Re: [Xen-devel] [PATCH v3 1/3] syscalls, x86 Expose arch_prctl on x86-32.

[Kyle Huey]

On Fri, Sep 16, 2016 at 12:50 AM, Thomas Gleixner  wrote:
> On Thu, 15 Sep 2016, Kyle Huey wrote:
>
> First of all, please add a cover letter [PATCH 0/N] to your patch series
> and send it with something which provides proper mail threading.
> See: git-send-email, quilt

I did ... seems like using git-send-email with
--cc-cmd=scripts/get_maintainer.pl is not a good idea since people get
CCd to some parts of the thread and not others.

https://lkml.org/lkml/2016/9/15/811

>> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
>> now. Rename the second arg to a more generic name.
>
> This changelog is useless.
>
> - it does not provide any rationale for this change, i.e. why this is
>   required. Just because its 64bit only is not a reason.
>
> - "Rename the second arg to a more generic name" does not give
>   any useful information.
>
> Misleading information is worse than no information.
>
> Further your patch does 5 things at once. It wants to be split into parts:
>
> 1) Rename do_arch_prctl() and change the argument name,
>
>> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
>> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long 
>> arg2)
>
> 2) Provide do_arch_prctl_common() and hook it up to the arch_prctl syscall
>
>> -long sys_arch_prctl(int code, unsigned long addr)
>> +SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
>>  {
>> - return do_arch_prctl(current, code, addr);
>> + long ret;
>> +
>> + ret = do_arch_prctl_64(current, code, arg2);
>> + if (ret == -EINVAL)
>> + ret = do_arch_prctl_common(current, code, arg2);
>> +
>> + return ret;
>>  }
>
> 3) Implement the compat version

Ok.

- Kyle

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Re: [Xen-devel] [PATCH v3 1/3] syscalls, x86 Expose arch_prctl on x86-32.

[Thomas Gleixner]

On Thu, 15 Sep 2016, Kyle Huey wrote:

First of all, please add a cover letter [PATCH 0/N] to your patch series
and send it with something which provides proper mail threading. 
See: git-send-email, quilt 

> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
> now. Rename the second arg to a more generic name.

This changelog is useless.

- it does not provide any rationale for this change, i.e. why this is
  required. Just because its 64bit only is not a reason.

- "Rename the second arg to a more generic name" does not give
  any useful information.

Misleading information is worse than no information.

Further your patch does 5 things at once. It wants to be split into parts:

1) Rename do_arch_prctl() and change the argument name,

> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long arg2)

2) Provide do_arch_prctl_common() and hook it up to the arch_prctl syscall

> -long sys_arch_prctl(int code, unsigned long addr)
> +SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
>  {
> - return do_arch_prctl(current, code, addr);
> + long ret;
> +
> + ret = do_arch_prctl_64(current, code, arg2);
> + if (ret == -EINVAL)
> + ret = do_arch_prctl_common(current, code, arg2);
> +
> + return ret;
>  }

3) Implement the compat version
  
Thanks,

tflx

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Re: [Xen-devel] [PATCH v3 1/3] syscalls, x86 Expose arch_prctl on x86-32.

[Andy Lutomirski]

On Thu, Sep 15, 2016 at 4:33 PM, Kyle Huey  wrote:
> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
> now. Rename the second arg to a more generic name.
>
> Signed-off-by: Kyle Huey 
> ---
>  arch/x86/entry/syscalls/syscall_32.tbl |  1 +
>  arch/x86/include/asm/proto.h   |  5 -
>  arch/x86/kernel/process.c  | 10 ++
>  arch/x86/kernel/process_64.c   | 33 +
>  arch/x86/kernel/ptrace.c   |  8 
>  arch/x86/um/Makefile   |  2 +-
>  arch/x86/um/syscalls_32.c  |  7 +++
>  arch/x86/um/syscalls_64.c  |  4 ++--
>  include/linux/compat.h |  2 ++
>  9 files changed, 52 insertions(+), 20 deletions(-)
>  create mode 100644 arch/x86/um/syscalls_32.c
>
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl 
> b/arch/x86/entry/syscalls/syscall_32.tbl
> index f848572..666fa61 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -386,3 +386,4 @@
>  377i386copy_file_range sys_copy_file_range
>  378i386preadv2 sys_preadv2 
> compat_sys_preadv2
>  379i386pwritev2sys_pwritev2
> compat_sys_pwritev2
> +380i386arch_prctl  compat_sys_arch_prctl   
> compat_sys_arch_prctl

Let's call this sys_arch_prctl_32, even if it's unconventional.  See below.

> diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
> index 9b9b30b..f0e86aa 100644
> --- a/arch/x86/include/asm/proto.h
> +++ b/arch/x86/include/asm/proto.h
> @@ -30,6 +30,9 @@ void x86_report_nx(void);
>
>  extern int reboot_force;
>
> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
> +long do_arch_prctl_common(struct task_struct *task, int code, unsigned long 
> addr);
> +#ifdef CONFIG_X86_64
> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long 
> addr);
> +#endif
>
>  #endif /* _ASM_X86_PROTO_H */
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 62c0b0e..1421451 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -567,3 +567,13 @@ unsigned long get_wchan(struct task_struct *p)
> } while (count++ < 16 && p->state != TASK_RUNNING);
> return 0;
>  }
> +
> +long do_arch_prctl_common(struct task_struct *task, int code, unsigned long 
> arg2)
> +{
> +   return -EINVAL;
> +}
> +
> +asmlinkage long compat_sys_arch_prctl(int code, unsigned long arg2)

I believe you mean COMPAT_SYSCALL_DEFINE2 here.

But I see what you're doing here.  Could you instead do:

#if defined(CONFIG_IA32_EMULATION) || defined(CONFIG_X86_32)
#ifdef CONFIG_X86_32
COMPAT_SYSCALL_DEFINE2(...)
#else
SYSCALL_DEFINE2(...)
#endif

... body here ...
#endif

and name the thing do_arch_prctl_32?

It's too bad we don't have a SYSCALL_DEFINE_32 macro.  But you could add one...


> diff --git a/arch/x86/um/syscalls_32.c b/arch/x86/um/syscalls_32.c
> new file mode 100644
> index 000..c6812c1
> --- /dev/null
> +++ b/arch/x86/um/syscalls_32.c
> @@ -0,0 +1,7 @@
> +#include 
> +#include 
> +
> +long compat_sys_arch_prctl(int code, unsigned long arg2)

COMPAT_SYSCALL_DEFINE2

Also, does this really need a new file?

> -long sys_arch_prctl(int code, unsigned long addr)
> +long sys_arch_prctl(int code, unsigned long arg2)

SYSCALL_DEFINE2

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