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SubjectRe: [RFC PATCH 2/3] objtool: Enable and implement 'mcount' subcommand
Christophe Leroy wrote:
>
>
> Le 18/03/2022 à 11:51, Sathvika Vasireddy a écrit :
>> This patch adds 'mcount' as a subcommand to objtool, and enables
>> the same for x86. objtool is built if CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
>> is selected. Additionally, architectures can select HAVE_NOP_MCOUNT
>> if they choose to nop out mcount call sites. If that config option is
>> selected, then --mnop is passed as an option to 'objtool mcount'
>>
>> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
>> ---
>> Makefile | 6 ++
>> arch/x86/Kconfig | 3 +-
>> scripts/Makefile.build | 12 +++
>> tools/objtool/Build | 2 +
>> tools/objtool/Makefile | 4 +-
>> tools/objtool/builtin-mcount.c | 74 +++++++++++++
>> tools/objtool/include/objtool/builtin.h | 4 +-
>> tools/objtool/include/objtool/objtool.h | 1 +
>> tools/objtool/mcount.c | 138 ++++++++++++++++++++++++
>> tools/objtool/objtool.c | 1 +
>> tools/objtool/weak.c | 5 +
>> 11 files changed, 247 insertions(+), 3 deletions(-)
>> create mode 100644 tools/objtool/builtin-mcount.c
>> create mode 100644 tools/objtool/mcount.c
>>
>> diff --git a/Makefile b/Makefile
>> index 55a30ca69350..316f7d08b30a 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -846,7 +846,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC
>> endif
>> endif
>> ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
>> + ifdef CONFIG_HAVE_NOP_MCOUNT
>> CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
>> + endif
>> endif
>> ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
>> ifdef CONFIG_HAVE_C_RECORDMCOUNT
>> @@ -1303,6 +1305,10 @@ ifdef CONFIG_STACK_VALIDATION
>> prepare: tools/objtool
>> endif
>>
>> +ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
>> +prepare: tools/objtool
>> +endif
>
> I don't think that will work for powerpc.
>
> See arch/powerpc/Makefile
>
> powerpc builds the VDSO under prepare: , and powerpc has
> CONFIG_HAVE_GENERIC_VDSO so there are some C files in that step that
> seem to use objtool, allthough that looks odd to me. Must be something
> to fix somewhere.
>
> powerpc64-linux-gcc
> -Wp,-MMD,arch/powerpc/kernel/vdso/.vgettimeofday-64.o.d -nostdinc
> -I./arch/powerpc/include -I./arch/powerpc/include/generated -I./include
> -I./arch/powerpc/include/uapi -I./arch/powerpc/include/generated/uapi
> -I./include/uapi -I./include/generated/uapi -include
> ./include/linux/compiler-version.h -include ./include/linux/kconfig.h
> -include ./include/linux/compiler_types.h -D__KERNEL__ -I ./arch/powerpc
> -DHAVE_AS_ATHIGH=1 -fmacro-prefix-map=./= -Wall -Wundef
> -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing
> -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration
> -Werror=implicit-int -Werror=return-type -Wno-format-security -std=gnu89
> -mbig-endian -m64 -msoft-float -pipe -mtraceback=no -mabi=elfv1
> -mcall-aixdesc -mcmodel=medium -mno-pointers-to-nested-functions
> -mtune=power7 -mcpu=power5 -mno-altivec -mno-vsx
> -fno-asynchronous-unwind-tables -mno-string -Wa,-maltivec -Wa,-mpower4
> -Wa,-many -mabi=elfv1 -mcall-aixdesc -mbig-endian
> -mstack-protector-guard=tls -mstack-protector-guard-reg=r13
> -fno-delete-null-pointer-checks -Wno-frame-address
> -Wno-format-truncation -Wno-format-overflow
> -Wno-address-of-packed-member -O2 -fno-allow-store-data-races
> -Wframe-larger-than=2048 -fstack-protector-strong
> -Wimplicit-fallthrough=5 -Wno-main -Wno-unused-but-set-variable
> -Wno-unused-const-variable -fno-stack-clash-protection
> -Wdeclaration-after-statement -Wvla -Wno-pointer-sign
> -Wcast-function-type -Wno-stringop-truncation -Wno-zero-length-bounds
> -Wno-array-bounds -Wno-stringop-overflow -Wno-restrict
> -Wno-maybe-uninitialized -Wno-alloc-size-larger-than
> -fno-strict-overflow -fno-stack-check -fconserve-stack -Werror=date-time
> -Werror=incompatible-pointer-types -Werror=designated-init
> -Wno-packed-not-aligned -mstack-protector-guard-offset=3200 -shared
> -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both -include
> /home/chleroy/linux-powerpc/lib/vdso/gettimeofday.c -fno-stack-protector
> -DDISABLE_BRANCH_PROFILING -ffreestanding -fasynchronous-unwind-tables
> -ffixed-r30
> -DKBUILD_MODFILE='"arch/powerpc/kernel/vdso/vgettimeofday-64"'
> -DKBUILD_BASENAME='"vgettimeofday_64"'
> -DKBUILD_MODNAME='"vgettimeofday_64"'
> -D__KBUILD_MODNAME=kmod_vgettimeofday_64 -c -o
> arch/powerpc/kernel/vdso/vgettimeofday-64.o
> arch/powerpc/kernel/vdso/vgettimeofday.c ; ./tools/objtool/objtool
> mcount arch/powerpc/kernel/vdso/vgettimeofday-64.o

We don't enable ftrace for vdso, so I suspect objtool run above will be
a no-op. This needs to be confirmed, of course.


- Naveen

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