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Message-Id: <20250409160251.work.914-kees@kernel.org>
Date: Wed, 9 Apr 2025 09:02:56 -0700
From: Kees Cook <kees@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>
Cc: Kees Cook <kees@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Nicolas Schier <nicolas@...sle.eu>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Konovalov <andreyknvl@...il.com>,
linux-kbuild@...r.kernel.org,
linux-hardening@...r.kernel.org,
kasan-dev@...glegroups.com,
Bill Wendling <morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>,
linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: [PATCH] gcc-plugins: Remove SANCOV plugin
There are very few users of this plugin[1], and since it's features
are available in GCC 6 and later (and Clang), users can update their
compilers if they need support on newer kernels.
Suggested-by: Arnd Bergmann <arnd@...db.de>
Link: https://lore.kernel.org/all/08393aa3-05a3-4e3f-8004-f374a3ec4b7e@app.fastmail.com/ [1]
Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Masahiro Yamada <masahiroy@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nicolas Schier <nicolas@...sle.eu>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>
Cc: linux-kbuild@...r.kernel.org
Cc: linux-hardening@...r.kernel.org
Cc: kasan-dev@...glegroups.com
---
lib/Kconfig.debug | 4 +-
scripts/Makefile.gcc-plugins | 2 -
scripts/Makefile.kcov | 1 -
scripts/gcc-plugins/Kconfig | 10 ---
scripts/gcc-plugins/sancov_plugin.c | 134 ----------------------------
5 files changed, 1 insertion(+), 150 deletions(-)
delete mode 100644 scripts/gcc-plugins/sancov_plugin.c
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af972a92d06..e7347419ffc5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2135,15 +2135,13 @@ config ARCH_HAS_KCOV
config CC_HAS_SANCOV_TRACE_PC
def_bool $(cc-option,-fsanitize-coverage=trace-pc)
-
config KCOV
bool "Code coverage for fuzzing"
depends on ARCH_HAS_KCOV
- depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
+ depends on CC_HAS_SANCOV_TRACE_PC
depends on !ARCH_WANTS_NO_INSTR || HAVE_NOINSTR_HACK || \
GCC_VERSION >= 120000 || CC_IS_CLANG
select DEBUG_FS
- select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
select OBJTOOL if HAVE_NOINSTR_HACK
help
KCOV exposes kernel code coverage information in a form suitable
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index e4deaf5fa571..6da109d563a5 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -52,8 +52,6 @@ KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
# Some plugins are enabled outside of this Makefile, but they still need to
# be included in GCC_PLUGIN so they can get built.
-gcc-plugin-external-$(CONFIG_GCC_PLUGIN_SANCOV) \
- += sancov_plugin.so
gcc-plugin-external-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) \
+= randomize_layout_plugin.so
diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
index 67e8cfe3474b..67de7942b3e7 100644
--- a/scripts/Makefile.kcov
+++ b/scripts/Makefile.kcov
@@ -1,6 +1,5 @@
# SPDX-License-Identifier: GPL-2.0-only
kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC) += -fsanitize-coverage=trace-pc
kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS) += -fsanitize-coverage=trace-cmp
-kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV) += -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
export CFLAGS_KCOV := $(kcov-flags-y)
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index e383cda05367..ba868d1eef3d 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -19,16 +19,6 @@ menuconfig GCC_PLUGINS
if GCC_PLUGINS
-config GCC_PLUGIN_SANCOV
- bool
- # Plugin can be removed once the kernel only supports GCC 6+
- depends on !CC_HAS_SANCOV_TRACE_PC
- help
- This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
- basic blocks. It supports all gcc versions with plugin support (from
- gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
- by Dmitry Vyukov <dvyukov@...gle.com>.
-
config GCC_PLUGIN_LATENT_ENTROPY
bool "Generate some entropy during boot and runtime"
help
diff --git a/scripts/gcc-plugins/sancov_plugin.c b/scripts/gcc-plugins/sancov_plugin.c
deleted file mode 100644
index b76cb9c42cec..000000000000
--- a/scripts/gcc-plugins/sancov_plugin.c
+++ /dev/null
@@ -1,134 +0,0 @@
-/*
- * Copyright 2011-2016 by Emese Revfy <re.emese@...il.com>
- * Licensed under the GPL v2, or (at your option) v3
- *
- * Homepage:
- * https://github.com/ephox-gcc-plugins/sancov
- *
- * This plugin inserts a __sanitizer_cov_trace_pc() call at the start of basic blocks.
