Re: [Qemu-trivial] [Qemu-devel] [PATCH] linux-user: fix signal() syscall on x86_64

[Peter Maydell]

On 2 July 2016 at 09:20, Laurent Vivier <address@hidden> wrote:
>
>
> Le 01/07/2016 à 15:35, Peter Maydell a écrit :
>> On 1 July 2016 at 12:59, Wirth, Allan <address@hidden> wrote:
>>> Linux on X86_64 does not use sel_arg_struct for select(), the args are
>>> passed directly. This patch switches a define so X86_64 uses the correct
>>> calling convention.
>>>
>>> Signed-off-by: Allan Wirth <address@hidden>
>>> ---
>>>  linux-user/syscall.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>>> index 8bf6205..209b2a7 100644
>>> --- a/linux-user/syscall.c
>>> +++ b/linux-user/syscall.c
>>> @@ -8002,7 +8002,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
>>> arg1,
>>>          break;
>>>  #if defined(TARGET_NR_select)
>>>      case TARGET_NR_select:
>>> -#if defined(TARGET_S390X) || defined(TARGET_ALPHA)
>>> +#if defined(TARGET_S390X) || defined(TARGET_ALPHA) || 
>>> defined(TARGET_X86_64)
>>>          ret = do_select(arg1, arg2, arg3, arg4, arg5);
>>>  #else
>>>          {
>>
>> There is a cleaner approach which we should use to fix this:
>> see my comments in reply to this recent patch trying to do
>> a similar thing:
>> https://patchwork.kernel.org/patch/9185927/
>
> syscall_nr.h are copies of unistd.h from kernel, so kernel uses also
> __NR_select and __NR__newselect.

Ugh, this is complicated. The syscall functions are sys_oldselect
and sys_select, but the syscall numbers are __NR_select and
__NR__newselect, and I'm not sure all the architectures are
using them consistently. For instance alpha in the kernel has
syscall 358 as __NR_select, but the syscall table directs it
to sys_select(), not sys_oldselect().

> I think the fix can be as simple as:
>
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -8372,7 +8372,7 @@ abi_long do_syscall(void *cpu_env, int num,
> abi_long arg1,
>          break;
>  #if defined(TARGET_NR_select)
>      case TARGET_NR_select:
> -#if defined(TARGET_S390X) || defined(TARGET_ALPHA)
> +#if !defined(TARGET_NR__new_select)
>          ret = do_select(arg1, arg2, arg3, arg4, arg5);
>  #else
>          {

This looks promising but I guess we need to fish through
all the kernel architectures comparing their syscall numbers
and which functions they dispatch to in their syscall tables.

thanks
-- PMM