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objtool: Add --mnop as an option to --mcount

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Some architectures (powerpc) may not support ftrace locations being nop'ed
out at build time. Introduce CONFIG_HAVE_OBJTOOL_NOP_MCOUNT for objtool, as
a means for architectures to enable nop'ing of ftrace locations. Add --mnop
as an option to objtool --mcount, to indicate support for the same.

Also, make sure that --mnop can be passed as an option to objtool only when
--mcount is passed.

Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221114175754.1131267-12-sv@linux.ibm.com
This commit is contained in:
Sathvika Vasireddy 2022-11-14 23:27:49 +05:30 committed by Michael Ellerman
parent 86ea7f3615
commit 280981d699
7 changed files with 39 additions and 10 deletions
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4
Makefile
View File

@ -933,7 +933,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC
endif
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
ifdef CONFIG_HAVE_OBJTOOL_NOP_MCOUNT
CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
endif
endif
ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
ifdef CONFIG_HAVE_C_RECORDMCOUNT

1
arch/x86/Kconfig
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@ -195,6 +195,7 @@ config X86
select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
select HAVE_C_RECORDMCOUNT
select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
select HAVE_OBJTOOL_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT
select HAVE_BUILDTIME_MCOUNT_SORT
select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_CONTIGUOUS

7
kernel/trace/Kconfig
View File

@ -82,6 +82,13 @@ config HAVE_OBJTOOL_MCOUNT
help
Arch supports objtool --mcount
config HAVE_OBJTOOL_NOP_MCOUNT
bool
help
Arch supports the objtool options --mcount with --mnop.
An architecture can select this if it wants to enable nop'ing
of ftrace locations.
config HAVE_C_RECORDMCOUNT
bool
help

3
scripts/Makefile.lib
View File

@ -256,6 +256,9 @@ objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK) += --hacks=jump_label
objtool-args-$(CONFIG_HAVE_NOINSTR_HACK) += --hacks=noinstr
objtool-args-$(CONFIG_X86_KERNEL_IBT) += --ibt
objtool-args-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL) += --mcount
ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
objtool-args-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT) += --mnop
endif
objtool-args-$(CONFIG_UNWINDER_ORC) += --orc
objtool-args-$(CONFIG_RETPOLINE) += --retpoline
objtool-args-$(CONFIG_RETHUNK) += --rethunk

14
tools/objtool/builtin-check.c
View File

@ -82,6 +82,7 @@ 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"),
@ -150,6 +151,16 @@ 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)
@ -198,6 +209,9 @@ 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;

19
tools/objtool/check.c
View File

@ -1256,18 +1256,19 @@ 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));
insn->type = INSN_NOP;
}
elf_write_insn(file->elf, insn->sec,
insn->offset, insn->len,
arch_nop_insn(insn->len));
insn->type = INSN_NOP;
list_add_tail(&insn->call_node, &file->mcount_loc_list);
return;
}

1
tools/objtool/include/objtool/builtin.h
View File

@ -31,6 +31,7 @@ struct opts {
bool backup;
bool dryrun;
bool link;
bool mnop;
bool module;
bool no_unreachable;
bool sec_address;