scripts/gcc-plugins/arm_ssp_per_task_plugin.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include "gcc-common.h"
   4
   5 __visible int plugin_is_GPL_compatible;
   6
   7 static unsigned int sp_mask, canary_offset;
   8
   9 static unsigned int arm_pertask_ssp_rtl_execute(void)
  10 {
  11         rtx_insn *insn;
  12
  13         for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) {
  14                 const char *sym;
  15                 rtx body;
  16                 rtx mask, masked_sp;
  17
  18                 /*
  19                  * Find a SET insn involving a SYMBOL_REF to __stack_chk_guard
  20                  */
  21                 if (!INSN_P(insn))
  22                         continue;
  23                 body = PATTERN(insn);
  24                 if (GET_CODE(body) != SET ||
  25                     GET_CODE(SET_SRC(body)) != SYMBOL_REF)
  26                         continue;
  27                 sym = XSTR(SET_SRC(body), 0);
  28                 if (strcmp(sym, "__stack_chk_guard"))
  29                         continue;
  30
  31                 /*
  32                  * Replace the source of the SET insn with an expression that
  33                  * produces the address of the copy of the stack canary value
  34                  * stored in struct thread_info
  35                  */
  36                 mask = GEN_INT(sext_hwi(sp_mask, GET_MODE_PRECISION(Pmode)));
  37                 masked_sp = gen_reg_rtx(Pmode);
  38
  39                 emit_insn_before(gen_rtx_set(masked_sp,
  40                                              gen_rtx_AND(Pmode,
  41                                                          stack_pointer_rtx,
  42                                                          mask)),
  43                                  insn);
  44
  45                 SET_SRC(body) = gen_rtx_PLUS(Pmode, masked_sp,
  46                                              GEN_INT(canary_offset));
  47         }
  48         return 0;
  49 }
  50
  51 #define PASS_NAME arm_pertask_ssp_rtl
  52
  53 #define NO_GATE
  54 #include "gcc-generate-rtl-pass.h"
  55
  56 #if BUILDING_GCC_VERSION >= 9000
  57 static bool no(void)
  58 {
  59         return false;
  60 }
  61
  62 static void arm_pertask_ssp_start_unit(void *gcc_data, void *user_data)
  63 {
  64         targetm.have_stack_protect_combined_set = no;
  65         targetm.have_stack_protect_combined_test = no;
  66 }
  67 #endif
  68
  69 __visible int plugin_init(struct plugin_name_args *plugin_info,
  70                           struct plugin_gcc_version *version)
  71 {
  72         const char * const plugin_name = plugin_info->base_name;
  73         const int argc = plugin_info->argc;
  74         const struct plugin_argument *argv = plugin_info->argv;
  75         int tso = 0;
  76         int i;
  77
  78         if (!plugin_default_version_check(version, &gcc_version)) {
  79                 error(G_("incompatible gcc/plugin versions"));
  80                 return 1;
  81         }
  82
  83         for (i = 0; i < argc; ++i) {
  84                 if (!strcmp(argv[i].key, "disable"))
  85                         return 0;
  86
  87                 /* all remaining options require a value */
  88                 if (!argv[i].value) {
  89                         error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
  90                               plugin_name, argv[i].key);
  91                         return 1;
  92                 }
  93
  94                 if (!strcmp(argv[i].key, "tso")) {
  95                         tso = atoi(argv[i].value);
  96                         continue;
  97                 }
  98
  99                 if (!strcmp(argv[i].key, "offset")) {
 100                         canary_offset = atoi(argv[i].value);
 101                         continue;
 102                 }
 103                 error(G_("unknown option '-fplugin-arg-%s-%s'"),
 104                       plugin_name, argv[i].key);
 105                 return 1;
 106         }
 107
 108         /* create the mask that produces the base of the stack */
 109         sp_mask = ~((1U << (12 + tso)) - 1);
 110
 111         PASS_INFO(arm_pertask_ssp_rtl, "expand", 1, PASS_POS_INSERT_AFTER);
 112
 113         register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,
 114                           NULL, &arm_pertask_ssp_rtl_pass_info);
 115
 116 #if BUILDING_GCC_VERSION >= 9000
 117         register_callback(plugin_info->base_name, PLUGIN_START_UNIT,
 118                           arm_pertask_ssp_start_unit, NULL);
 119 #endif
 120
 121         return 0;
 122 }