On Thu, 6 Sep 2018 12:49:39 +0200 Peter Oberparleiter <oberpar@xxxxxxxxxxxxx> wrote: > On 28.08.2018 02:43, Masami Hiramatsu wrote: > > I recently added a gcov profiling for ftrace, following Documentation/dev-tools/gcov.rst. > > 6b7dca401cb1 ("tracing: Allow gcov profiling on only ftrace subsystem") > > > > and it caused may orphan section warnings/errors on arm and powerpc64. > > We also found same error happens when CONFIG_GCOV_PROFILE_ALL=y. > > So I guess GCOV kernel subsystem broken in some environment. > > I can confirm that these issues are unrelated to your commit which only > made the existing problems visible by enabling gcov-kernel profiling for > allyesconfig builds. Both problems already exist in v4.18 and likely > earlier versions. > > Problem 1: link failure on arm > (https://lkml.org/lkml/2018/8/24/345) > > The root cause appears to be that the arm linker script only partially > discards unneeded sections generated by the compiler when gcov-kernel > profiling is enabled. > > Problem 2: linker warnings on powerpc > (https://lkml.org/lkml/2018/8/24/72) > > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y adds compiler flag > -fdata-sections. This option causes GCC to create separate data sections > for data objects, including those generated by GCC internally for gcov > profiling. Since the name of these internal data objects starts with a . > (.LPBX0, .LPBX1), the resulting section name starts with "data..". As > section names starting with "data.." are used for specific purposes in > the Linux kernel, the linker script does not automatically handle them, > resulting in the "orphan section" linker warnings. Good catch! I didn't know that option. > > I've attached a quick fix that should address both problems. I'd > appreciate if this patch could get some testing before I post proper fix > patches. Hmm, I'm still not able to reproduce it on powerpc cross build even with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y ... So, sorry I couldn't test this patch. > > -- >8 -- > diff --git a/arch/arm/kernel/vmlinux.lds.h b/arch/arm/kernel/vmlinux.lds.h > index ae5fdff18406..2ca33277a28b 100644 > --- a/arch/arm/kernel/vmlinux.lds.h > +++ b/arch/arm/kernel/vmlinux.lds.h > @@ -48,6 +48,7 @@ > > #define ARM_DISCARD \ > *(.ARM.exidx.exit.text) \ > + *(.ARM.exidx.text.exit) \ BTW, why would we need this? Thanks, > *(.ARM.extab.exit.text) \ > ARM_CPU_DISCARD(*(.ARM.exidx.cpuexit.text)) \ > ARM_CPU_DISCARD(*(.ARM.extab.cpuexit.text)) \ > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 7b75ff6e2fce..5cf3b90c5592 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -68,7 +68,7 @@ > */ > #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION > #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* > -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* > +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* > #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* > #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* > #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* > @@ -613,7 +613,7 @@ > > #define EXIT_DATA \ > *(.exit.data .exit.data.*) \ > - *(.fini_array) \ > + *(.fini_array .fini_array.*) \ > *(.dtors) \ > MEM_DISCARD(exit.data*) \ > MEM_DISCARD(exit.rodata*) > -- > Peter Oberparleiter > Linux on Z Development - IBM Germany > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>