannot be
> +   used. */
> +# define I386_DO_SYSCALL_STRING "__libc_do_syscall_int80"
> +#else
> +# define I386_DO_SYSCALL_STRING "__libc_do_syscall"
> +#endif
> +
>  #ifdef __ASSEMBLER__
>
>  /* Linux uses a negative return value to indicate syscall errors,
> @@ -301,7 +310,7 @@ struct libc_do_syscall_args
>      };                                                                 \
>      asm volatile (                                                     \
>      "movl %1, %%eax\n\t"                                               \
> -    "call __libc_do_syscall"                                           \
> +    "call " I386_DO_SYSCALL_STRING                                     \
>      : "=a" (resultvar)                                                 \
>      : "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \
>      : "memory", "cc")
> @@ -315,7 +324,7 @@ struct libc_do_syscall_args
>      };                                                                 \
>      asm volatile (                                                     \
>      "movl %1, %%eax\n\t"                                               \
> -    "call __libc_do_syscall"                                           \
> +    "call " I386_DO_SYSCALL_STRING                                     \
>      : "=a" (resultvar)                                                 \
>      : "a" (name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv)       \
>      : "memory", "cc")
> --
> 2.35.1
>
>

LGTM.

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

Thanks.