Re: [PATCH V17 0/7] Rust Support for powerpc

[Nathan Chancellor <nathan@kernel.org>]

Hi Mukesh,

On Wed, Aug 05, 2026 at 05:59:14PM +0530, Mukesh Kumar Chaurasiya wrote:
> On Tue, Aug 04, 2026 at 10:40:35PM +0900, FUJITA Tomonori wrote:
> > On Tue, 4 Aug 2026 12:11:57 +0200
> > Link Mauve <linkmauve@linkmauve.fr> wrote:
> > > I just tested those again in linux-next, with the Wii support series on
> > > top, but now the kernel fails to build due to ARCH_WARN_ASM and
> > > ARCH_WARN_REACHABLE not being defined on PowerPC:
> > > ```
> > > error: no rules expected `ARCH_WARN_ASM`
> > >    --> /home/linkmauve/dev/linux/wii/rust/kernel/generated_arch_warn_asm.rs:1:28
> > >     |
> > >   1 | ::kernel::concat_literals!(ARCH_WARN_ASM("{file}", "{line}", "{flags}", "{size}"))
> > >     |                            ^^^^^^^^^^^^^ no rules expected this token in macro call
> > >     |
> > >    ::: ../rust/kernel/lib.rs:279:1
> > >     |
> > > 279 | macro_rules! concat_literals {
> > >     | ---------------------------- when calling this macro
> > >     |
> > >     = note: while trying to match sequence start
> > > 
> > > error: no rules expected `ARCH_WARN_REACHABLE`
> > >    --> /home/linkmauve/dev/linux/wii/rust/kernel/generated_arch_reachable_asm.rs:1:28
> > >     |
> > >   1 | ::kernel::concat_literals!(ARCH_WARN_REACHABLE)
> > >     |                            ^^^^^^^^^^^^^^^^^^^ no rules expected this token in macro call
> > >     |
> > >    ::: ../rust/kernel/lib.rs:279:1
> > >     |
> > > 279 | macro_rules! concat_literals {
> > >     | ---------------------------- when calling this macro
> > >     |
> > >     = note: while trying to match sequence start
> > > 
> > > error: aborting due to 2 previous errors
> > > ```
> > 
> > Looks like powerpc needs something like the followings:
> > 
> > diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> > index 0db48977c70c..8aba39e0cf26 100644
> > --- a/arch/powerpc/include/asm/bug.h
> > +++ b/arch/powerpc/include/asm/bug.h
> > @@ -32,34 +32,38 @@
> >  #endif /* verbose */
> >  
> >  #else /* !__ASSEMBLER__ */
> > -/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
> > -   sizeof(struct bug_entry), respectively */
> >  #ifdef CONFIG_DEBUG_BUGVERBOSE
> > -#define _EMIT_BUG_ENTRY				\
> > +#define _EMIT_BUG_ENTRY(file, line, flags)	\
> >  	".section __bug_table,\"aw\"\n"		\
> >  	"2:	.4byte 1b - .\n"		\
> > -	"	.4byte %0 - .\n"		\
> > -	"	.short %1, %2\n"		\
> > -	".org 2b+%3\n"				\
> > -	".previous\n"
> > +	"	.4byte " file " - .\n"		\
> > +	"	.short " line ", " flags "\n"
> >  #else
> > -#define _EMIT_BUG_ENTRY				\
> > +#define _EMIT_BUG_ENTRY(file, line, flags)	\
> >  	".section __bug_table,\"aw\"\n"		\
> >  	"2:	.4byte 1b - .\n"		\
> > -	"	.short %2\n"			\
> > -	".org 2b+%3\n"				\
> > -	".previous\n"
> > +	"	.short " flags "\n"
> >  #endif
> >  
> >  #define BUG_ENTRY(cond_str, insn, flags, ...)		\
> >  	__asm__ __volatile__(				\
> >  		"1:	" insn "\n"			\
> > -		_EMIT_BUG_ENTRY				\
> > +		_EMIT_BUG_ENTRY("%0", "%1", "%2")	\
> > +		".org 2b+%3\n"				\
> > +		".previous\n"				\
> >  		: : "i" (WARN_CONDITION_STR(cond_str) __FILE__), "i" (__LINE__),	\
> >  		  "i" (flags),				\
> >  		  "i" (sizeof(struct bug_entry)),	\
> >  		  ##__VA_ARGS__)
> >  
> > +#define ARCH_WARN_ASM(file, line, flags, size)		\
> > +		"1:	twi 31, 0, 0\n"			\
> > +		_EMIT_BUG_ENTRY(file, line, flags)	\
> > +		".org 2b+" size "\n"			\
> > +		".previous\n"
> > +
> > +#define ARCH_WARN_REACHABLE
> > +
> >  /*
> >   * BUG_ON() and WARN_ON() do their best to cooperate with compile-time
> >   * optimisations. However depending on the complexity of the condition
> 
> Yeah, This makes sense.
> 
> I'll work on this and send out a fix soon.

Did a fix for this ever materialize? I am still seeing the errors that
Link posted above in next-20260817.

-- 
Cheers,
Nathan