This plugins comes into play before the final 2 RTL passes of GCC and detects switch-tables that are to be outputed in the ELF and writes information in an "objtool_data" section which will be used by objtool.
Signed-off-by: Raphael Gault <[email protected]> --- scripts/Makefile.gcc-plugins | 2 + scripts/gcc-plugins/Kconfig | 9 +++ .../arm64_switch_table_detection_plugin.c | 58 +++++++++++++++++++ 3 files changed, 69 insertions(+) create mode 100644 scripts/gcc-plugins/arm64_switch_table_detection_plugin.c diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 5f7df50cfe7a..a56736df9dc2 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -44,6 +44,8 @@ ifdef CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK endif export DISABLE_ARM_SSP_PER_TASK_PLUGIN +gcc-plugin-$(CONFIG_GCC_PLUGIN_SWITCH_TABLES) += arm64_switch_table_detection_plugin.so + # 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 d33de0b9f4f5..1daeffb55dce 100644 --- a/scripts/gcc-plugins/Kconfig +++ b/scripts/gcc-plugins/Kconfig @@ -113,4 +113,13 @@ config GCC_PLUGIN_ARM_SSP_PER_TASK bool depends on GCC_PLUGINS && ARM +config GCC_PLUGIN_SWITCH_TABLES + bool "GCC Plugin: Identify switch tables at compile time" + default y + depends on STACK_VALIDATION && ARM64 + help + Plugin to identify switch tables generated at compile time and store + them in a .objtool_data section. Objtool will then use that section + to analyse the different execution path of the switch table. + endmenu diff --git a/scripts/gcc-plugins/arm64_switch_table_detection_plugin.c b/scripts/gcc-plugins/arm64_switch_table_detection_plugin.c new file mode 100644 index 000000000000..d7f0e13910d5 --- /dev/null +++ b/scripts/gcc-plugins/arm64_switch_table_detection_plugin.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <stdio.h> +#include "gcc-common.h" + +__visible int plugin_is_GPL_compatible; + +static unsigned int arm64_switchtbl_rtl_execute(void) +{ + rtx_insn *insn; + rtx_insn *labelp = NULL; + rtx_jump_table_data *tablep = NULL; + section *sec = get_section(".objtool_data", SECTION_STRINGS, NULL); + section *curr_sec = current_function_section(); + + for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) { + /* + * Find a tablejump_p INSN (using a dispatch table) + */ + if (!tablejump_p(insn, &labelp, &tablep)) + continue; + + if (labelp && tablep) { + switch_to_section(sec); + assemble_integer_with_op(".quad ", gen_rtx_LABEL_REF(Pmode, labelp)); + assemble_integer_with_op(".quad ", GEN_INT(GET_NUM_ELEM(tablep->get_labels()))); + assemble_integer_with_op(".quad ", GEN_INT(ADDR_DIFF_VEC_FLAGS(tablep).offset_unsigned)); + switch_to_section(curr_sec); + } + } + return 0; +} + +#define PASS_NAME arm64_switchtbl_rtl + +#define NO_GATE +#include "gcc-generate-rtl-pass.h" + +__visible int plugin_init(struct plugin_name_args *plugin_info, + struct plugin_gcc_version *version) +{ + const char * const plugin_name = plugin_info->base_name; + int tso = 0; + int i; + + if (!plugin_default_version_check(version, &gcc_version)) { + error(G_("incompatible gcc/plugin versions")); + return 1; + } + + PASS_INFO(arm64_switchtbl_rtl, "outof_cfglayout", 1, + PASS_POS_INSERT_AFTER); + + register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, + NULL, &arm64_switchtbl_rtl_pass_info); + + return 0; +} -- 2.17.1
