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From: Nick Desaulniers <ndesaulniers@google.com>
Date: Wed, 3 Jan 2024 08:50:19 -0800
Message-ID: <CAKwvOdn2Tm6C4Q-GWfh7e2N8rQKAHYyGM9Cn6vb1CUzCORiaAg@mail.gmail.com>
Subject: Re: [PATCH] x86/syscalls: shrink entry/syscall_32.i via IWYU
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tanzir Hasan <tanzirh@google.com>, Andy Lutomirski <luto@kernel.org>, 
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, 
	"H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org, 
	Nick Desaulniers <nnn@google.com>
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On Wed, Dec 27, 2023 at 4:45=E2=80=AFPM Al Viro <viro@zeniv.linux.org.uk> w=
rote:
>
> On Wed, Dec 27, 2023 at 11:34:44PM +0000, Al Viro wrote:
>
> > That's _it_.  The same goes for syscall_64.c and syscall_x32.c.
> > Oh, and lose the __visible/asmlinkage junk in there - none of that
> > stuff is used from asm these days.  See the patch below -
> > Untested But Should Work(tm):
>
> Unfortunately, there's this in kernel/trace/trace_syscalls.c:
>
> unsigned long __init __weak arch_syscall_addr(int nr)
> {
>         return (unsigned long)sys_call_table[nr];
> }
>
> How is that supposed to work for anything biarch?  Including
> amd64 with CONFIG_COMPAT enabled?

commit f431b634f24d ("tracing/syscalls: Allow archs to ignore tracing
compat syscalls")

added a comment block about ARCH_TRACE_IGNORE_COMPAT_SYSCALLS, which
is defined for x86 in arch/x86/include/asm/ftrace.h.

The implementation of arch_syscall_addr for mips is quite complex;
dependent on quite a few different configs.

--=20
Thanks,
~Nick Desaulniers