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 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                 masked_sp = gen_reg_rtx(Pmode);
  37
  38                 emit_insn_before(gen_rtx_SET(masked_sp,
  39                                              gen_rtx_AND(Pmode,
  40                                                          stack_pointer_rtx,
  41                                                          GEN_INT(sp_mask))),
  42                                  insn);
  43
  44                 SET_SRC(body) = gen_rtx_PLUS(Pmode, masked_sp,
  45                                              GEN_INT(canary_offset));
  46         }
  47         return 0;
  48 }
  49
  50 #define PASS_NAME arm_pertask_ssp_rtl
  51
  52 #define NO_GATE
  53 #include "gcc-generate-rtl-pass.h"
  54
  55 __visible int plugin_init(struct plugin_name_args *plugin_info,
  56                           struct plugin_gcc_version *version)
  57 {
  58         const char * const plugin_name = plugin_info->base_name;
  59         const int argc = plugin_info->argc;
  60         const struct plugin_argument *argv = plugin_info->argv;
  61         int tso = 0;
  62         int i;
  63
  64         if (!plugin_default_version_check(version, &gcc_version)) {
  65                 error(G_("incompatible gcc/plugin versions"));
  66                 return 1;
  67         }
  68
  69         for (i = 0; i < argc; ++i) {
  70                 if (!strcmp(argv[i].key, "disable"))
  71                         return 0;
  72
  73                 /* all remaining options require a value */
  74                 if (!argv[i].value) {
  75                         error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
  76                               plugin_name, argv[i].key);
  77                         return 1;
  78                 }
  79
  80                 if (!strcmp(argv[i].key, "tso")) {
  81                         tso = atoi(argv[i].value);
  82                         continue;
  83                 }
  84
  85                 if (!strcmp(argv[i].key, "offset")) {
  86                         canary_offset = atoi(argv[i].value);
  87                         continue;
  88                 }
  89                 error(G_("unknown option '-fplugin-arg-%s-%s'"),
  90                       plugin_name, argv[i].key);
  91                 return 1;
  92         }
  93
  94         /* create the mask that produces the base of the stack */
  95         sp_mask = ~((1U << (12 + tso)) - 1);
  96
  97         PASS_INFO(arm_pertask_ssp_rtl, "expand", 1, PASS_POS_INSERT_AFTER);
  98
  99         register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,
 100                           NULL, &arm_pertask_ssp_rtl_pass_info);
 101
 102         return 0;
 103 }