[PATCH V3] powerpc/bug: Add ARCH_WARN_ASM and refactor _EMIT_BUG_ENTRY for Rust support

[Mukesh Kumar Chaurasiya]

On Thu, Sep 10, 2026 at 01:05:27PM +0100, Gary Guo wrote:
> On Thu Sep 10, 2026 at 11:08 AM BST, Mukesh Kumar Chaurasiya (IBM) wrote:
> > The Rust kernel infrastructure generates inline asm for WARN() via
> > ARCH_WARN_ASM(file, line, flags, size), expanding it through a C
> > preprocessor pass (generated_arch_warn_asm.rs.S) to produce an
> > arch-specific asm template string for use in Rust's core::arch macros.
> >
> > powerpc currently lacks ARCH_WARN_ASM and ARCH_WARN_REACHABLE, causing
> > Rust builds to fail on powerpc with
> > ```
> > 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}"))
> 
> I think we probably want to catch this earlier by have something like
> 
> #ifndef ARCH_WARN_ASM
> #error "ARCH_WARM_ASM is not defined"
> #endif
> 
> in generated_arch_warn_asm.rs.S.
> 
Hey Gary,

Sounds good.
[...]
> >
> >  arch/powerpc/include/asm/bug.h | 36 +++++++++++++++++++---------------
> >  1 file changed, 20 insertions(+), 16 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> > index 0db48977c70c..df2183c35945 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				\
> > -	".section __bug_table,\"aw\"\n"		\
> > -	"2:	.4byte 1b - .\n"		\
> > -	"	.4byte %0 - .\n"		\
> > -	"	.short %1, %2\n"		\
> > -	".org 2b+%3\n"				\
> > -	".previous\n"
> > +#define _EMIT_BUG_ENTRY(label, file, line, flags)	\
> > +	".section __bug_table,\"aw\"\n"			\
> > +	"2:	.4byte " label "b - .\n"		\
> 
> "b" is part of the label. "1b" itself is a label and "1" is just an integer.
> 
> If the code uses
> 
>     _EMIT_BUG_ENTRY(..)
>     "1: ..."
> 
> then the correct label would be "1f".
> 
> Best,
> Gary
> 
Thanks, I missed that part.

Will fix it and send it out.

Regards,
Mukesh
> 
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