Re: [PATCH 09/10] arm64: select DYNAMIC_DEBUG_RELATIVE_POINTERS

[Arnd Bergmann <arnd@arndb.de>]

On Tue, Apr 9, 2019 at 11:26 PM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> Similar to GENERIC_BUG_RELATIVE_POINTERS, one can now relativize the
> four const char* members of struct _ddebug, thus saving 16 bytes per
> instance (one for each pr_debug(), dev_debug() etc. in a
> CONFIG_DYNAMIC_DEBUG kernel). The asm-generic implementation seems to
> work out-of-the-box, though this is only compile-tested.
>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

This causes a build regression when compiling with clang,
see http://staging-storage.kernelci.org/next-clang/master/next-20190424/arm64/allmodconfig/clang-8/build.log

../init/initramfs.c:477:3: error: invalid operand in inline asm:
'.ifndef __UNIQUE_ID_ddebug18.pushsection __verbose,"aw".type
__UNIQUE_ID_ddebug18, STT_OBJECT.size __UNIQUE_ID_ddebug18,
${5:c}1:__UNIQUE_ID_ddebug18: .int ${0:c} - 1b /*
_ddebug::modname_disp */ .int ${1:c} - 1b /* _ddebug::function_disp */
.int ${2:c} - 1b /* _ddebug::filename_disp */ .int ${3:c} - 1b /*
_ddebug::format_disp */ .int ${4:c}      /* _ddebug::flags_lineno */
.org 1b+${5:c}.popsection.set __UNIQUE_ID_ddebug18.ddebug.once,
${6:c}.elseif __UNIQUE_ID_ddebug18.ddebug.once - ${6:c}.line 477 -
1.error "'__UNIQUE_ID_ddebug18' used as _ddebug identifier more than
once".endif'
                pr_debug("Detected %s compressed data\n", compress_name);
                ^
../include/linux/printk.h:336:2: note: expanded from macro 'pr_debug'
        dynamic_pr_debug(fmt, ##__VA_ARGS__)
        ^
../include/linux/dynamic_debug.h:158:2: note: expanded from macro
'dynamic_pr_debug'
        _dynamic_func_call(fmt, __dynamic_pr_debug,             \
        ^
../include/linux/dynamic_debug.h:148:2: note: expanded from macro
'_dynamic_func_call'
        __dynamic_func_call(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)
        ^
../include/linux/dynamic_debug.h:128:2: note: expanded from macro
'__dynamic_func_call'
        DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt);         \
        ^
../include/asm-generic/dynamic_debug.h:92:15: note: expanded from
macro 'DEFINE_DYNAMIC_DEBUG_METADATA'
        asm volatile(".ifndef " __stringify(name) "\n"                  \
                     ^

I assume the same thing happens on the other architectures as well.

        Arnd

> ---
>  arch/arm64/Kconfig            | 1 +
>  arch/arm64/include/asm/Kbuild | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 7e34b9eba5de..d0871d523d5d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -83,6 +83,7 @@ config ARM64
>         select CRC32
>         select DCACHE_WORD_ACCESS
>         select DMA_DIRECT_REMAP
> +       select DYNAMIC_DEBUG_RELATIVE_POINTERS
>         select EDAC_SUPPORT
>         select FRAME_POINTER
>         select GENERIC_ALLOCATOR
> diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
> index 1e17ea5c372b..1ead0d645686 100644
> --- a/arch/arm64/include/asm/Kbuild
> +++ b/arch/arm64/include/asm/Kbuild
> @@ -3,6 +3,7 @@ generic-y += delay.h
>  generic-y += div64.h
>  generic-y += dma.h
>  generic-y += dma-contiguous.h
> +generic-y += dynamic_debug.h
>  generic-y += early_ioremap.h
>  generic-y += emergency-restart.h
>  generic-y += hw_irq.h
> --
> 2.20.1
>
>
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