- * It supports all gcc versions with plugin support (from gcc-4.5 on).
- * It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov <dvyukov@...gle.com>.
- *
- * You can read about it more here:
- * https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296
- * https://lwn.net/Articles/674854/
- * https://github.com/google/syzkaller
- * https://lwn.net/Articles/677764/
- *
- * Usage:
- * make run
- */
-
-#include "gcc-common.h"
-
-__visible int plugin_is_GPL_compatible;
-
-tree sancov_fndecl;
-
-static struct plugin_info sancov_plugin_info = {
- .version = PLUGIN_VERSION,
- .help = "sancov plugin\n",
-};
-
-static unsigned int sancov_execute(void)
-{
- basic_block bb;
-
- /* Remove this line when this plugin and kcov will be in the kernel.
- if (!strcmp(DECL_NAME_POINTER(current_function_decl), DECL_NAME_POINTER(sancov_fndecl)))
- return 0;
- */
-
- FOR_EACH_BB_FN(bb, cfun) {
- const_gimple stmt;
- gcall *gcall;
- gimple_stmt_iterator gsi = gsi_after_labels(bb);
-
- if (gsi_end_p(gsi))
- continue;
-
- stmt = gsi_stmt(gsi);
- gcall = as_a_gcall(gimple_build_call(sancov_fndecl, 0));
- gimple_set_location(gcall, gimple_location(stmt));
- gsi_insert_before(&gsi, gcall, GSI_SAME_STMT);
- }
- return 0;
-}
-
-#define PASS_NAME sancov
-
-#define NO_GATE
-#define TODO_FLAGS_FINISH TODO_dump_func | TODO_verify_stmts | TODO_update_ssa_no_phi | TODO_verify_flow
-
-#include "gcc-generate-gimple-pass.h"
-
-static void sancov_start_unit(void __unused *gcc_data, void __unused *user_data)
-{
- tree leaf_attr, nothrow_attr;
- tree BT_FN_VOID = build_function_type_list(void_type_node, NULL_TREE);
-
- sancov_fndecl = build_fn_decl("__sanitizer_cov_trace_pc", BT_FN_VOID);
-
- DECL_ASSEMBLER_NAME(sancov_fndecl);
- TREE_PUBLIC(sancov_fndecl) = 1;
- DECL_EXTERNAL(sancov_fndecl) = 1;
- DECL_ARTIFICIAL(sancov_fndecl) = 1;
- DECL_PRESERVE_P(sancov_fndecl) = 1;
- DECL_UNINLINABLE(sancov_fndecl) = 1;
- TREE_USED(sancov_fndecl) = 1;
-
- nothrow_attr = tree_cons(get_identifier("nothrow"), NULL, NULL);
- decl_attributes(&sancov_fndecl, nothrow_attr, 0);
- gcc_assert(TREE_NOTHROW(sancov_fndecl));
- leaf_attr = tree_cons(get_identifier("leaf"), NULL, NULL);
- decl_attributes(&sancov_fndecl, leaf_attr, 0);
-}
-
-__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
-{
- int i;
- const char * const plugin_name = plugin_info->base_name;
- const int argc = plugin_info->argc;
- const struct plugin_argument * const argv = plugin_info->argv;
- bool enable = true;
-
- static const struct ggc_root_tab gt_ggc_r_gt_sancov[] = {
- {
- .base = &sancov_fndecl,
- .nelt = 1,
- .stride = sizeof(sancov_fndecl),
- .cb = >_ggc_mx_tree_node,
- .pchw = >_pch_nx_tree_node
- },
- LAST_GGC_ROOT_TAB
- };
-
- /* BBs can be split afterwards?? */
- PASS_INFO(sancov, "asan", 0, PASS_POS_INSERT_BEFORE);
-
- if (!plugin_default_version_check(version, &gcc_version)) {
- error(G_("incompatible gcc/plugin versions"));
- return 1;
- }
-
- for (i = 0; i < argc; ++i) {
- if (!strcmp(argv[i].key, "no-sancov")) {
- enable = false;
- continue;
- }
- error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
- }
-
- register_callback(plugin_name, PLUGIN_INFO, NULL, &sancov_plugin_info);
-
- if (!enable)
- return 0;
-
-#if BUILDING_GCC_VERSION < 6000
- register_callback(plugin_name, PLUGIN_START_UNIT, &sancov_start_unit, NULL);
- register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL, (void *)>_ggc_r_gt_sancov);
- register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &sancov_pass_info);
-#endif
-
- return 0;
-}
--
2.34.1
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