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Message-ID: <26c7bfc8-3089-034a-70c0-8857d7cd3a99@csgroup.eu>
Date: Tue, 24 May 2022 08:54:38 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Sathvika Vasireddy <sv@...ux.ibm.com>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jpoimboe@...hat.com" <jpoimboe@...hat.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"mbenes@...e.cz" <mbenes@...e.cz>, "aik@...abs.ru" <aik@...abs.ru>,
"mpe@...erman.id.au" <mpe@...erman.id.au>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount
Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
> 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,
> along with --mcount.
>
Is there a reason not to nop out mcount call sites on powerpc as well ?
> Also, make sure that --mnop can be passed as an option
> to objtool only when --mcount is passed.
>
> Signed-off-by: Sathvika Vasireddy <sv@...ux.ibm.com>
> ---
> Makefile | 4 +++-
> arch/x86/Kconfig | 1 +
> scripts/Makefile.build | 1 +
> tools/objtool/builtin-check.c | 14 ++++++++++++++
> tools/objtool/check.c | 19 ++++++++++---------
> tools/objtool/include/objtool/builtin.h | 1 +
> 6 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 250707647359..acaf88e3c694 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -851,7 +851,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC
> endif
> endif
> ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
> - CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
> + 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
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 1847d6e974a1..4a41bfb644f0 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -189,6 +189,7 @@ config X86
> select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
> select HAVE_C_RECORDMCOUNT
> select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
> + select HAVE_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT
> select HAVE_BUILDTIME_MCOUNT_SORT
> select HAVE_DEBUG_KMEMLEAK
> select HAVE_DMA_CONTIGUOUS
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index ac8167227bc0..2e0c3f9c1459 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -231,6 +231,7 @@ objtool_args = \
> $(if $(CONFIG_HAVE_NOINSTR_HACK), --hacks=noinstr) \
> $(if $(CONFIG_X86_KERNEL_IBT), --ibt) \
> $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \
> + $(if $(CONFIG_HAVE_NOP_MCOUNT), --mnop) \
> $(if $(CONFIG_UNWINDER_ORC), --orc) \
> $(if $(CONFIG_RETPOLINE), --retpoline) \
> $(if $(CONFIG_SLS), --sls) \
> diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
> index f4c3a5091737..b05e2108c0c3 100644
> --- a/tools/objtool/builtin-check.c
> +++ b/tools/objtool/builtin-check.c
> @@ -80,6 +80,7 @@ const struct option check_options[] = {
> OPT_BOOLEAN(0, "dry-run", &opts.dryrun, "don't write modifications"),
> OPT_BOOLEAN(0, "link", &opts.link, "object is a linked object"),
> OPT_BOOLEAN(0, "module", &opts.module, "object is part of a kernel module"),
> + OPT_BOOLEAN(0, "mnop", &opts.mnop, "nop out mcount call sites"),
> OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
> OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
> OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
> @@ -142,6 +143,16 @@ static bool opts_valid(void)
> return false;
> }
>
> +static bool mnop_opts_valid(void)
> +{
> + if (opts.mnop && !opts.mcount) {
> + ERROR("--mnop requires --mcount");
> + return false;
> + }
> +
> + return true;
> +}
> +
> static bool link_opts_valid(struct objtool_file *file)
> {
> if (opts.link)
> @@ -185,6 +196,9 @@ int objtool_run(int argc, const char **argv)
> if (!file)
> return 1;
>
> + if (!mnop_opts_valid())
> + return 1;
> +
> if (!link_opts_valid(file))
> return 1;
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 190b2f6e360a..056302d58e23 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -1175,17 +1175,18 @@ static void annotate_call_site(struct objtool_file *file,
> if (opts.mcount && sym->fentry) {
> if (sibling)
> WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
> + if (opts.mnop) {
> + if (reloc) {
> + reloc->type = R_NONE;
> + elf_write_reloc(file->elf, reloc);
> + }
>
> - if (reloc) {
> - reloc->type = R_NONE;
> - elf_write_reloc(file->elf, reloc);
> - }
> -
> - elf_write_insn(file->elf, insn->sec,
> - insn->offset, insn->len,
> - arch_nop_insn(insn->len));
> + elf_write_insn(file->elf, insn->sec,
> + insn->offset, insn->len,
> + arch_nop_insn(insn->len));
>
> - insn->type = INSN_NOP;
> + insn->type = INSN_NOP;
> + }
>
> list_add_tail(&insn->call_node, &file->mcount_loc_list);
> return;
> diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
> index 280ea18b7f2b..71ed3152a18e 100644
> --- a/tools/objtool/include/objtool/builtin.h
> +++ b/tools/objtool/include/objtool/builtin.h
> @@ -29,6 +29,7 @@ struct opts {
> bool backup;
> bool dryrun;
> bool link;
> + bool mnop;
> bool module;
> bool no_unreachable;
> bool sec_address;
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