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Re: [PATCH] x86-64: Add p{read,write}[v]64 to syscalls.list [BZ #20348]
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Tue, 12 Jul 2016 15:04:04 +0100
- Subject: Re: [PATCH] x86-64: Add p{read,write}[v]64 to syscalls.list [BZ #20348]
- Authentication-results: sourceware.org; auth=none
- References: <20160712132628.GA7361@intel.com>
On 12/07/2016 14:26, H.J. Lu wrote:
> 64-bit off_t in pread64, preadv, pwrite64 and pwritev syscalls is pased
> in one 64-bit register for both x32 and x86-64. Since the inline
> asm statement only passes long, which is 32-bit for x32, in registers,
> 64-bit off_t is truncated to 32-bit on x32. Since __ASSUME_PREADV and
> __ASSUME_PWRITEV are defined unconditionally, these syscalls can be
> implemented in syscalls.list to pass 64-bit off_t in one 64-bit register.
>
> Tested on x86-64 and x32 with off_t > 4GB on pread64/pwrite64 and
> preadv64/pwritev64.
>
> OK for master?
>
> H.J.
> ---
> [BZ #20348]
> * sysdeps/unix/sysv/linux/x86_64/syscalls.list: Add pread64,
> preadv64, pwrite64 and pwritev64.
> ---
> sysdeps/unix/sysv/linux/x86_64/syscalls.list | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/x86_64/syscalls.list b/sysdeps/unix/sysv/linux/x86_64/syscalls.list
> index d09d101..bcf6370 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/syscalls.list
> +++ b/sysdeps/unix/sysv/linux/x86_64/syscalls.list
> @@ -6,6 +6,10 @@ msgctl - msgctl i:iip __msgctl msgctl
> msgget - msgget i:ii __msgget msgget
> msgrcv - msgrcv Ci:ibnii __msgrcv msgrcv
> msgsnd - msgsnd Ci:ibni __msgsnd msgsnd
> +pread64 - pread64 Ci:ipii __libc_pread __libc_pread64 __pread64 pread64 __pread pread
> +preadv64 - preadv Ci:ipii preadv64 preadv
> +pwrite64 - pwrite64 Ci:ipii __libc_pwrite __pwrite64 pwrite64 __pwrite pwrite
> +pwritev64 - pwritev Ci:ipii pwritev64 pwritev
> shmat - shmat i:ipi __shmat shmat
> shmctl - shmctl i:iip __shmctl shmctl
> shmdt - shmdt i:s __shmdt shmdt
>
This is pretty much what I suggested [1] with the difference that my
idea is to re-add the auto-generated wrappers just for x32. I would
prefer to keep x86_64 continue to use default implementation and
work on fix {INLINE,INTERNAL}_SYSCALL to work with 64-bit arguments
in x32.
Also, I think we should remove the first try to fix LO_HI_LONG [2],
since 64 bits argument does not work correct in x32 anyway.
[1] https://sourceware.org/ml/libc-alpha/2016-07/msg00318.html
[2] https://sourceware.org/git/?p=glibc.git;a=commit;h=cf1ad5b3add36790cbf58a3972c492a8f1632929