Re: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled

Re: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled

[kernel test robot]

Hi Rong,

kernel test robot noticed the following build errors:

[auto build test ERROR on eb952c47d154ba2aac794b99c66c3c45eb4cc4ec]

url:    https://github.com/intel-lab-lkp/linux/commits/Rong-Xu/Add-AutoFDO-support-for-Clang-build/20241024-064725
base:   eb952c47d154ba2aac794b99c66c3c45eb4cc4ec
patch link:    https://lore.kernel.org/r/20241023224409.201771-4-xur%40google.com
patch subject: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled
config: sparc-sparc64_defconfig (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 13.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410251411.eRNArTOZ-lkp@intel.com/

All errors (new ones prefixed by >>):

>> sparc64-linux-ld: Error: sparc64 early assembler too large

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled

[Rong Xu]

I can reproduce the build error.

The reason for the error is because in CONFIG_SPARC64, the symbol
swapper_tsb needs to have a fixed address of 0x0000000000408000.

In arch/sparc/kernel/vmlinux.lds.S
 37 #ifdef CONFIG_SPARC64
 38 ASSERT((swapper_tsb == 0x0000000000408000), "Error: sparc64 early
assembler too large")
 39 #endif

This symbol resides in the .text section. The patch relocates "cold"
functions (tagged by .text.unlikely) to precede other symbols within
the .text section. This pushes swapper_tsb to a higher memory address,
and we have the assertion.

However, this sparc code appears incompatible with the original linker
script. The original script prioritized .text.hot symbols, placing
them before others in the .text section. Currently, no functions are
marked as "hot" in the source code.  If a function were marked with
__attribute__((hot)), the build would also fail.

I don't know a good solution other than adding a branch to the
include/asm-generic/vmlinux.lds.h.

@Masahiro Yamada: I'd appreciate any further suggestions you might have.

Best regards,

-Rong

On Thu, Oct 24, 2024 at 11:47 PM kernel test robot <lkp@intel.com> wrote:
>
> Hi Rong,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on eb952c47d154ba2aac794b99c66c3c45eb4cc4ec]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Rong-Xu/Add-AutoFDO-support-for-Clang-build/20241024-064725
> base:   eb952c47d154ba2aac794b99c66c3c45eb4cc4ec
> patch link:    https://lore.kernel.org/r/20241023224409.201771-4-xur%40google.com
> patch subject: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled
> config: sparc-sparc64_defconfig (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/config)
> compiler: sparc64-linux-gcc (GCC) 13.3.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202410251411.eRNArTOZ-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> sparc64-linux-ld: Error: sparc64 early assembler too large
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Re: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled

[Rong Xu]

OK. Here is a simple fix to the issue.

diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
index d317a843f7ea9..f1b86eb303404 100644
--- a/arch/sparc/kernel/vmlinux.lds.S
+++ b/arch/sparc/kernel/vmlinux.lds.S
@@ -48,6 +48,11 @@ SECTIONS
        {
                _text = .;
                HEAD_TEXT
+               ALIGN_FUNCTION();
+#ifdef CONFIG_SPARC64
+               /* Match text section symbols in head_64.S first */
+               *head_64.o(.text)
+#endif
                TEXT_TEXT
                SCHED_TEXT
                LOCK_TEXT

If this is OK, I'll send the updated patch.

-Rong

On Fri, Oct 25, 2024 at 11:14 AM Rong Xu <xur@google.com> wrote:
>
> I can reproduce the build error.
>
> The reason for the error is because in CONFIG_SPARC64, the symbol
> swapper_tsb needs to have a fixed address of 0x0000000000408000.
>
> In arch/sparc/kernel/vmlinux.lds.S
>  37 #ifdef CONFIG_SPARC64
>  38 ASSERT((swapper_tsb == 0x0000000000408000), "Error: sparc64 early
> assembler too large")
>  39 #endif
>
> This symbol resides in the .text section. The patch relocates "cold"
> functions (tagged by .text.unlikely) to precede other symbols within
> the .text section. This pushes swapper_tsb to a higher memory address,
> and we have the assertion.
>
> However, this sparc code appears incompatible with the original linker
> script. The original script prioritized .text.hot symbols, placing
> them before others in the .text section. Currently, no functions are
> marked as "hot" in the source code.  If a function were marked with
> __attribute__((hot)), the build would also fail.
>
> I don't know a good solution other than adding a branch to the
> include/asm-generic/vmlinux.lds.h.
>
> @Masahiro Yamada: I'd appreciate any further suggestions you might have.
>
> Best regards,
>
> -Rong
>
> On Thu, Oct 24, 2024 at 11:47 PM kernel test robot <lkp@intel.com> wrote:
> >
> > Hi Rong,
> >
> > kernel test robot noticed the following build errors:
> >
> > [auto build test ERROR on eb952c47d154ba2aac794b99c66c3c45eb4cc4ec]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Rong-Xu/Add-AutoFDO-support-for-Clang-build/20241024-064725
> > base:   eb952c47d154ba2aac794b99c66c3c45eb4cc4ec
> > patch link:    https://lore.kernel.org/r/20241023224409.201771-4-xur%40google.com
> > patch subject: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled
> > config: sparc-sparc64_defconfig (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/config)
> > compiler: sparc64-linux-gcc (GCC) 13.3.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202410251411.eRNArTOZ-lkp@intel.com/
> >
> > All errors (new ones prefixed by >>):
> >
> > >> sparc64-linux-ld: Error: sparc64 early assembler too large
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki

