linux-kernel - Re: warning: cast removes address space '_

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Message-ID: <CAFGhKbzJ-icVy-YmPVSNd4O4AA-4QGiaYZWM+2T=xq5_-MB4MA@mail.gmail.com>
Date: Wed, 3 Apr 2024 09:14:48 +0200
From: Charlemagne Lasse <charlemagnelasse@...il.com>
To: Uros Bizjak <ubizjak@...il.com>, linux-sparse@...r.kernel.org
Cc: x86@...nel.org, LKML <linux-kernel@...r.kernel.org>, 
	Luc Van Oostenryck <lucvoo@...nel.org>, Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>, 
	Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, 
	"H . Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: warning: cast removes address space '__percpu' of expression

Am Di., 2. Apr. 2024 um 22:40 Uhr schrieb Uros Bizjak <ubizjak@...il.com>:
[snip]
> > ```
> > git reset --hard ed2f752e0e0a21d941ca0ee539ef3d4cd576bc5e
> > git cherry-pick 3a1d3829e193c091475ceab481c5f8deab385023
> > patch -p1 -i ~/p.diff.txt
> > git clean -dfx
> > make allnoconfig -j$(nproc)
> > make kvm_guest.config
> > echo CONFIG_MODULES=y >> .config
> > echo CONFIG_NET_9P_VIRTIO=m >> .config
> > make olddefconfig
> > make prepare -j$(nproc)
> > touch net/9p/trans_virtio.c
> > make C=1 M=net/9p/ trans_virtio.o CHECK="sparse -Wconstexpr-not-const"
> > ```
> >
> > This now shows the warning:
> >
> > ```
> > net/9p/trans_virtio.c:831:1: warning: non-constant initializer for static object
> > net/9p/trans_virtio.c:832:1: warning: non-constant initializer for static object
> > ```
[snip]
> It's this part:
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index d7779a18b24fc3..bf9815eaf4aabf 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -212,7 +212,7 @@ void ftrace_likely_update(struct
> ftrace_likely_data *f, int val,
> */
> #define ___ADDRESSABLE(sym, __attrs) \
> static void * __used __attrs \
> - __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
> + __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym;
> #define __ADDRESSABLE(sym) \
> ___ADDRESSABLE(sym, __section(".discard.addressable"))
>
> But ... how is this not const?

@Luc Van Oostenryck Do you have any idea how to correctly implement it
to make sparse happy?