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Message-Id: <b326eeb9c33231b9dfbb925f194ed7ee40edcd7c.1650300597.git.jpoimboe@redhat.com>
Date: Mon, 18 Apr 2022 09:50:40 -0700
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: x86@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH v2 21/25] objtool: Make noinstr hacks optional
Objtool has some hacks in place to workaround toolchain limitations
which otherwise would break no-instrumentation rules. Make the hacks
explicit (and optional for other arches) by turning it into a cmdline
option and kernel config option.
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
arch/Kconfig | 3 +++
arch/x86/Kconfig | 1 +
lib/Kconfig.debug | 4 ++--
lib/Kconfig.kcsan | 5 +++--
scripts/Makefile.build | 1 +
scripts/link-vmlinux.sh | 4 ++++
tools/objtool/builtin-check.c | 8 +++++++-
tools/objtool/check.c | 2 +-
tools/objtool/include/objtool/builtin.h | 1 +
9 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 9dce6d6e3bc3..6ba6e34db0ea 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1035,6 +1035,9 @@ config HAVE_OBJTOOL
config HAVE_JUMP_LABEL_HACK
bool
+config HAVE_NOINSTR_HACK
+ bool
+
config HAVE_STACK_VALIDATION
bool
help
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 46218967129f..cc7cca041745 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -231,6 +231,7 @@ config X86
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_MOVE_PMD
select HAVE_MOVE_PUD
+ select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
select HAVE_NMI
select HAVE_OBJTOOL if X86_64
select HAVE_OPTPROBES
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c0e4e47f3ce3..7d2bbc3e558e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2036,11 +2036,11 @@ config KCOV
bool "Code coverage for fuzzing"
depends on ARCH_HAS_KCOV
depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
- depends on !ARCH_WANTS_NO_INSTR || HAVE_OBJTOOL || \
+ depends on !ARCH_WANTS_NO_INSTR || HAVE_NOINSTR_HACK || \
GCC_VERSION >= 120000 || CLANG_VERSION >= 130000
select DEBUG_FS
select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
- select OBJTOOL if HAVE_OBJTOOL
+ select OBJTOOL if HAVE_NOINSTR_HACK
help
KCOV exposes kernel code coverage information in a form suitable
for coverage-guided fuzzing (randomized testing).
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 901c3b509aca..47a693c45864 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -187,8 +187,9 @@ config KCSAN_WEAK_MEMORY
# We can either let objtool nop __tsan_func_{entry,exit}() and builtin
# atomics instrumentation in .noinstr.text, or use a compiler that can
# implement __no_kcsan to really remove all instrumentation.
- depends on HAVE_OBJTOOL || CC_IS_GCC || CLANG_VERSION >= 140000
- select OBJTOOL if HAVE_OBJTOOL
+ depends on !ARCH_WANTS_NO_INSTR || HAVE_NOINSTR_HACK || \
+ CC_IS_GCC || CLANG_VERSION >= 140000
+ select OBJTOOL if HAVE_NOINSTR_HACK
help
Enable support for modeling a subset of weak memory, which allows
detecting a subset of data races due to missing memory barriers.
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index f1d2c2e4f15b..6c206a1bab97 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -228,6 +228,7 @@ objtool := $(objtree)/tools/objtool/objtool
objtool_args = \
$(if $(CONFIG_HAVE_JUMP_LABEL_HACK), --hacks=jump_label) \
+ $(if $(CONFIG_HAVE_NOINSTR_HACK), --hacks=noinstr) \
$(if $(CONFIG_X86_KERNEL_IBT), --lto --ibt) \
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \
$(if $(CONFIG_UNWINDER_ORC), --orc) \
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index fa1f16840e76..90c9c4c05d95 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -121,6 +121,10 @@ objtool_link()
objtoolopt="${objtoolopt} --hacks=jump_label"
fi
+ if is_enabled CONFIG_HAVE_NOINSTR_HACK; then
+ objtoolopt="${objtoolopt} --hacks=noinstr"
+ fi
+
if is_enabled CONFIG_X86_KERNEL_IBT; then
objtoolopt="${objtoolopt} --ibt"
fi
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index b2c626d9e2bf..1803a63147e4 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -47,12 +47,17 @@ static int parse_hacks(const struct option *opt, const char *str, int unset)
found = true;
}
+ if (!str || strstr(str, "noinstr")) {
+ opts.hack_noinstr = true;
+ found = true;
+ }
+
return found ? 0 : -1;
}
const struct option check_options[] = {
OPT_GROUP("Actions:"),
- OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label", "patch toolchain bugs/limitations", parse_hacks),
+ OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr", "patch toolchain bugs/limitations", parse_hacks),
OPT_BOOLEAN('i', "ibt", &opts.ibt, "validate and annotate IBT"),
OPT_BOOLEAN('m', "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"),
OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"),
@@ -108,6 +113,7 @@ int cmd_parse_options(int argc, const char **argv, const char * const usage[])
static bool opts_valid(void)
{
if (opts.hack_jump_label ||
+ opts.hack_noinstr ||
opts.ibt ||
opts.mcount ||
opts.noinstr ||
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index eb3dffab8767..6a7b5fa3fe1b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1145,7 +1145,7 @@ static void annotate_call_site(struct objtool_file *file,
* attribute so they need a little help, NOP out any such calls from
* noinstr text.
*/
- if (insn->sec->noinstr && sym->profiling_func) {
+ if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
if (reloc) {
reloc->type = R_NONE;
elf_write_reloc(file->elf, reloc);
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index c6acf05ec859..f3a1a754b5c4 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -13,6 +13,7 @@ struct opts {
/* actions: */
bool dump_orc;
bool hack_jump_label;
+ bool hack_noinstr;
bool ibt;
bool mcount;
bool noinstr;
--
2.34.1
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