Re: [PATCH] x86/asm/entry: (Re-)rename __NR_entry_INT80_compat_max to __NR_syscall_compat_max

[Brian Gerst]

On Mon, Jun 8, 2015 at 3:25 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> * Brian Gerst <brgerst@xxxxxxxxx> wrote:
>
>> > diff --git a/arch/x86/entry/syscall_32.c b/arch/x86/entry/syscall_32.c
>> > index 3777189..e398d03 100644
>> > --- a/arch/x86/entry/syscall_32.c
>> > +++ b/arch/x86/entry/syscall_32.c
>> > @@ -10,7 +10,7 @@
>> >  #else
>> >  #define SYM(sym, compat) sym
>> >  #define ia32_sys_call_table sys_call_table
>> > -#define __NR_ia32_syscall_max __NR_syscall_max
>> > +#define __NR_entry_INT80_compat_max __NR_syscall_max
>> >  #endif
>>
>> This change doesn't look intended.  __NR_ia32_syscall_max is used by
>> all compat entry points, not just INT80,
>
> Indeed!
>
> How about the patch below?
>
> Thanks,
>
>         Ingo
>
> ================>
> From 42b9d9a463bfb7252ede4eac24e50a4f013c6717 Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <mingo@xxxxxxxxxx>
> Date: Mon, 8 Jun 2015 21:20:26 +0200
> Subject: [PATCH] x86/asm/entry: (Re-)rename __NR_entry_INT80_compat_max to __NR_syscall_compat_max
>
> Brian Gerst noticed that I did a weird rename in the following commit:
>
>    b2502b418e63 ("x86/asm/entry: Untangle 'system_call' into two entry points: entry_SYSCALL_64 and entry_INT80_32")
>
> which renamed __NR_ia32_syscall_max to __NR_entry_INT80_compat_max.
>
> Now the original name was a misnomer, but the new one is a misnomer as well,
> as all compat syscall ABIs (such as x32) share the system call table, not just
> INT80 based ones.

Not quite true.  X32 is really an extension of the 64-bit ABI to
support the ILP32 data model.  It uses the 64-bit SYSCALL entry point
and table, but with different syscall numbers for the syscalls that
need 32-bit pointer handling in data structures.

So, __NR_syscall_compat_max is only for the 32-bit ABI compat syscall
entries (int80, sysenter, and syscall from 32-bit mode), and not X32.

--
Brian Gerst
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