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Message-ID: <b06bb9bc-22d1-acce-fe68-c7c4cb7c15b5@csgroup.eu>
Date: Mon, 21 Mar 2022 08:26:55 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
Sathvika Vasireddy <sv@...ux.ibm.com>
CC: "aik@...abs.ru" <aik@...abs.ru>,
"jpoimboe@...hat.com" <jpoimboe@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>
Subject: Re: [RFC PATCH 2/3] objtool: Enable and implement 'mcount' subcommand
Le 21/03/2022 à 09:19, Naveen N. Rao a écrit :
> 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@...ux.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.
>
I just checked without the series: recordmcount isn't run for VDSO, so
objtool shouldn't be run either when the series is applied.
Christophe
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