[PATCH] gcc-plugins: Remove ARM_SSP_PER_TASK plugin
Ard Biesheuvel
ardb at kernel.org
Wed Apr 9 09:08:19 PDT 2025
On Wed, 9 Apr 2025 at 18:04, Kees Cook <kees at kernel.org> wrote:
>
> As part of trying to remove GCC plugins from Linux, drop the
> ARM_SSP_PER_TASK plugin. The feature is available upstream since GCC
> 12, so anyone needing newer kernels with per-task ssp can update their
> compiler[1].
>
> Suggested-by: Arnd Bergmann <arnd at arndb.de>
> Link: https://lore.kernel.org/all/08393aa3-05a3-4e3f-8004-f374a3ec4b7e@app.fastmail.com/ [1]
> Signed-off-by: Kees Cook <kees at kernel.org>
> ---
> Cc: Ard Biesheuvel <ardb at kernel.org>
> Cc: Chris Packham <chris.packham at alliedtelesis.co.nz>
> Cc: Douglas Anderson <dianders at chromium.org>
> Cc: Russell King <linux at armlinux.org.uk>
> Cc: Masahiro Yamada <masahiroy at kernel.org>
> Cc: Nathan Chancellor <nathan at kernel.org>
> Cc: Nicolas Schier <nicolas at fjasle.eu>
> Cc: "Russell King (Oracle)" <rmk+kernel at armlinux.org.uk>
> Cc: Linus Walleij <linus.walleij at linaro.org>
> Cc: Andrew Davis <afd at ti.com>
> Cc: Seung-Woo Kim <sw0312.kim at samsung.com>
> Cc: Xin Li <xin3.li at intel.com>
> Cc: Jinjie Ruan <ruanjinjie at huawei.com>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-hardening at vger.kernel.org
> Cc: linux-kbuild at vger.kernel.org
> ---
> arch/arm/Kconfig | 3 +-
> arch/arm/boot/compressed/Makefile | 2 +-
> scripts/Makefile.gcc-plugins | 6 -
> scripts/gcc-plugins/Kconfig | 4 -
> scripts/gcc-plugins/arm_ssp_per_task_plugin.c | 107 ------------------
> 5 files changed, 2 insertions(+), 120 deletions(-)
> delete mode 100644 scripts/gcc-plugins/arm_ssp_per_task_plugin.c
>
Acked-by: Ard Biesheuvel <ardb at kernel.org>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 835b5f100e92..6f037edf0f41 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1379,8 +1379,7 @@ config CC_HAVE_STACKPROTECTOR_TLS
> config STACKPROTECTOR_PER_TASK
> bool "Use a unique stack canary value for each task"
> depends on STACKPROTECTOR && CURRENT_POINTER_IN_TPIDRURO && !XIP_DEFLATED_DATA
> - depends on GCC_PLUGINS || CC_HAVE_STACKPROTECTOR_TLS
> - select GCC_PLUGIN_ARM_SSP_PER_TASK if !CC_HAVE_STACKPROTECTOR_TLS
> + depends on CC_HAVE_STACKPROTECTOR_TLS
> default y
> help
> Due to the fact that GCC uses an ordinary symbol reference from
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 945b5975fce2..d61369b1eabe 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -96,7 +96,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
>
> ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
> -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
> - -I$(obj) $(DISABLE_ARM_SSP_PER_TASK_PLUGIN)
> + -I$(obj)
> ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg
> asflags-y := -DZIMAGE
>
> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
> index 6da109d563a5..194122d969a8 100644
> --- a/scripts/Makefile.gcc-plugins
> +++ b/scripts/Makefile.gcc-plugins
> @@ -36,12 +36,6 @@ ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> endif
> export DISABLE_STACKLEAK_PLUGIN
>
> -gcc-plugin-$(CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK) += arm_ssp_per_task_plugin.so
> -ifdef CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK
> - DISABLE_ARM_SSP_PER_TASK_PLUGIN += -fplugin-arg-arm_ssp_per_task_plugin-disable
> -endif
> -export DISABLE_ARM_SSP_PER_TASK_PLUGIN
> -
> # All the plugin CFLAGS are collected here in case a build target needs to
> # filter them out of the KBUILD_CFLAGS.
> GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
> diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
> index ba868d1eef3d..6b34ba19358d 100644
> --- a/scripts/gcc-plugins/Kconfig
> +++ b/scripts/gcc-plugins/Kconfig
> @@ -36,8 +36,4 @@ config GCC_PLUGIN_LATENT_ENTROPY
> * https://grsecurity.net/
> * https://pax.grsecurity.net/
>
> -config GCC_PLUGIN_ARM_SSP_PER_TASK
> - bool
> - depends on GCC_PLUGINS && ARM
> -
> endif
> diff --git a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c b/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
> deleted file mode 100644
> index 7328d037f975..000000000000
> --- a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
> +++ /dev/null
> @@ -1,107 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -
> -#include "gcc-common.h"
> -
> -__visible int plugin_is_GPL_compatible;
> -
> -static unsigned int canary_offset;
> -
> -static unsigned int arm_pertask_ssp_rtl_execute(void)
> -{
> - rtx_insn *insn;
> -
> - for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) {
> - const char *sym;
> - rtx body;
> - rtx current;
> -
> - /*
> - * Find a SET insn involving a SYMBOL_REF to __stack_chk_guard
> - */
> - if (!INSN_P(insn))
> - continue;
> - body = PATTERN(insn);
> - if (GET_CODE(body) != SET ||
> - GET_CODE(SET_SRC(body)) != SYMBOL_REF)
> - continue;
> - sym = XSTR(SET_SRC(body), 0);
> - if (strcmp(sym, "__stack_chk_guard"))
> - continue;
> -
> - /*
> - * Replace the source of the SET insn with an expression that
> - * produces the address of the current task's stack canary value
> - */
> - current = gen_reg_rtx(Pmode);
> -
> - emit_insn_before(gen_load_tp_hard(current), insn);
> -
> - SET_SRC(body) = gen_rtx_PLUS(Pmode, current,
> - GEN_INT(canary_offset));
> - }
> - return 0;
> -}
> -
> -#define PASS_NAME arm_pertask_ssp_rtl
> -
> -#define NO_GATE
> -#include "gcc-generate-rtl-pass.h"
> -
> -#if BUILDING_GCC_VERSION >= 9000
> -static bool no(void)
> -{
> - return false;
> -}
> -
> -static void arm_pertask_ssp_start_unit(void *gcc_data, void *user_data)
> -{
> - targetm.have_stack_protect_combined_set = no;
> - targetm.have_stack_protect_combined_test = no;
> -}
> -#endif
> -
> -__visible int plugin_init(struct plugin_name_args *plugin_info,
> - struct plugin_gcc_version *version)
> -{
> - const char * const plugin_name = plugin_info->base_name;
> - const int argc = plugin_info->argc;
> - const struct plugin_argument *argv = plugin_info->argv;
> - int i;
> -
> - 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, "disable"))
> - return 0;
> -
> - /* all remaining options require a value */
> - if (!argv[i].value) {
> - error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
> - plugin_name, argv[i].key);
> - return 1;
> - }
> -
> - if (!strcmp(argv[i].key, "offset")) {
> - canary_offset = atoi(argv[i].value);
> - continue;
> - }
> - error(G_("unknown option '-fplugin-arg-%s-%s'"),
> - plugin_name, argv[i].key);
> - return 1;
> - }
> -
> - PASS_INFO(arm_pertask_ssp_rtl, "expand", 1, PASS_POS_INSERT_AFTER);
> -
> - register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,
> - NULL, &arm_pertask_ssp_rtl_pass_info);
> -
> -#if BUILDING_GCC_VERSION >= 9000
> - register_callback(plugin_info->base_name, PLUGIN_START_UNIT,
> - arm_pertask_ssp_start_unit, NULL);
> -#endif
> -
> - return 0;
> -}
> --
> 2.34.1
>
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