Commit eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input
sections") added ".text.unlikely.*" and ".text.hot.*" due to an LLVM
change [1].
After another LLVM change [2], these sections are seen in some PowerPC
builds, where there is a orphan section warning then build failure:
$ make -skj"$(nproc)" \
ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 O=out \
distclean powernv_defconfig zImage.epapr
ld.lld: warning: kernel/built-in.a(panic.o):(.text.unlikely.) is being placed in '.text.unlikely.'
...
ld.lld: warning: address (0xc000000000009314) of section .text is not a multiple of alignment (256)
...
ERROR: start_text address is c000000000009400, should be c000000000008000
ERROR: try to enable LD_HEAD_STUB_CATCH config option
ERROR: see comments in arch/powerpc/tools/head_check.sh
...
Explicitly handle these sections like in the main linker script so
there is no more build failure.
[1]: https://reviews.llvm.org/D79600
[2]: https://reviews.llvm.org/D92493
Cc: [email protected]
Fixes: 83a092cf95f2 ("powerpc: Link warning for orphan sections")
Link: https://github.com/ClangBuiltLinux/linux/issues/1218
Signed-off-by: Nathan Chancellor <[email protected]>
---
v1 -> v2:
* Add missing [1] and [2] references in commit message. Thanks to Sedat
Dilek for pointing it out!
arch/powerpc/kernel/vmlinux.lds.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 0318ba436f34..8e0b1298bf19 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -85,7 +85,7 @@ SECTIONS
ALIGN_FUNCTION();
#endif
/* careful! __ftr_alt_* sections need to be close to .text */
- *(.text.hot TEXT_MAIN .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text);
+ *(.text.hot .text.hot.* TEXT_MAIN .text.fixup .text.unlikely .text.unlikely.* .fixup __ftr_alt_* .ref.text);
#ifdef CONFIG_PPC64
*(.tramp.ftrace.text);
#endif
base-commit: d8a4f20584d5906093a8fc6aa06622102a501095
--
2.30.0
On Mon, 4 Jan 2021 13:59:53 -0700, Nathan Chancellor wrote:
> Commit eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input
> sections") added ".text.unlikely.*" and ".text.hot.*" due to an LLVM
> change [1].
>
> After another LLVM change [2], these sections are seen in some PowerPC
> builds, where there is a orphan section warning then build failure:
>
> [...]
Applied to powerpc/fixes.
[1/1] powerpc: Handle .text.{hot,unlikely}.* in linker script
https://git.kernel.org/powerpc/c/3ce47d95b7346dcafd9bed3556a8d072cb2b8571
cheers
On Sat, Jan 16, 2021 at 12:44:38PM -0600, Segher Boessenkool wrote:
> Hi!
>
> Very late of course, and the patch is fine, but:
>
> On Mon, Jan 04, 2021 at 01:59:53PM -0700, Nathan Chancellor wrote:
> > Commit eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input
> > sections") added ".text.unlikely.*" and ".text.hot.*" due to an LLVM
> > change [1].
> >
> > After another LLVM change [2], these sections are seen in some PowerPC
> > builds, where there is a orphan section warning then build failure:
> >
> > $ make -skj"$(nproc)" \
> > ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 O=out \
> > distclean powernv_defconfig zImage.epapr
> > ld.lld: warning: kernel/built-in.a(panic.o):(.text.unlikely.) is being placed in '.text.unlikely.'
>
> Is the section really called ".text.unlikely.", i.e. the name ending in
> a dot? How very unusual, is there some bug elsewhere?
No, this was an intention change done by LLVM:
https://reviews.llvm.org/D79600
Cheers,
Nathan
Hi!
Very late of course, and the patch is fine, but:
On Mon, Jan 04, 2021 at 01:59:53PM -0700, Nathan Chancellor wrote:
> Commit eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input
> sections") added ".text.unlikely.*" and ".text.hot.*" due to an LLVM
> change [1].
>
> After another LLVM change [2], these sections are seen in some PowerPC
> builds, where there is a orphan section warning then build failure:
>
> $ make -skj"$(nproc)" \
> ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 O=out \
> distclean powernv_defconfig zImage.epapr
> ld.lld: warning: kernel/built-in.a(panic.o):(.text.unlikely.) is being placed in '.text.unlikely.'
Is the section really called ".text.unlikely.", i.e. the name ending in
a dot? How very unusual, is there some bug elsewhere?
Segher