| Message ID | 20260819084825.969116-1-mkchauras@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | powerpc/bug: Add ARCH_WARN_ASM and refactor _EMIT_BUG_ENTRY for Rust support | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
On Wed, Aug 19, 2026 at 10:48 AM Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com> wrote: > > This brings powerpc into line with x86, arm64, s390, and riscv, all of > which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE. > > Suggested-by: FUJITA Tomonori <tomo@flapping.org> Should this be Reported-by? In addition, probably we want a Link to the original report, and a Fixes tag. Ideally, please include the error message in the commit message -- it helps to triaging and also to search it later on etc. Thanks! Cheers, Miguel
On Wed, Aug 19, 2026 at 12:02:01PM +0200, Miguel Ojeda wrote: > On Wed, Aug 19, 2026 at 10:48 AM Mukesh Kumar Chaurasiya (IBM) > <mkchauras@gmail.com> wrote: > > > > This brings powerpc into line with x86, arm64, s390, and riscv, all of > > which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE. > > > > Suggested-by: FUJITA Tomonori <tomo@flapping.org> > > Should this be Reported-by? > The change itself is suggested by Tomonori so i was not sure. Yeah there should be Reported-by: Link Mauve <linkmauve@linkmauve.fr> Closes: https://lore.kernel.org/all/anG67Q6Y59kDqh-c@desktop Fixes: 73b741adb264 ("rust: Add PowerPC support") > In addition, probably we want a Link to the original report, and a Fixes tag. > > Ideally, please include the error message in the commit message -- it > helps to triaging and also to search it later on etc. > Sure i'll add the error to the commit message and send out a new revision. > Thanks! > > Cheers, > Miguel Thanks for the quick review. Regards, Mukesh
Le 19/08/2026 à 10:48, Mukesh Kumar Chaurasiya (IBM) a écrit : > 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. > > Refactor _EMIT_BUG_ENTRY to accept explicit (file, line, flags) string > arguments rather than relying on positional asm operand references > (%0, %1, %2, %3). This allows the macro to be composed as a plain > string concatenation, which is required for ARCH_WARN_ASM where no asm > operand context exists. > > Move the .org and .previous directives out of _EMIT_BUG_ENTRY and into > the BUG_ENTRY() call site to preserve existing behaviour while enabling > ARCH_WARN_ASM to supply its own size operand independently. > > Add ARCH_WARN_REACHABLE as an empty define, matching the arm64 > convention, indicating that no additional reachability annotation is > needed after a WARN on powerpc. > > This brings powerpc into line with x86, arm64, s390, and riscv, all of > which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE. > > Suggested-by: FUJITA Tomonori <tomo@flapping.org> > Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com> > --- > arch/powerpc/include/asm/bug.h | 28 ++++++++++++++++------------ > 1 file changed, 16 insertions(+), 12 deletions(-) > > 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__ */ Sorry, I still don't understand. The only place the new macro is used is a .S file (namely rust/kernel/generated_arch_warn_asm.rs.S), and the change this patch implements is inside a #if !__ASSEMBLER__. What am I missing ? Christophe > -/* _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
On Wed, Aug 19, 2026 at 01:50:43PM +0200, Christophe Leroy (CS GROUP) wrote: > > > Le 19/08/2026 à 10:48, Mukesh Kumar Chaurasiya (IBM) a écrit : > > 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. > > > > Refactor _EMIT_BUG_ENTRY to accept explicit (file, line, flags) string > > arguments rather than relying on positional asm operand references > > (%0, %1, %2, %3). This allows the macro to be composed as a plain > > string concatenation, which is required for ARCH_WARN_ASM where no asm > > operand context exists. > > > > Move the .org and .previous directives out of _EMIT_BUG_ENTRY and into > > the BUG_ENTRY() call site to preserve existing behaviour while enabling > > ARCH_WARN_ASM to supply its own size operand independently. > > > > Add ARCH_WARN_REACHABLE as an empty define, matching the arm64 > > convention, indicating that no additional reachability annotation is > > needed after a WARN on powerpc. > > > > This brings powerpc into line with x86, arm64, s390, and riscv, all of > > which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE. > > > > Suggested-by: FUJITA Tomonori <tomo@flapping.org> > > Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com> > > --- > > arch/powerpc/include/asm/bug.h | 28 ++++++++++++++++------------ > > 1 file changed, 16 insertions(+), 12 deletions(-) > > > > 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__ */ > > Sorry, I still don't understand. The only place the new macro is used is a > .S file (namely rust/kernel/generated_arch_warn_asm.rs.S), and the change > this patch implements is inside a #if !__ASSEMBLER__. > > What am I missing ? > > Christophe Hey Christophe, The code calling ARCH_WARN_ASM is a .rs.S file that goes through the C preprocessor as part of the Rust build machinery. The intended mechanism is essentially generated_arch_warn_asm.rs.S | v CPP | | includes <linux/bug.h> | v ARCH_WARN_ASM(...) gets expanded | v Rust source containing the generated assembly string The patch therefore needs ARCH_WARN_ASM in the non-__ASSEMBLER__ section, because that section is where the macros intended for C preprocessing are defined. The thing is .rs.S is not using ARCH_WARN_ASM as an assembler-time macro, it is using the C preprocessor to expand ARCH_WARN_ASM before the Rust/assembly processing stage. This is my understanding of things, if i am wrong somewhere maybe someone can clarify. Regards, Mukesh [...]
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
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. Refactor _EMIT_BUG_ENTRY to accept explicit (file, line, flags) string arguments rather than relying on positional asm operand references (%0, %1, %2, %3). This allows the macro to be composed as a plain string concatenation, which is required for ARCH_WARN_ASM where no asm operand context exists. Move the .org and .previous directives out of _EMIT_BUG_ENTRY and into the BUG_ENTRY() call site to preserve existing behaviour while enabling ARCH_WARN_ASM to supply its own size operand independently. Add ARCH_WARN_REACHABLE as an empty define, matching the arm64 convention, indicating that no additional reachability annotation is needed after a WARN on powerpc. This brings powerpc into line with x86, arm64, s390, and riscv, all of which already define ARCH_WARN_ASM and ARCH_WARN_REACHABLE. Suggested-by: FUJITA Tomonori <tomo@flapping.org> Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com> --- arch/powerpc/include/asm/bug.h | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-)