Re: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled

[Rong Xu]

The fix is now included in v6 of the patch series for review.

On Fri, Oct 25, 2024 at 5:27 PM Rong Xu <xur@google.com> wrote:
>
> OK. Here is a simple fix to the issue.
>
> diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
> index d317a843f7ea9..f1b86eb303404 100644
> --- a/arch/sparc/kernel/vmlinux.lds.S
> +++ b/arch/sparc/kernel/vmlinux.lds.S
> @@ -48,6 +48,11 @@ SECTIONS
>         {
>                 _text = .;
>                 HEAD_TEXT
> +               ALIGN_FUNCTION();
> +#ifdef CONFIG_SPARC64
> +               /* Match text section symbols in head_64.S first */
> +               *head_64.o(.text)
> +#endif
>                 TEXT_TEXT
>                 SCHED_TEXT
>                 LOCK_TEXT
>
> If this is OK, I'll send the updated patch.
>
> -Rong
>
> On Fri, Oct 25, 2024 at 11:14 AM Rong Xu <xur@google.com> wrote:
> >
> > I can reproduce the build error.
> >
> > The reason for the error is because in CONFIG_SPARC64, the symbol
> > swapper_tsb needs to have a fixed address of 0x0000000000408000.
> >
> > In arch/sparc/kernel/vmlinux.lds.S
> >  37 #ifdef CONFIG_SPARC64
> >  38 ASSERT((swapper_tsb == 0x0000000000408000), "Error: sparc64 early
> > assembler too large")
> >  39 #endif
> >
> > This symbol resides in the .text section. The patch relocates "cold"
> > functions (tagged by .text.unlikely) to precede other symbols within
> > the .text section. This pushes swapper_tsb to a higher memory address,
> > and we have the assertion.
> >
> > However, this sparc code appears incompatible with the original linker
> > script. The original script prioritized .text.hot symbols, placing
> > them before others in the .text section. Currently, no functions are
> > marked as "hot" in the source code.  If a function were marked with
> > __attribute__((hot)), the build would also fail.
> >
> > I don't know a good solution other than adding a branch to the
> > include/asm-generic/vmlinux.lds.h.
> >
> > @Masahiro Yamada: I'd appreciate any further suggestions you might have.
> >
> > Best regards,
> >
> > -Rong
> >
> > On Thu, Oct 24, 2024 at 11:47 PM kernel test robot <lkp@intel.com> wrote:
> > >
> > > Hi Rong,
> > >
> > > kernel test robot noticed the following build errors:
> > >
> > > [auto build test ERROR on eb952c47d154ba2aac794b99c66c3c45eb4cc4ec]
> > >
> > > url:    https://github.com/intel-lab-lkp/linux/commits/Rong-Xu/Add-AutoFDO-support-for-Clang-build/20241024-064725
> > > base:   eb952c47d154ba2aac794b99c66c3c45eb4cc4ec
> > > patch link:    https://lore.kernel.org/r/20241023224409.201771-4-xur%40google.com
> > > patch subject: [PATCH v5 3/7] Change the symbols order when --ffunction-sections is enabled
> > > config: sparc-sparc64_defconfig (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/config)
> > > compiler: sparc64-linux-gcc (GCC) 13.3.0
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241025/202410251411.eRNArTOZ-lkp@intel.com/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202410251411.eRNArTOZ-lkp@intel.com/
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > > >> sparc64-linux-ld: Error: sparc64 early assembler too large
> > >
> > > --
> > > 0-DAY CI Kernel Test Service
> > > https://github.com/intel/lkp-tests/wiki